Jean Jalbert

Patrick Grillas

Jean-Jacques Bravais

Florence Daubigney

Marie-Antoinette Diaz

« Respire

Claire Respire »

Jean-Claude Pic

Cécile Olivier Pineau

Bon, Vezzetti, Mégias, Mondrolini, Daujat, Vadon, Grand, Plagne, Gauthier, Grossi M M Callet

Roche Anne Vadon

Marie Granier

Gilbert Lanne

Vincent Couderc

Sylvestre Delmotte

Chacha Chacha

Françoise Bis

Andy Jacques

Fiona

Martin Léa

Samuel Lei

Après le tamisage de 2 684 paquets de terre, l'identification de 135 512 graines, l'élevage de 20 canetons dans la cuisine, le comptage de 32 684 oiseaux lors de 76 sorties diurnes et nocturnes en Camargue et à Doñana, plus de 50 000 km parcourus entre Vercelli, Wilhelmshaven, Tokyo, Séville, San Francisco et České Budějovice, 36 cheveux blancs et 1 kg d'ongles grignotés ce que je retiens avant tout de ces trois ans est l'aventure humaine. J'espère que le compte sera bon et que je n'oublierai personne. D'avance pardon si ce n'est pas le cas.

Ma mère dit toujours avec une pointe d'humour qu'elle a passé son bac à quatre (« A4 », nom donné au bac littéraire à son époque). En énumérant les prénoms de ceux qui ont participé activement, je peux affirmer que j'ai fait une thèse « A 29». Cette thèse est un orchestre sans chef issu de l'association de cerveaux bien pensants et surtout d'une sacrée bande de joyeux lurons, de personnages, tous aussi intéressants les uns que les autres.

Au commencement, il y a Matthieu Guillemain. Cette aventure a commencé bien avant le début de ma thèse. En Février 2010, alors que je finissais mon master sur le canard Merganette au Chili, je cherchais à poursuivre mes travaux de recherche au côté d'un réel Duck Teur! Et c'est tout logiquement que je te contactais. Matthieu, reçois toute ma gratitude pour le temps passé à accompagner mon cheminement intellectuel, à corriger mes écrits jusqu'à des heures tardives et à m'encourager. A travers cette thèse, tu m'as permis de me réconcilier avec mes cinq ans d'étude d'ingénieur agricole, me laissant carte blanche pour développer le projet en écologie appliquée dont je rêvais. « Alors ? Ça cartonne? » « Sri Lanka ! », nous y sommes arrivés ! Michel Gauthier-Clerc n'a jamais été très loin depuis son chantier de construction de zoo pour suivre mes avancées et me rappeler que recherche rime avec « questions, hypothèses et prédictions » et conservation rime avec intégration dans un territoire. Je te remercie Michel d'avoir apporté un regard constructif aux travaux développés et de m'avoir encouragée dans mes démarches de transfert de connaissances en Camargue.

Je tiens à exprimer ma profonde gratitude aux membres du jury d'avoir accepté de se pencher sur ce travail malgré leur planning chargé : les rapporteurs qui rendent réelle la conservation, William Sutherland et Reto Spaar, thank you very much, les examinateurs et invités, doux mélange d'écologues et d'agronomes convaincus qu'une amélioration de la matrice agricole est possible, Claude Miaud, Jean-Louis Martin, Alexandre Millon, Jean-Marc Barbier et Jean-Claude Mouret. Qu'ils soient remerciés pour le temps consacré à évaluer ce travail.

Je tiens également à remercier mes mentors qui ont eu le droit à trois comités de thèse : Jean-Claude Mouret pour m'avoir ouvert les portes de la riziculture en Camargue, David Gremillet pour m'avoir fait garder l'espoir que l'on pouvait naître dans l'Allier et faire de la recherche en ornithologie, même sur les oiseaux marins! François Mesléard pour avoir été présent lors des réflexions de recherche en amont, en aval et avoir avalé bon nombre de corrections lors du dernier round, merci pour tes commentaires farfelus, Arnaud Béchet pour avoir été d'un bon soutien lors de la valorisation de mes résultats de recherche, Jean-Baptiste Mouronval pour m'avoir appuyée dans l'identification et la quête de petites graines, et Olivier Boutron pour m'avoir fait comprendre que l'on pouvait parler de modélisation en souriant.

REMERCIEMENTS ! ! O!

Ma reconnaissance s'adresse également à Pierre Migot, Nirmala Séon-Massin, Catherine Jochum de la Direction de la Recherche et de l'Expertise de l'ONCFS, ainsi que toute l'équipe de l'Unité Avifaune Migratrice en particulier les grands chefs, Jean-Marie Boutin, Yves Ferrand et leurs petites mains habiles, Valérie Guérineau, Anne Floch. Et Laétitia pour l'aide à la mise en page finale. Merci pour le soutien financier, personnel et administratif qu'ils ont apporté au programme et pour avoir financé cette thèse par le biais d'un contrat doctoral aux 35 heures avec tous les avantages sociaux possibles et inimaginables. Ma future retraite vous en remercie! Les travaux de cette thèse

 (E!H(*@! .$1>%;7?1!89--@/E!5*XD(=!A=!BC@F$(=@B=?E!/5Y1E!;&WT=@T7(C'=@B=E!H(*@B=! 1W*I&@*D=>(! 8%22A#16!B(9--+8.9/C!/@G$@&=>(E!6.8H3E!;(%=?E!H(*@B=! #&(=BD=>(! :1%;<8%?D!E.,E9+,E!/@G$@&=>(E!/.2;T-52!/@@C'*D&C@E!5C@D)=%%&=(E!H(*@B=! /@'&D$! :1%;<5$%671!8@(,+)E!/@G$@&=>(E!/.2;T-52!/@@C'*D&C@E!5C@D)=%%&=(E!H(*@B=! /@'&D$! P! P! P! P! P! P! P! P! P! P! P! P! P! P! P! P! P! P! P! P! P! P! P! P! P! P! P! P! P! P! P! P! P! P! P! P! P! P! P! P! P! P! P! P! P! P! P! P! P! P! P! P! P! P! P! P! -En Italie, Giuseppe Bogliani et Franco Tesio. Grazie per il vostro aiuto! -En Espagne, au Delta de l'Ebre Antoni Curcó Masip, à l'Albulfera de Valencia Bosco Dies, à Doñana Andy Green et Jordi Figuerola. Muchas gracias a ustedes y a Rocio, Adam y los asistantes de terreno y a José Luis, Miguel Angel, Isabela por su apoyo technico.

! ! N! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! "!#$
-En Californie, John Eadie, Robert Blenk, Matthew Miller and Robert McLandres, thank you for your warm welcome, valuating my work and giving me the opportunity to work with you.

-En France, Jean-Patrice Robin, merci pour le broyage de graines et la détermination de leur contenu énergétique.

-Les experts sur les interactions riz-oiseaux qui ont répondu à mes questions et en particulier: Chris Elphick, Tatsuya Amano, Richard Mauro Fasola, Richard Smedley, Bernard Poujols. Thank you for your corrections when you were reviewers, and your expertise.

INTRODUCTION

I. Agroecosystems: threats and opportunities

Thesis contents and structure

The initial focus of the project was the use of post-harvest rice fields by wintering ducks and the influence of agricultural practices on such use. With time, this topic was gradually widened to a more global questioning about the general management of rice fields and the opportunities to provide mutual benefits for wintering ducks and farmers. The structure of the thesis manuscript reveals such gradual progress in the thinking, and the will to cover aspects ranging from purely ecological questions (e.g. variation in the energy density of seeds available to ducks across the winter) to an assessment of the agronomical and economical realism of such suggested procedures, as well as a future proper test of management procedures via modelling. This dissertation consists of six parts. First, a synthesis of the thesis in French is provided, second a general introduction presents the theoretical framework within which research was carried out, and introduces the main hypotheses and questions. Three chapters then constitute the core of the thesis and aim at providing answers to these questions, via empirical fieldwork and experimental tests. The first chapter is a review of the literature focusing on waterfowl and ricefield relationships worldwide; the second chapter studies the influence of post-harvest practices on seed availability and duck use; the third chapter concentrates on the potential agronomic benefits provided by ricefield winter flooding and ducks attracted in flooded rice fields. Finally, a general discussion comprising the economic 4,+K.5+M4,NK.5+! ! PP! analysis leads from waterbird ecology to more general habitat conservation issues and innovative agricultural management perspectives.

The main papers are enclosed into their respective chapters. The main results of each are linked together in a short introductive text at the beginning of the corresponding chapter (except for two introductive papers not directly linked to the main topic, which can be found in the Appendices together with the paper from the economic analysis). The Appendices also comprise the list of communications made at scientific conferences during the PhD, as well as the popularisation documents prepared for farmers and land managers from the scientific results.

It is my hope that this research will serve rice producers, decision makers, wildlife researchers, land managers, students, and outdoor enthusiasts alike to promote compatibility between wildlife conservation and human activities.

I hope the reading will be enjoyable.

INTRODUCTION

I. Les agroécosystèmes: menaces et opportunités

I.1 L'Agroécosystème, comme un élément intégré dans le paysage L'expansion et l'intensification de l'agriculture sont reconnues comme étant deux importantes menaces pour la biodiversité et le bon fonctionnement des écosystèmes [START_REF] Donald | Further evidence of continent-wide impacts of agricultural intensification on European farmland birds, 1990-2000[END_REF]. Face à l'augmentation croissante de la demande alimentaire [START_REF] Tilman | Forecasting agriculturally driven global environmental change[END_REF], des mesures d'urgence doivent être prises afin d'assurer la durabilité de la production agricole.

Couvrant 24% de la surface terrestre et plus de 45% de l'Europe [START_REF] Henle | Identifying and managing the conflicts between agriculture and biodiversity conservation in Europe-A review[END_REF], les systèmes cultivés dominent le paysage (MEA, 2005). La moitié des terres agricoles et 60% des services écosystémiques (à savoir les services d'approvisionnement, de support, de régulation et les services culturels rendus par les écosystèmes) sont dégradés (MEA, 2005). Compte tenu du rôle écologique de la biodiversité fonctionnelle pour la production agricole [START_REF] Altieri | The ecological role of biodiversity in agroecosystems[END_REF], il est nécessaire de gérer les paysages agricoles de manière à également promouvoir la biodiversité [START_REF] Scherr | Biodiversity conservation and agricultural sustainability: towards a new paradigm of 'ecoagriculture'landscapes[END_REF].

La production de ressources a été historiquement considérée comme l'unique service rendu par les paysages agricoles (service d'approvisionnement). Toutefois ces paysages ont rarement été identifiés comme producteurs de services de support, de régulation ou culturels [START_REF] Power | Ecosystem services and agriculture: tradeoffs and synergies[END_REF]. Au contraire, les agroécosystèmes sont souvent identifiés comme source destructrice des services fournis par les écosystèmes naturels, alors qu'ils en dépendent largement pour leur propre entretien [START_REF] Power | Ecosystem services and agriculture: tradeoffs and synergies[END_REF]. Dans quelle mesure les agroécosystèmes interagissent avec les habitats naturels et peuvent ou non fournir des services autres que la production agricole dépend largement de la façon dont ils sont gérés [START_REF] Altieri | The ecological role of biodiversity in agroecosystems[END_REF][START_REF] Swift | Biodiversity and ecosystem services in agricultural landscapes-are we asking the right questions? Agriculture[END_REF][START_REF] Power | Ecosystem services and agriculture: tradeoffs and synergies[END_REF].

Du point de vue agronomique, la présence de la biodiversité fonctionnelle dans les champs cultivés peut être encouragée par l'agro-écologie ou la gestion intégrée des adventices et des ravageurs de culture [START_REF] Shennan | Biotic interactions, ecological knowledge and agriculture[END_REF]. Ces approches considèrent qu'une meilleure intégration des mécanismes écologiques, émergeant de l'étude des écosystèmes naturels, peut fournir des indications sur la façon dont les interactions biotiques déterminent les fonctions des agroécosystèmes [START_REF] Ormerod | Meeting the ecological challenges of agricultural change, editors' introduction[END_REF]. La tendance est aujourd'hui aux études visant à combler le fossé entre l'agronomie et l'écologie par la promotion de mesures de gestion qui favorisent les interactions biotiques bénéfiques et minimisent les indésirables dans les agroécosystèmes [START_REF] Shennan | Biotic interactions, ecological knowledge and agriculture[END_REF].

Le concept d' « intensification écologique » implique la protection des services écosystémiques pour une agriculture durable, et l'augmentation de la production alimentaire dans les terres agricoles déjà existantes. Son développement a été identifié comme l'une des priorités de conservation pour 2015 (Sutherland et al., 2015).

I.2 Pertinence du modèle canard-riziculture

Les rizières couvrent environ 1% de la surface du globe (FAO-STAT, 2013) et représentent 15% de la surface totale en zones humides [START_REF] Lawler | Rice fields as temporary wetlands: a review[END_REF]. Elles sont une menace pour les zones humides naturelles (conversion, agriculture intensive) mais ont également été reconnues par la Convention de Ramsar comme un écosystème important pour la biodiversité [START_REF] Dean-Speirs | Analysis of Decisions from the 10th Meeting of Contracting Parties (COP10) to the Ramsar Convention[END_REF].

La capacité des rizières à atténuer la perte des zones humides naturelles est largement discutée, principalement en Méditerranée (ex : Tourenq et al., 2001;Toral et Figuerola, 2010). Dans cette région, 80 à 90% des zones humides naturelles ont disparu (Finlayson et al., 1992) et environ 23% des zones humides restantes sont artificielles [START_REF] Perennou | Existingareas and past changes of wetland extent in the Mediterranean region: an overview[END_REF]. L'importance des rizières pour la conservation des oiseaux d'eau est aussi largement reconnue [START_REF] Czech | Agricultural wetlands and waterbirds: a review[END_REF]Elphick et al., 2010), y compris en Europe (Longoni et al., 2010;[START_REF] Sánchez-Guzmán | Identifying new buffer areas for conserving waterbirds in the Mediterranean basin: the importance of the rice fields in Extremadura, Spain[END_REF].

Contrairement aux passereaux [START_REF] Pain | Farming and birds in Europe: the Common Agricultural Policy and its implications for bird conservation[END_REF][START_REF] Wilson | Bird conservation and agriculture[END_REF], les conséquences des pratiques agricoles sur les populations d'Anatidés, en particulier de canards, ont reçu une attention moindre (Thomas, 1982, Van Eerden et al., 1996;Duncan et al., 1999), alors que cette famille d'oiseaux fournit de nombreux services écosystémiques [START_REF] Green | Ecosystem services provided by waterbirds[END_REF]. Les bénéfices agronomiques potentiellement apportés par les Anatidés aux riziculteurs ont surtout été étudiés en Amérique du Nord (Anders et al., 2008). En Europe, les questions de tels services écosystémiques n'ont été abordées que récemment, à travers une étude sur le recyclage des nutriments par les oiseaux d'eau [START_REF] Navedo | Unravelling trophic subsidies of agroecosystems for biodiversity conservation: food consumption and nutrient recycling by waterbirds in Mediterranean rice fields[END_REF]. Une des explications probables à ce manque de connaissance est liée au fait que les canards européens utilisent principalement les terres agricoles comme sites d'alimentation nocturne (Tamisier et Dehorter, 1999;[START_REF] Pirot | Effects of agri-environmental schemes on farmland birds: do food availability measurements improve patterns obtained from simple habitat models?[END_REF]Mesléard et al., 1995), ce qui rend souvent difficile leur observation.

Près d'un quart des espèces d'Anatidés est actuellement menacé (Wetlands International, 2013). [START_REF] Green | Analyses of globally threatened Anatidae in relation to threats, distribution, migration patterns, and habitat use[END_REF] a identifié la perte de zones humides comme principale cause de déclin. De leur côté, [START_REF] Long | Ecological factors and human threats both drive wildfowl population declines[END_REF] ont identifié les changements de gestion des terres agricoles comme principale menace. La plupart des zones rizicoles européennes sont souvent situées à proximité des plus grands quartiers d'hivernage de canards. Une gestion appropriée de ces espaces pourrait participer à leur conservation. Les Anatidés utilisant surtout les rizières pour leur alimentation, l'approvisionnement en ressources suffisamment abondantes et accessibles déterminera donc l'utilisation de ces habitats par ces oiseaux.

I.3 L'intensification de l'agriculture et le déclin des oiseaux des terres cultivables en Europe: une question de ressources pour les granivores

En raison de l'intensification des cultures ou de l'abandon des terres, les activités agricoles sont actuellement responsables d'une perte massive de biodiversité, menaçant entre autres les oiseaux. La Politique Agricole Commune (PAC) mise en place après la seconde guerre mondiale pour moderniser le secteur et augmenter la productivité agricole a été la force motrice derrière l'intensification et la spécialisation des cultures arables en Europe [START_REF] Pain | Farming and birds in Europe: the Common Agricultural Policy and its implications for bird conservation[END_REF]Donald et al., 2001). L'utilisation accrue d'engrais et de pesticides, la mécanisation, la simplification des rotations de cultures et la perte de nombreux éléments naturels (par exemple des haies) ont conduit à une réduction de la diversité des paysages, à la dégradation des sols, à la pollution de l'eau et à la perturbation de la chaîne alimentaire [START_REF] Stoate | Ecological impacts of arable intensification in Europe[END_REF], affectant à la fois la flore [START_REF] Marshall | The role of weeds in supporting biological diversity within crop fields[END_REF] et les populations animales [START_REF] Wilson | A review of the abundance and diversity of invertebrate and plant foods of granivorous birds in northern Europe in relation to agricultural change[END_REF]. En conséquence, depuis les années 1970 les oiseaux des terres agricoles ont diminué en abondance plus que toute autre communauté d'avifaune en Europe (Donald et al., 2001;2006). Environ la moitié de ces espèces est aujourd'hui en déclin ou menacée [START_REF] Pain | Farming and birds in Europe: the Common Agricultural Policy and its implications for bird conservation[END_REF].

Afin d'enrayer ces baisses d'effectifs, il est nécessaire d'acquérir une bonne compréhension de l'utilisation de l'habitat par les espèces ainsi que d'identifier les facteurs limitants et les possibles mesures de gestion de l'habitat [START_REF] Sutherland | Managing habitats for conservation[END_REF][START_REF] Fuller | Birds and habitat: relationships in changing landscapes[END_REF]. Bien que chaque espèce puisse répondre de manière particulière aux changements de pratiques agricoles, certains groupes d'espèces partagent des facteurs de causalité communs de déclin [START_REF] Newton | The recent declines of farmland bird populations in Britain: an appraisal of causal factors and conservation actions[END_REF]. Par exemple, le déclin des oiseaux des terres agricoles a été associé à une réduction de la disponibilité des ressources en graines pendant la saison hivernale [START_REF] Wilson | A review of the abundance and diversity of invertebrate and plant foods of granivorous birds in northern Europe in relation to agricultural change[END_REF][START_REF] Moorcroft | The selection of stubble fields by wintering granivorous birds reflects vegetation cover and food abundance[END_REF][START_REF] Robinson | Post-war changes in arable farming and biodiversity in Great Britain[END_REF].

L'abondance et l'accessibilité déterminent conjointement la disponibilité des ressources alimentaires et agissent comme facteurs clés limitant la valeur sélective des consommateurs ainsi que la taille de leurs populations [START_REF] Newton | Population limitation in birds[END_REF]. Comprendre la dynamique des ressources alimentaires dans un habitat est important pour déterminer sa capacité d'accueil potentielle pour les oiseaux et les autres consommateurs. La capacité d'accueil a été classiquement définie comme le nombre maximum d'individus-jours que peut supporter un habitat étant donné les ressources alimentaires qu'il contient [START_REF] Goss-Custard | Carrying capacity in overwintering birds: when are spatial models needed[END_REF]. Pour les les espèces qui nous intéressent, la capacité d'accueil a été définie par le nombre de canards-jours (duck-use-days, DUD) (Reinecke et al., 1989). Le DUD est le nombre de canards qui peuvent survivre pendant une journée sur un hectare d'habitat. Il est calculé à partir de la formule suivante:

Une gestion appropriée de l'habitat hivernal permettant une plus grande disponibilité des ressources constitue un moyen d'accroître sa capacité d'accueil [START_REF] Ma | Managing wetland habitats for waterbirds: an international perspective[END_REF], comme cela peut être le cas pour les canards hivernants dans les rizières.

I.4 De la science à la politique à la science: la mise en oeuvre des mesures agro-environnementales au cours de la période hivernale

Les mesures agro-environnementales (MAE) mises en place au milieu des années 1980 par la communauté européenne sont l'instrument politique le plus important pour contrer les effets négatifs de l'agriculture moderne sur l'environnement. Elles permettent aux agriculteurs de recevoir des incitations financières pour l'adoption de pratiques respectueuses de l'environnement (EC General Directorate for Agriculture and Rural Development, 2005).

Plusieurs MAE ont été mises en place afin de maximiser les ressources en graines dans une tentative d'enrayer le déclin des oiseaux granivores (ex : couverts faune sauvage, [START_REF] Stoate | Development of an agri-environment scheme option: seed-bearing crops for farmland birds[END_REF], agrainage, Siriwardena et al., 2007, non-labour du sol, Cunningham et al., 2005). Le maintien des chaumes s'est aussi montré efficace pour l'augmentation des populations d'oiseaux des terres agricoles (Sutherland, 2015).

Des sommes d'argent conséquentes sont dépensées chaque année dans le cadre des MAE (UE: 3,7 milliards € en 2003, [START_REF] Kleijn | Mixed biodiversity benefits of agri-environment schemes in five European countries[END_REF]. Ceci nécessite donc une évaluation par les gouvernements de l'efficacité des mesures mises en place; une question largement débattue par la communauté scientifique [START_REF] Kleijn | How effective are European agri-environment schemes in conserving and promoting biodiversity?[END_REF][START_REF] Kleijn | Mixed biodiversity benefits of agri-environment schemes in five European countries[END_REF].

II. Canards et riziculture dans le paysage camarguais: structure et objectifs de la thèse L'objectif de cette thèse était d'évaluer s'il existe des pratiques inter-culturales « gagnant-gagnant » pour les riziculteurs et pour la conservation des canards hivernants dans les zones de production intensive du riz en Europe et plus particulièrement en Camargue (France).

II.1 Etat de l'art: riziculture et conservation des Anatidés

La littérature sur les canards sauvages et la production rizicole est disproportionnellement représentée par des etudes réalisées aux Etats-Unis se concentrant sur la gestion des rizières en interculture en tant qu'habitat d'alimentation pour les oiseaux sauvages hivernants (Eadie et al., 2008). Les études en Asie sont au contraire plutôt focalisées sur les avantages agronomiques apportés par l'élevage de canards de ferme dans les systèmes d'agriculture intégrée « riz-canard » [START_REF] Furuno | The Power of Duck: Integrated Rice and Duck Farming[END_REF]. Ce travail vise, à travers une approche combinant agronomie et écologie, à identifier les pratiques post-récolte offrant le plus de services écosystémiques. Pour atteindre ce but, nous avons d'abord réalisé une revue bibliographique pour établir l'état de l'art sur la conservation des canards et la production rizicole dans le monde, compte tenu en particulier des études américaines et asiatiques (Chapitre I, Article 1).

L'hypothèse que nous cherchions à tester était qu'il existe des mesures de gestion qui favorisent les interactions bénéfiques entre les canards sauvages et la production rizicole, et minimisent celles qui sont indésirables.

II.2 Paysages rizicoles et pratiques post-récolte bénéfiques aux canards

L'objectif spécifique du Chapitre II était de caractériser les pratiques agricoles postrécolte pratiquées dans les principales régions rizicoles d'Europe, qui appartiennent à la voie de migration Est-Atlantique et d'identifier celles qui favorisent la disponibilité des ressources en graines et la présence de canards en Camargue (France).

L'impact de la gestion de la paille sur la disponibilité en graines et l'utilisation des rizières par les canards ont été étudiés aux États-Unis (Eadie et al., 2008;Elphick et al., 2010). La quantité de résidus de culture disponible pour les Anatidés y est réduite par l'utilisation de variétés de riz à croissance rapide (Stafford et al., 2010), l'utilisation de moissonneuses batteuses modernes [START_REF] Fleskes | Waste rice seed in conventional and stripper-head harvested fields in California: Implications for wintering waterfowl[END_REF] et le labour (Stafford et al., 2010). On ignore toujours dans quelle mesure la gestion de la paille (brûlage, broyage, déchaumage) peut influencer l'utilisation des champs par les canards (Elphick et al., 2010). Cependant, l'efficacité de l'inondation hivernale pour attirer les canards dans les rizières a été démontrée, tant aux États-Unis qu'au Japon (Elphick et Oring, 2003;Tajiri et Ohkawara, 2013).

C'est sur la base de ces connaissances qu'une MAE ''inondation hivernale des rizières'' a été mise en place pour les oiseaux d'eau sur des sites Ramsar espagnols (Albufera de Valencia, Delta de l'Ebre) au début des années 2000. Elle consiste à maintenir les surfaces de rizières inondées pendant 3,5 à 4 mois l'hiver. L'extension de l'utilisation de cette pratique en Europe et la réponse des populations d'oiseaux d'eau à cette MAE n'avaient jusqu'à présent pas été évaluées.

Sur la base de ces résultats, les hypothèses testées dans ce chapitre étaient les suivantes:

-Le nombre de canards dans les principales régions rizicoles d'Europe de l'Ouest est positivement corrélé à la superficie en rizières inondées en hiver (Article 2).

-La MAE « inondation hivernale des rizières » engendre un plus grand nombre de canards hivernants sur les sites espagnols (Article 2).

-La disponibilité des ressources en graines dans les rizières est affectée négativement par le labour (Article 3).

-L'inondation hivernale des rizières est le principal facteur expliquant l'utilisation des rizières par les canards hivernants (Article 3).

Nous avons comparé les paysages agricoles de cinq grandes régions rizicoles d'Europe occidentale, appartenant toutes à la même voie de migration (Est-Atlantique, voir délimitations des voies de migration dans Scott et Rose, 1996), et la relation entre leurs paysages et le nombre de canards hivernants qu'elles hébergent. Nous avons considéré les six espèces européennes les plus communes de canards de surface: le canard colvert Anas platyrhynchos, la sarcelle d'hiver A. crecca, le canard pilet A. acuta, le canard souchet A. clypeata, le canard siffleur Mareca penelope et le canard chipeau M. strepera (Article 2). Après cette analyse à l'échelle internationale, nous avons étudié plus précisément la disponibilité en ressources et l'utilisation des rizières par les canards en fonction des pratiques post-récolte (brûlage, broyage, inondations, labour) en Camargue (Article 3).

II.3 Bénéfices agronomiques potentiels de la mise en eau hivernale des rizières et de l'attraction des canards dans ces dernières

Le Chapitre III traite des services écosystémiques potentiels apportés aux agriculteurs par l'inondation hivernale des rizières et l'attraction des canards dans ces dernières. Il aborde à travers des tests expérimentaux les principaux problèmes agronomiques que doivent affronter les riziculteurs: la gestion des adventices (services de régulation) et celle de la paille (services de support).

Des études antérieures ont montré que l'inondation des rizières en hiver peut améliorer la décomposition de la paille et réduire la biomasse d'adventices (Manley et al., 2005) ou la viabilité de leurs graines (Fogliatto et al., 2010;Baek et Chung, 2012). Ces effets qui peuvent être accentués par la présence de canards sauvages s'alimentant sur ces rizières (Bird et al., 2000[START_REF] Van Groenigen | Effects of foraging waterfowl in winter flooded rice fields on weed stress and residue decomposition[END_REF]. En parallèle, d'autres études ont indiqué que l'élevage des canards sur les rizières en Asie empêche la croissance de nombreuses adventices et réduit leur biomasse par piétinement et consommation des jeunes plants et des graines [START_REF] Furuno | The Power of Duck: Integrated Rice and Duck Farming[END_REF].

Sur la base de ces résultats, nos hypothèses étaient les suivantes:

-L'inondation hivernale des rizières est une gestion biologique efficace pour contrôler les adventices de riz grâce à l'augmentation de la dégradation des graines (Article 4) -Les canards attirés dans les rizières inondées après la récolte profitent aux agriculteurs à travers la réduction de la banque de graines et la réduction des chaumes de riz (Article 5)

Les rizières de Camargue sont traditionnellement inondées d'avril à septembre, entre le semis et la récolte, puis gardés en chaumes, déchaumées ou labourées pendant l'hiver (Mañosa i Rifé, 1997). Actuellement, environ 75% des résidus de paille de riz sont brûlés; le reste étant broyé (Monier et al., 2009). L'écobuage de la paille est toléré par dérogation, mais des préoccupations croissantes concernant la pollution de l'air engendrée pourraient bientôt provoquer des décisions politiques qui limiteraient ou interdiraient complètement cette pratique (Couderc, 2013). Dans ce contexte, des modes de gestion de la paille alternatifs sont donc nécessaires. La petite proportion de rizières inondées en hiver en Camargue l'est surtout à des fins cynégétiques (Mathevet et Mesléard, 2002). Le désherbage est aussi une préoccupation pour les riziculteurs français, car les conditions climatiques et un accès plus limité aux pesticides en France rendent la production de riz moins compétitive que celle des Espagnols ou des Italiens. En outre, le plan national Ecophyto décidé lors du Grenelle de l'Environnement (2007) vise à réduire de 50% l'utilisation des pesticides d'ici à 2018. Dans ces conditions, l'inondation des rizières en hiver peut apparaître comme une technique alternative pour limiter simultanément les adventices et dégrader les chaumes. Nous avons évalué expérimentalement la détérioration sous serre du riz et des graines d'adventices au cours d'un hiver en conditions sèches ou inondées (Article 4). Nous avons également testé en enclos en plein champ l'effet des canards hivernants et des canards d'élevage sur la banque de graines et sur les chaumes après un hiver (Article 5).

II.4 Evaluation économique de l'inondation hivernale en Camargue

L'évaluation économique des services écosystémiques est préconisée par un nombre croissant d'écologues ; comme une stratégie à court terme pour communiquer sur la valeur de la biodiversité dans une langue qui reflète les opinions politiques et économiques dominantes. Elle peut aussi fournir des indications complémentaires aux résultats purement écologiques (Turner et al., 2000). Pour conclure le raisonnement développé dans les Chapitres II et III, nous avons effectué une analyse coûts-bénéfices pour évaluer la pertinence de l'inondation des rizières en hiver en France (Article 6, Annexe I.1).

Nos hypothèses étaient les suivantes:

-L'inondation hivernale des rizières en Camargue est économiquement réaliste pour l'agriculteur (Article 6, Annexe I.1) -L'inondation hivernale des rizières en Camargue est économiquement réaliste et souhaitable du point de vue de la société locale (Article 6, Annexe I.1)

CHAPITRE I. ÉTAT DE L'ART: RIZICULTURE ET CONSERVATION DES ANATIDÉS ! I.1 Contexte général

Les revues de la littérature sont une source importante d'information scientifique pour les gestionnaires et les décideurs, leur permettant d'évaluer l'efficacité d'interventions de gestion ou de politiques de conservation (ex: [START_REF] Pullin | Do conservation managers use scientific evidence to support their decision-making?[END_REF]Pullin et Stewart, 2006;[START_REF] Roberts | Are review articles a reliable source of evidence to support conservation and environmental management? A comparison with medicine[END_REF].

Cette revue bibliographique (Article 1) expose les interactions positives et négatives entre les rizières et les canards (sauvages et d'élevage) dans le monde, dans une perspective plus large que le seul sujet de la thèse, qui elle se concentre sur une zone géographique, la Camargue, et une période, l'hiver. Elle fournit une compréhension générale du contexte dans lequel les questions de la thèse sont développées. Elle met aussi en en évidence des leviers, freins et manques de connaissances ainsi que les mesures de gestion à mettre en place pour diminuer les contraintes et améliorer les bénéfices.

Pour la réalisation de cette revue, nous avons tenté de suivre l'approche d'une revue systématique comme le Centre for Evidence-Based Conservation (http://www.conservationevidence.com) et le Collaboration for Environmental Evidence (www.environmentalevidence.org) le conseillent. Ceci a impliqué 1) une recherche systématique de la littérature combinant plusieurs sources d'information (revues de littérature, articles scientifiques, littérature grise d'organisations non-gouvernementales, de gouvernements et d'experts clés), 2) une présentation des données chiffrées sous la forme de tableaux et graphiques et 3) une exposition claire des données et résultats utiles à la conservation, une identification des lacunes dans les données et une liste de conseils de gestion (cf. tous les critères dans [START_REF] Roberts | Are review articles a reliable source of evidence to support conservation and environmental management? A comparison with medicine[END_REF].

I.2 Résultats clés

Nous soulignons ici uniquement les résultats concernant l'option de gestion qui semble la plus favorable aux canards et aux riziculteurs et a ensuite été testée durant le reste de ce travail de thèse, à savoir l'inondation hivernale des rizières (Article 1).

Une batterie de résultats a montré que l'inondation hivernale: -Améliore l'accessibilité des canards aux ressources alimentaires dans les rizières. Une telle gestion augmente instantanément le nombre de canards s'alimentant ainsi que la fréquentation globale des rizières (ex: Day et Colwell, 1998;Shimada et al., 2000;Elphick et Oring, 2003;. Havens et al., 2009;Tajiri et Ohkawara, 2013).

-Offre des avantages agronomiques aux agriculteurs grâce à l'augmentation du recyclage des éléments nutritifs (Manley et al., 1999;[START_REF] Eagle | Soil management. Rice yield and nitrogen utilization efficiency under alternative straw management practices[END_REF], de la décomposition de la paille (Manley et al., 2005) et de la réduction de la viabilité des graines d'adventices (Street et Bollich, 2003;Manley et al., 2005;Fogliatto et al., 2010;Baek et Chung, 2012) -A son action accentuée par les canards attirés dans les rizières inondées, qui peuvent également accroître la décomposition de la paille et diminuer la biomasse d'adventices au printemps (ex: Bird et al., 2000;[START_REF] Van Groenigen | Effects of foraging waterfowl in winter flooded rice fields on weed stress and residue decomposition[END_REF]Van Diepen et al., 2004 et Tableau 2 de l'Article 1).

La revue de la littérature a aussi souligné certains manques de connaissances:

-1) Elphick et al. (2010b) ont signalé que l'on ignore comment la gestion de la paille peut influencer l'utilisation des rizières par des canards.

-2) Les comptages nocturnes existants [START_REF] Rave | Time-activity budget of Northern Pintails using nonhunted rice fields in Southwest Louisiana[END_REF][START_REF] Cox | Use of habitats by female northern pintails wintering in southwestern Louisiana[END_REF]Tamisier et Dehorter, 1999;[START_REF] Pirot | Effects of agri-environmental schemes on farmland birds: do food availability measurements improve patterns obtained from simple habitat models?[END_REF]Mesléard et al, 1995) ont révélé que l'utilisation que font les canards des rizières en chaume est importante et mérite un meilleur suivi. La plupart des comptages existants sont pourtant diurnes (Twedt et Nelms, 1999;Tourenq et al., 2001;Elphick et Oring, 2003).

-3) La disponibilité de toutes les sources de nourriture pendant l'hiver (Manley et al., 2004;Stafford et al., 2006;Greer et al., 2009;Stafford et al., 2010), la quantité d'énergie fournie par ces ressources (Kaminski et al., 2003) et la variabilité de l'énergie au cours de l'hiver. (Nelms et Twedt, 1996) nécessitent une estimation plus précise pour une meilleure évaluation de la capacité d'accueil des rizières.

-4) [START_REF] King | Effects of landscapefeatures on waterbird use of rice fields[END_REF] considèrent que des études au niveau du paysage rizicole sont nécessaires afin de mettre en oeuvre des plans de conservation à des échelles plus grandes, impliquant à la fois les zones humides naturelles et les terres agricoles inondées. Mieux comprendre les facteurs à l'origine des mouvements des canards entre les zones humides naturelles et artificielles, ainsi qu'entre leur remise diurne et leurs sites d'alimentation nocturnes, permettrait une meilleure évaluation de l'effet des caractéristiques du paysage et de son hétérogénéité sur ces espèces [START_REF] Chan | The effect of ricefield fragmentation on wintering waterbirds at the landscape level[END_REF][START_REF] Elphick | Landscape effects on waterbird densities in California rice fields: taxonomic differences, scale-dependence, and conservation implications[END_REF].

-5) Stafford et al. (2010) ont appelé les chercheurs à employer des outils modernes de télédétection pour étudier l'évolution des surfaces cultivées en riz à travers le monde. D'autres outils modernes de modélisation tels que les modèles énergétiques ou les modèles multi-agents [START_REF] Amano | Decision-making in group foragers with incomplete information: test of individual-based model in geese[END_REF]Petrie et al., 2014;Miller et al., 2014) permettraient de prédire les mouvements et l'utilisation des rizières par les canards hivernants, et de fournir des informations pour guider de futurs plans de conservation.

-6) Eadie et al. (2008) et Anders et al. (2008) estiment nécessaire une évaluation économique précise des coûts et bénéfices de l'inondation hivernale des rizières considérant les coûts agronomiques évités, des opérations de travail du sol, de pompage de l'eau, mais également les bénéfices d'un potentiel revenu de la chasse ou d'activités écotouristiques.

I.3 Liens avec les prochains chapitres de la thèse

Nous avons utilisé les principaux résultats de la revue bibliographique (Article 1) afin de guider les études empiriques et expérimentales mises en place sur le terrain et au laboratoire au cours de cette thèse, en essayant de couvrir une partie des manques de connaissances énumérés ci-dessus et nécessitant de plus amples recherches:

-Des comptages nocturnes de canards ont été réalisés dans les rizières de Camargue soumises à différentes pratiques post-récolte (Article 3, couvrant les points 1 et 2 ci-dessus).

-La disponibilité en graines après la récolte et la déplétion des ressources en graines au cours de l'hiver ont été étudiées en Camargue, ce qui a permis d'estimer avec précision le Duck Use-Days (Article 3, couvrant le point 3 ci-dessus).

-Le contenu énergétique et la dégradation des graines d'adventices au cours de l'hiver ont été évalués de manière expérimentale (Article 4, couvrant le point 3 ci-dessus).

-La télédétection a été utilisée pour étudier cinq paysages rizicoles européens (Article 2) et une première mise en application du modèle multi-agents SWAMP est actuellement prévue en Camargue (projet SWAMP présenté en discussion) (couvrant les points 4 et 5 ci-dessus).

-Une évaluation complète des coûts et bénéfices de l'inondation hivernale en Camargue a été effectuée afin de déterminer si une telle gestion serait économiquement acceptable par les agriculteurs et la société en Camargue (Article 6, Annexe 3 couvrant le point 7 ci-dessus).

CHAPITRE II. INFLUENCE DES PRATIQUES EN INTERCULTURE SUR LA DISPONIBILITÉ DES GRAINES ET L'UTILISATION DES RIZIÈRES PAR LES CANARDS

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II.1 Contexte général

Le Chapitre II vise à déterminer quelles sont les pratiques en interculture les plus appropriées pour fournir un habitat d'alimentation aux canards hivernants dans les zones rizicoles européennes.

Nous avons mis l'accent sur l'inondation hivernale des rizières, identifiée dans le Chapitre I (Article 1) comme la mesure de gestion la plus favorable aux canards et aux riziculteurs. Nous avons évalué l'utilisation de cette pratique en Europe de l'Ouest sur cinq grandes régions rizicoles (Article 2), puis les conséquences de différentes pratiques en interculture sur la disponibilité des ressources en graines et la fréquentation de ces habitats par les canards spécifiquement en Camargue (Article 3).

Des études antérieures ont porté sur la disponibilité des ressources alimentaires et la fréquentation nocturne des rizières et marais peu profonds par les canards (Tamisier et Dehorter, 1999;[START_REF] Pirot | Effects of agri-environmental schemes on farmland birds: do food availability measurements improve patterns obtained from simple habitat models?[END_REF]Mesléard et al., 1995). Elles ont suggéré que les rizières inondées représentaient un habitat d'alimentation important pour les canards granivores. Par opposition à ces auteurs, [START_REF] Tourenq | Valeurs et fonctions des rizières pour les communautés d'oiseaux d'eau en Camargue[END_REF] a conclu que seulement 6% des rizières de Camargue étaient inondées pendant l'hiver (environ 10% d'après [START_REF] Pirot | Effects of agri-environmental schemes on farmland birds: do food availability measurements improve patterns obtained from simple habitat models?[END_REF] et ne constituaient pas un habitat très important pour ces oiseaux. Une mise à jour du degré d'utilisation de l'inondation hivernale et de la fréquentation des rizières par les canards en hiver était donc nécessaire.

II.2 Résultats clés

Les études présentées dans les articles de ce chapitre fournissent de nouveaux résultats scientifiques qui peuvent être utiles à la conservation des zones humides et des oiseaux d'eau, car ils ont permis:

1/ d'obtenir une évaluation actualisée de l'état de conservation des zones humides et de l'utilisation de l'inondation hivernale des rizières dans de grandes régions rizicoles européennes, ainsi que de mesurer la contribution de ces éléments du paysage pour la conservation des canards. Les cinq régions d'étude présentent des paysages très contrastés en terme de proportions de surfaces couvertes par les zones humides naturelles et les rizières.

Les pratiques post-récolte diffèrent aussi grandement ; la proportion de rizières inondées en hiver variant de 0,17 à 62%. En Camargue, seuls 9% des rizières sont inondés, à des fins cynégétiques. Le rôle des différences d'incitation financière (MAE) dans l'existence de telles disparités à l'échelle européenne est évalué (Article 2).

2/ de rouvrir le débat sur les complémentarités entre zones humides et champs de riz. L'abondance de canards hivernants est positivement liée à la présence de zones humides au sens large, c'est-à-dire à la somme des surfaces en zones humides naturelles et des rizières inondées (Article 2).

3/ d'estimer la disponibilité en graines dans les rizières après la récolte, et leur déplétion au cours de l'hiver. Une demi-tonne de graines en moyenne était disponible après récolte à la surface d'environ 50 rizières échantillonnées en Camargue au cours des hivers 2012-2013 et 2013-2014 (riz: 349,9 kg/ha ± 57,6 SE; adventices: 141,6 kg/ha ± 21,3 SE). L'abondance de cette ressource alimentaire ne dépendait pas de la gestion de la paille (brûlure, broyage ou déchaumage) mais diminuait fortement au cours de l'hiver (-89% pour le riz et -69% pour les adventices) ; cette déplétion étant accentuée par la pratique d'un labour (Article 3). 4/ d'examiner l'influence des pratiques en interculture sur l'utilisation des rizières par les canards. L'inondation des rizières en hiver est le principal facteur explicatif de la présence de canards sur les rizières (Articles 2 et 3). L'abondance de canards sur les zones rizicoles européennes était plus grande dans les régions où plus de rizières étaient inondées après récolte (Articles 2). L'inondation hivernale était également le principal facteur explicatif de la fréquentation nocturne des rizières par les canards en Camargue (24 canards/ha en moyenne dans les parcelles inondées et 0,3 dans les sèches) (Articles 3). Aucun effet évident de la gestion post-récolte sur la fréquentation des rizières par les canards n'a été détecté tant que les champs étaient inondés (Articles 3). 5/ de tester l'efficacité de la mesure agri-environnementale « inondation hivernale des rizières » en Espagne. Depuis la mise en place de cette MAE au début des années 2000, les deux régions espagnoles ont vu leurs effectifs de canards hivernants augmenter considérablement (+6 et +12%, alors qu'avant la MAE les tendances étaient négatives).

CHAPITRE III. BÉNÉFICES AGRONOMIQUES POTENTIELS DE LA MISE EN EAU HIVERNALE DES RIZIÈRES ET DE L'ATTRACTION DES CANARDS DANS CES DERNIÈRES

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III.1 Contexte général

Le Chapitre III traite des bénéfices agronomiques que pourraient apporter aux agriculteurs par l'inondation hivernale des rizières et l'attraction des canards dans ces dernières aux agriculteurs. Il aborde, à travers des tests expérimentaux, les principaux problèmes agronomiques que doivent affronter les riziculteurs: la gestion des adventices (services de régulation) et celle de la paille (services de régulation).

Ces avantages agronomiques potentiels ont été résumés par Anders et al. (2008) pour les États-Unis, puis discutés en parallèle des bénéfices agronomiques de l'élevage de canards dans les systèmes d'agriculture intégrée « riz-canard » dans le Tableau 2 de l'Article 1 (Chapitre I). Des études empiriques et expérimentales antérieures ont montré que les canards peuvent apporter des avantages agronomiques aux riziculteurs, mais cela n'a qu'à une seule reprise en Europe [START_REF] Navedo | Unravelling trophic subsidies of agroecosystems for biodiversity conservation: food consumption and nutrient recycling by waterbirds in Mediterranean rice fields[END_REF]. Nous avons donc évalué expérimentalement l'effet de l'inondation hivernale des rizières sur la détérioration du riz et des graines d'adventices, ainsi que l'effet des canards hivernants et des canards d'élevage sur la banque de graines et sur les chaumes après un hiver.

III.2 Résultats clés

Les études présentées dans les articles de ce chapitre fournissent de nouveaux résultats démontrant que l'inondation hivernale des rizières et l'attraction des canards dans celles-ci peuvent bénéficier aux agriculteurs par le biais d'une augmentation de la décomposition de la paille, mais ne permettent pas forcément une réduction significative de la banque de graines d'adventices :

1/ L'inondation hivernale ne favorise la dégradation que de certaines graines (Article 4).

La masse des graines décline clairement au cours de l'hiver (-38,4% en moyenne), particulièrement en condition inondée, avec des taux qui différent d'une espèce à l'autre (voir aussi Nelms et Twedt, 1996;Foster et al., 2010;[START_REF] Collins | Decomposition of Three Common Moist-Soil Managed Wetland Plant Species[END_REF]. Les graines de riz cultivé et de riz crodo ont perdu significativement plus de masse au cours de l'hiver en condition inondée qu'en condition sèche: le riz cultivé a perdu en moyenne 46,2% de sa masse en condition sèche, contre 62,3% en condition inondée. Les chiffres correspondants pour le riz crodo étaient 26,6% et 45,3%. Pour les autres espèces (Echinochloa crus-galli, Bolboshoenus maritimus), aucun effet de l'inondation sur la perte de masse des graines n'a été détecté.

La viabilité des graines a généralement diminué au fil du temps (-43,1% en moyenne) mais l'amplitude de cette diminution n'a été significativement plus élevée en condition inondée que pour le riz cultivé. La viabilité moyenne du riz cultivé a diminué de 99,0% au début de l'hiver à 54,2% en fin de saison en condition sèche, contre 13,0% en condition inondée. Pour les autres espèces de graines, aucun effet de l'inondation sur la viabilité n'a été détecté.

Nous avons également considéré le contenu énergique des graines dans le but d'évaluer les changements de leur qualité nutritive pour les canards. Les riziculteurs pourraient également être intéressés par le contenu énergique des graines s'il existe un seuil en-dessous duquel les graines perdent leur capacité à germer. Nous avons observé que la densité d'énergie (kJ/g) demeure relativement constante au cours de l'hiver, montrant en fait une très légère augmentation, en particulier en condition inondée: +3,75% au cours de l'hiver. La quantité totale d'énergie disponible pour les canards à partir d'un échantillon de graines donné diminue donc au cours de la saison, essentiellement en raison de la perte de masse car elle n'est pas compensée par la faible concentration de l'énergie. Cette perte d'énergie brute au cours de l'hiver était relativement similaire en condition inondée ou sèche pour la plupart des graines. La seule exception est le riz crodo, dont la perte d'énergie brute était de 42,4% en condition inondée, contre seulement 26,2% en condition sèche.

En résumé, nous n'avons pas constaté que l'inondation des rizières en hiver pouvait être une pratique bénéfique pour les agriculteurs en terme de réduction de la viabilité de la banque de graines à la fin de l'hiver, contrairement à des études antérieures (Street et Bollich, 2003;Manley et al., 2005;Anders et al., 2008;Fogliatto et al., 2010;Baek et Chung, 2012).

Cependant, il reste à établir (en particulier pour le riz crodo) si les graines germeraient et les plantules croîtraient de manière similaire après inondation par rapport au traitement à sec, en étudiant les taux de germination et la biomasse des plants d'adventices le printemps suivant (Manley et al., 2005). Pour les canards, nos résultats suggèrent que la quantité et non la qualité des ressources en graines diminue au cours de l'hiver.

2/ Les canards n'ont pas d'effet significatif sur la banque de graines et ceci peut être expliqué par la répartition des graines (Article 5).

Nous avons testé, sur la banque de graines d'une rizière inondée, l'effet de canards se nourrissant pendant tout un hiver à trois densités: 5 canards.ha -1 (densité historique de canards sauvages), 23 canards.ha -1 (densité actuelle de canards sauvages) et 300 canards.ha -1 (densité en système intégré « riz-canard »). Le pâturage saisonnier sur une surface donnée était simulé par une charge instantanée élevée dans de petits enclos expérimentaux.

Les canards n'ont pas eu d'effet significatif sur la banque de graines. Par rapport à la situation initiale, les canards n'ont diminué le nombre moyen de graines par échantillon que de 3% seulement, à la plus forte densité d'oiseaux, et la masse des graines d'environ 21%, mais ceci n'était pas significatif. L'absence d'effets significatifs des canards sur les semences peut s'expliquer par la répartition agrégative des graines au sein de la rizière; ce qui entraîne un nombre très variable de graines par échantillon.

3/ Les canard réduisent de manière significative les chaumes et contribuent à leur immersion, ce qui peut augmenter la décomposition de la paille (Article 5).

Deux études californiennes ont précédemment observé par des tests expérimentaux que le piétinement des canards a un effet mécanique direct sur la paille, entraînant une intensification des contacts entre celle-ci et le sol, donc une plus grande accessibilité de la paille à la flore microbienne (Bird et al., 2000;[START_REF] Van Groenigen | Effects of foraging waterfowl in winter flooded rice fields on weed stress and residue decomposition[END_REF]. Les canards contribuaient à réduire les concentrations de lignine et d'azote dans le résidu de surface, augmentant la décomposition de la paille de riz, la disponibilité en azote du sol et l'incorporation de la paille dans le sol. Avec de fortes densités de canards, la diminution de la masse de la paille résiduelle de surface pouvait atteindre 76% (Bird et al., 2000). [START_REF] Van Groenigen | Effects of foraging waterfowl in winter flooded rice fields on weed stress and residue decomposition[END_REF] ont également observé que la réduction de la biomasse de paille dans les champs inondés était plus de deux fois plus grande en présence de canards.

Nos tests ont montré que les canards réduisent de manière significative le nombre de chaumes de paille dressées et que cette réduction augmente avec la densité de canards: -27% pour 5 canards.ha -1 , -52% pour 23 canards.ha -1 , -91% pour 300 canards.ha -1 . L'attraction des canards dans les rizières inondées permettrait la diminution du nombre de chaumes debout et donc une augmentation de la décomposition de la paille par l'action conjuguée de l'eau et du piétinement des canards.

IV. DISCUSSION %

IV.1 Un changement des pratiques agricoles en interculture pourrait-il être bénéfique pour les canards hivernants et les riziculteurs?

Afin de déterminer s'il existe des pratiques inter-culturales « gagnant-gagnant » pour les riziculteurs et pour la conservation des canards hivernants dans les zones de production intensive de riz en Europe et plus particulièrement en Camargue (France), nous nous sommes appuyés sur une variété d'approches, notamment une revue bibliographique (Chapitre I, Article 1), des études empiriques (Chapitre II, Articles 2 et 3) et expérimentales (Chapitre III, Articles 4 et 5) dans le cadre conceptuel général de la théorie de l'approvisionnement optimal, de l'agro-écologie et des services écosystémiques.

L'analyse de la littérature scientifique nous a permis d'identifier l'inondation hivernale des rizières comme une gestion de l'habitat offrant des avantages pour les canards grâce à l'utilisation directe des champs en chaumes. Du point de vue des agriculteurs, elle augmente la décomposition de la paille et diminue la viabilité des graines d'adventices par l'action conjuguée de l'eau et du piétinement des canards (Article 1). Les études mises en oeuvre au cours de cette thèse confirment que des avantages similaires peuvent être attendus en Europe. Une corrélation positive entre la superficie en rizières inondées et le nombre de canards hivernants par site a été démontrée à l'échelle d'une aire globale d'hivernage (Article 2). Grâce à l'étude des processus en jeu à une échelle plus locale, en Camargue, nous avons conclu que toute mise en eau des rizières non-labourées serait une gestion appropriée pour les canards hivernants, leur permettant d'accéder au stock abondant de graines (Article 3). En retour, les riziculteurs peuvent attendre une participation des canards attirés sur les rizières au processus de décomposition de la paille (Article 5). Sur la base de ces résultats écologiques et agronomiques, nous concluons que l'inondation hivernale devrait être encouragée pour les canards en Camargue et partout ailleurs où sa mise en place serait techniquement possible. La mesure agri-environnementale « inondation hivernale des rizières » en Espagne a prouvé son efficacité, en se traduisant par une amélioration des tendances d'évolution des effectifs locaux de canards (Article 2).

Bien que les résultats de ce projet de recherche soient clairs et concordants d'une étude à l'autre, cette étude présente néanmoins ses propres limites.

La revue de la littérature n'a couvert que 14 des 27 critères méthodologiques définissant une revue bibliographique systématique selon la définition de Roberts et al. (2006) (Article 1). Parmi les critères non respectés figurent l'exécution d'une méta-analyse ou d'une analyse de sensibilité. Plusieurs de ces limitations sont dues aux sources de la littérature ellesmêmes, qui souvent ne fournissaient que des informations quantitatives et/ou difficiles à comparer entre elles.

Les liens possibles entre l'inondation hivernale des rizières et l'abondance régionale des canards ont été évalués dans cinq paysages d'Europe occidentale. Ces zones étaient très contrastées en termes de superficies couvertes par des zones humides naturelles par rapport à celles en rizières, et en terme d'inondation hivernale des rizières. Ces différences massives de paysages peuvent conduire à surestimer l'impact potentiel de l'inondation hivernale sur les effectifs de canards dans des paysages « moyens ». Cependant, les résultats de cette étude de corrélation sont soutenus par le test de l'efficacité de la mesure agri-environnementale « inondation hivernale des rizières » mise en place en Espagne, qui a effectivement conduit à des changements positifs dans les tendances démographiques des canards (Article 2).

Il n'a pas été possible d'obtenir un échantillonnage réellement aléatoire des diverses pratiques en interculture sur les 50 parcelles échantillonnées au sein des 9 exploitations agricoles de Camargue étudiées (Article 3). En effet, la plupart des agriculteurs n'ont pas accepté de modifier profondément leurs pratiques pour le projet, sans soutien financier.

Les comptages nocturnes avec l'amplificateur de lumière ont fourni des informations sur la fréquentation des rizières par les canards (Article 3) mais ne renseignent pas sur les préférences ou la sélection de certains habitats, puisque seules les rizières étaient étudiées. D'autres études sur l'alimentation et la disponibilité des ressources dans les autres habitats d'alimentation (zones humides naturelles ainsi que marais agrainés), conduites avec des équipements de télémétrie type GPS aideraient à améliorer notre compréhension des mouvements et des préférences des canards au sein de l'ensemble des habitats d'alimentation disponibles. Concernant les comptages nocturnes de canards, malgré les potentielles erreurs d'estimation, doubles comptages ou détectabilité imparfaite, les résultats ont été très explicites puisque la densité nocturne de canards dans les rizières inondées était parmi les plus élevées jamais enregistrées en Camargue (24 canards/ha, quand les moyennes historiques maximales variaient entre 5 et 15 canards/ha [START_REF] Pirot | Effects of agri-environmental schemes on farmland birds: do food availability measurements improve patterns obtained from simple habitat models?[END_REF]Mesléard et al., 1995). Au contraire, les champs secs étaient pratiquement dépourvus de canards la nuit (Article 3). Bien que la tendance soit claire, la précision des mesures pourrait être améliorée en corrigeant notamment par la détectabilité [START_REF] Defos Du Rau | Estimating breeding population size of the red-crested pochard (Netta rufina) in the Camargue (southern France) taking into account detection probability: implications for conservation[END_REF].

Les deux études expérimentales ont été mises en place afin d'isoler certains processus liés aux bénéfices agronomiques potentiels pour les agriculteurs en s'affranchissant de possibles facteurs confondants qui auraient été rencontrés sur le terrain. Les processus en jeu sont clairement identifiés et les différents résultats sont à la fois cohérents et convaincants (Articles 4 et 5). Néanmoins, il ne faut pas oublier la situation artificielle des expériences.

IV.2 Qu'implique une gestion particulière des rizières en interculture pour la conservation des canards?

Les canards de surface hivernants dans les régions rizicoles d'Europe n'appartiennent pas à des populations menacées (IUCN, 2014) ; leurs effectifs globaux sont en augmentation (canard chipeau, sarcelle d'hiver, colvert), stables (siffleur, souchet) ou fluctuants (pilet) [START_REF] Szabolcs | Report on the Conservation Status of Migratory Waterbirds in the Agreement Area[END_REF]. Quoi qu'il en soit, ces oiseaux fournissent des services écosystémiques culturels importants, en particulier à travers leur valeur esthétique et la chasse (Mathevet, 2000), et sont parmi les espèces d'oiseaux d'eau reconnus pour être particulièrement sensibles aux changements dans l'utilisation des terres à l'échelle locale (ex, Duncan et al., 1999;[START_REF] Mathevet | Creation of a nature reserve, its effects on hunting management and waterfowl distribution in the Camargue (southern France)[END_REF]. La Camargue est le premier quartier d'hivernage français pour plusieurs espèces de canards et l'une des zones les plus importantes à l'échelle des voies de migration européenne (Critical Site Network Tool, 2015). Il était donc pertinent d'évaluer comment les changements dans la gestion de l'habitat camarguais peuvent influer les processus de migration de ces oiseaux et la dynamique de leurs populations, à la fois localement et à l'échelle des voies de migration (voir aussi [START_REF] Rendón | Status, distribution and long-term changes in the waterbird community wintering in Doñana, southwest Spain[END_REF]et Toral et Figuerola, 2010). Nos résultats suggèrent effectivement que la gestion de ces espaces rizicoles pourrait avoir un impact important sur les populations de canards (Article 2).

Etant donné qu'en Camargue: 1) la disponibilité des sites d'alimentation nocturnes a été identifiée comme un facteur limitant pour les canards (Brochet et al., 2009), 2) que ces oiseaux sont relativement fidèles à leur remise diurne [START_REF] Guillemain | Winter site fidelity is higher than expected for Eurasian Teal Anas crecca in the Camargue, France[END_REF]2010) et volent sur de courtes distances pour leur alimentation nocturne [START_REF] Guillemain | Hunting bag and distance from nearest day-roost in Camargue ducks[END_REF], et 3) que de nombreuses aires d'alimentation potentielles existent dans les rizières moissonnées mais ne sont pas utilisées par les canards car gardées en chaumes sèches, nous pouvons supposer que l'inondation hivernale des rizières pourrait immédiatement profiter aux canards hivernants. Grâce à une plus grande attractivité de sites d'hivernage gérés de la sorte, nous pouvons émettre l'hypothèse que des changements de leur temps de résidence (Delta de l'Ebre: [START_REF] Ferrer | Els poblaments hivernals d'anàtids[END_REF]versus Oltra et al., 2001 Nous pouvons donc émettre l'hypothèse que la mise en oeuvre de façon extensive de l'inondation hivernale des rizières en Camargue influencerait les mouvements et la distribution locale des canards et aurait un effet positif plus large sur leurs populations. Cependant, nous ignorons largement ce qui se passerait simultanément dans les autres habitats d'alimentation naturels (zones humides peu profondes ou marais de chasse). De plus, à plus grande échelle le changement climatique provoque le déplacement de certaines espèces de canards vers le nord-est [START_REF] Gunnarsson | Direct and indirect effects of winter harshness on the survival of Mallards Anas platyrhynchos in northwest Europe[END_REF][START_REF] Lehikoinen | Rapid climate driven shifts in wintering distributions of three common waterbird species[END_REF][START_REF] Dalby | Waterfowl, duck distribution and a changing climate[END_REF][START_REF] Guillemain | The Teal[END_REF] Par conséquent, au-delà d'une amélioration générale des conditions locales de l'habitat pour les canards, il est difficile de prédire à partir d'études empiriques et expérimentales telles que celles présentées dans cette thèse quelles pourraient être localement les conséquences de changements massifs des pratiques inter-culturales. Cependant, ces études peuvent déjà fournir certains des paramètres nécessaires à un exercice de modélisation. Ceci constitue un projet initié au cours de cette thèse et que nous développerons d'avantage dans un futur proche.

L'objectif est d'utiliser la modélisation prédictive afin d'évaluer les conséquences probables de l'inondation hivernale des rizières dans la mosaïque paysagère camarguaise sur certaines variables individuelles des canards de surface telles que leur condition physique, leur survie, leurs modes d'utilisation de l'habitat ou leur budget temps. Pour atteindre cet objectif nous avons mis en place une collaboration avec le professeur John Eadie et son équipe à l'Université de Davis (Californie), qui ont développé un modèle multi-agents spatialement explicite appelé SWAMP (Spatially-explicit Waterbird Agent-based Modeling Program: Miller et al., 2014). Ce modèle est relativement similaire au modèle européen MORPH [START_REF] Stillman | MORPH-an individual-based model to predict the effect of environmental change on foraging animal populations[END_REF]. La version la plus récente (jusqu'ici non publiée) de SWAMP est parfaitement adaptée à notre question, car elle permet l'intégration par système d'information géografique d'un paysage agricole. Le programme simule ensuite les mouvements de canards entre leurs remises diurnes et les gagnages nocturnes. En outre, il est beaucoup plus précis que les modèles énergétiques (ex : TRUEMET: Petrie et al., 2014) car il considère l'hétérogénéité des comportements individuels et des conditions corporelles (détails dans la Discussion en anglais).

Grâce à une bourse à la mobilité internationale de l'Ecole Doctorale de l'Université de Montpellier, j'ai pu réaliser un séjour de trois semaines en février 2015 dans le laboratoire du Professeur J. Eadie. Cette période a été consacrée à la prise en main du modèle SWAMP, à la définition de scénarios potentiels de gestion en Camargue, à des premiers tests de simulation et à l'identification des modifications nécessaires à une utilisation complète en Camargue (modifications de code et paramètres manquants). Une fois adaptés et paramétrés, l'application de SWAMP au cas camarguais apportera des arguments solides aux gestionnaires et aux politiciens à l'horizon de la PAC 2017. Les agriculteurs et les décideurs de Camargue sont déjà familiarisés à l'exercice de simulation pour collaborer avec les scientifiques (ex : logiciel Mar O Sel, http://www.mar-o-sel.net, [START_REF] Lefebvre | Contribution of rainfall vs. water management to Mediterranean wetland hydrology: Development of an interactive simulation tool to foster adaptation to climate variability[END_REF]. Nous croyons que la mise à disposition d'un modèle multi-agents puissant aiderait les riziculteurs et les gestionnaires à tenir compte des conséquences des pratiques de gestion des rizières en interculture, et à adopter celles que nous avons démontrées dans cette thèse être les plus bénéfiques à la conservation des canards.

IV.3 Qu'implique une gestion particulière des rizières en interculture pour les riziculteurs, pour la société et pour les décideurs?

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Nous avons effectué une analyse coûts-bénéfices prenant en compte tous les coûts marchands et non-marchands (agronomiques et environnementaux) afin d'évaluer si l'inondation hivernale des rizières en France serait économiquement réaliste pour l'agriculteur compte tenu des contraintes économiques liées notamment aux coûts du pompage de l'eau. Pour la société nous avons aussi considéré les émissions de gaz à effet de serre ainsi que les services culturels apportés par les rizières inondées (écotourisme, chasse) (Article 6, Annexe I.1).

Pour résumer brièvement les résultats de cette analyse, la pratique du brûlage-labour traditionnel tolérée en Camargue atteint à peine l'équilibre financier pour l'agriculteur et n'est pas économiquement acceptable pour la société (bénéfices sur coûts <1), principalement en raison des coûts liés aux gaz à effet de serre et à l'absence d'avantages écosystémiques associés à l'inondation. Les autres itinéraires techniques étaient tous économiquement réalistes à la fois pour l'agriculteur et pour la société (bénéfices sur coûts >1). La récolte du riz dans les champs inondés apparaît comme quatre fois plus rentable pour les agriculteurs et plus de huit fois plus pour la société camarguaise que le brûlage-labour traditionnel (ratio bénéfices/coûts pour les agriculteurs 4,15 vs 1,02, pour la société 6,67 vs 0,78). L'analyse de sensibilité a confirmé la robustesse des résultats. L'inondation hivernale est donc économiquement réaliste pour les agriculteurs et fortement bénéfique pour l'environnement et mérite d'être encouragée.

La production de riz en Europe ne représente que 0,5% de la production mondiale (FAOSTAT, 2012). La production française représente 4% du total européen et a une faible productivité et compétitivité en raison de conditions climatiques relativement inappropriées et un accès aux pesticides plus réduit que les plus grandes et puissantes productions de riz espagnole et italienne (C. Thomas, com. pers.). En conséquence, la production de riz française fluctue fortement en fonction des incitations financières nationales et des prix du marché mondial (entre 32 000 ha en 1960 et 4 000 ha en 1981) qui induisent des changements rapides de l'activité économique, des stratégies des exploitations agricoles et donc du paysage camarguais [START_REF] Picon | L'espace et le temps en Camargue: essai d'écologie sociale[END_REF] (détails dans la Discussion en anglais). Le riz est actuellement la culture la plus répandue dans le delta (61,5% des surfaces cultivées en 2011, PNRC, 2013a). La réforme de la PAC 2015 a toutefois déjà provoqué de nouveaux changements dans le paysage. Avec la suppression du soutien financier spécifique à la culture de la riziculture (aides découplées), des changements dans les cultures camarguaises ont déjà été observés, avec une réduction de 28% de la superficie de riz entre 2012 et 2014, et le remplacement de ces dernières par des cultures sèches comme le blé ou les cultures maraichères.

Dans le cadre de la réforme de la PAC 2015, une série de mesures agrienvironnementales et climatiques associées à la production de riz a été introduite pour compenser le manque à gagner d'environ 250 €/ha par rapport à la situation antérieure. A titre comparatif, l'inondation hivernale des rizières dans les sites Ramsar espagnols est soutenue à hauteur de 60 €/ha. Fournir des incitations financières aux riziculteurs français pour inonder les champs, comme en Espagne, peut être nécessaire pour leur permettre de réaliser les avantages (y compris agronomiques) de cette pratique. Les ratios bénéfices sur coûts de l'inondation hivernale pour la société sont si élevés qu'ils resteraient bien au-dessus de 1 (donc toujours économiquement bénéfiques), même si une incitation financière était versée aux agriculteurs. L'inondation des rizières ne peut cependant être considérée comme une panacée, car cette pratique pourrait être en conflit avec les programmes de réduction des émissions de gaz à effet de serre (http://www.greenrice.eu/about-us/, http : //www.sostrice.eu/en/), sauf si cette mesure est prise comme alternative à l'écobuage de la paille de riz (Couderc, 2013). Elle peut également aller à l'encontre des efforts pour réduire la consommation d'eau (http://www.greenrice.eu/about-us/) ou pour promouvoir l'agriculture biologique (Mouret, 2013) car l'inondation hivernale des rizières implique des années successives de production de riz, tandis que la culture biologique du riz repose souvent sur une rotation régulière avec d'autres cultures. Cependant, cette pratique est en conformité avec la plupart des autres programmes des organisations européennes ou françaises de production de riz : la recherche d'alternatives à l'écobuage de la paille de riz (Monier et al., 2009 en France; ECORICE-LIFE04 ENV/ES/000184, Albufera de Valencia), la réduction des pesticides (Plan national Ecophyto 2018 en France), et la réduction de la salinité du sol (sélection de variétés de riz tolérantes au sel, France AgriMer, NEURICE). Dans ce contexte, la "crise" actuelle du riz appelle à de nouvelles recherches et la gestion alternative par inondation hivernale proposée ici pourrait être considérée pour les avantages agronomiques et environnementaux qu'elle peut apporter, ouvrant ainsi la voie à une nouvelle source de revenu pour les producteurs de riz dans une période difficile pour eux.

IV.4 CONCLUSION: Ce que ces résultats impliquent -et n'impliquent pas -pour la gestion des terres de Camargue

Ce travail de thèse a porté exclusivement sur la communauté de canards de surface utilisant des rizières pendant la période interculturale. Nous sommes conscients que les canards ne constituent pas l'ensemble de la communauté d'oiseaux qui utilisent ces habitats, et que la période post-récolte n'évalue pas l'importance de la production de riz pour les oiseaux en général [START_REF] Tourenq | Valeurs et fonctions des rizières pour les communautés d'oiseaux d'eau en Camargue[END_REF][START_REF] Toral | Agricultura y Conservación en Doñana: La Importancia del Arrozal para las Aves Acuáticas[END_REF]. Au cours de la période interculturale, les rizières sont également importantes pour d'autres oiseaux d'eau tels que la barge à queue noire Limosa limosa (Lourenço et Piersma, 2008;[START_REF] Lourenço | Site selection and resource depletion in Black-tailed Godwits Limosa l. limosa eating rice during northward migration[END_REF], les bécassines Gallinago gallinago [START_REF] Beck | Impact of winter management of the Camargue rice fields on the aquatic macroinvertebrates and the common snipe (Gallinago gallinago)[END_REF], la cigogne blanche Ciconia ciconia ou la spatule blanche Platalea leucorodia [START_REF] Marti | Atlas de las aves reproductoras de Espana[END_REF]. Ces espèces ne seraient pas nécessairement favorisées par les mêmes niveaux d'eau ou pratiques post-récolte que les canards (Toral et al., 2011). L'inondation hivernale des rizières elle-même peut être défavorable pour d'autres espèces de rapaces, fringilles ou colombidés, qui utilisent essentiellement les rizières sèches (Elphick, 2004). En Camargue, un important hivernage de grues cendrées (Grus grus) se développe ainsi depuis quelques années dans les rizières non inondées.

Des recherches antérieures en Camargue, menées à la fois sur la période de culture et d'interculture, mais limitées à des comptages diurnes, ont conclu que la diversité des oiseaux était plus faible dans les rizières (31 espèces) que dans les marais naturels (59 espèces) (Tourenq et al., 2001). Nos résultats montrent que les zones humides naturelles et les rizières inondées sont complémentaires. Nous ne négligeons pas que la riziculture, n'est pas nécessairement la meilleure option pour la biodiversité en général [START_REF] Tamisier | A review of habitat changes in the Camargue: assessment of the effects of the loss of biological diversity on the wintering waterfowl community[END_REF], mais notre objectif ici était de rétablir la fonction d'habitat d'alimentation pour les canards que peuvent jouer les rizières. Il est important de noter que nous ne préconisons pas la conversion de marais naturels en rizières, seulement un changement dans la gestion des champs existants pour les rendre accessibles aux canards pour leur alimentation.

L'option mutuellement bénéfique que pourrait représenter l'inondation hivernale des rizières pour les canards et les agriculteurs ouvre le dialogue et appelle à la collaboration scientifique entre écologues et agronomes. Les agronomes ont commencé à travailler sur de nouvelles stratégies agricoles en Camargue (ex: Jaek, 2010; [START_REF] Mouret | Compte rendu d'étude scientifique. Plan d'adaptation de la filière riz (année 5)[END_REF]. Cependant, ces études considèrent surtout la promotion de l'agriculture biologique localement. La question de comment améliorer la riziculture conventionnelle, qui domine actuellement le paysage, en intégrant des approches agronomiques et écologiques a au contraire reçu une attention très limitée jusqu'ici. L'introduction à grande échelle de l'inondation hivernale pourrait être un bon moyen de tirer le meilleur de la connaissance récente obtenue dans ces deux disciplines. Dans le contexte des problèmes actuels de production de riz, provoquant une baisse de la superficie rizicole en Camargue, l'inondation hivernale pourrait aussi ouvrir la voie à de nouveaux revenus pour les producteurs de riz et contribuer à surmonter la crise.

La réforme de la Politique Agricole Commune 2015 a entraîné récemment une réduction de la surface rizicole d'un tiers, induisant deux changements majeurs dans le paysage: l'augmentation des friches agricoles et le développement de cultures sèches. L'augmentation de la superficie en friches avait déjà été remarquée en 2011 lors de l'étude de l'occupation du sol en Camargue (PNRC, 2013a), et il est attendu qu'elles continuent à s'étendre, principalement sur les terres salées de basse altitude. Ces zones peuvent représenter une bonne occasion pour des projets de restauration des zones humides. Comme pour la zone de production rizicole de Doñana dans le delta du Guadalquivir, la restauration d'anciennes rizières en marais (Mesléard et al., 1995;[START_REF] Muller | Restauration de marais temporaires et de pelouses méso-xériques à partir d'anciennes rizières: Rôle respectif des filtres dans l'assemblage des communautés[END_REF] pourrait compléter le maintien de rizières inondées en hiver. Ceci représentait une stratégie plus écologique que la transformation de ces rizières abandonnées en champs de coton (Doñana), de tomates (Camargue) ou en fermes solaires [START_REF] Toral | Agricultura y Conservación en Doñana: La Importancia del Arrozal para las Aves Acuáticas[END_REF].

Au début de cette thèse, nous nous demandions si une « intensification durable » serait possible dans les rizières européennes. Nous avons pu démontrer que des scénarios agricoles "gagnant-gagnant" pour les riziculteurs et la conservation des canards sont envisageables au sein de ces zones de production intensive, notamment en France. La dernière étape du cadre conceptuel de gestion adaptative est le transfert de connaissances. Une telle communication est nécessaire pour combler le fossé entre les chercheurs, les gestionnaires (y compris les agriculteurs) et les décideurs, afin de confronter leurs visions communes ou parfois divergentes du paysage [START_REF] Vuillot | Paysages agricoles et biodiversité dans les représentations sociales et les modèles mentaux des agriculteurs. Une approche comparée de quatre régions françaises[END_REF], en vue de faciliter une mise en oeuvre pratique. Nous avons initié ce transfert auprès de tels publics, tant à l'échelle camarguaise qu'européenne (Annexe III). Les résultats de nos recherches ont été bien accueillis par les agriculteurs, les chasseurs, les gestionnaires d'espaces naturels et les personnes en charge de la conservation des zones humides et des oiseaux d'eau. En raison de la nature itérative du cycle de gestion adaptative, cette étape finale de transfert et d'apprentissage est souvent aussi un apport important pour les prochaines étapes du cycle du projet. Nous espérons que les résultats de cette thèse vont contribuer à augmenter la valeur de conservation des rizières, tout en maintenant la viabilité économique d'une l'agriculture durable et productive.

INTRODUCTION %

I. Agroecosystems: threats and opportunities

I.1 Agroecosystems as integrated elements of the landscape

Agriculture expansion and intensification are recognized as two of the most important global threats to biodiversity [START_REF] Donald | Further evidence of continent-wide impacts of agricultural intensification on European farmland birds, 1990-2000[END_REF], causing generalized disruptions of ecosystem functions. Continued human population growth induces an increased demand for food, which is projected to double by 2050 [START_REF] Tilman | Forecasting agriculturally driven global environmental change[END_REF], and more recently for biofuel [START_REF] Miyake | Land-use and environmental pressures resulting from current and future bioenergy crop expansion: A review[END_REF]. This situation causes the rise of two major threats: conversion of pristine habitats into crops in developing countries (mostly in South America and Western Africa), and intensification of existing agricultural systems in more developed nations [START_REF] Donald | Further evidence of continent-wide impacts of agricultural intensification on European farmland birds, 1990-2000[END_REF]. In the short to medium term, urgent measures thus need to be taken to ensure food production sustainability.

The dominant late twentieth century model of land use clearly segregated areas of agricultural production from areas managed to conserve biodiversity. Cultivated systems are currently the dominant landscape, accounting for 24% of the Earth's terrestrial surface (MEA, 2005). In Europe they represent one of the most widespread forms of land use, over 45% of the enlarged European Union (EU 27) area [START_REF] Henle | Identifying and managing the conflicts between agriculture and biodiversity conservation in Europe-A review[END_REF]. Up to 50% of the globe's agricultural lands and 60% of ecosystem services (i.e. the benefits people obtain from ecosystems, MEA, 2005) are now affected by some degree of degradation themselves (MEA, 2005). Given the recognised ecological role of functional biodiversity for crop production [START_REF] Altieri | The ecological role of biodiversity in agroecosystems[END_REF], agricultural landscapes have to be managed to promote biodiversity, which often can induce positive effects on agricultural production and livelihoods [START_REF] Scherr | Biodiversity conservation and agricultural sustainability: towards a new paradigm of 'ecoagriculture'landscapes[END_REF].

According to the Millennium Ecosystem Assessment, ecosystem services can be classified in four categories: provisioning services which are products obtained from ecosystems, such as food, fibres, fuel, genetic resources, medicine and water; supporting services, necessary for primary production such as soil formation, photosynthesis, nutrient and water cycling; regulating services which correspond to benefits obtained from the regulation of ecosystem processes, such as pollination, pest regulation, air quality, climate, flood, erosion regulation; and cultural services such as recreational, spiritual, and other nonmaterial benefits (MEA, 2005).

According to [START_REF] Swift | Biodiversity and ecosystem services in agricultural landscapes-are we asking the right questions? Agriculture[END_REF] agroecosystems are:%"(natural) ecosystems that have been deliberately simplified by people for the purpose of production of specific goods of value to humans". Provisioning ecosystem services (the crop production) have historically been considered as the highest priority service provided by agricultural landscapes, but these landscapes are seldom viewed as potential producers of supporting&% regulating or cultural% ecosystem services [START_REF] Power | Ecosystem services and agriculture: tradeoffs and synergies[END_REF]. In parallel, agricultural ecosystems are often considered as a source of numerous disservices, including the destruction of natural ecosystem services. However, agroecosystems largely require natural ecosystem services for their own maintenance (e.g. pollination, pest control) [START_REF] Power | Ecosystem services and agriculture: tradeoffs and synergies[END_REF]. How agroecosystems are integrated and interact with natural features or habitats in the landscape, and whether agroecosystems may or may not themselves provide ecosystem services other than crop yield largely depends on how they are managed [START_REF] Altieri | The ecological role of biodiversity in agroecosystems[END_REF][START_REF] Swift | Biodiversity and ecosystem services in agricultural landscapes-are we asking the right questions? Agriculture[END_REF][START_REF] Power | Ecosystem services and agriculture: tradeoffs and synergies[END_REF], see also the importance of farm management on the ecosystem service flow: Figure 1). From the agronomic point of view, functional biodiversity in crop fields can be promoted through agroecology, a discipline taking into account the effects of the integration of plant and animal biodiversity to enhance complex interactions, hence simulating natural ecosystem complexity and functions (e.g. Agroforestry or ''Integrated Rice Duck Farming'' in Asia). Similarly, integrated weed, pest and disease management aims at reducing such hurdles to cultivation by considering the biotic interactions among multiple components of the pest complex present in the ecosystem [START_REF] Shennan | Biotic interactions, ecological knowledge and agriculture[END_REF]. This approach considers that a better integration of ecological mechanisms such as disturbance or interaction complexity, emerging from the study of natural ecosystems, can provide insights into how biotic interactions may determine agroecosystem function (e.g. [START_REF] Ormerod | Meeting the ecological challenges of agricultural change, editors' introduction[END_REF]. Currently, research studies aim at filling the gap between agronomy and ecology by promoting management procedures that encourage beneficial biotic interactions within agroecosystems, and minimize undesired ones [START_REF] Shennan | Biotic interactions, ecological knowledge and agriculture[END_REF]. Ecologically-based management concepts are developed at larger scales, that take into consideration the whole system and not only one field or one production, e.g. the "Ecoagriculture landscape" [START_REF] Scherr | Biodiversity conservation and agricultural sustainability: towards a new paradigm of 'ecoagriculture'landscapes[END_REF].

In order to satisfy growing food needs, and to integrate biodiversity components into agriculture, the concept of ecological intensification inducing sustainable intensification has been proposed [START_REF] Bommarco | Ecological intensification: harnessing ecosystem services for food security[END_REF]. This implies the protection of ecosystem services for environmentally sustainable agriculture and the increase of food production from existing agricultural lands without further environmental damage. This is a tremendous challenge for intensive agricultural areas, which has been identified as one of the main and urgent conservation issues for 2015 (Sutherland et al., 2015).

I.2 Relevance of the Ricefield-Duck model

Rice is the second most widely grown cereal in the world, covering almost one percent of the Earth surface (FAO-STAT, 2013;[START_REF] Lawler | Rice fields as temporary wetlands: a review[END_REF]. This production represents a threat for wetland ecosystems where ricelands are implanted on converted former natural habitats (e.g. Western Africa) and where rice is intensively produced (as is the case in Europe). On the other hand, rice fields are artificial wetlands and represent 15% of the world's total wetland area [START_REF] Lawler | Rice fields as temporary wetlands: a review[END_REF]. They have been recognized by the Ramsar Convention Resolution X.31 as an important ecosystem for "supporting biodiversity and livelihoods as wetland systems" (Nagoya conference, COP 10, Dean-Speirs et al., 2010).

Rice fields are generally inserted into a more complex landscape of natural or seminatural wetlands, and thus show biotic interactions with these [START_REF] King | Effects of landscapefeatures on waterbird use of rice fields[END_REF]. Their capacity to mitigate the loss of natural wetland habitats, or at least to complement more natural or semi-natural wetlands is discussed, particularly in the North Mediterranean (e.g. [START_REF] Fasola | The value of rice fields as substitutes for natural wetlands for waterbirds in the Mediterranean region[END_REF]Tourenq et al., 2001;Toral and Figuerola, 2010). In the Mediterranean region, 80 to 90% of natural wetlands have been lost (Finlayson et al., 1992), and ca. 23% of the remaining wetlands are artificial (including rice fields, salt pans or irrigation reservoirs) [START_REF] Perennou | Existingareas and past changes of wetland extent in the Mediterranean region: an overview[END_REF]. The importance of these agricultural wetlands for biodiversity, and more precisely for waterbird conservation, has been recognized worldwide [START_REF] Czech | Agricultural wetlands and waterbirds: a review[END_REF]Elphick et al., 2010) including in Europe (e.g. Longoni et al., 2010;[START_REF] Sánchez-Guzmán | Identifying new buffer areas for conserving waterbirds in the Mediterranean basin: the importance of the rice fields in Extremadura, Spain[END_REF]Toral and Figuerola, 2010;Masero et al., 2010).

Birds are recognized to be sensitive to agricultural management change, and have been widely studied [START_REF] Pain | Farming and birds in Europe: the Common Agricultural Policy and its implications for bird conservation[END_REF][START_REF] Wilson | Bird conservation and agriculture[END_REF][START_REF] Fuller | Birds and habitat: relationships in changing landscapes[END_REF]. Farmland birds, in particular, have been reported to be threatened by agriculture intensification for multiple reasons (see section below), while simultaneously providing many different ecosystem services (Whelan et al., 2008;Weeny et al., 2011). However, most research on farmland birds has focused on passerines and other dry land birds in Europe (e.g. [START_REF] Pain | Farming and birds in Europe: the Common Agricultural Policy and its implications for bird conservation[END_REF][START_REF] Wilson | Bird conservation and agriculture[END_REF]. Conversely, the use of croplands and the consequences of agricultural land transformation and agricultural practices on duck populations have received more limited attention (see however e.g. Thomas, 1982, Van Eerden et al., 1996;Duncan et al., 1999). Waterfowl potentially provide a myriad of ecosystem services [START_REF] Green | Ecosystem services provided by waterbirds[END_REF], poorly explored in an agronomic perspective.

The main exception concerns the potential benefit brought by waterfowl to rice farmers, but this has almost exclusively been studied in North America (e.g. Anders et al., 2008), while virtually nothing is known for such systems in Europe (except for the recent work on nutrient recycling by waterbirds in [START_REF] Navedo | Unravelling trophic subsidies of agroecosystems for biodiversity conservation: food consumption and nutrient recycling by waterbirds in Mediterranean rice fields[END_REF]. One explanation to this lack of studies is that European ducks mostly use agricultural lands as nocturnal foraging grounds (Tamisier and Dehorter, 1999;[START_REF] Pirot | Effects of agri-environmental schemes on farmland birds: do food availability measurements improve patterns obtained from simple habitat models?[END_REF]Mesléard et al., 1995), which often makes observation arduous in the field.

Currently, 24% of the waterfowl species are considered endangered (Wetlands International, 2013), compared to 19% for all bird species [START_REF] Butchart | Measuring global trends in the status of biodiversity: Red List Indices for birds[END_REF]. [START_REF] Green | Analyses of globally threatened Anatidae in relation to threats, distribution, migration patterns, and habitat use[END_REF] identified wetland loss as the main cause of many such declines, and [START_REF] Long | Ecological factors and human threats both drive wildfowl population declines[END_REF] reported changes of the agricultural land -interpreted as a proxy for wetland loss -as the main threat. Because the main European ricefield regions are often situated close to or embedded within the largest waterfowl winter quarters, appropriate management of such croplands could benefit waterfowl conservation. 9/),@0(5)9@/!

! Z]! Like many other crop productions, rice cultivation intensified after the Second World War, with observed negative impacts on biodiversity [START_REF] Donald | Biodiversity impacts of some agricultural commodity production systems[END_REF]. Rice intensification does represent a threat to some waterfowl species (e.g. Madagascar Pochard Aythya innotata, or Philippine Duck Anas luzonica, IUCN, 2014). On the other hand, it can simultaneously boost other threatened species (e.g. West Indian Whistling Duck Dendrocygna arborea in Cuba, Acosta et al., 2010, or Baikal Teal Sibirionetta formosa in Japan, [START_REF] Tajiri | Foraging site selection and conservation of the Baikal Teal in rice fields around Katano-kamoike, Kaga City Japan[END_REF] to the extent that some can even become crop pests (White-faced Whistling Duck Dendrocygna viduata in Africa, Katondo, 1996, or Spot-billed Duck Anas poecilorhyncha in Asia, [START_REF] Lane | Wildfowl damage to agriculture in Japan[END_REF]. Changes in rice farming practices towards intensification may also cause declines in common waterfowl species traditionally using such habitats, calling for waterfowl-friendly management of rice fields (in Japan, [START_REF] Kasahara | Population trends of common wintering waterfowl in Japan: participatory monitoring data from 1996 to 2009[END_REF]. Many waterfowl species worldwide are directly or indirectly relying on rice production areas during at least one stage of their life cycle (Elphick et al., 2010). Like other bird species relying on agricultural ecosystems, waterfowl mostly use rice fields for foraging purposes, so whether such fields can provide suitable and accessible food resources will largely determine their potential use by ducks.

I.3 Agriculture intensification and farmland bird decline in Europe: food resources matter for seed-eating birds

In Europe, arable farming has a long history from its origins in the eastern Mediterranean 10,000 years ago, creating a tremendous variety of so-called agricultural landscapes [START_REF] Stoate | Ecological impacts of arable intensification in Europe[END_REF]. After millennia of agricultural expansion and despite their artificial nature, a wide range of species have adapted to these extensively managed landscapes, resulting in the development of many anthropogenic species-rich agroecosystems [START_REF] Kleijn | Mixed biodiversity benefits of agri-environment schemes in five European countries[END_REF]. Among farmland ecosystems, lowlands support the largest number of bird species, nearly 120 "Species of European Conservation Concern" across Europe [START_REF] Tucker | Priorities for bird conservation in Europe: the importance of the farmed landscape[END_REF]. Bird populations and agricultural landscapes are therefore often tightly linked. In Europe, as much as 30% of observed variation in bird population trends can be explained by fluctuations in cereal production (Donald et al., 2001).

As a result of land intensification or abandonment, current agricultural activities are responsible for a widespread loss of biodiversity, threatening farmland birds among other taxa. In the second half of the 20th century, ecosystems changed more rapidly than at any other time in recorded human history. In fact, more land was converted to cropland in the 30 years after 1950 than in the 150 years between 1700 and 1850 (MEA, 2005). In Europe, the modern agricultural policy has its origins in the drive to increase production right after the Second World War [START_REF] Pain | Farming and birds in Europe: the Common Agricultural Policy and its implications for bird conservation[END_REF]. By the advances in technology and high prices support for increased productivity, the Common Agricultural Policy (CAP) has been the driving force behind intensification and specialisation of arable farming in Europe (Donald et al., 2001). In these agroecosystems, increased use of fertilisers and pesticides, greater mechanisation, simplification of crop rotations and loss of many natural features (e.g. hedgerows) have led to a reduction in landscape diversity, soil deterioration, water pollution and disruption of food chains [START_REF] Stoate | Ecological impacts of arable intensification in Europe[END_REF], affecting both plant (e.g. [START_REF] Marshall | The role of weeds in supporting biological diversity within crop fields[END_REF] and animal populations (e.g. [START_REF] Wilson | A review of the abundance and diversity of invertebrate and plant foods of granivorous birds in northern Europe in relation to agricultural change[END_REF]. Since the 1970s, farmland birds decreased in abundance more than any other bird community in Europe (Donald et al., 2001;2006). A recent study showed that over the past three decades, more than 420 million birds have disappeared from the European continent, agricultural intensification being one of the main causes of this reduction [START_REF] Inger | Common European birds are declining rapidly while less abundant species' numbers are rising[END_REF]. About a half of farmland birds are in decline or threatened in Europe [START_REF] Pain | Farming and birds in Europe: the Common Agricultural Policy and its implications for bird conservation[END_REF]. 9/),@0(5)9@/! ! Z^! Halting such declines requires a good understanding of species habitat use and requirements through the identification of limiting factors, critical habitat needs and possible habitat management (e.g. [START_REF] Sutherland | Managing habitats for conservation[END_REF] for birds in Fuller, 2012). [START_REF] Fuller | Birds and habitat: relationships in changing landscapes[END_REF] referred to habitat use as « the way that an individual or population uses habitat. Similar to habitat occupancy but implies a need to specify the type of activity, e.g. nesting, roosting, foraging », and to habitat preference as « a positive association (usually of individuals in a population) with a defined habitat type, i.e. non-random distribution resulting in a disproportionately high number of individuals in certain habitat types relative to their availability ».

A complex array of agricultural management factors might influence population changes in plants, insects and birds (Figure 2). Although species responds individually to each particular change in arable management, certain groups of species share common causal factors [START_REF] Newton | The recent declines of farmland bird populations in Britain: an appraisal of causal factors and conservation actions[END_REF]. For instance, declines of seed-eating birds have been associated primarily with a reduction of seed food resources during the non-breeding season due to weed-control, mainly through the use of broader-spectrum herbicide combinations, change from spring-sown to autumn-sown crops, associated with earlier ploughing of stubbles [START_REF] Wilson | A review of the abundance and diversity of invertebrate and plant foods of granivorous birds in northern Europe in relation to agricultural change[END_REF][START_REF] Moorcroft | The selection of stubble fields by wintering granivorous birds reflects vegetation cover and food abundance[END_REF][START_REF] Robinson | Post-war changes in arable farming and biodiversity in Great Britain[END_REF][START_REF] Marshall | The role of weeds in supporting biological diversity within crop fields[END_REF] and more recently by the use of stripper-header harvesters (Stafford et al., 2006;[START_REF] Fleskes | Waste rice seed in conventional and stripper-head harvested fields in California: Implications for wintering waterfowl[END_REF]. Ecologists are now convinced that weeds have a role within the agroecosystem in generally supporting biodiversity [START_REF] Marshall | The role of weeds in supporting biological diversity within crop fields[END_REF]. As a consequence, the spatial and temporal distribution of seed resources as well as seed availability is better taken into account, and the extent to which particular management might affect seeds is analysed through empirical or modelling studies [START_REF] Butler | Resource availability and the persistence of seedeating bird populations in agricultural landscapes: a mechanistic modelling approach[END_REF][START_REF] Evans | Seeds in farmland food-webs: resource importance, distribution and the impacts of farm management[END_REF]Ponce et al., 2014). 9/),@0(5)9@/! ! O"! Among the activities of organisms, acquisition of food resources is of particular importance. In fact food consumption, the necessary means to extract energy from the environment and fulfil daily energetic requirements, is a vital priority allowing survival, growth and reproduction of individuals [START_REF] Stephens | Foraging theory[END_REF]. Exploitation of a resource by organisms involves a wide range of components interacting with a list of processes that constraint or favours the use of a potential habitat (Figure 3). Consequently the abundance and accessibility, that jointly determine the availability of food resources, act as key factors limiting individual fitness and the size of populations in most systems [START_REF] Newton | Population limitation in birds[END_REF]. It is important to consider that:

1) all potential food present in a habitat patch is not necessary available to an organism, as availability depends on the consumer's foraging habits and behaviour (granivores, herbivores, etc..), its morphological capacity (e.g. bill size) as well as food characteristics (size, shape, energetic content; [START_REF] Sutherland | From individual behaviour to population ecology[END_REF]e.g. for ducks, Guillemain et al., 1999).

2) food availability for a given individual may change over time and with environmental factors. Depletion is a key process influencing resource availability, since such consumptive use by foragers gradually reduces resource abundance [START_REF] Sutherland | From individual behaviour to population ecology[END_REF]. For seed banks in agroecosystems, declining resource availability can also be the product of potential seed degradation by rotting, or seed disappearance by germination as well as tillage agricultural practices making seeds inaccessible (e.g. for waterfowl, Geer et al., 2009). Because it affects food intake rate, change in seed availability may affect the distribution of the foraging birds within the habitat matrix [START_REF] Sutherland | From individual behaviour to population ecology[END_REF]. 9/),@0(5)9@/! ! OP! 3) apart from predation risk and competition [START_REF] Guillemain | Switching to a feeding method that obstructs vision increases head-up vigilance in dabbling ducks[END_REF], accessibility of available food resources depends essentially on abiotic factors, i.e. for granivorous waterbirds the water depth, the type of soil and the relative abundance and nature of plant, shell debris, and other mineral materials (Tamisier, 1971;[START_REF] Gurd | Predicting resource partitioning and community organization of filterfeeding dabbling ducks from functional morphology[END_REF]. Another factor influencing the potential use of a given food source is the energy dissipated in locating and ingesting it [START_REF] Stephens | Foraging theory[END_REF]. Under a certain threshold, resources are too scattered and require such an expenditure of energy from the organism to find them that the calories they contain are no longer sufficient to balance the foraging costs. Below this threshold, resources are considered no longer profitable. This theoretical threshold, called giving-up density (GUD), hence represents the limit in food abundance below which an organism ceases foraging (Reinecke et al., 1989). For waterfowl in post-harvest rice fields, the GUD has been estimated by Reinecke et al. (1989) andGeer et al. (2009) as ca. 50 kg/ha.

Understanding the dynamics of food resources in a habitat is important for determining its potential carrying capacity for birds and other consumers. Carrying capacity has been classically defined as the maximum number of individual-days that can be supported by the food supplies of a habitat [START_REF] Goss-Custard | Carrying capacity in overwintering birds: when are spatial models needed[END_REF]. Following that definition, carrying capacity of foraging habitats for waterfowl is defined as duck-use-days (DUD's) (Prince, 1979;Reinecke et al., 1989). DUD's are the number of ducks that can survive for one day per ha. They have often been calculated as follows: DUD = [food available (g dry mass)* metabolizable energy (kcal/g dry mass)]

[individual bird daily energy requirements (kcal/day)]

In overwintering migrating birds, carrying capacity has also been defined as the maximum number of individuals that can survive the non-breeding season [START_REF] Goss-Custard | Carrying capacity in overwintering migratory birds[END_REF]. This can be estimated using spatial depletion models (SDM), in which patches of differing food density are treated separately [START_REF] Goss-Custard | Carrying capacity in overwintering birds: when are spatial models needed[END_REF][START_REF] Sutherland | From individual behaviour to population ecology[END_REF].

Appropriate winter habitat management, sometimes including specific agricultural practices, should be regarded as an opportunity to promote carrying capacity for wintering waterfowl through increased food availability, including in riceland ecosystems [START_REF] Ma | Managing wetland habitats for waterbirds: an international perspective[END_REF].

I.4 From science to policy to science: implementation of Agri-environment schemes during the winter period

In the 1970s, the destructive impact of agriculture became increasingly evident, together with the need to better protect the environment and the realization that alternative agricultural practices were possible. As a result, since the mid-1980s, European governments and the European community began to embark upon the implementation of a common agrienvironmental policy. Legislation about conservation of biodiversity in the EU is primarily founded on two Directives, the Birds Directive (1979) and the Habitats Directive (1992). Agri-environment schemes (AES) are considered the most important policy instruments to counteract the negative effects of modern agriculture on the environment by providing financial incentives to farmers for adopting environment-friendly practices, i.e. those in line with the Birds and Habitats Directives. Farmers contract those AES through the Common Agricultural Policy (CAP) (EC Directorate General for Agriculture and Rural Development, 2005).

[f (g ry s) gy ( /g ry s)] [individual bird daily energy requirements (kcal/day)] 9/),@0(5)9@/! ! ON! Several agri-environnement schemes have been set up in the EU to maximize seed food resources in an attempt to halt the decline of seed-eating birds. For instance, game cover crops [START_REF] Stoate | Development of an agri-environment scheme option: seed-bearing crops for farmland birds[END_REF], supplementary winter seed resources [START_REF] Siriwardena | The effect of supplementary winter seed food on breeding populations of farmland birds: evidence from two large-scale experiments[END_REF] or non-inversion tillage (Cunningham et al., 2005) are applied to farmlands in the UK as agrienvironment schemes. Non-inversion tillage means that farmers prepare a seedbed at shallower depths (10-15cm) than the conventional ploughing (20-25cm) with a combination of tines, discs and harrows [START_REF] Cunningham | Non-inversion tillage and farmland birds: a review with special reference to the UK and Europe[END_REF]. Leaving overwinter stubbles on dry crop has also been tested for seed-eating farmland birds through various schemes in the UK and has proved to be efficient for farmland bird population increase (Sutherland, 2015).

The large sums of money that are spent on such schemes annually (3.7 billion € in 2003 at the scale of the whole EU in [START_REF] Kleijn | Mixed biodiversity benefits of agri-environment schemes in five European countries[END_REF] necessitate a clear understanding and a quantification of the response of wildlife to the implementation of particular measures, to assess AES efficiency through cost-benefit analyses and to improve scheme performance if necessary. This question is debated [START_REF] Kleijn | How effective are European agri-environment schemes in conserving and promoting biodiversity?[END_REF][START_REF] Vickery | The role of agri-environment schemes and farm management practices in reversing the decline of farmland birds in England[END_REF][START_REF] Kleijn | Mixed biodiversity benefits of agri-environment schemes in five European countries[END_REF]. Governments regularly need to review AES in the light of new research results following an adaptive management or evidence-based approach, in order to increase the costefficiency of their investments in AES.

II. Ducks and rice in the French Camargue landscape: the structure and aims of this thesis

Based on the potential links between agro-ecosystems and wildlife described above, considering that the duck-rice system is appropriate for investigating such relationships and in the general framework of optimal foraging and habitat use by these birds in riceland landscapes, the aim of this thesis was to investigate whether 'win-win' agricultural scenarios for rice producers and waterfowl conservation could exist and be further promoted within intensive rice production areas, especially in France.

II.1 Rice farming and duck conservation

The literature on wild ducks in rice fields is disproportionately represented by studies in the United States, focusing on winter riceland management as a profitable waterfowl habitat during the post-harvest period (Eadie et al., 2008). Studies in Asia rather addressed the agronomic benefits of breeding farm ducks in Integrated Rice-Duck Farming systems [START_REF] Furuno | The Power of Duck: Integrated Rice and Duck Farming[END_REF]. The possibility of specific waterfowl-friendly management procedures providing benefits to farmers for their production and the society through the provision of several ecosystem services has received even less attention (first studies in the U.S. in Anders et al., 2008). Besides the purely agronomic aspects (what the ducks can bring to farmers) and the purely ecological considerations (how field management can promote duck conservation), the present work aimed at following a comprehensive approach to identify the post-harvest practices providing the most ecosystem services. To reach this, we first carried out a literature review trying to summarize the state of the art in waterfowl and rice production relationships worldwide, considering both American and Asiatic studies (Chapter 1, Article 1).

Our hypothesis was:

-There are management procedures that promote mutually beneficial wild duck-rice farming interactions, and minimize the undesired ones. 9/),@0(5)9@/!

! OZ!

The main issues addressed were:

-What are the principal constraints and levers of action associated with the management of rice-production areas in a waterfowl-friendly way? -Are there management procedures that simultaneously promote rice farming and duck conservation?

II.2 Rice farming landscapes and post-harvest practices beneficial to ducks

Two studies indirectly linked to this thesis allowed us demonstrating the combined importance of local habitat management and broader environmental changes at the flyway scale for population size in a given winter quarter (e.g. migration and habitat use strategies of Common Teal Anas crecca and Mallard A. platyrhynchos, Appendix I.2 and Appendix I.3). In the present work, we considered post-harvest ricefield habitats not only in the Camargue (France), but also in other rice production areas belonging to the East Atlantic Flyway.

The specific objective of Chapter II was to characterize the post-harvest managements practiced in the main rice production regions of Europe, and identify those favouring seed resource availability and duck presence.

Straw management impact on seed availability and duck habitat use on rice fields has already been discussed in the US (Eadie et al., 2008;Elphick et al., 2010). The amount of residual grain available to migratory waterfowl at their winter quarters is reduced by the use of faster-growing rice varieties (Stafford et al., 2010), stripper-header harvesters (Stafford et al., 2006;[START_REF] Fleskes | Waste rice seed in conventional and stripper-head harvested fields in California: Implications for wintering waterfowl[END_REF] and ploughing (e.g. in the US, [START_REF] Miller | Rice available to waterfowl in harvested fields in the Sacramento Valley, California[END_REF]in Stafford et al., 2010). The extent to which straw management (burning, chopping, disking) can influence the use of fields by ducks is unclear (Elphick et al., 2010). However, winter flooding has been proven in the US and in Japan to attract ducks (e.g. Day and Colwell, 1998;Shimada et al., 2000;Elphick and Oring, 2003;Havens et al., 2009;Tajiri and Ohkawara, 2013).

% Building on such knowledge, an agri-environment scheme specifically developed for rice cultivation has been implemented recently in Spanish Ramsar sites for waterbirds through the promotion of winter flooding. The AES ''ricefield winter-flooding'' consists of maintaining the ricefield surface under flooding for at least 3.5 months in Albufera de Valencia (Law: RD 4/2001 andRD 708/2002) and at least 4 months in the Ebro Delta (Council Regulation (EC) No 1257/1999). The extension of the use of such practice in areas where it is not so far financially supported and the response to this AES implementation by waterbird populations had not so far been assessed. However, Toral and Figuerola (2010) showed that population trends at the flyway scale were connected to an index of ricefield availability and use during the autumn in Spain, suggesting that a ricefield winter flooding AES could be very effective to provide suitable waterfowl habitat.

% Based on these results, our hypotheses were:

-The regional numbers of dabbling ducks in major rice production regions of the Western Europe are positively correlated with the area of winter flooded ricefields (Article 2).

9/),@0(5)9@/! ! OO! -The AES ''ricefield winter-flooding'' implemented in Spanish sites over the last fifteen years is an efficient waterfowl-friendly management that does translate into greater duck numbers during winter (Article 2).

-Availability of seed resources in rice fields is negatively affected by ploughing (Article 3).

-Winter flooding is the major driver of use of rice fields by wintering ducks (Article 3).

The main issues addressed were:

- In Article 2, we compared the agricultural landscapes of five major rice production regions of Western Europe, all belonging to the same duck flyway (East Atlantic Flyway, see flyway delineations in Scott and Rose, 1996) and assessed their relationship with the number of ducks present on a given site. We considered the six most common European dabbling duck species, i.e. Mallard, Common Teal (hereafter Teal), Northern Pintail A. acuta (hereafter Pintail), Northern Shoveler A. clypeata (hereafter Shoveler), Eurasian Wigeon Mareca penelope (hereafter Wigeon) and Gadwall M. strepera. Article 3 rather focused on one single winter quarter (the Camargue, southern France), where we studied duck foraging use and preference of rice fields depending on post-harvest practices (straw burning, chopping, flooding, ploughing etc…). Due to human and predation disturbance, wintering ducks developed nocturnal foraging strategies (Guillemain et al., 2002;Legagneux, 2007;[START_REF] Martin | Birds by night[END_REF]. We hence considered rice fields as a potential nocturnal foraging habitat for wintering ducks, evaluated seed banks in such fields and their fate across the winter. Only seeds were considered as part of the duck diet, although we do not ignore that other sources of food such as invertebrates could be available for foraging, and that other seed consumers can be depleting the seed bank besides ducks.

The Camargue was a suitable site for such a study since, as opposed to the other European rice production regions, natural and semi-natural wetlands are still quite well conserved thanks to the combination of large private marshes partly managed for hunting (85% of the area) and many protected natural wetlands (Camargue National Reserve: 13,000 ha, Tour du Valat Regional Nature Reserve: 1,500 ha, Marais du Vigueirat Nature Reserve: 9/),@0(5)9@/! ! O[! 1,000 ha, 'Imperial-Malagroy' departmental reserve: 2,700 ha). The whole Camargue represents ca. 145,000 ha between the two arms of the Rhône river and the Mediterranean sea, 60,000 ha of the delta still being made of wetlands including rice fields (Tamisier and Dehorter, 1999 for detailed site description, see Figure 4). Rice is the most widespread crop in the delta (15,000 ha, 61.5 % of the crop in 2011, PNRC, 2013a), either in rotation with wheat, alfalfa (on high lands) or in monoculture (on low saline lands), alternative crops being limited by soil salinity (Barbier and Mouret, 1992). The Camargue is also the most important winter quarter at the national scale for four of the six studied duck species (i.e., mallard, common teal, wigeon and gadwall, Deceuninck et al., 2014) and one of the most important winter quarters for dabbling ducks at the European flyway scale (Critical Site Network Tool, 2015). Earlier studies have shown the strong degree of interdependence between the various Camargue habitats: ducks mainly gather during the day on natural or semi-natural wetlands with relatively high water levels in protected areas. They only disperse at dusk to reach shallow feeding grounds, principally located in natural marshes and semi-natural hunted marshes, but also including rice fields (Tamisier and Dehorter, 1999, Figure 4). The way by which post-harvest practices affect seed abundance and accessibility hence largely determines the possible use of rice fields by wintering ducks for foraging during the night, hence possibly also the overall number of wintering birds in the duck community.

II.3 Waterfowl-friendly management providing ecosystem services to farmers

Chapter III deals with the ecosystem services that ricefield winter flooding and ducks attracted into flooded fields can bring to farmers. We considered two regulating and supporting ecosystem services, namely weed regulation and straw decomposition improvement. Disposal of rice straw and weed seed management are the main constraints for rice production. In fact, the high silica content of rice straw makes it resistant to decomposition and abrasive, resulting in increased wear and tear of machinery and preventing most of the uses generally made with straw from other crops (Monier et al., 2009). Weeds are also a challenge for rice farmers as they represent a major cause of yield loss (ca. 10 % of total loss on average, Oerke, 2006).

Previous studies showed that winter flooding can improve straw decomposition and reduce weed seed biomass (Manley et al., 2005) or seed viability (Fogliatto et al., 2010;Baek and Chung, 2012), both effects that can be accentuated by foraging wild waterfowl (Bird et al., 2000[START_REF] Van Groenigen | Effects of foraging waterfowl in winter flooded rice fields on weed stress and residue decomposition[END_REF]. In parallel, other studies reported that rearing farmed ducks on ricelands in Asia prevents the growth of many weeds, and reduces existing weed biomass by trampling and foraging young weed plants and weed seeds [START_REF] Furuno | The Power of Duck: Integrated Rice and Duck Farming[END_REF].

Based on these results, our hypotheses were: Camargue rice fields are traditionally flooded between seeding and harvest, i.e., from April to September, then kept dry either in stubble, early disked, or ploughed during winter (Mañosa i Rifé, 1997). Currently, approximately 75 % of residual rice straw is burned, the remainder chopped (Monier et al., 2009). While burning straw is currently tolerated, concerns surrounding air pollution through CO 2 Greenhouse gas emissions might soon bring about policy changes that limit or eliminate the practice entirely (Couderc, 2013). In this context, alternative straw management is needed. The small area currently flooded during winter is mostly inundated for waterfowl hunting purposes rather than straw disposal (Mathevet and Mesléard, 2002). Weed control is also a concern for rice growers because climatic conditions and a lower access to pesticides in France (some being non-registered in France while they are in other countries) make the French rice production less competitive than the Spanish or the Italian ones. Furthermore, the Ecophyto national plan decided during the Grenelle Environment Forum (2007) aims to reduce by 50% the use of pesticides in agricultural and non-agricultural areas by 2018. In these conditions, flooding the fields may be an alternative technique to simultaneously limit the weeds and degrade the stalks. In Article 4, we experimentally assessed rice and weed seed deterioration in dry and flooding condition across the winter in a greenhouse. An experimental approach was also followed in Article 5, although the tests were this time carried out directly in the rice fields, where we assessed the impact of foraging wing-clipped ducks on the weed seed bank and stalks in enclosures.

-

II.4 Economic valuation of winter flooding in Camargue

Economic valuation of ecosystem services has been advocated by a growing number of environmentalists as a short-term strategy to communicate the value of biodiversity in a language that reflects dominant political and economic views. It can provide complementary insights to purely ecological study results into sustainable ecosystem management and policy (Turner et al., 2000). Several studies have considered wetland or waterfowl ecosystem services, generally documenting a long list of potential benefits and hence calling for a better conservation of these birds or habitats [START_REF] Green | Ecosystem services provided by waterbirds[END_REF].

After Chapters II and III, that assessed the potential of post-harvest practices to provide foraging habitat to wintering ducks and the way by which these birds could in return bring agronomic benefits to farmers, we carried out in the Discussion a cost-benefit analysis to evaluate whether winter flooding in France would be economically realistic considering constraints such as water pumping costs, as well as the potential agronomic and environmental advantages for the farmer, and at a greater scale for society (Article 6, Appendix I.1).

One of the main conclusions of Manley's (2008) book on "Conservation in riceland of North America" was that a precise economic evaluation of winter flooding was still greatly needed. This evaluation should consider the costs of tillage operations, water, reduced input costs, and also potential income from hunting or ecotourism. Such a comprehensive analysis had not so far been carried out, except for the preliminary approach on savings on direct costs by Manley et al. (1999;2005). This is what we have attempted to complete for the Camargue.

In addition to consider herbicides and fertilizers saving though agronomic benefits, this economic valuation also included other ecosystem services provided by ricefield winter flooding and associated use by wintering ducks, such as cultural services (hunting, birdwatching).

III. Schematic overview of the PhD thesis

The following framework represents a schematic overview of the thesis organisation, and how the chapters and articles are linked with each other (Figure 5). In addition to trying to improve scientific knowledge, the goal was also to provide evidence for practitioners and decision makers and assess the effectiveness of management interventions or support conservation policy. It is for this reason that a few pages expose the general context and methodology then provide the key messages and supporting evidence from the articles at the beginning of each chapter, following recommendation from the Centre for Evidence-Based Conservation website (www.conservationevidence.com). % !

CHAPTER I. STATE-OF-THE-ART ON RICE FARMING AND DUCK CONSERVATION

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I.1 Background information

Literature reviews are an important source of evidence for practitioners and decision makers, to assess the effectiveness of management interventions or support conservation policy (e.g. [START_REF] Pullin | Do conservation managers use scientific evidence to support their decision-making?[END_REF][START_REF] Pullin | Guidelines for systematic review in conservation and environmental management[END_REF][START_REF] Roberts | Are review articles a reliable source of evidence to support conservation and environmental management? A comparison with medicine[END_REF]. The Centre for Evidence-Based Conservation (www.conservationevidence.com) and the Collaboration for Environmental Evidence (www.environmentalevidence.org), a consortium of conservation scientists based in the UK, summarize and synthesize the most relevant knowledge from scientific conservation journals worldwide, paying particular attention to such review articles (Sutherland et al., 2015).

These two consortiums call for ecologists to rely on "systematic reviews", inducing a rigorous methodology, instead of the traditional ''narrative review'' often providing only a qualitative assessment based on the experience and subjective judgment of the author(s) [START_REF] Gates | Review of methodology of quantitative reviews using meta-analysis in ecology[END_REF][START_REF] Roberts | Are review articles a reliable source of evidence to support conservation and environmental management? A comparison with medicine[END_REF]. Systematic reviews are largely used in medical science, and follow a standardized evidence-based framework (Cochrane method, CRD, 2001). Such methodology has not so far been widely implemented in applied ecological studies (see first attempt in [START_REF] Stewart | Applying evidence-based practice in conservation management: lessons from the first systematic review and dissemination projects[END_REF].

The review article (Article 1) presented in this chapter aimed at providing a state-ofthe-art summary of the relationships between rice farming and ducks (both farmed and wild), in a broader perspective than the sole topic of the thesis, which focuses on one geographic area (the Camargue) and one period, the winter. As such, this review provides a general understanding of the worldwide context in which the questions of this thesis are framed. We first compiled the known positive and negative effects of rice farming for duck populations and vice versa, then identified the management options by which mutually positive interactions could be promoted and negative ones be relieved. Particular attention was paid to the identification of the economic, social and cultural constraints and the levers of actions. Finally, we pointed out gaps in knowledge and future research needs.

Although this exercise was not a systematic review in itself, our work has attempted to follow this approach by: 1) carrying out a detailed systematic literature search combining many sources of information (review articles, scientific articles, grey literature from nongovernmental organisations, governmental departments and key experts), 2) presenting quantified data as graphs and tables, including very large summary tables, and 3) reporting the key conservation evidences, identifying evidence gaps and providing management recommendations.

The resources and information used for this review were extracted from:

-Two main reviews themselves prepared by Elphick et al. (2010), "Ecology and Conservation of Birds in Rice fields: A Global Review" and Manley (2008), "Conservation in Ricelands of North America".

-Scientific literature indexed in the standard Isi Web of Science electronic database (140 references).

-Grey literature from non-governmental and governmental organisation websites, including for instance: the FAO-STAT database, the IUCN Red List of Threatened Species webpage, the Critical Site Network Tool for bird distribution, the Birdlife Important Bird and Biodiversity Areas website (7 references).

5*.4)+,!QR!,95+!K.,89/B!S!0(5T!5@/'+,I.)9@/! ! [N! -Grey literature from Master and PhD theses, conference proceedings, technical agronomic or management program reports, such as for example the Proceedings of the first international conference on organic rice farming, the 5th North American Duck Symposium or the 27 th International Ornithological Conference; the special issue on Riz et rizicultures: innovation paysannes et dynamiques scientifiques by Ahamadi et al. (2013) The main body of our review was a narrative synthesis, however we also compiled quantitative information on graphs and tables whenever possible (e.g. repartition of rice cover in the world put in parallel with the number of Anatidae species that use rice fields and are categorized as pest, threatened or vulnerable species). We also tabulated the duck species that have been classified as rice pests in the literature, the ones which have been recorded breeding in ricelands and finally the agronomic benefits of winter flooding and foraging by wild or farm ducks.

I.2 Key messages and supporting evidence

As suggested by [START_REF] Roberts | Are review articles a reliable source of evidence to support conservation and environmental management? A comparison with medicine[END_REF] for what systematic reviews should eventually come up with, Article 1 provides a list of key findings. We only highlight here those concerning the management option seemingly benefiting to ducks and farmers the most, which has then been tested in Camargue during the rest of this PhD work, i.e. rice field winter flooding.

Converging evidence points that winter flooding: 1.

improves food resource accessibility to waterfowl in rice fields. Post-harvest rice fields are readily translated into wintering duck habitat by flooding (review in Eadie et al., 2008). Such management increases the instantaneous number of foraging ducks as well as overall field frequentation (e.g. Day and Colwell, 1998;Shimada et al., 2000;Elphick and Oring, 2003;Havens et al., 2009;Tajiri and Ohkawara, 2013), and can have carry-over consequences on duck population dynamics by influencing their distribution, body condition and survival rates [START_REF] Fleskes | Waterfowl Distribution, Movements and Habitat Use Relative to Recent Habitat Changes in the Central Valley of California: A Cooperative Project to Investigate Impacts of the Central Valley Habitat Joint Venture and Changing Agricultural Practices on the Ecology of Wintering Waterfowl[END_REF][START_REF] Fleskes | Pintail and mallard survival in California relative to habitat, abundance, and hunting[END_REF](Fleskes et al., , 2009)).

2.

provides agronomic benefits to farmers through the increase of nutrient recycling (Manley et al., 1999;[START_REF] Eagle | Soil management. Rice yield and nitrogen utilization efficiency under alternative straw management practices[END_REF], straw decomposition rate (Manley et al., 2005) and the reduction of weed seed viability (Street and Bollich, 2003;Manley et al., 2005;Fogliatto et al., 2010;Baek and Chung, 2012) (review in Anders et al., 2008 and Table 2 in Article 1).

3.

furthermore, researchers observed that waterfowl attracted by flooding can further enhance the benefits of the sole presence of water. Through trampling and foraging, the birds can further increase straw decomposition, as well as decrease weed biomass in spring (e.g. Smith and Sullivan, 1980;Bird et al., 2000;[START_REF] Van Groenigen | Effects of foraging waterfowl in winter flooded rice fields on weed stress and residue decomposition[END_REF]Van Diepen et al., 2004 and Table 2 in Article 1).

The literature review also highlighted some important gaps in knowledge regarding the importance of harvested rice fields for waterfowl and the drivers of their use by these birds: 4. Elphick et al. (2010b) reported that the extent to which straw management can influence the use of fields by ducks was unclear.

5.

Existing nocturnal surveys [START_REF] Rave | Time-activity budget of Northern Pintails using nonhunted rice fields in Southwest Louisiana[END_REF][START_REF] Cox | Use of habitats by female northern pintails wintering in southwestern Louisiana[END_REF]Tamisier and Dehorter, 1999;[START_REF] Pirot | Effects of agri-environmental schemes on farmland birds: do food availability measurements improve patterns obtained from simple habitat models?[END_REF]Mesléard et al., 1995) revealed that duck nocturnal use of harvested fields is important and deserves a better assessment. Most of the existing waterfowl surveys in ricelands were so far performed during daylight hours (Twedt and Nelms, 1999;Tourenq et al., 2001;Elphick and Oring, 2003;Toral et al., 2011).

6.

Consideration on availability of all food sources during winter (Manley et al., 2004;Stafford et al., 2006;Greer et al., 2009;Stafford et al., 2010), the amount of energy and nutrition provided by these resources (Kaminski et al., 2003), and how such calorific value might change across the winter (Nelms and Twedt, 1996) all needed to be more accurately estimated for Duck Use-Days and general carrying capacity of such wintering grounds to be better evaluated.

7. Elphick et al. (2010b) and [START_REF] Green | Ecosystem services provided by waterbirds[END_REF] highlighted that the actual food intake and behaviour of the foraging ducks facing various rice post-harvest practices deserved more attention.

8. [START_REF] King | Effects of landscapefeatures on waterbird use of rice fields[END_REF] reported that riceland habitat studies are necessary to implement landscape-scale conservation plans involving both wetlands and flooded agricultural land. Better understanding the drivers behind the movements of waterfowl between natural and artificial wetlands, as well as between their day roosts and nocturnal foraging grounds-i.e., provide a better assessment of the effect of riceland landscape features and heterogeneity [START_REF] Chan | The effect of ricefield fragmentation on wintering waterbirds at the landscape level[END_REF][START_REF] Elphick | Landscape effects on waterbird densities in California rice fields: taxonomic differences, scale-dependence, and conservation implications[END_REF][START_REF] King | Effects of landscapefeatures on waterbird use of rice fields[END_REF][START_REF] Amano | Avian responses to heterogeneity in ricefields at local, landscape and macro scales[END_REF]-is therefore badly needed.

9.

Stafford et al. ( 2010) called researchers for employing modern tools, such as remote sensing, to investigate trends in rice agriculture worldwide. Other modern modeling tools such as energetic models or multi-agent behaviour-based models [START_REF] Amano | Decision-making in group foragers with incomplete information: test of individual-based model in geese[END_REF]Petrie et al., 2014;Miller et al., 2014) would help predict the movements and use of the fields by wintering ducks and provide information to guide future conservation planning.

10. Eadie et al. (2008) and Anders et al. (2008) reported that a precise economic evaluation of winter flooding considering the costs of tillage operations, water, reduced input costs, but also potential income from hunting or ecotourism is required. % % % % 5*.4)+,!QR!,95+!K.,89/B!S!0(5T!5@/'+,I.)9@/! ! [O!

I.3 Links with the next chapters of the thesis

We used the main results of Article 1 to guide the empirical and experimental studies set-up in the field and in the lab during this thesis, trying to cover some of the gaps in knowledge listed above and warranted additional research: 11.

Nocturnal duck surveys were carried out in Camargue rice fields subjected to different post-harvest practices (Article 3, covering points 4 and 5 above).

12.

Seed availability after harvest and depletion across the winter were studied in Camargue, which helped to accurately estimate the Duck Use-Days (Article 3, covering point 6 above).

13. Energetic content and weed seed degradation across the winter were assessed through an experimental test (Article 4, covering point 6 above).

14. Point 7 has not been addressed directly in this PhD thesis but is considered in another PhD work and will result in a joint modeling exercise (refer to SWAMP project in the Discussion).

15.

Remote sensing has been used to evaluate the composition of European ricelands (Article 2) and a first run of the SWAMP multi-agent behaviour-based model (Miller et al., 2014) is currently planned (SWAMP project in the Discussion) (covering points 8 and 9 above).

16.

A full accounting of the market and non-markets costs and benefits of winter flooding in Camargue has been performed to assess whether such management would be economically acceptable by farmers and by society as a whole (Article 6 directly covering point 10 above).

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E a s t e r n A s i a C e n t r a l A s i a a n d I n d i . . O c c i d e n t a l A f r i c a S o u t h A m e r i c a O r i e n t a l A f r i c a N o r t h A m e r i c a C e n t r a l A m e r i c a C e n t r a l A f r i c a N o r t h A f r i c a E u r o p e S o u t h A f r i c a W e s t e

II.1 Background information

This second chapter considers the influence of agronomic management procedures, especially the means of straw disposal, on wintering waterfowl conservation. It aims at determining the most suitable post-harvest agricultural practices in rice fields for providing foraging habitat to wintering ducks in Europe by assessing seed resource availability as well as duck use through direct and indirect estimates of duck abundance (Figure 6). Figure 6. Integration of agronomic values and wildlife conservation in ricelands. Only links from agronomy to wildlife conservation have been kept from the initial framework (reproduced from Eadie et al. 2008, with kind permission from S. Manley). In red colour the elements that were studied in this chapter.

We particularly focused on winter flooding, identified in Chapter I (Article 1) as the best waterfowl-friendly management procedure in harvested rice fields. We estimated the extent to which such practice is used at the European flyway scale (Article 2), and then evaluated its consequences for ducks through empirical studies in the French rice production area (Camargue) (Article 3).

We first assessed the importance of coarse landscape factors (i.e. wetland habitat types) in explaining the number of wintering ducks in five rice-growing regions of Spain, France and Italy (Article 2). Seed availability and nocturnal duck use of rice fields submitted to a diversity of straw management procedures were then measured specifically in southern France (Camargue) (Article 3).

Historical studies in the 80's and the 90's monitored food resources availability and nocturnal duck frequentation in flooded rice fields, fallow rice fields and natural shallow wetlands in Camargue (Tamisier and Dehorter, 1999;[START_REF] Pirot | Effects of agri-environmental schemes on farmland birds: do food availability measurements improve patterns obtained from simple habitat models?[END_REF]Mesléard et al., 1995). They suggested that flooded rice fields represented an important foraging habitat for granivorous ducks, which frequently visited those natural and artificial wetlands. These results were reviewed in Tamisier and Dehorter (1999) and then compared with the data from other Italian and Spanish rice production regions in Mañosa i Rifé (1997), which constituted the basic historical information for developing the questions of Chapter II (Articles 2, 3). As opposed to these former authors, [START_REF] Tourenq | Valeurs et fonctions des rizières pour les communautés d'oiseaux d'eau en Camargue[END_REF] conversely concluded that a mere 6% of the Camargue rice fields were flooded during winter (as opposed to ca. 10% in [START_REF] Pirot | Effects of agri-environmental schemes on farmland birds: do food availability measurements improve patterns obtained from simple habitat models?[END_REF] and were not a major habitat for ducks, while [START_REF] Pirot | Effects of agri-environmental schemes on farmland birds: do food availability measurements improve patterns obtained from simple habitat models?[END_REF] estimated that these hosted 40% of the Camargue granivorous duck population. Updating of the estimation of winter flooding and duck use of flooded fields was therefore required to better understand the system.

Wildlife Abundance & Diversity

Waterfowl

II.2 Key messages and supporting evidence

The studies presented in the articles of this chapter provided new evidence which may benefit wetland and waterbird conservation, as they allowed:

1/ to get an updated evaluation of the conservation importance of major European rice production areas for waterfowl, and the contribution of ricefield winter flooding to such importance.

An estimated 80-90% of the natural wetlands in the Mediterranean region have been lost, and ca. 23% of the remaining wetlands are artificial (Finlayson et al., 1992;Perennou et al., 2012, respectively).

The five study regions present much contrasted landscapes in terms of wetland/rice ratios, ranging from 1 to 75%. Post-harvest practices also greatly differ, with 0.17 to 62% of the rice fields getting flooded during winter. In Camargue, the 9% of rice fields that are flooded get so for hunting purposes. The use of winter flooding varies considerably depending on the implementation of this practice through a "Winter Flooding" Agri-Environmental Scheme (AES). The results show that mean dabbling duck numbers were positively correlated with wetland area in the broad sense, i.e. natural wetlands plus winter flooded ricefield areas (Article 2).

2/ to reopen the debate on complementarities between wetlands and rice fields.

Most studies aiming at determining if rice fields could be valuable substitutes or complements to natural wetlands in terms of waterbird conservation considered the diurnal bird communities, and came to different conclusions (e.g. [START_REF] Fasola | The value of rice fields as substitutes for natural wetlands for waterbirds in the Mediterranean region[END_REF][START_REF] Toral | Agricultura y Conservación en Doñana: La Importancia del Arrozal para las Aves Acuáticas[END_REF]Figuerola, 2010 versus Tourenq et al., 2001;[START_REF] Bellio | Natural versus artificial-wetlands and their waterbirds in Sri Lanka[END_REF]. However, the importance of such potential complementary can be underestimated by diurnal censuses, since many species such as ducks and waders using fishponds or marshes as daily refuges only commute to the rice fields for foraging at night (Toral et al., 2011). Therefore, surveys conducted in rice fields during daylight hours may entirely miss the nocturnal influx of foraging birds (McNeil et al., 1992;[START_REF] Martin | Birds by night[END_REF]. The results of Article 2 and those from the nocturnal duck surveys in Camargue in Article 3 do highlight the complementarities between natural wetlands and rice fields.

In Camargue, while most of the major duck day roosts are clearly identified and receive some degree of protection, the provision of more nocturnal foraging grounds and a better protection of some of these have now been identified as priorities for conservation (Brochet et al., 2009). The way birds disperse from their main day-roosts to rice fields for nocturnal foraging purposes may greatly differ between winter quarters (Figure 7), owing to both the structure of the habitat matrix and the behavioural strategies of the birds. Studying the spatial organisation of the natural wetlands with deeper waters (used as day-roosts) and shallow foraging habitats including flooded rice fields is therefore crucial, as this could profoundly affect the nocturnal movement patterns of the birds and hence the energetic costs to access to food resources (refer to the description of the modeling SWAMP project in the Discussion).

3/ to estimate seed availability in French post-harvest rice fields and how it changes with post-harvest practices and across the winter.

An average of half a ton of seeds were available after harvest in the first 5 cm of ca. 50 French rice fields sampled during the winters of 2012-2013 and 2013-2014 (rice: 349.9 kg/ha ± 57.6 SE; weed seeds: 141.6 kg/ha ± 21.3 SE). The abundance of this food resource was highly variable among and between fields, and was not dependent on initial straw management procedures (burning, chopping or disking). Average rice density however subsequently decreased by 89% and weed seed density by 69% between post-harvest and late winter. Seed depletion rate was highly dependent on initial seed density, and was greatest in ploughed fields (Article 3). We advise landowners to refrain from winter ploughing or to delay it as long as possible, as this activity greatly reduces seed forage available to wintering birds.

4/ to examine the influence of ricefield management practices on bird use: the best for ducks, the best for the rest of the community? Articles 2 and 3 reach the same conclusion that winter flooding is the main driver of duck presence in rice fields. Wintering duck abundance was greater in regions with more rice fields flooded after harvest, i.e. providing more potential nocturnal foraging grounds (Article 2). Comparing the actual bird densities within the harvested rice fields of a given region (Camargue), the importance of flooding for nocturnal duck use has been demonstrated, since 23.5 ducks were recorded per hectare of flooded field (± 2.3 SE), versus 0.3 in unflooded fields (± 0.1 SE) (Article 3). In our study in Camargue, duck numbers were greatest in fields under 5-10 cm of water, which corresponds to the preferred foraging depths and postures of these birds as they likely allow greater foraging efficiency (e.g. Guillemain et al., 2002aGuillemain et al., , 2002b)). With an average of ca. 6 cm between October and February (PNRC, 2013b), Camargue rainfall alone could provide the minimum suitable depth for dabbling ducks if farmers simply closed field water gates after harvest (Article 3).

Except for soil ploughing that should be avoided because it greatly reduces seed availability (e.g. in US, [START_REF] Miller | Rice available to waterfowl in harvested fields in the Sacramento Valley, California[END_REF]in Stafford et al., 2010;in Japan, Lee et al., 2007in Fujioka et al., 2010, Article 3), no clear effect of post-harvest management on seed availability and duck use was detected as long as water covered the fields, suggesting that any flooded non-ploughing agricultural management would be suitable to wintering waterfowl. , 2009). Certain populations of birds rely heavily on these agricultural habitats, and in turn can influence farming activities and crop output (e.g. Donald et al. 2001, Whelan et al. 2008). Food availability and dietary requirements have been quantified for some avifauna inhabiting European agricultural landscapes, but research has focused primarily on dry crops and passerines [START_REF] Holland | A review of invertebrates and seed bearing plants as food for farmland birds in Europe[END_REF][START_REF] Eraud | Weed seeds, not grain, contribute to the diet of wintering skylarks in arable farmlands of Western France[END_REF]. However, rice fields are typically semiaquatic environments, and have been recognized as a globally important foraging habitat for waterbirds (Elphick et al. 2010a). The extent to which these artificial agricultural wetland habitats are used by wintering waterfowl in Europe has not been deeply described (Longoni 2010). In addition, foraging habits are likely more difficult to determine in European ricegrowing regions because waterfowl hunting and other disturbances result in most foraging activity to occur at night (McNeil et al. 1992, Tamisier andDehorter 1999). Furthermore, the variability of post-harvest management practices, such as the extent to which ricefield are flooded during winter, may cause food accessibility and field use to greatly fluctuate at the flyway scale, complicating estimates regarding the importance of ricefield management practices to migratory waterbirds (Pernollet et al. 2015). This knowledge is critical given that rice fields represent one third of the suitable waterbird habitats in southern Europe (Toral and Figuerola, 2010), and that their use of these habitats in winter has likely been greatly underestimated (Tourenq et al. 2001a).

North American researchers have reported high quantities of incidental waste rice following harvest (Eadie et al. 2008, Stafford et al. 2010), a food supply readily exploited by numerous species of waterfowl. Additionally, the seeds of weeds found in rice fields are also known to be consumed by waterfowl (Stafford et al. 2010). The extent to which post-harvest farming practices influence rice and more particularly weed seed availability has received very limited attention (except for Manley et al. 2004, and[START_REF] Marty | Waste rice and natural seed abundances in rice fields in the Louisiana and Texas Coastal Prairies[END_REF], and very few studies have tried to link food availability to the use of fields by waterfowl, an important step in understanding their role in depletion of the seed bank (waste rice and weed seeds; see Havens et al. 2009, Geer et al. 2009). As a result, the extent to which straw management (burning, chopping), mechanical treatment (disking, plowing), type of farming (organic, conventional), crop rotation (number of years under rice cultivation) and winter flooding influence the seed bank and the relationship between seed abundance and field use by ducks remains unclear (Elphick et al., 2010b). ! Food availability studies (Pirot et al. 1982, Tamisier andDehorter 1999) and nocturnal duck surveys [START_REF] Pirot | Exploitation alimentaire nocturne des grands types de milieux camarguais par cinq espèces de canards de surface en hivernage et en transit[END_REF], Mesléard et al. 1995) in flooded rice fields and natural wetlands have been conducted in southern France in the past. The present study is however the first to focus on rice fields and consider all post-harvest management techniques practiced in the area. Such a study is particularly relevant given that recent changes in duck migration phenology seem to be attributed to local habitat changes (Guillemain et al. 2015); that rice and associated weed seeds comprise a huge portion of the diet of ducks wintering in the Camargue (Brochet et al. 2012); and because the provision and protection of nocturnal foraging grounds are paramount to the conservation of waterfowl in the Camargue (Brochet et al. 2009), the most important winter quarter for waterfowl in France and one of the most important in Europe (Deceuninck et al. 2014, Critical Site Network Tool 2015).

!

In undertaking this study, our objectives were to (1) quantify and characterize the seed bank available to waterfowl at the onset of winter, expecting similar seed densities to those described in North America, where farming practices are equivalent, (2) test the effects of farming practices on initial seed mass and on seed depletion through the winter, expecting

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greater seed availability in unburnt fields, especially when only a light superficial treatment of the soil is practiced, as opposed to plowing, and (3) determine which variables best explain nocturnal duck abundance, expecting a major influence of winter flooding. We then provide an updated estimate of carrying capacity for foraging waterfowl on post-harvest Camargue rice fields (duck-use days/ha, (hereafter DUDs), Reinecke et al. 1989), and discuss how the promotion of specific post-harvest practices could potentially improve carrying capacity.

STUDY AREA

This study was conducted on the Rhône River delta known as the Camargue, southern France (43°30'N, 04°30'E). Virtually all rice grown in France comes from this area. The Camargue climate is typically Mediterranean, with hot, dry summers, mild winters, and rainfall concentrated during fall and spring. This, combined with saline soils, restricts agricultural crops to either rice monoculture (sometimes more than 50 successive years of rice cultivation in the same field) or rice-wheat-alfalfa rotation (on average 3-5 consecutive years for each crop) (Barbier and Mouret 1992). 60,000 ha of the delta's 145,000 ha are wetlands, of which ca. 15,000 ha are rice fields (details in Tamisier and Dehorter 1999). On average, approximately 6 % of the area is cultivated under organic farming, with two years of organic rice cultivation generally being possible before weed encroachment significantly reduces yield (INRA 2012). The Camargue is one of the most important winter quarters for dabbling ducks at the European flyway scale (Critical Site Network Tool 2015). Migratory waterfowl begin arriving from September-October and numbers are at a maximum in January (Tamisier and Dehorter 1999). ! Camargue rice fields are typically flooded between seeding and harvest (April to September), and kept dry in stubble until being plowed or disked for straw incorporation, usually early in winter. Disposal of rice straw is a challenge because of its high silica content which makes it resistant to decomposition (Monier et al. 2009). Currently, approximately 75 % of residual rice straw is burned, the remainder chopped (Monier et al. 2009). While burning straw is currently tolerated, concerns surrounding air pollution might soon bring about policy changes that limit or eliminate the practice entirely (Couderc 2013). About 9% of the Camargue rice area is flooded post-harvest for waterfowl hunting purposes (Pernollet et al. 2015), with most hunting occurring on private estates from late August to late January (Mathevet and Mesléard 2002).

METHODS

Seed sampling design

Core samples were collected from 52 post-harvest rice fields on farms scattered across the delta. 16 fields on 5 farms were sampled during the 2012-2013 winter season, and 36 fields on 8 farms during the 2013-2014 winter season (two farms were sampled both years). Fields were selected to represent the main post-harvest practices employed by rice farmers in the Camargue and to provide a broad geographic coverage of the area (Fig. 1, Table 1). The average area of these fields was 3.27 ha ± 0.26 SE (range: 1.12-8.49 ha). 1 to 8 fields were selected per farm, and fields of the same farm were generally adjacent to each other. Sampling occurred in a randomized block design on fields managed conventionally or organically, with or without flooding, and treated post-harvest by either burning, chopping, disking, or plowing the field (Table 1). !

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We collected soil samples from all fields three times per year over the two wintering seasons -for our purposes, "wintering season" is the period during which migratory waterfowl are present on their southern (i.e. winter) territory, and designations of early, mid, and late winter do not coincide with the winter season in the traditional sense. The first round of sampling occurred in late October/early November (early winter) immediately following harvest, the second in mid-December (mid-winter), and the third in early February (late winter). Seeds were collected in a uniform grid across the field of 9 standard cylindrical core samples, with a corer 10 cm in diameter and 5 cm deep (392.5 cm 3 , 78.5 cm 2 ) (Manley et al. 2004) -the 5 cm depth corresponds roughly with the maximum depth reachable by dabbling ducks foraging in sediment (e.g. mallard Anas platyrhynchos average bill length is 4.2cm in males, 3.9cm in females after Baldassarre 2014). To make our seed availability data comparable to North American studies that used soil corers 10 cm in diameter and 10 cm deep (i.e. 784.4 cm 3 , 78.5 cm 2 , Manley et al. 2004), we randomly selected a core from each field in each sampling period and double-sampled it, giving a 0-5 and 5-10 cm stacked sample from a single hole. In fields where straw was burned we took 9 samples in the rows where straw was concentrated by the combined harvester and subsequently burned, and another 9 samples from the rows largely devoid of burned material. This protocol was also used in the three fields where the farmer disked several bands of chopped stubble for hunting purposes. 502 and 1,358 core samples were collected and processed from the 2012-2013 and 2013-2014 winter seasons respectively.! ! Laboratory procedures and seed depletion rates ! Core samples were frozen immediately following collection and remained frozen until processing. They were then sieved to 300 µm in accordance with the smallest space between duck bill lamellae (eg. in eurasian teal Anas crecca, Thomas 1982). Soil and organic matter were separated from seeds, which were then oven-dried at 70°C for 24 hours. Each seed was identified to the species and counted using a binocular magnifier (W-PI 10x/23) and reference literature [START_REF] Cappers | Digital seed atlas of the Netherlands[END_REF]. Red rice (Oryza sativa var.) was differentiated from cultivated rice by shape (round vs long) or by manually removing the endosperm and counting the white and red grains. Only fully intact rice and weed seeds were counted and included in the analyses.

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The number of seeds per species was transformed into biomass using the LEDA database (see [START_REF] Kleyer | The LEDA Traitbase: a database of life history traits of the Northwest European flora[END_REF]) and a reference publication [START_REF] Arzel | Average mass of seeds encountered by foraging dabbling ducks in Western Europe[END_REF], along with an unpublished Camargue database (data provided by A.-L. Brochet and J.-B. Mouronval). When species mass was not available (e.g. for rare unidentified species), a sample of seeds was weighed to the nearest 0.1 mg. ! Because seeds degrade and decrease in mass over the course of winter (Nelms and Twedt 1996), we devised a greenhouse experiment to test the rates of deterioration of cultivated rice and the three principal rice weeds (Oryza sativa var., Bolboschoenus maritimus, Echinochloa sp.), and found that seed mass decreased at rates that vary under dry and flooded conditions (Pernollet et al. in prep). While dry seed masses from the literature were used for samples collected during early winter, a correction factor derived from our experiment (mean seed mass decrease for each of the four species in dry or flooded conditions) was applied to the four tested plant species from the mid-and late winter sampling periods (i.e. cultivated rice, -16% to -64%, red rice, -7% to -52%, etc). Mean rates of seed mass decrease for the three weed species tested in the greenhouse were applied to the untested weed seed plant species identified in the samples (i.e. -11% to -37%) (details in Pernollet et al. in prep). After applying the corrections, the resulting masses of rice and weed seeds per core sample were converted to kilograms per hectare for analysis. ! Because samples were not necessarily taken at the exact same spot within the fields across sampling occasions, seed depletion was analysed at the field level rather than for each core. We sampled 52 fields over two separate time periods (early to mid-, and mid-to late winter), giving a sample size of 104. Because the time interval between sampling sessions varied (14 to 56 days early to mid-winter, 51 to 64 days mid-to late winter), we computed the daily mass loss rate per field separately for rice and weed seeds based on changes in seed mass and time elapsed between successive samples, and divided this by the initial mean seed density in that field to obtain a rate expressed as the proportional loss of seed mass per day (hereafter seed depletion rate). If the average seed density at t+1 was greater than at t, owing to variance in seed distribution within the field, seed depletion rate could be negative. Seed depletion rate could not be calculated for rice in four fields because the initial seed mass was zero, thus the final sample size for rice was 100 instead of 104. ! Nocturnal waterfowl surveys ! Duck surveys were conducted weekly from 19 November 2013 to 26 February 2014 (except for two weeks around Christmas) on 34 of the 37 fields where soil samples were taken during the second winter (3 fields could not be counted due to inaccessibility), and on an additional 12 adjacent fields where agricultural practices were known -these 12 were not sampled for seed density and so were excluded from models where seed density was used as a potential fixed factor. Two consecutive nights of counting each week allowed all 46 fields to be counted 13 times across the winter, except for on 1 farm with 9 fields where access difficulties permitted only 7 counts per field. Counts were done between 10:00 pm and 02:00 am (peak foraging period for dabbling ducks in Camargue, Tamisier and Dehorter 1999), with the order fields were visited being shifted each time to avoid potential time biases. Surveys were performed by walking along field edges to flush birds and count them in flight using a 4x light amplifier!(Thomson, TRT Defense, see also Guillemain et al. 2002). Identification of ducks (and other waterbird species) was often aided by recognition of species-specific alarm calls. When individuals could not be identified to the species, they were recorded to the genus or family level, e.g. Anas sp. Stopping regularly to scan the field with the light amplifier ensured that birds reluctant to flush were not absent from our counts. Upon flushing, attention was paid to the direction the birds flew to avoid double counting them in adjacent fields. Birds detected flying overhead were not counted unless they were seen taking flight from one of the surveyed fields. ! Agricultural management techniques observed on each field were recorded during each nocturnal count (e.g. plowed, disked, etc.). Water levels of flooded fields were recorded three times between November and February, on the day preceding or following nocturnal surveys by measuring depth to the nearest millimeter at 5 points on each field diagonal. Mean water levels associated with the corresponding nocturnal survey were used in the analyses. Daily rainfall records taken at the Tour du Valat and Réserve Naturelle Nationale de Camargue (Chauvelon, Tour du Valat, unpublished data) for the same period were used to determine unintentional flooding due to rain on dry rice fields.

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We defined five water levels (dry, rain, low, medium, high) based on recent precipitation and the water depths known to provoke different feeding postures in eurasian teal and mallard (postures, from Thomas, 1982). "Dry" fields were not intentionally flooded and did not receive heavy rain (< 30 mm) the week before the survey; "rain" corresponded to fields left dry by farmers but which received heavy rain during the week preceding the survey (cumulative rainfall ≥ 30 mm, dabbling); "low" corresponded to intentionally flooded fields where measured water depth was less than 5cm (dabbling); "medium" corresponded to intentionally flooded fields where measured water depth ranged between 5 (inclusive) and 10 cm (head under); "high" corresponded to intentionally flooded fields where measured water depth was at least 10 cm (dipping or upending). We calculated field areas and the distance (km) of each field from the nearest potential duck day roost site using Geoportail (http://www.geoportail.gouv.fr/accueil).

Statistical analyses

The seed bank was described for each sampling period, and included the average density (kg/ha) and abundance of seeds (number of seeds) of all species across all cores and fields.

Because the number of seed species increased with increasing number of cores within a field, species occurrence (proportion of fields where a given species occurred, at each sampling date) was computed by pooling the list of species from all cores from each field and computing the percentage of fields containing a given species. Total rice and weed depletion across the winter was expressed as a percentage. The dabbling duck community was described as the mean density of birds per species recorded during a weekly nocturnal survey, pooling all surveyed fields and averaging over the number of weeks of the study.

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We used generalized linear mixed-effects models (GLMM) to assess the variables influencing initial rice and weed seed availability, rice and weed seed depletion rate, and field use by duck.

Starting with a full model including all possible 2-way interactions, we used the Akaike's Information Criterion (AIC) for model selection (Burnham and Anderson 2002). All models were tested and only a suite of candidate models whose AIC was lower than the null model are presented in the result tables. We ranked models by AIC, and to better interpret the relative likelihood of a given model we computed the Akaike weight (w i , the weight of evidence in favour of model "i") for each model. Finally, we calculated the relative importance of each explanatory variable by summing w i for all models containing that variable (Burnham and Anderson 2002). We used model averaging to extract parameter estimates (SE and 95% CI) from the best models (∆AIC < 2) (Function model.avg of package MuMIn), and when a significant effect was detected (deviance test, P < 0.05) we performed pair-wise comparisons of means using Tukey's post hoc test to determine which categories differed from each other (procedure details in Burnham and Anderson 2002).

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In testing the variables explaining initial post-harvest rice and weed seed availability, it was necessary to exclude from the analysis eight fields that suffered heavy damage from wild boar [Sus scrofa] and consequently had low yields (averages of 3 t/ha -range 1.5 to 4.5-compared to 5.12 t/ha in other fields) and large quantities of waste rice. These fields had the same cultivation historic and post-harvest straw management, so that including them in the analysis of the straw management procedures would have inflated the potential effect of the latter factors. However, these fields were included in analyses of seed depletion rate -since this was corrected for initial seed density -and duck use. transformation did not improve the distribution of the residuals and the Arcsine transformation was not possible due to negative seed loss values. GLMM however is robust enough to support such non normality [START_REF] Zuur | A protocol for data exploration to avoid common statistical problems[END_REF], so the analyses were run with the raw data. Field number, farm identity and year were tested as random factors in the seed availability analysis. To explain initial rice and weed seed availability (early winter), we considered the following as fixed variables: weed seed density (to explain variation in rice seed density), rice seed density (to explain variation in weed seed density), straw management (chopping, disking, burning, with cores of burned and unburned lines of the same field first considered together and then separately), type of farming (organic or conventional), and number of years cultivated in rice. Number of years cultivated in rice was treated as a continuous variable. The only interaction considered in the analyses was between number of years in rice cultivation and type of farming.

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To explain seed depletion rate we considered the following as fixed variables: the sample period (first: early to mid-winter, second : mid-to late winter), initial mean seed density (rice and weed seeds) per core sample at the beginning of the corresponding sample period, agricultural practices employed during that period (disked, plowed, none) and winter flooding.

In fact, once the straw of a field had been chopped, burnt or disked during or right after harvest, three post-harvest practices were distinguished in the depletion analysis: "disked", "plowed", or "none", depending on what the farmer did between two soil sampling sessions. Finally, for this analysis winter flooding was considered a binary variable (Y/N). ! Function glmmadmb of package glmmADMB [START_REF] Fournier | AD Model Builder: using automatic differentiation for statistical inference of highly parameterized complex nonlinear models[END_REF]) was used to apply a negative binomial distribution to the duck data, which were over-dispersed. The total number of dabbling ducks recorded in each field during each weekly survey was used as the response variable. The field area (ha) was used as an offset term in the GLMM (field size ranged from 1.24 to 6.91 ha) [START_REF] Yan | Applications of the offset in propertycasualty predictive modeling[END_REF]). Field number, farm identity and week of survey were tested as random factors. To explain the number of ducks per field we considered the following as fixed variables: total seed availability (rice plus weeds, kg/ha), water level (dry, rain, low, medium, high), straw management (burning, chopping, disking, chopping-disking or plowing) and distance from the field to the nearest potential diurnal roost (km). Using the seed mass depletion rates described above, we extrapolated seed availability from the core samples and the number of days elapsed since the last seed sampling session. Legagneux 2007). For these calculations, winter consisted of 120 days and daily energy requirement was 285 kcal per individual, based on mallard ducks (Prince 1979).

RESULTS

Initial seed bank

A total of 111 seed species were identified in 1,860 core samples collected from 52 rice fields over two winters that could be analysed (See Appendix 1 for details on mean seed number, density and species occurrence). An average of 349.9 kg/ha (± 57.6 SE, n = 52 fields) of rice seeds were left in the fields after harvest. Weed seed densities averaged 141.6 kg/ha (± 21.3 SE, n = 52) in the studied fields, with three species representing 82% of the mean weed seed density. Of the total mean seed density, 47% was red rice (Oryza sativa var.), 25% Echinochloa spp., and 10% Bolboschoenus maritimus. Rice grains were the most abundant seeds in all sampling periods. However, rice seed density gradually decreased across the season, to 146.7 kg/ha (± 27.5 SE, n = 52) in mid-winter and 38.1 kg/ha (± 11.5 SE, n = 52) in late winter. The mean density of weed seeds also gradually decreased to 70.3 kg/ha (± 8.8 SE, n = 52) in mid-winter and 44.5 kg/ha (± 5.7 SE, n = 52) in late winter (Fig. 2). Mean rice density decreased on average by 311.8 kg/ha (89%) from early to late winter, and weed density by 97.0 kg/ha (69%). !

Factors influencing initial seed densities

The total seed mass immediately following harvest was highly variable across samples from a single field (maximum range 131.3 kg/ha to 9,582.9 kg/ha after extrapolation from two core samples from the same field), as well as from one field to another (maximum range 51.6 kg/ha ± 10.8 SE and 2,712.6 kg/ha ± 1,144.4 SE in two fields, n = 9 cores in both cases). ! Table 2 shows the 22 models that were significantly better than the null model at explaining the variation in rice seed density per core collected immediately following harvest. Among these models, four factors and two interactions stood out as the most important as judged from cumulative AIC weights: log(weed seed density) (relative importance, cumulative AIC weight = 1.00), number of years the field had been cultivated in rice (1.00), farming type (0.37), straw management procedure (0.16), the interaction between log(weed seed density) and number of years the field had been cultivated in rice (0.28), and the interaction between number of years the field had been cultivated in rice and type of farming (0.12). Based on ∆AIC values, three models performed better than the others at explaining variation in rice seed density per core sample. All three included effects of weed seed density and the number of years the field had been cultivated in rice, one included the interaction between the log(weed seed density) and the number of years the field had been cultivated in rice, and another included type of farming instead of the interaction (Table 2). Taken together, the three best models accumulated 68% of AIC weight. These showed a significant positive relationship between log(rice seed density) and log(weed seed density) in the same core (Model averaged estimate: β = 0.53 ± 0.11 SE), while the other model-averaged estimates were non-significant (Table 7). Notably, no significant difference in early winter rice density was observed between fields where straw was burned, chopped or disked. However, in fields where straw was burned there were significantly more rice grains in the burned lines than in unburned lines of the field (burned fields: log(rice density)~straw management +(1|field.fac)+(1|farm.fac), β = -0.60 ± 0.18 SE, P =!0.001).

Table 3 shows that 24 models were significantly better than the null model at explaining variation in log(weed seed density) immediately following harvest. Among these models, four factors and two interactions stood out as the most important as judged from cumulative AIC weights: number of years the field had been cultivated in rice (cumulative AIC weight = 1.00), log(rice seed density) (0.99), type of farming (0.84), straw management procedure (0.42), the interaction between number of years the field had been cultivated in rice and type of farming (0.79), and the interaction between log(rice seed density) and number of years the field had been cultivated in rice (0.27).

Based on ∆AIC values, three models performed better than the others at explaining variation in weed seed density per core sample. All three included effects of rice seed density in the same core, the number of years the field had been cultivated in rice, the type of farming, and the interaction between number of years the field had been cultivated in rice and farming type. One model also included the straw management procedure, and another included the interaction between log(rice seed density) and number of years the field had been cultivated in rice (Table 3). Taken together, the three best models accumulated 71% of AIC weight. These showed a significant positive relationship between log(weed seed density) and log(rice seed density) in the same core (Model averaged estimate: β = 0.07 ± 0.01 SE), a lower density of weed seeds in the organic fields than conventional fields (Model averaged estimate for Organic: β = -2.50 ± 0.88 SE), and a positive relationship between log(weed seed density) and the interaction between number of years the field had been cultivated in rice and type of farming (Model averaged estimate for Organic: β =1.51 ± 0.51 SE). No significant difference

Seed depletion rate across the winter

Table 4 shows the 12 models that were significantly better than the null model at explaining rice depletion rate. Among these models, four factors stood out as the most important as judged from cumulative AIC weights: average seed density (rice and weed seeds) per field at the beginning of the corresponding time period (cumulative AIC weight = 0.91), agricultural practice applied during that period (0.83), time periods (0.30), and winter flooding (0.30).

Based on ∆AIC values, three models performed better than the others at explaining variation in rice depletion rate. All three included effects of seed density in the field at the beginning of the corresponding time period and the agricultural practice applied during that period. One also included winter flooding, while another included the time period (Table 4). Taken together, the three best models accumulated 69% of AIC weight. These showed a significant positive relationship between rice depletion rate and seed density in the field at the beginning of the corresponding time period (Table 7). Applying the Tukey post-hoc test three times to each of the three best models showed that rice depletion rate was higher in plowed fields than in stubble fields or fields that did not receive any agricultural treatment during a given time interval ("none" compared to "plowed" in the three models: P = 0.022, P = 0.020, P = 0.0224, respectively, Fig. 3). The figure represents the minimum, the first quartile, the median, the third quartile, and the maximum. Post-hoc Tukey tests at P < 0.05 indicated that depletion rates of rice were greater in plowed fields than in stubble fields or fields with no agricultural treatments ("None"). There were no significant differences between the other treatments (see text).

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Table 5 shows that 12 models explained weed seed depletion rate significantly better than the null model. Among these models, four factors stood out as the most important as judged from cumulative AIC weights: average seed density (rice and weed seeds) per field at the beginning of the corresponding time period (cumulative AIC weight = 0.98), time periods (0.56), agricultural practice applied during that period (0.46), and winter flooding (0.28). Based on ∆AIC values, six models explained variation in weed seed depletion rate better than the others. All six models included effects of seed density in the field at the beginning of the corresponding time period, alone or in combination with some of the other factors (Table 5).

Taken together, the six best models accumulated 86% of AIC and showed a significant positive relationship between weed seed depletion rate and seed density at the beginning of the corresponding time period (Table 7). The Tukey post-hoc tests!applied to each of the six best models including agricultural practices showed that weed seed depletion rate was not significantly different for any agricultural treatments (data not shown).

Nocturnal waterfowl densities

Mallards and eurasian teal were the most numerous waterfowl species recorded during the surveys (69.5 % ± 5.6 SE and 25.5 % ± 4.8 of total bird numbers on average, respectively, n = 13 weekly counts), followed by pintail Anas acuta, gadwall Anas stepera and northern shoveler Anas clypeata (4. Apart from dabbling ducks, two other waterfowl species, common shelduck Tadorna tadorna and greylag goose Anser anser were observed (ten individuals over three nights and nine individuals over three nights, respectively), as well as an assortment of other waterbirds (Other waterbirds: common snipe Gallinago gallinago (44%), Tringa and Calidris sp. (24%), northern lapwing Vanellus vanellus (16%), greater flamingo Phoenicopterus roseus (7%), grey heron Ardea cinerea (5%), laridae (2%), common crane Grus grus (2%), eurasian curlew Numenius arquata (1%) and little egret Egretta garzetta (0.1%)).

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Table 6 shows the 15 models that were significantly better than the null model at explaining the number of ducks in post-harvest rice fields. Among these models, four factors stood out as the most important as judged from cumulative AIC weights: water level (cumulative AIC weight = 1.00), straw management (0.77), distance from the field to the nearest potential diurnal roost (km) (0.49), and log(seed density) (0.28). Based on ∆AIC values, four models performed better than the others at explaining variation in the number of ducks per field. All four included water level, three included straw management, two included distance to the nearest potential duck day-roost, and one included log(seed density) (Table 6). Taken together, the four best models accumulated 85% of AIC weight. Ducks were significantly more numerous in flooded than in dry fields, regardless of water level (weekly average: flooded: 23.5 ducks/ha ± 2.3 SE; dry: 0.3 ± 0.1 SE. n = 13 weeks in both cases; see also Fig. 5 and model averaged estimates in Table 7). Duck numbers were significantly lower in rice fields where straw was burned compared to those where straw was disked, chopped, or chopped and partly disked (Table 7). The value of parameter estimates, standard-errors and 95% confidence intervals of the variables present in models for seed depletion rates were multiplied by 10 000 for easier reading. We considered coefficient estimates with 95% CI that did not overlap zero to be significant.

Camargue carrying capacity of wintering ducks

The average seed density at the beginning of the winter was 465.6 g/ha (five most abundant seed species), which would represent 1,531,308.4 kcal/ha. Given that mallards require 285 kcal per day per individual, an average Camargue ricefield at the beginning of the winter could theoretically host 5,373 DUDs/ha. In a theoretical winter season of 120 days, during which no mechanism for seed depletion exists other than foraging ducks, the carrying capacity would be 45 mallard-sized ducks per hectare per day. Considering that approximately 10,000 ha in Camargue are cultivated in rice-rice rotation and 9% of these are flooded and are thus available to ducks, the region could therefore accommodate 4,835,700 duck.days, i.e. 40,297 ducks per day on average. If all fields in rice-rice rotation were to be flooded, the carrying capacity would increase to 53,730,000 duck.days, i.e. 447,750 ducks per day on average.

DISCUSSION

Residual rice and weed seeds were abundant in Camargue rice fields immediately following harvest, but quickly disappeared as winter progressed. Nocturnal surveys indicated that ducks readily use flooded rice fields as foraging grounds. ! Post-harvest rice and weed seed densities were highly variable both within and between fields, and so were hardly predictable. Immediately following harvest we measured an average of 350 kg/ha of rice in the first 5 cm of soil. Farmers reported an average yield of 4,769 kg/ha in the 52 studied fields. Our seed samples suggest that yield loss in these fields averaged 7.9% (± 1.5 SE), which was consistent with the 8.7% reported by Manley et al. (2004) in the Mississippi Alluvial Valley (MAV hereafter) and slightly greater than the 3-6% reported by Eadie et al. (2008), in which data was assessed from all relevant US studies. However, when the 8 fields that suffered wild boar damage were excluded from the calculation, yield loss here dropped to 4.8% (± 0.8 SE, n = 44 fields), within range of these American studies. ! Where cores were double-sampled for inter-study comparability purposes with North American studies, the abundance and mass of seeds in the 0-5 and the 5-10 cm samples were similar, thus the average density of seeds following harvest in the first 10 cm of soil could simply be double that of the first five centimetres (i.e. 700 kg/ha for rice and 283 kg/ha for weed seeds). This average rice density falls within the upper ranges of densities reported in North American studies by Eadie et al. (2008) ). However, if the ideal and so promoted growing conditions for rice also benefit weed growth, the relatively ineffective weed controls employed in Camargue would allow the rice yield and weed seed bank to fluctuate in tandem.

Many studies have investigated the influence of post-harvest practices on residual rice seed availability and accessibility to waterfowl, the majority being from the U.S. and Japan (Elphick et al. 2010b, Stafford et al. 2010). However, the extent to which straw management practices employed immediately following harvest can influence seed availability and use of fields by ducks remains uncertain (see Stafford et al. 2005 andElphick et al. 2010, respectively). Our findings indicate that initial rice and weed seed densities were not significantly influenced by post-harvest straw management practices, except for in plowed fields where rice and weed seed depletion rates were significantly higher, a result shared with [START_REF] Miller | Rice available to waterfowl in harvested fields in the Sacramento Valley, California[END_REF], Anamo et al. (2006) and [START_REF] Lee | Winter foraging of threatened cranes in the Demilitarized Zone of Korea: behavioral evidence for the conservation importance of unplowed rice fields[END_REF]. While no straw management practice had a clear effect on seed densities at the beginning of winter, the spatial distribution of rice seeds was different between fields that were burned and chopped. In burned fields the combine harvester concentrates straw -and rice, incidentally -into rows, which are subsequently burned; in fields where straw is chopped, straw and seeds are spread uniformly behind the machine. In terms of foraging efficiency, the concentration of waste rice in burned rows likely increases ducks' use of a field; burning increases foraging efficiency by improving seed access (Havens et al. 2009), even if it can also reduce quantities of waste rice by ca. 30% [START_REF] Miller | Rice available to waterfowl in harvested fields in the Sacramento Valley, California[END_REF]). Moreover, burned rows are likely easily located by their black color. All of this could explain why ducks preferentially selected burned fields in Havens et al. (2009). Surprisingly, we observed a lower number of ducks in rice fields where straw was burned compared to those where it was disked, chopped, or chopped and partly disked.

Although beyond the scope of our analysis, it should be noted that all of the fields we surveyed that were both flooded and burned were surrounded by hedges, a landscape feature known to reduce nocturnal use of rice fields by Greater Flamingo in the same area (Tourenq et al. 2001b).

!

The factor that best explained nocturnal duck use of rice fields was winter flooding, be it intentional or caused by heavy rain. This is consistent with earlier results in Japan (Shimada et al. 2000, Tajiri andOhkawara 2013), Europe (Lourenço and Piersma 2009) and the US (Day and Colwell 1998[START_REF] Elphick | Winter management of Californian ricefields for waterbirds[END_REF], 2003, Strum et al. 2013), and can be explained by the need for ducks foraging for seeds on dry land to rely on water for handling their food (Guillemain et al. 1999). Beyond the local scale, ducks are reportedly more numerous in a given winter quarter when flooding is greater (Toral et al. 2011) and are even known to distribute among winter quarters at the flyway scale depending on the intensity of ricefield flooding (Pernollet et al. 2015). Elphick and Oring (2003) reported that 14 to 22 cm water depth was ideal for ducks; in our study duck numbers were greatest in fields under 5-10 cm of water, owing perhaps to the relative abundance of small Eurasian Teal in our duck community. Contrary to the results of Strum et al. (2013) in California -an arid region currently in drought -our results demonstrate that rainfall alone could provide the minimum suitable depth of 5 cm for dabbling ducks during winter in Camargue (average of 58,0 mm rain between October and February, maximum in October 90. 6 mm, 19776 mm, -20066 mm, (PNRC 2013))). ! Since dabbling ducks rely heavily on water for foraging, it makes sense that we found flooding to be the primary determinant of duck numbers on rice fields, and not seed availability. Furthermore, average seed densities were high, so birds may not have been foodlimited in the study area. That flooded fields attract ducks is also apparent from the high concentrations of birds we detected during nocturnal surveys (2,400 birds/km²) compared to diurnal surveys in rice field areas: 5-10 birds/km² in Camargue (Tourenq et al. 2001a), 5-10 birds/km 2 in the MAV (Twedt and Nelms 1999), 30 birds/km² in Japan (Fujioka et al. 2010), and the high 730 birds/km² in California (Elphick and Oring 2003). Our recorded nocturnal densities are also much greater than the mean 500 birds/km² (max 1500 birds/km²) reported in historical nocturnal surveys in the Camargue [START_REF] Pirot | Exploitation alimentaire nocturne des grands types de milieux camarguais par cinq espèces de canards de surface en hivernage et en transit[END_REF], Mesléard et al. 1995). This apparent increase in wintering bird nocturnal density is consistent with the increased importance of rice and rice weed seeds in the diets of Camargue Eurasian Teal and mallard compared to that in the 1960s and 1970s (Brochet et al. 2012). Because the majority of the 7-12 % of Camargue rice fields that are flooded are done so for hunting purposes (Pernollet et al. 2015), it is possible that limited flooded area (ca. 1000 ha) and habitat management practices dedicated to ameliorating duck numbers are responsible for the high concentrations we observed during nocturnal surveys. ! Wintering ducks arrive in Camargue gradually, with maximum numbers occurring in January and diminishing when the spring migration begins in February (Tamisier and Dehorter 1999). Over this same period of time we found that seed availability decreased by 89% and 69% from early to late winter for rice and weeds, respectively. Each of these two seed types alone were still above the 50 kg/ha duck Giving-Up Density (GUD, Reinecke et al. 1989, Geer et al. 2009) at the end of the winter, so plenty of food was still available when the ducks left. ! Several studies in California and the MAV showed that depletion of rice seed during winter ranged from 66-79%, and that waterfowl consumed up to 30% of the rice available during early winter (Manley et al. 2004, Eadie et al. 2008). Decomposition, granivory and germination are the primary mechanisms of rice seed loss after harvest (respectively 58%, 14% and 8% in the MAV after [START_REF] Stafford | Abundance and conservation of waste rice for wintering waterfowl in the Mississippi Alluvial Valley[END_REF]in Stafford et al. 2006). According to Geer et al. ( 2009), depletion by waterfowl ranged between 25 % and 48% in the MAV, while seed deterioration represented slightly more than 40 %. In our area, no differences in seed depletion rates were observed between flooded and non-flooded fields, even when taking into account a correction factor for non-consumptive seed mass loss in water (experimental test explained in the Methods section, Pernollet et al. in prep.). This may mean that granivores other than ducks deplete the rice/weed seed bank in dry fields as ducks do in flooded fields.

For instance, wild boar and common cranes are increasing in numbers in the area, and are known to forage heavily in dry rice fields [START_REF] Blondel | L'Encyclopédie de la Camargue[END_REF]. Since lack of flooding is an excluding factor for duck use (Pernollet et al. 2015), resources on dry fields are free to be exploited by other granivorous vertebrates (e.g. passerines, Elphick 2004). Seed depletion rate was first explained by seed density, followed by post-harvest agricultural practices, with greater reduction in seed availability occurring after plowing than after other treatments or no treatment at all. Eadie et al. (2008) also reported that U.S studies showed greater seed depletion rates in fields where initial post-harvest seed density was the greatest. This means that depletion of seeds was density-dependent, as observed by Geer et al. (2009).

According to the seed densities at the beginning of winter, the carrying capacity in Camargue is 5,373 DUDs/ha or 45 ducks/ha per day for a 120 days winter. This value is markedly higher than the 1.7 to 2.3 Anatidae and Coots per hectare estimated by Tamisier and Dehorter (1999) on 60,000 ha of Camargue natural wetlands. Based on the analysis of food availability on both rice fields and wetlands, these authors concluded that the Camargue could provide winter forage for more than 400,000 ducks and coots. This value is much lower than the 53,730,000 ducks during a whole winter season we calculated if all Camargue rice fields were to be flooded. When considering that only 9% of rice fields are actually flooded, carrying capacity decreases to 4,835,700, but remains much higher than the Tamisier and Dehorter (1999) estimate.

! It is important to note that we did not include seed deterioration in our carrying capacity calculations. In the U.S., the accuracy of rice field carrying capacity estimates excluding this factor have been debated, and recent data suggest actual carrying capacities are lower than have been reported (Manley et al. 2004, Stafford et al. 2006). The MAV carrying capacity estimate of 1,800 DUDs/ha [START_REF] Loesch | Lower Mississippi Valley Joint Venture Evaluation Plan[END_REF]) was calculated without the inclusion of seed deterioration, a value that Stafford et al. (2006) recommend be reduced to 325 DUDs/ha, which is more in accordance with the 265-686 DUDs/ha previously reported by Manley et al. (2004), who also considered seed depletion and furthermore all food types (rice and weed seeds). Though we should revise our carrying capacity estimate to include seed deterioration, 5,373 duck-use days/ha in Camargue is still very high compared to the US results, such as estimation in wild rice paddies in Minnesota [START_REF]Oral presentation on the PhD project to the Wildfowl and Wetlands Trust. Slimbridge, UK. Pictures of several meetings: Vercelli, Tour du Valat, French Rice Centre !"#$%&%'"($)%#$%*+,%"-#+.#'+#/,"%#$%0+,1.#2","#-3.#2"03.# $%*+,%"%0+.4#53,#+--3#.+,$"#$%0+,+."%0+#(3%.+,*",#-"#677# +%#.2"9"#:#2,3;3*+,#-"#$%&%'"($)%#"#-3#-",/3#'+#-"#*<"# '# ;$/,"($)%=# +;2+>"%'3# 23,# -".# ,+/$3%+.# '3%'+# -"# ;":3,#2",0+#'+#-3.#?&;+'"-+.#%"0&,"-+.#'+."2",+($+,3%=# (3;# +.# +-# (".3# +%# -"# *"--+# '+-# ,$3# 5@# +%# A0"-$"4# 8%# -"# B";",/&"# .+# +.0"# --+*"%'3# "# ("C3# &%# "%D-$[END_REF]200 DUDs/ha in [START_REF] Huseby | Dabbling duck production from a wild rice farming landscape in northwest Minnesota[END_REF]. Moreover, other foraging habitats are available in Camargue whose carrying capacities have not been thoroughly investigated and may influence local and regional abundances, such as marshes including some that are illegally baited during the hunting season.

MANAGEMENT IMPLICATIONS

At the scale of a field (the scale at which farmers and managers will likely act), winter flooding of rice fields is the most popular duck-friendly post-rice harvest agricultural practice worldwide because it is relatively easy to implement, can provide agronomic benefits (Bird et al. 2000, Manley et al. 2005, Anders et al. 2008, Brogi et al. 2015), and makes waste seeds accessible to waterbirds (Eadie et al. 2008), (see also review by Pernollet et al, in press).

According to Kross et al. (2006), the methods that most benefit both farmers and ducks include flooding fields and leaving standing-stubble post-harvest, incomplete burns postharvest, and generally practices that minimize mechanical treatment. In our case, we advise landowners to refrain from winter plowing or to delay it as long as possible, as this activity greatly reduces seed forage available to birds. We also recommend conservation planners to promote winter flooding of harvested fields. Where active flooding is deemed impossible or infeasible, passive flooding, achieved by closing field water gates to retain rain water, is done with success in Portugal (Lourenço and Piersma 2009) and is another practice worth promoting. In devising management plans and financial structures, managers can look to surrounding areas where support systems are already in place, such as in regions of Spain

CHAPTER III. POTENTIAL AGRONOMIC BENEFITS OF RICEFIELD WINTER FLOODING AND DUCK USE OF FLOODED FIELDS

Experimental tests, Claire Pernollet

III.1 Background information

This third chapter deals with the ecosystem services that winter flooding and ducks foraging into flooded rice fields can bring to farmers. Considering that the main constraints on rice cultivation are straw disposal and weeds, we particularly focused on weed regulation and straw decomposition improvement (Figure 8). These respectively represent regulating and supporting ecosystem services that could be brought to rice farmers by flooding fields and duck use. Such potential agronomic benefits have been summarized by Anders et al. (2008) for the United States, then discussed in parallel to the agronomic benefits from farming ducks in the traditional Asian ''Integrated Rice Duck Farming'' (IRDF, [START_REF] Furuno | The Power of Duck: Integrated Rice and Duck Farming[END_REF] in Table 2 of Article 1 (Chapter I). Previous empirical and experimental studies showed that ducks can bring agronomic benefits to rice farmers, but this had never been tested in Europe (except for the recently published work on nutrient recycling by waterbird in rice fields during winter by [START_REF] Navedo | Unravelling trophic subsidies of agroecosystems for biodiversity conservation: food consumption and nutrient recycling by waterbirds in Mediterranean rice fields[END_REF]. We thus experimentally assessed here the effect of ricefield winter flooding on weed seed deterioration and the effects of wintering and farming ducks on weed seed banks and straw stalks.

III.2 Methods: the advantages of the experimental approach

In ecological studies, a multiplicity of factors such as site, weather or animal behaviour can affect the response variables and the precision of the measurements. The experimental approach, in which each factor is controlled for and the different parameters are precisely measured, is sometimes the best option to answer a precise question. Examples of experimental approaches for topics similar to ours include a study of buried seed samples degradation in rice fields by Fogliatto et al. (2010), or the effects of enclosed wing-clipped We assessed rice and main weed seed deterioration in dry and flooded conditions throughout the winter in a greenhouse to control for granivory by vertebrates or large invertebrates, seed quality, water and substrate heterogeneity from one field to another (Article 4).

We evaluated the impact of ducks on the weed seed bank and standing stalks with wing-clipped mallards in enclosures settled directly on the field to control for granivory by other vertebrates. By testing different duck densities we could also compare the potential effects of wild ducks extensively using ricelands versus high-density farmed ducks in riceduck agroecological systems (Article 5).

III.3 Key messages and supporting evidence

The studies presented in the papers of this chapter provided new evidence that waterfowl-friendly management can benefit farmers through increased straw degradation, but not necessary through a reduction of the weed seed bank. These articles showed that:

1/ winter flooding increases cultivated rice and weedy rice seed mass loss, and decrease cultivated rice viability. Gross energy loss throughout the winter was greater for weedy rice in flooded fields than dry ones. No significant differences were found between dry and flooded conditions for seed mass loss, energy density or survival in barnyard grass (Echinochloa crus-galli) and sea clubrush (Bolboshoenus maritimus)(Article 4).

Besides depletion by granivorous waterfowl and other foragers, the seed bank of rice fields (rice and weeds) is reduced across the winter by seed deterioration (Geer et al., 2009). Our results showed that seeds from different species are not similarly affected by flooding, i.e. effect could be on mass loss, viability or energetic content, and differ in magnitude.

We observed seed mass to clearly decline across the winter (-38.4% on average for all species), especially so under flooded conditions, while at different rates between seed species (see also Nelms and Twedt, 1996;Foster et al., 2010;[START_REF] Collins | Decomposition of Three Common Moist-Soil Managed Wetland Plant Species[END_REF]. Cultivated rice and weedy rice lost significantly more mass across the winter under flooded than dry ricefield conditions: cultivated rice lost 46.2% of its mass under dry conditions on average, versus 62.3% if flooded; the corresponding figures in weedy rice were 26.6% and 45.3%. The magnitude of these differences was comparable to the results of Foster et al. (2010) for agricultural seeds. For the other species (barnyard grass and sea clubrush), no clear effect of flooding on seed mass loss could be detected here.

Viability of seeds generally decreased over time (-43.1% on average for all species), but the rate of such decline was greater under flooded conditions only for cultivated rice. Mean cultivated rice seed viability decreased from 99.0% at the beginning of the winter to 54.2% at the end of the season under dry conditions, versus 13.0% if flooded. For the other seed species, no clear effect of flooding on viability was detected.

In our study, we also considered seed energetic contents, with the aim to assess the value of seeds as waterfowl food. Rice farmers could be also interested in seed energetic contents if there is a threshold below which seed loose their capacity to germinate. We observed that energy density remained relatively constant, the mean number of kJ per gram seed only increasing by 3.75% over the winter, although greater under flooded conditions. The total amount of energy available to ducks from a given seed sample hence decreased, largely owing to the loss of mass not being compensated by the slight concentration of energy. Such loss of gross energy through the winter was relatively similar between flooded and dry conditions for most seeds. The only exception was weedy rice, whose gross energy loss was 42.4% if flooded, versus only 26.2% under dry conditions.

Contrary to earlier studies, we therefore did not observe ricefield winter flooding to be a beneficial practice for farmers in terms of reduction of the seed bank viability by the end of the winter (Street and Bollich, 2003;Manley et al., 2005;Anders et al., 2008;Fogliatto et al., 2010;Baek and Chung, 2012). However, it remains to be established (in particular for weedy rice) whether seeds would sprout and seedlings would grow to a similar extent after a flooded versus dry treatment by now studying germination rates and grown weed biomass (e.g. repeat Manley et al., 2005 methodology in dry and flooded conditions). For ducks, our results suggest that the quantity but not the quality of seed food decreases across the winter.

2/ no significant effect of duck foraging was found on the seed bank, which may be explained by the patchy distribution of the seeds (Article 5).

We tested the effect of ducks foraging during a whole winter on the seed bank at three densities: 5 ducks ha -1 (historical nocturnal wild duck density), 23 ducks ha -1 (current nocturnal wild duck density), and 300 ducks ha -1 (Asian rice-duck farming density).

The consequence of duck foraging on the seed bank of weeds and rice leftovers was not significant. In fact, compared to the initial situation, the ducks decreased the mean number of seeds per core sample by only 3% at the highest bird density, and the seed mass by about 21% (at both the lowest and highest duck densities), which was not significant. The lack of significant effects of the ducks on the seeds may be due to the very patchy distribution of the seeds in the rice field, resulting in a highly variable number of seeds per core sample.

These results are in opposition with previous studies, which showed wintering wild ducks to significantly reduce weeds (weed biomass was reduced from 204 to 89 kg/ha in van [START_REF] Van Groenigen | Effects of foraging waterfowl in winter flooded rice fields on weed stress and residue decomposition[END_REF]. However, despite these effects on seed density, [START_REF] Van Groenigen | Effects of foraging waterfowl in winter flooded rice fields on weed stress and residue decomposition[END_REF] did not observed differences in yield between areas that were visited by waterfowl and those where waterfowl were excluded. These results suggest that either the weed densities were not sufficient to impact yield, or that farmers were in all cases adequately controlling their weeds through other management approaches. This would also suggest that the direct benefits from waterfowl activity may be confined to extremely weedy fields, situations where farmers are not depending on herbicides for weed control, such as in organic production, or when waterfowl use the fields during the rice growing period rather than the winter inter-crop season (IRDF, Furuno et al., 2001).

3/ duck trampling and foraging on straw significantly reduce the standing stalks and contribute to their immersion, which may increase straw decomposition rate further still (Article 5).

Two Californian studies previously tested the hypothesis that foraging activities of waterfowl could facilitate straw decomposition in winter (Bird et al., 2000;[START_REF] Van Kempen | !-%)-&$.)-#'+A#->) ! "%%! ! "%&! II[END_REF] al., 2003). Both observed through experimental tests that the trampling of the ducks had a direct effect on the straw by flattening and cracking it, resulting in an increased contact with the soil and greater accessibility for microbial decomposers. Such waterfowl activity helped to reduce lignin and nitrogen concentrations in the surface residue, increasing rice straw decomposition, soil nitrogen availability, and straw incorporation into the soil. With high duck densities, disappearance of residual surface straw could increase by up to 76% (Bird et al., 2000). [START_REF] Van Groenigen | Effects of foraging waterfowl in winter flooded rice fields on weed stress and residue decomposition[END_REF] observed that straw biomass reduction in flooded fields with waterfowl was more than twice greater than without waterfowl. This is the first time that stalks have been considered since previous studies concentrated on lying residual straw. We simulated with many birds in a small enclosure over a short period of time the presence of a lower density of ducks during one whole winter. This prevented us from measuring straw decomposition over several months, but only stalk submersion (as opposed to Bird et al., 2000). The tests however showed that ducks reduced the stalks significantly, and that reduction increased with duck density: -27 % for 5 ducks ha -1 over a whole winter, -52 % for 23 ducks ha -1 , and -91 % for 300 ducks ha -1 , the Asian riceduck farming density. The results of these three studies demonstrate that rice farmers can expect winterflooding to promote straw decomposition but likely not a reduction of the weed seed bank by the end of the season. They also show that the expected benefits in terms of straw disposal can be enhanced further by the presence of foraging waterfowl.

!

INTRODUCTION

During winter, leftover seeds on the soil surface of rice fields are viewed as potentially troublesome weeds or rice yield loss by agronomists and farmers, while they are considered as a potentially valuable source of food for wintering wildlife by conservation practitioners (Rodenburg & Johnson, 2009, Stafford et al., 2010, respectively). The points of view of both groups of stakeholders are not necessarily mutually exclusive, since granivorous birds such as waterfowl can contribute to weed control (e.g. Smith & Sullivan, 1980;[START_REF] Van Groenigen | Effects of foraging waterfowl in winter flooded rice fields on weed stress and residue decomposition[END_REF] and some waterfowl-friendly management of the fields may also induce greater weed degradation (e.g. Street & Bollich, 2003, Manley et al., 2005).

Among such waterfowl-friendly post-harvest agricultural practices in rice fields, winter flooding is the most popular because it is relatively easy to implement, can readily provide significant agronomic benefits (Anders et al., 2008;Brogi et al., 2015), and makes waste seeds accessible to waterbirds (Eadie et al., 2008). This winter management practice is mainly applied in the U.S (Eadie et al., 2008) and in some regions of Japan (Fujioka et al., 2010), and to a much lesser extent in Europe (Pernollet et al., 2015a). In fact, most rice fields worldwide are kept dry during the post-harvest period. Besides the fact that dry conditions prevent most waterfowl foraging (Guillemain et al., 1999), the consequences of dry vs. flooded management for seed deterioration across the winter have been little studied (except for Foster et al., 2010;Fogliatto, Vidotto & Ferrero, 2010;Baek & Chung, 2012). Some similar comparative studies are available on seed dormancy break and germination [START_REF] Baskin | 0'5/5.+!(:&/&-+%6(5-(D+/%&'(-,552+/0(1(23!4(36&( ! $)$! and germination in Heteranthera limosa (Pontederiaceae), a summer annual weed of rice fields[END_REF].

Previous studies have reported that rice seeds are more resistant to decomposition under flooded conditions than some weed seeds and have higher nutritional values than other seed crops, hence being an important source of potential food to wintering birds (Nelms & Twedt, 1996;Kaminski et al., 2003). However, the rate of seed deterioration into water has been shown to differ between plant species (Nelms & Twedt 1996), some plants actually being favoured (Maria del Mar Catala com. pers.) or highly resistant [START_REF] Mesléard | Effects of seasonal flooding and grazing on the vegetation of former ricefields in the Rhône delta (Southern France)[END_REF], while others could be greatly reduced. For example, winter flooding has been reported as an efficient technique to reduce weedy red rice Oryza sativa var. (Fogliatto, Vidotto & Ferrero, 2010;Baek & Chung, 2012).

Published over-winter depletion rates of rice seeds in the U.S. ranged from 66 to 79% (Manley et al., 2004;Eadie et al., 2008), while a 89% and a 69% mass decrease have been recorded for rice and weeds in France, respectively (Pernollet et al., unpublished data). Decomposition, granivory and germination are the primary mechanisms of seed loss after harvest (respectively for rice: 58%, 14% and 8% in the Mississippi Alluvial Valley [MAV] after [START_REF] Stafford | Abundance and conservation of waste rice for wintering waterfowl in the Mississippi Alluvial Valley[END_REF], slightly more than 40% for rice deterioration according to Geer et al., 2009). Decomposition is usually defined as seed mass loss (Nelms & Twedt, 1996;Foster et al., 2010;[START_REF] Collins | Decomposition of Three Common Moist-Soil Managed Wetland Plant Species[END_REF], sometimes for specific weeds as decreased seed viability or germination capacity (Fogliatto, Vidotto & Ferrero, 2010;Baek & Chung, 2012), or as a reduction of weed plant biomass in spring (Manley et al., 2005). The potential decrease in seed energetic content is an important element to take into account when considering seed decomposition. Energetic content is obviously also of paramount importance to foraging animals, such that one of the criticisms made by Elphick et al. (2010) at the end of their literature review on rice farming and waterbirds was that scientists generally ignore the amount of energy and the nutrition value provided by these seeds for waterbirds (Checkett et al., 2002;Kaminski et al., 2003), and how that value might change throughout the winter (Nelms & Twedt, 1996). On the other hand, rice farmers may seem less interested in seed energetic content. However, the ability of plants to germinate and grow is clearly linked to the available energy in the seed that will be used the first days by the seedling [START_REF] Come | Les obstacles à la germination[END_REF], so whether or not a given winter practice may reduce weed seed viability is likely the most important issue to them. The simultaneous consideration of seed mass, seed energetic content and seed variability should help agronomists and ecologists to better understand the mechanisms of seed deterioration across the winter, and provide shared currencies for these stakeholders to evaluate the potential benefits brought by winter flooding of the rice fields.

This study undertook an evaluation of the effects of post-harvest ricefield flooding on changes in these three determinant variables across an entire winter for cultivated rice as well as three main weed seeds (Oryza sativa var., Echinochloa crus-galli and Bolboshoenus maritimus) which rice growers have to face. The test was conducted under laboratory conditions to focus on the effects of seed deterioration, discarding the potential effect of depletion by granivorous vertebrates and potentially also some invertebrates. An experimental approach was selected so as to isolate the deterioration processes at play while avoiding potential confounding effects from field conditions and to test whether winter flooding, 1) led to differential seed deterioration rates across the winter in terms of seed mass loss, changes in energetic content and seed viability, and how these variables were related to each other, 2) affected some seed species more than others, in particular rice versus weed seeds, and 3) determine what these results imply for rice growers and waterfowl conservation planners.

Methods

Study area, species, treatments and response variables

The experiment was conducted during the winter 2014-2015 in microcosms consisting of plastic trays positioned in a greenhouse (without temperature regulation) at the Tour du Valat Research Center situated in the delta of the Rhône River, Camargue, Southern France (43°30'N, 04°40'E). This delta, one of the only regions in France where rice is grown (around 15 000 ha of rice fields embedded into a 60 000 ha wetlands complex), constitutes the most important winter quarter for ducks in the country, and one of the most important at the European scale for these duck species (Tamisier & Dehorter, 1999;Critical Site Network Tool, 2015).

We assessed seed deterioration of cultivated rice (Oryza sativa L., common round bred cultivar "Gageron") and three rice weeds, i.e. two Poaceae (weedy rice Oryza sativa and barnyardgrass Echinochloa crus-galli) and one Cyperaceae (sea clubrush Bolboshoenus maritimus). These species were selected because they constitute the main rice weeds in the Camargue as well as in Europe [START_REF] Marnotte | Plantes des rizières de Camargue[END_REF], and because of their high occurrence in studies of migrating and wintering ducks' diet [START_REF] Guillemain | What is the spatial unit for a wintering teal Anas crecca? Weekly day roost fidelity inferred from nasal saddles in the Camargue, southern France[END_REF], i.e. they are important food to waterfowl.

At the end of October 2014, samples of soil and fresh mature seeds were hand collected just before rice harvesting time from twelve different rice fields cultivated in the conventional way (i.e. non-organic) from three different farms. All collected soil samples were mixed with each other before the experiments. The mature seeds were directly picked from the plants, and dried at 30°C to constant mass. The seeds from each species were then placed into labelled fine mesh polyester bags (mesh <0.05 mm) securely closed with staples in order to avoid contamination of the samples with seeds potentially present in the ricefield substrate, whilst at the same time still allowing chemical, gas and microbial exchanges with the substrate. Three sets of two grams of fresh seeds (from only one seed species at a time) were weighed to the nearest 0.1 mg and put in each bag. A first set of seed samples was prepared at the beginning of the tests but did not receive any treatment, and was considered as our initial starting point: "Time 1" (early winter, mid-October). The samples for Time 1 were as numerous as the samples for the other two times. The two other sets of seed samples received special treatments (described below) and were sampled (i.e. taken back from the microcosms) at two different periods during the winter ("Time 2" and "Time 3" described below). A total of 216 samples of 2 grams of each seed species were thus used (4 species x 3 treatments x 3 measurement periods x 6 replicates).

There were on average 79.8 ± 0.9 seeds of cultivated rice, 89.0 ± 2.0 seeds of weedy rice, 687.6 ± 0.2 seeds of barnyardgrass and 1156.3 ± 0.4 seeds of sea clubrush. Seeds of cultivated rice and weedy rice were counted in each sample, while the number of seeds per sample of the two other (much smaller) seed species were estimated by weighting 20 seeds 20 times, hence the difference in relative error compared to mean number of seeds above.

Three different environmental treatments were applied to the seed samples, contained in microcosms of 18 plastic trays (10 cm high and 8 liters volume), i.e. 3 treatments x 6 replicates = 18 trays per species and time period:

(1) "NON-FLOODED": the seed bags were buried within the upper 5 cm of the substrate, which was kept dry throughout the winter.

(2) "FLOODED": the seed bags were buried within the upper 5 cm of the substrate, which was flooded under 7 cm of water from the rice field irrigation network.

(3) "CONTROL": the seeds bags were left in water without ricefield substrate. This last treatment was identified as the control because it allowed us to assess if seed deterioration was due to water itself and/or the additive effect of the substrate and the microorganisms present in it.

Seed samples were progressively recovered from the trays and analysed at three times during the duck wintering time (between September and March), "Time 1" is hereafter referred to as T1 (prior to any treatment, early winter, 20th October), "Time 2" as T2 (mid-winter, 17th December, i.e. after 58 days of treatment) and "Time 3" as T3 (late winter, 20th February, i.e. after 123 days of treatment). The later period is comparable to the longest length of time that the rice fields in the area are submerged if they get flooded (October to mid-February; Pernollet et al., 2015).

At each time period three response variables were measured: remaining seed mass from the initial 2 grams (g), seed energetic content (kJ/g), and seed viability rate (ratio of live embryos to total live+dead ones).

Measurements

Prior to measurements of the seed samples at Times 2 and 3, the samples were lightly washed through a 300 µm sieve to remove silt and clay particles.

Seed viability

We used five randomly chosen seeds from each sample to estimate embryo viability using the standard tetrazolium method (De [START_REF] Vlaming | Dispersal of aquatic organisms: viability of seeds recovered from the droppings of captive killdeer and mallard ducks[END_REF]. Seeds were cut to expose embryos and put on a filter paper saturated with 1% tetrazolium solution in a Petri dish, then placed in the dark at room temperature for 24h. Seeds with a positive tetrazolium response (i.e. embryos were respiring and turning pink) were assumed to be viable [START_REF] Nachlas | Sites of electron transfer to tetrazolium salts in the succinoxidase system[END_REF]. Note that for cultivated and weedy rice, whose seeds are relatively heavy, five additional seeds were added to the initial 2 grams in each sample, in prevision for these viability tests. The seeds used for testing viability in these species were therefore not included in the weight measurement.

Remaining seed mass

Each sample was dried over several days at 30°C to constant mass, then weighed to the nearest 0.1 mg.

Seed energetic density

All samples were then placed into a Petri dish and sent to the CNRS Strasbourg university laboratory (Northern France). Each seed sample was freeze-dried (Lyophilizer Christ Alpha 1-4) to constant mass and ground to a fine homogeneous powder using a grinder (Retsch ZM1). Energy content was determined on c.a. 0.4 -1.4 g dry aliquots, weighed to the nearest 0.1 mg, using a calorimeter (Parr Instrument 6200) standardized with benzoic acid. We checked that there was a linear relationship between the mass of the samples and their energy content over this range of masses (r2=0,999, p<0.001, n= 20). For 57 % of the samples (depending on the total amount of powder available per sample) measurements were performed in duplicate (measurement reproducibility between duplicates = 0.6± 0.2%). We obtained energetic content per gram of dry mass, i.e. energetic density (KJ/g) for all 6 replicates of each seed sample for each treatment and each of the 3 time periods.

Statistical analyses

In order to test for potential differences among plant species in terms of seed mass loss over time and depending on treatment, we used the remaining mass of seeds (from the initial 2g) measured at Time 2 and Time 3, and ran a set of generalized linear mixed models (GLMM) with a Gaussian error structure including plant species, treatment (non-flooded, flooded, control), their interaction, and date to compare short vs. long floods/drought (Oct-Dec vs Oct-Feb) as fixed factors, and considered replicate (i.e., tray) ID as a random factor to take into account the pseudo-replication induced by the fact that some seed samples were in the same plastic tray.

For the energetic density of seeds, we first compared the mean species-specific values at the beginning of the experiment (T1). As significant differences were detected between plants (cf. results), we then considered the energetic density loss or gain ratio, i.e. differences between energetic densities in T2 or T3 and the average value in T1, divided by the average value in T1. GLMMs with the same fixed and random factors as above were then used.

For seed viability, each tested seed was attributed the value 0 when dead or 1 when alive. As above, we first compared mean viability rates between species at the beginning of the experiment (T1). We then ran GLMMs with viability data in December (T2) and February For mass analyses and energetic density of seeds, normal distribution of the residuals was tested prior to further analyses (Shapiro Wilk test) and no transformation was necessary.

For each of the three response variables, all plausible models were ranked and the best models were selected using the Akaike Information Criterion (AIC) considering all models with ∆AIC < 2 from the best model as equally good at fitting the data. The relative performance of the models was assessed by their AIC weight (Burnham & Anderson, 2002). Overall significance of fixed variables was tested by analysis of deviance. When a significant effect was detected (deviance test, P < 0.05), we performed pair-wise comparisons of means using Tukey's post-hoc test to assess whether the differences between the components of the variables were significant or not for the target modelled variables (procedure details in Burnham & Anderson, 2002).

Unless otherwise stated, all information presented in the text and in the graphs refer to predicted values extracted from the best models. Means are given with their 95 % confidence intervals or range. All analyses were conducted using R version 3.1.3 (R Core Team, 2013), with libraries 'lme4' (Bates et al., 2014), 'nlme' [START_REF] Pinheiro | nlme: Linear and Nonlinear Mixed Effects Models[END_REF] 'AICcmodavg' [START_REF] Mazerolle | AICcmodavg: Model selection and multimodel inference based on (Q)AIC(c). R package version 2[END_REF] and 'multcomp' [START_REF] Hothorn | Multcomp: simultaneous inference in general parametric models[END_REF].

RESULTS

Remaining seed mass

The best model for explaining remaining seed mass across the winter was the full model including all tested variables, i.e, species, treatment, their interaction and the time period (GLMM, X 3 15 = 222.66, P < 0.001, Table 1). This model accumulated 99% of AIC weight and all included variables were significant at P < 0.001. Mean remaining seed mass differed between seed species (F 3,116 = 59.07, P < 0.001), with sea clubrush samples retaining a greater mass over time than cultivated rice (z = 5.31, P < 0.001), barnyardgrass (z = 3.72, P = 0.001) and weedy rice (z = 3.09, P = 0.01) (the other pairwise differences between species being non-significant). Non-flooded, flooded and the water control treatment had a different influence on remaining seed mass (F 2,15 = 17.78, P < 0.001), with greater average remaining mass in non-flooded than flooded (z = -5.43, P < 0.001) and non-flooded vs. control (water alone: z = 3.22, P = 0.004) conditions. Flooded conditions with only water (i.e. control) did not induce different average remaining seed mass than the proper flooded treatment with ricefield substrate (z = -2.21, P = 0.07) (Fig. 1). The period effect was significant (F 1,116 = 245.91, P < 0.001), with lower remaining seed mass at T3 than T2, i.e. longer treatments having a greater effect on remaining seed mass (z = -15.68, P <0.001). Considering the effect of the species-treatment interaction and discarding the control treatment, we found seed mass lower in flooded than non-flooded conditions for cultivated rice and weedy rice (respectively: z = -4.67, P < 0.01; z = -5.43, P <0.01). The treatment effect was not statistically significant for barnyardgrass and sea clubrush seeds (respectively: z = -1.57, P = 0.92; z = -0.51, P = 1.00).

Across the winter, model estimates suggest cultivated rice lost 46. 2% [41.3-51.2] of its mass under dry conditions on average, versus 62.3% [57.4-67.3] if flooded; weedy rice lost 26.6% [21.6-31.5] of its mass under dry condition versus 45.3% [40.4-50.3] 6% [35.7-45.6] and 24.4% [19.4-29.3] of their mass across the winter, respectively (Fig. 1).

Seed energetic density

Mean energetic density differed among seed species at the beginning of the experiment (F 3,68 = 275.8, P < 0.001, Adjusted R 2 : 0.92). From the richest to the poorest, we found sea clubrush (19.7 kJ/g [19.5-19.9]) > barnyardgrass (18.3 kJ/g [18.2-18.4]) > weedy rice (16.9 kJ/g [16.8-17.0]) > cultivated rice (16.5 kJ/g [16.3-16.8]).

The best model for explaining change of seed energetic density across the winter was the same as for remaining seed mass, i.e. the full model including all tested variables: species, treatment, their interaction and period (GLMM, X 3 15 = 114.2, P < 0.001, Table 2). This model accumulated 92% of AIC weight; all single variables were significant at P < 0.001 and the species-treatment interaction at P = 0.016. Energetic density of seed increased across the winter (Period: F 1,115 = 39.41, P < 0.0001), with a greater effect from T1 to T2 than from T1 to T3 (z = 6.24, P < 0.0001). Non-flooded, flooded and the water control treatment had a different influence on changes in seed energetic density (F 2,15 = 61.43, P < 0.001), with a lower positive effect in non-flooded than flooded (z = 6.31, P < 0.0001) or non-flooded than control (water alone: z = -5.23, P = 0.004) treatments, while the effects of control and flooded conditions did not differ (z = 1.08, P = 0.53) (Fig. 2). Considering the species-treatment interaction, and discarding the control treatment, we found flooded conditions induced a greater increase in seed energetic density than dry conditions for all species, except for sea clubrush where no significant treatment effect was detected (z = 2.21, P = 0.54).

Across the winter, all seed species concentrated energy under all treatments, but estimates from the best model suggested cultivated rice concentrated 4% more energy per gram on average when flooded compared to non-flooded, with similar effects of flooding compared to non-flooding being 4.5% for weedy rice, and 4% for barnyardgrass (Fig. 2).

Table 2 Model selection to evaluate the influence of species (rice, weedy rice, barnyardgrass, cosmopolitan bulrush), treatment (non-flooded, flooded, control), species*treatment and period (T2, T3) on energetic density change (difference between energetic density at T2 or T3 and the average value at T1, divided by the average value in T1). Numbers of parameters (K), Akaike's Information Criterion (AIC), difference from lowest AIC value (∆ AIC), and model weight (wi) are provided for plausible model sets involving main effects and the key interaction. Random factor: replicate (i.e. tray) ID.

Model

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Seed viability

Seed viability differed among plant species at the beginning of the experiment (F 3,30 = 4.90, P < 0.007, Adjusted R 2 : 0.26). This viability was significantly higher for cultivated and weedy rice than for sea clubrush (t = -3.68, P = 0.005 and t = -2.98, P = 0.03, respectively) while the other comparisons yielded non-significant results. From the greatest to the lowest initial seed viability we found cultivated rice (99.0% [96.9-100]) > weedy rice (96.9% [93.0-100]) > barnyardgrass (93.3 [89.6-97.1]) > sea clubrush (88.9% [84.5-93.2]).

The best model for explaining viability of seeds across the winter was, as above, the full model including all the tested variables i.e, species, treatment, their interaction and period (GLMM, X 2 14 = 79.92, P < 0.001, Table 3). This model accumulated 99% of AIC weight; period and the species-treatment interaction had a significant effect at P < 0.001, species and treatment were significant at P = 0.001 and P = 0.002, respectively. Viability of seeds decreased across the winter (T2 compared to T3, z = -4.00, P < 0.0001). Average seed viability was greater in non-flooded conditions than in the water-only control (z = 2.86, P = 0.01) but was not different from the flooded treatment (z = -2.05, P = 0.10), which itself did not differ from the water-only control (z = 0.87, P = 0.66). Considering the species-treatment interaction, and disregarding the control treatment, cultivated rice was the only species with lower seed viability in flooded than in non-flooded conditions (z = -4.50, P < 0.01) (Fig. 3). Across the winter, mean cultivated rice seed viability decreased from 99.0% [96.9-100] at T1 to a mean of 54. 2% [39.2-68.4] at T3 under dry conditions, versus 13.0% [6.7-23.9] at T3 if flooded. Weedy rice seed viability changed from 96. 93% [92.98-100] at T1 to a mean of 66. 7% [51.6-78.9] in dry and flooded condition at T3. Barnyardgrass seed viability decreased 9% [45.7-74.2] in dry and flooded condition at T3. Finally, sea clubrush seed viability changed from 88. 9% [84.5-93.2] at T1 to a mean of 57.0% [41.8-71.0] in dry and flooded condition at T3 (Fig. 3).

Table 3 Model selection to evaluate the influence of species (rice, weedy rice, barnyardgrass, sea clubrush), treatment (non flooded, flooded, control), period (T2, T3) and species*treatment on seed viability across the winter 2014-2015, in microcosms positioned in a greenhouse at the Tour du Valat Research Center, Camargue, Southern France. Numbers of parameters (K), Akaike's Information Criterion (AIC), difference from lowest AIC value (∆ AIC), and model weight (wi) are provided for plausible model sets involving main effects and the key interaction. Random factor: replicate (i.e. tray) ID.

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Fig. 3 Predicted viability (%) for seeds of cultivated rice and the three main rice weeds (weedy rice, barnyardgrass, sea clubrush) computed from estimates from the best selected model (cf. Table 3), after being left in dry ricefield substrate or submerged in flooded ricefield substrate during the winter 2014-2015, in microcosms positioned in a greenhouse at the Tour du Valat Research Center, Camargue, Southern France. Viability of seeds was estimated at T2 (58 days) and T3 (123 days)(vertical lines). The control treatment (water only, with no substrate in trays) did not significantly differ from flooded (see text) and is therefore not represented.

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DISCUSSION

The fate of rice leftovers and weed seeds across the intercrop season is important to farmers and conservationists alike: for the former, reducing the weed seed bank may be a major issue since encroachment by undesired plants is a major limiting factor of rice cultivation worldwide (Baki et al., 2000;Oerke, 2006;[START_REF] Marnotte | Plantes des rizières de Camargue[END_REF]Anders et al., 2008;Rodenburg & Johnson, 2009). For the latter, who view harvested rice fields as a potential foraging habitat for wildlife, seed abundance across the winter may determine field attractiveness and overall habitat carrying capacity (e.g. Manley et al. 2004, Stafford et al. 2006,). Despite the fact that the objectives of these two categories of stakeholders are different, some agricultural practices, especially the winter flooding of the harvested fields, have been recognised as mutually beneficial since they allow reduction of weed abundance while making the seeds available to foraging waterfowl (Eadie et al., 2008versus Anders et al., 2008).

Besides depletion by granivorous waterfowl and other vertebrate and invertebrate foragers, the seed bank of rice fields is decreased across the winter by seed deterioration (Geer et al., 2009). Agronomists have mostly considered such deterioration through the proportion of viable seeds at the end of the winter, as this will determine weed infestation of the next crop (Baek & Chung, 2012). Ecologists and wildlife managers have rather been interested in the mass of seeds available to foraging animals (Nelms & Twedt, 1996;Foster et al., 2010;[START_REF] Collins | Decomposition of Three Common Moist-Soil Managed Wetland Plant Species[END_REF]. With a few exceptions (studies on seed dormancy break and germination : Fogliatto, Vidotto & Ferrero, 2010;Baek & Chung, 2012), seed deterioration has in both cases mostly been evaluated through field experiments (on weedy rice from ecologists and agronomists, respectively: Manley et al., 2005 andFogliatto, Vidotto &Ferrero, 2010). Albeit very conclusive in most cases, and often showing a positive effect of winter flooding on seed deterioration rates, such field studies do not easily allow assessing the mechanism by which the seed bank is reduced (e.g. loss of seed components, death of the seeds, depletion by invertebrates, etc). By isolating factors in microcosms in a greenhouse experiment, this experiment allowed us to assess more precisely some of the mechanisms by which seed deteriorate across the winter, and the effect of flooding without any consumption by vertebrates and large invertebrates. In particular this experiment allowed us to study the importance of seed energetic contents on the deterioration process, which had not so far been analysed. The measurement of mass and energy help us to have a clear idea of what may provide the flooding of rice fields to birds during the wintering season [START_REF] Miller | The allometric relationship between resting metabolic rate and body mass in wild waterfowl (Anatidae) and an application to estimation of winter habitat requirements[END_REF] on waterfowl energetic requirements).

As expected, we observed seed mass to clearly decline across the winter, especially so under flooded conditions, and at different rates between seed species (Nelms & Twedt, 1996;Foster et al., 2010;[START_REF] Collins | Decomposition of Three Common Moist-Soil Managed Wetland Plant Species[END_REF]. Energy density remained relatively constant, since the average 3.75% increase in kJ/g was statistically significant, but likely biologically insignificant. Viability of seeds generally decreased over time (-43.1% on average for all species), but the rate of such decline was greater under flooded conditions only for cultivated rice.

Seeds lost 38.4% of their initial mass on average. Flooding led to cultivated and weedy rice seeds to loose 1.35 and 1.70 times more mass than under dry conditions, respectively, which is comparable to the 1.4-3.3 times increase recorded by Foster et al. (2010) for agricultural seeds under flooded versus dry conditions. These authors hypothesized that the differences in rates of loss between seed species could be due to easier microbe colonization after differential softening, dwelling and deterioration of seed coat by water. The similarity in seed mass deterioration between the water-only and the water+sediment treatments in our experiments, suggests a major role of water and water microorganisms per se than the soil chemicals and microbial activity. Following on to Foster et al.'s (2010) hypotheses, the cultivated and weedy rice seed coat, in particular, may have been particularly deteriorated by water in our study. Our mean rice seed mass loss under flooded conditions (62.3%) was somewhat greater than the value obtained by Geer et al. (2009) in field experiments (44 to 47%) or the results of Nelms & Twedt (1996), i.e. 20% rice seed mass loss, which led these authors to conclude that rice seeds were particularly resistant to deterioration in water than most grains and natural foods. It is possible that the experimental conditions in trays (e.g. different temperature regimes) led to a greater rice mass loss than what would have been observed if the seeds had remained in the sediment of a proper field. However, under similar conditions the mass of the different seed species tested decreased at different rates, and not all seeds were similarly affected by flooding.

Earlier studies considered that seed mass loss and nutrient loss were likely correlated for most plant species (McGinn & Glasgow, 1965). However, some authors conversely hypothesized that seed deterioration through mass loss to winter flooding may actually reduce the value of seeds to foraging waterfowl by the end of the winter (Naylor et al., unpublished). Our results clearly showed that energy density was not gradually lost through the winter but rather slightly increased, especially under flooded conditions, although to a very moderate extent (3.75%). We can hypothesize that some of the energy reserves initially present in the seeds possibly became slightly concentrated in the developing embryo during the winter, but the main result is therefore that the intrinsic quality of the seed material remained globally constant throughout the winter, regardless of flooded/dry conditions.

From the point of view of waterfowl, the slight gradual concentration of energy in the seeds did not compensate for the general loss of seed mass, so that the total energy available (expressed in kJ rather than kJ/g seeds) markedly declined over the winter (range -22.3 to -62.3%, Table 4). The gross energy loss through the winter was relatively similar between flooded and dry conditions for most seeds. The only exception was weedy rice, whose gross energy loss (for one initial gram of seeds) was 42.4% if flooded, versus only 26.2% under dry conditions. As opposed to earlier studies suggesting that cultivated rice would represent a better forage to waterfowl than weeds (Kaminski et al., 2003), our results conversely suggest that, for a similar initial mass of seeds, cultivated rice was the poorest food resource and sea clubrush the richest, the difference between these seed species gradually increasing across the winter in both flooded and dry conditions (Table 4). Besides energy density, it is a fact that seeds vary in size, morphology, digestibility and chemical composition among species, all of which influence potential energy gain for waterfowl (Hagy & Kaminsky, 2015). The true metabolizable energy of seeds has already been quantified in earlier studies, and found to be 3.34 kcal/g for cultivated and weedy rice (Reinecke et al., 1989), 2.61 kcal/g for barnyardgrass seeds (Checkett et al., 2002) and 3.12 kcal/g for sea clubrush (Legagneux, 2007). Although rice would therefore seem more digestible than the weed seeds, this suggests the latter are, for a similar seed mass, a more profitable food resource for wintering waterfowl owing to the overall lower gross energy content of cultivated rice. Some authors also highlighted that rice seeds alone cannot provide a balanced diet, as they have high carbohydrate contents and are poorer in protein, fat, potassium, calcium and nitrogen than moist-soil seeds (Eadie et al., 2008;Stafford et al., 2010). The greater size of rice seeds compared to weeds may potentially (partly) compensate for the lower energy content of the former, through more efficient foraging by the ducks (e.g. Van Eerden and Munsterman, 1997). This can explain why rice, although not as energy-rich than some weed seeds, nevertheless represents a significant part of the wintering duck's diet wherever available (e.g. Brochet et al., 2012). Apart from weedy rice, which may deteriorate more rapidly if flooded, our experiments finally suggest that flooding harvested rice fields would not cause a faster decline of the energy available to waterfowl compared to dry conditions.

From the point of view of the farmers, what matters the most is whether the decreased seed mass and gross energy recorded above would translate into a reduced development of the weeds during the following cropping season. We did observe a general decrease in seed viability from post-harvest (October) to late winter (February): while most seeds were initially alive, only 56.9% were so on average at the end of the experiment. This may be related to the general loss of energy per seed we recorded (seed energy density per gram slightly increased while seed mass markedly declined over the winter). In fact, the results above indicate a similar rate of gross energy loss between flooded and dry conditions for most seeds (Table 4), and viability of such seeds also declined at similar rates whatever the treatment received by the seeds, suggesting a mechanistic link between the two parameters. The only exception was cultivated rice, whose viability was reduced to ca. 13% in flooded trays compared to only 54% in dry ones. Rice was also the species that lost the most mass across the experiment and had the lowest remaining energy content at the end of the winter, especially under flooded conditions.

As opposed to earlier studies, our results suggest limited impact of winter flooding on weed seed viability, while Fogliatto et al. (2010) recorded a 95% decrease for weedy rice in flooded fields compared to 26-77% if unflooded, and the same figures in Baek & Chung (2012) were 49% versus 10%. In our study, the average 96.93% [92.98-100] viable weedy rice seeds showed a reduction of 22.8% [12.5-37.8] of their viability under dry condition, versus 43.8 [29.7-59.0] if flooded, which was not significantly different. It is a fact that the tetrazolium test we used to assess seed viability is relatively difficult to interpret [START_REF] Justice | Essentials of seed testing[END_REF], so that the great variability in viability rates may have prevented the detection of a significant difference in weedy rice. It is also possible that the climatic conditions this winter were relatively comfortable for the seeds, so that overall mortality was low. In particular, the 2014-2015 winter was particularly mild in the Camargue, with a month of November that was the hottest since 1963, the temperature of December above the average (8.45°C versus 7.2°C) and only 4 days of frost in December and January (frost above -1°C) (P. Chauvelon, Tour du Valat, unpublished data). Colder weather may have a differential effect on the seeds, which could potentially suffer greater mortality under flooded conditions if the water freezes (Baek & Chung, 2012).

To summarize, our study provides another demonstration that rice and weed seeds lose mass and viability during the winter. Our experiments in microcosms showed that seed energy density remained relatively constant, but the gradual loss in seed mass led to a declining gross energy per seed, which may have been the cause of decreased seed survival. Gross energy loss for a given seed species was generally similar between flooded and dry conditions, as was seed viability in weeds. As opposed to earlier studies, we did not observe post-harvest flooding to be a beneficial practice for farmers in terms of reduction of the seed bank viability by the end of the winter (Street and Bollich, 2003;Manley et al., 2005;Anders et al., 2008;Fogliatto, Vidotto & Ferrero, 2010;Baek & Chung, 2012). This cannot therefore be recommended specifically for this purpose, but it remains to be established whether seeds would sprout and seedlings would grow to a similar extent after a flooded versus dry treatment. In any case, other studies showed that winter flooding could bring other benefits to farmers in terms of straw disposal (Brogi et al., 2015) or income from hunting (Niang et al., submitted). Our results also suggest that post-harvest practices would hardly affect energy availability to ducks, which would decrease across the winter in any case. However, water is necessary for these birds to efficiently forage (Guillemain et al., 1999), so that this practice should be promoted to increase waterfowl habitat availability. Several countries have already recognised the potential of ricefield flooding to create suitable habitat for wintering waterfowl, and help farmers to implement this technique via financial incentives such as agrienvironment schemes (Pernollet et al., 2015b). The present results suggest that gross energy available to ducks would not be reduced through seed deterioration by this practice, which should therefore be further implemented in wider geographic areas.

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The "first fruit" made with duck feathers by Samuel Lei, California

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IV.1 Could a change in postharvest agricultural practices be simultaneously beneficial to rice farmers and wintering ducks?

To investigate whether 'win-win' agricultural scenarios for rice producers and waterfowl conservation could exist within intensive European rice production areas, especially in France, we relied on a variety of approaches including a literature review (Chapter I, Article 1), empirical (Chapter II, Articles 2 and 3) and experimental studies (Chapter III, Articles 4 and 5) in the general conceptual framework of optimal foraging by birds, agro-ecology and ecosystem services.

Reviewing the scientific literature on rice farming and duck conservation worldwide, we identified winter flooding of rice fields as a valuable habitat management, providing potential benefits to ducks through the direct @'$! 0A! +B*&%@C,@*+C! A&$C1'! +'! D&.,$*&.B! E+F&,+,', and to farmers through the increase of straw decomposition rate and the reduction of weed seed viability by water and waterfowl action (Article 1). The studies implemented here to test whether similar benefits could be expected in Europe and most particularly in France confirmed that winter flooding of harvested rice fields is indeed a valuable management option, with identified benefits for both wild ducks and farmers. We demonstrated a general pattern of positive correlation between ricefield winter flooding area and the size of regional wintering duck populations along their flyway in south Western Europe (Article 2). Through the study of the processes at play at a more local scale, we concluded that any flooded nonploughing agricultural management would actually be suitable to wintering waterfowl in Camargue, as any of these options would readily allow waterfowl accessing the abundant seed food stocks (Article 3). Relatively simple management procedures such as winter flooding can therefore be adopted to improve the usability of these habitats for wintering waterfowl. In return, rice farmers can expect straw disposal to be enhanced by the presence of foraging waterfowl in winter flooded fields (Article 5). Based on these ecological and agronomical results, we conclude that winter flooding should be promoted for waterbirds in Camargue and anywhere else it is technically feasible. When implemented through Agri-Environment Schemes (AES) in Spain such a practice has proven to be an efficient measure, quickly translating into improved local duck population trends (Article 2).

Although the results of this research project are clear and the various facets of the analyses are consistent with each other (compare the various papers), this study has its own limits.

The literature review only met 14 of the 27 methodological criteria defining a systematic review according to [START_REF] Roberts | Are review articles a reliable source of evidence to support conservation and environmental management? A comparison with medicine[END_REF] (Article 1). Among the criteria that were not met is for instance the detailed explanation for inclusion/exclusion of studies, the performing of a meta-analysis, and the sensitivity analyses. Several of these limitations are actually due to the literature sources themselves, which often did not provide proper quantitative information and/or were difficult to compare to each other owing to their own very qualitative narrative style. Nevertheless, particular attention was paid to consider both negative and positive interactions between rice farming and duck conservation, to cover all the geographic areas and to mix sources of information as much as possible, as a fully systematic review would require. The literature review also allowed identifying evidence gaps or areas lacking knowledge to tackle the relevant issues initially defined, and provided recommendations for future topics still requiring investigation. Nevertheless, this review did not allow us to answer all the initial questions, particularly those related with potential

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conflicts between ricefield winter flooding for waterfowl and alternative practices aiming at other environmental goals (e.g. reduction of greenhouse gas emissions). Still, it provided a valuable basis within which to frame the overall thesis. In particular, this called for a precise examination of the potentially mutually beneficial relationships between farming practices and waterfowl conservation within any given study area (Chapters II and III), as well as a proper economic evaluation of the balance between expected costs and benefits of winter flooding for the rice farmers and the local society, which is presented below (Article 6).

The possible links between postharvest flooding of rice fields and regional abundance of wintering waterfowl were assessed in five Western European landscapes. These areas were highly contrasted in terms of relative natural or semi-natural wetlands versus ricefield areas, and differed markedly in the proportion of rice fields being flooded. Such massive differences in overall habitats may have somewhat over-amplified the positive correlative relationship between flooded habitat cover and the number of counted ducks (Article 2). In other words, flooding a given previously dry ricefield region may not necessarily always induce an increase in duck numbers of the same order of magnitude than the differences we recorded between our Spanish, French and Italian regions. However, this correlation study was also backed up by the « experiment » caused by the introduction of the AES winter flooding in Spain, which effectively led to positive changes in long-term population trends. It is true that some of these new birds may have come from the Camargue, so that this latter site could maybe not be considered as a proper control when assessing trends in duck numbers, but once again the results were so clear and consistent that we are confident that winter flooding of rice fields does translate into higher duck numbers. We do not recognize the latitude as a factor explaining the small number of ducks wintering in the Italian study area rather than the lack of winter flooding, as there are major duck wintering sites at the same latitude (e.g. Venice Lagoon, [START_REF] Heath | Important bird areas in Europe: priority regions for conservation: Southern Europe[END_REF], and recent studies showed that in response to the increasingly mild winter conditions and hot summers, some wintering European duck species are shifting north-eastwards [START_REF] Gunnarsson | Direct and indirect effects of winter harshness on the survival of Mallards Anas platyrhynchos in northwest Europe[END_REF][START_REF] Lehikoinen | Rapid climate driven shifts in wintering distributions of three common waterbird species[END_REF]. The potential of improving the agricultural matrix for waterbirds in the Pô Plain through the introduction of ricefield winter flooding hence sounds realistic, and such new artificial wetlands would likely be readily used by ducks short-stopping (sensu [START_REF] Elmberg | Interpreting seasonal range shifts in migratory birds: a critical assessment of 'short-stopping' and a suggested terminology[END_REF] along their flyway.

When trying to assess how habitat use by ducks could be modified by such possible changes in agricultural practices, through the empirical study of food resources in Camargue rice fields and nocturnal ducks counts, it was not possible to obtain a proper random sampling of the post-harvest practices in the 50 rice fields (Article 3). Indeed, most farmers did not accept to profoundly alter their practices for the project without financial support. We thus had to select farmers that already flooded their fields during winter, most of them doing so year after years for duck hunting purposes. Such stability in the practices may cause habituation of the birds to the use of some fields (wintering ducks can be very faithful to restricted geographic areas, e.g. [START_REF] Guillemain | What is the spatial unit for a wintering teal Anas crecca? Weekly day roost fidelity inferred from nasal saddles in the Camargue, southern France[END_REF], which could be a different behaviour than if the rice fields where flooded for the first time and each farm was covered by a greater diversity of practices. However, admittedly the idea would be that winter flooding becomes a traditional practice in Camargue in the future, which Article 2 showed could sustain greater wintering duck numbers in the long run.

The nocturnal surveys with the light amplifier presented in Article 3 only provided information about duck numbers and ricefield use, but did not inform about habitat preferences or selection, since only rice fields were investigated. Further studies on food resource availability in other foraging habitats (natural wetlands as well as artificially baited

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ones) and with radio tagged or gps-tagged birds would help to improve our understanding of duck movements and preferences for foraging habitats including rice fields, natural wetlands, wetlands managed for hunting etc...

It is true that such nocturnal counts could potentially be biased by imperfect estimation of bird numbers, double counts or imperfect detection. However, the rice fields are small (2.5 ha on average in the Camargue, Mouret, pers. comm.) and we counted birds once flying, which reduced our probability to miss ducks standing in the stubble. In any case the results were very explicit, since nocturnal duck density in flooded Camargue rice fields was among the highest ever recorded (our mean nocturnal density was 24 ducks/ha, when maximum historical averages ranged between 5 and 15 ducks/ha: [START_REF] Pirot | Effects of agri-environmental schemes on farmland birds: do food availability measurements improve patterns obtained from simple habitat models?[END_REF]Mesléard et al., 1995), while dry fields were virtually devoid of any waterfowl during the night. Although the precision of the measurements could probably be improved (e.g. by correcting for detectability, Defos du Rau, 2003), the pattern is therefore very clear and established.

The two experimental tests were set up so as to isolate some of the processes related to agronomic benefits to farmers. Again the results were clear, with ducks in flooded fields bringing benefits in terms of straw disposal, but little effects of the birds or flooding itself in terms of depletion of the seed bank (Articles 4 and 5). Owing to the artificial situation of the experiments, these obviously had their own limits too. For example, the climatic conditions inside the greenhouse may have been different than in the proper fields, which may have caused different seed degradation rates (Article 4). The greenhouse experiment could also be extended in the future to consider seed germination and seedlings emergence after the flooding treatment, to properly assess the potential of winter flooding to organically control the weed plants during the next cultivation cycle, not just the viability of the weed seeds at the end of winter.

The test with the wing-clipped ducks also had to be conducted over a limited period of time for obvious constraints linked with the use of penned birds. We simulated the presence of a lower density of ducks during one whole winter by using many birds in a small enclosure over a short period of time. This prevented us from measuring straw decomposition over several months, but only stalk submersion (Article 5). However, in these two experimental papers the processes at play are clearly identified and the trends in the results are consistent and convincing. These studies hence already provide valuable results, which could be further improved by future complementary experiments.

IV.2 What could habitat management on rice production sites imply for duck conservation?

The dabbling ducks wintering in the rice field regions of Europe belong to several flyways or populations (depending on species, refer to delineations in [START_REF] Szabolcs | Report on the Conservation Status of Migratory Waterbirds in the Agreement Area[END_REF]. These populations do not currently cause major conservation concerns at the flyway scale and are all classified as "least concern" by the IUCN (2014) because their numbers are increasing (Gadwall, Teal, Mallard), stable (Wigeon, Shoveler) or fluctuating (Pintail) [START_REF] Szabolcs | Report on the Conservation Status of Migratory Waterbirds in the Agreement Area[END_REF]. Anyway, these birds provide important cultural ecosystem services, in particular through their aesthetical value and through hunting (Mathevet, 2000). Although their population trends are generally positive, dabbling ducks are nevertheless among the waterbird species known to be particularly affected by changes in land use at the local scale, be these positive or negative (e.g., Duncan et al., 1999;[START_REF] Mathevet | Creation of a nature reserve, its effects on hunting management and waterfowl distribution in the Camargue (southern France)[END_REF].

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The Camargue is the most important winter quarter at the national scale for four of the six studied duck species (i.e., Mallard, Teal, Wigeon and Gadwall, Deceuninck et al., 2014), and hosts a significant proportion of the total French numbers: on average over the surveys 1965-2015 28% of the gadwalls, 26% of the shovelers, 21% of the wigeons, 20% of the teal, 10% of the pintails and 8% of the mallards (Deceuninck et al., 2014;A. Tamisier, M. Gauthier-Clerc and J.B. Mouronval unpublished data). It is also one of the most important winter quarters for dabbling ducks in general at the European flyway scale (Critical Site Network Tool, 2015). It is therefore relevant to assess how changes in Camargue habitat management may impact duck migration processes and population dynamics, both locally and at the flyway scale, especially when breeding and wintering habitat modifications, wetland disappearance or degradation are considered as the most important threats for these species (Cahiers Habitat Natura 2000[START_REF] Fuller | Birds and habitat: relationships in changing landscapes[END_REF].

The link between local land use changes and waterbird population trends at local and flyway scales have been established in two previous studies showing that waterbirds using rice fields show more positive population trends both in Spain [START_REF] Rendón | Status, distribution and long-term changes in the waterbird community wintering in Doñana, southwest Spain[END_REF] and in Europe (Toral and Figuerola, 2010). The results of the Article 2 also suggest that agriculture management could have an important impact on duck populations at both the local and the flyway scales. Now considering that in Camargue: 1) availability of nocturnal foraging sites has been identified as a limiting factor for ducks (Brochet et al., 2009), 2) ducks are relatively faithful to their roosting sites across the winter [START_REF] Guillemain | Winter site fidelity is higher than expected for Eurasian Teal Anas crecca in the Camargue, France[END_REF]2010) and fly short distances for feeding [START_REF] Guillemain | Hunting bag and distance from nearest day-roost in Camargue ducks[END_REF], and 3) many potential foraging grounds in harvested fields exist but are not used by ducks because they are kept dry during winter, we can safely hypothesize that ricefield winter flooding would immediately benefit to wintering ducks, which would start relying on these on a regular basis during the winter. Through greater wintering site attractiveness, we can hypothesize changes in residence time (Spanish Ebro Delta [START_REF] Ferrer | Els poblaments hivernals d'anàtids[END_REF]versus Oltra et al., 2001; for Camargue Teal: Guillemain et al., 2015a in Appendix I.2), and changes in duck distribution (California duck wintering range shifted towards the Sacramento Valley when rice fields got flooded, [START_REF] Fleskes | Waterfowl Distribution, Movements and Habitat Use Relative to Recent Habitat Changes in the Central Valley of California: A Cooperative Project to Investigate Impacts of the Central Valley Habitat Joint Venture and Changing Agricultural Practices on the Ecology of Wintering Waterfowl[END_REF]. All of this would imply that the provision of flooded rice fields would not only translate into a punctual or seasonal use by ducks during a given winter, but that strong wintering traditions could develop in these valuable habitats (see also Guillemain et al., 2015a in Appendix I.2), hence translating into improvement of population dynamics rather than only the temporary satisfaction of bird energy needs. Indeed population trends actually increased after ricefield winter flooding AES implementation in the Spanish regions (Article 2).

We can hypothesize that a wide implementation of ricefield winter flooding in Camargue would influence duck movements and distribution locally, and have a positive effect more broadly on the duck populations. However, we largely ignore what would simultaneously happen in the other foraging habitats (shallow natural wetlands or hunting marshes) of the Camargue agricultural-wetland mosaic. Furthermore, at a larger scale, northeastwards distribution shifting of wintering populations [START_REF] Gunnarsson | Direct and indirect effects of winter harshness on the survival of Mallards Anas platyrhynchos in northwest Europe[END_REF][START_REF] Lehikoinen | Rapid climate driven shifts in wintering distributions of three common waterbird species[END_REF][START_REF] Dalby | Waterfowl, duck distribution and a changing climate[END_REF][START_REF] Elmberg | Interpreting seasonal range shifts in migratory birds: a critical assessment of 'short-stopping' and a suggested terminology[END_REF] are currently occurring, largely due to favorable wintering conditions at higher latitudes. Changes in duck migration patterns at any given site result from both the changes in habitats of that area and those up and down the flyway (Guillemain et al., 2015a;2015b Therefore, beyond an expected general improvement of the local habitat conditions for ducks, it is hard to predict from empirical and experimental studies such as those presented in this thesis what the consequences could be locally in terms of nocturnal duck distribution, and at the larger scale in terms of population dynamics. However, such studies like ours can provide valuable parameter values to feed modelling exercises. This is a project we have started to implement during this PhD, and plan to develop further in the near future.

The aim is to rely on predictive modelling to evaluate the likely consequences of alternative ricefield management in the Camargue -namely winter flooding at a large scale within the Camargue mosaic-on dabbling duck individual variables (i.e., body condition, survival, habitat use and time budget). To reach this goal we set-up a collaboration with Professor John Eadie and his team at the University of Davis (California), who have been developing a powerful spatially-explicit agent-based model called SWAMP (Spatially-explicit Waterbird Agent-based Modeling Program: Miller et al., 2014). This model is relatively similar to the European MORPH model [START_REF] Stillman | MORPH-an individual-based model to predict the effect of environmental change on foraging animal populations[END_REF]. The most recent (so far unpublished) version of SWAMP is really adapted to our question as it allows the integration of agricultural landscape GIS and simulates the movements of ducks between daily roosting areas and nocturnal foraging patches. Furthermore, it is far more precise than energetic models (e.g. TRUEMET: Petrie et al., 2014), as it does consider heterogeneity in individual behaviour and body condition (allowing to run simulations with ducks having different lipid reserves).

SWAMP simulates the movements of a target community of ducks (Forager list) considering for each species their own diet (Diet Type) within a landscape (vector GIS layer) composed of patches (Patch type) of rice (dry, flooded, ploughed), moist soil wetland reserves (private, public) and maize Zea mays more or less forageable, considered as roosting, foraging or both habitats and including food items (gathered in a Food list) (see model flowchart on Figure 9). Each food is characterized by its own density, attack rate, handling time and decay (e.g. rice, maize, Echinochloa crus-galli, Crypsis schoenoides, Polygonum spp.). It is possible to add Disturbance Events (X times per hour) where ducks are flushed from the patch and fly to the closest patch but are not killed. The foragers enter progressively into the system across the winter, simulating gradual migration, and disperse to landscape foraging patches. They learn from each other and go foraging to the closer patch below a maximum duck density until reaching their lipid reserve needs or resource depletion reaches the giving-up density. Competition between foragers is indirect: depletion of food resources by one forager reduces the efficiency of subsequent foragers on that patch. After a simulation of one night, outputs are provided in terms of amount of energy remaining in the landscape, number of birds below their minimum lipid reserves and dying, total and average energy intake and demand of the duck community, use of each patch by the ducks and their timebudget, etc. A grant from the Doctoral School of the University of Montpellier allowed for a threeweek internship with Professor Eadie and his team in California in February 2015. This period was spent learning about the model and its constituents, and determining the required changes for applying SWAMP to Camargue agricultural scenarios. During the internship we could run two preliminary simulations, one with Camargue rice fields flooded and one with only dry rice fields, which aimed at testing the integration of the GIS layer (relying on a land use study made in 2011 by the Camargue Natural Park, PNRC, 2013a) with defined roosting wetlands and rice fields and the real Camargue ducks numbers (average aerial counts per species per month 2000-2012), but without changing the species diet and food availability compared to the Californian settings. Food items (Tamisier and Dehorter, Article 5), Food availability (Tamisier and Dehorter, 1999, natural seed degradation : Article 3, Article 5), and Diet Type (for Teal and Mallard, Brochet et al., 2012) data are all available and will be considered in future model runs. We will validate that the model produces reasonable outputs using our food depletion data (Article 3), the data from our nocturnal surveys in rice fields (Article 3), and existing hunting bag data (J.-Y. Mondain-Monval unpublished data). However, modelling the movements of the wintering ducks between roosting and foraging sites in Camargue will demand some code modifications, to include seed consumption by other granivores (cranes that forage on dry rice fields, wildboars, rats, etc), hunting processes (baiting, disturbance, actual mortality of the ducks) and large-scale duck movements during

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the winter (resident versus transient individuals, [START_REF] Guillemain | What is the spatial unit for a wintering teal Anas crecca? Weekly day roost fidelity inferred from nasal saddles in the Camargue, southern France[END_REF]. Finally there is relatively little information available on food availability in natural wetlands (Tamisier and Dehorter, 1999), so the sensitivity of the model to such parameters should be evaluated. ( Miller et al. (2014) proved that SWAMP can be implemented to make predictions about duck conservation issues and help in management decision-making by testing different landscape change scenarios, hence helping current and future waterfowl management in California. Applying SWAMP in Camargue will allow similar projections to be made, and is among the next steps we plan to implement in the near future. Camargue farmers, stakeholders and decision makers are used to collaborate with scientists through joint modeling exercises (e.g. in the Tour du Valat Research Center: Mar Ô Sel software, http://www.mar-o-sel.net, [START_REF] Lefebvre | Contribution of rainfall vs. water management to Mediterranean wetland hydrology: Development of an interactive simulation tool to foster adaptation to climate variability[END_REF]. We believe that the provision of a powerful spatially-explicit agent-based model would greatly help rice farmers and land managers consider the consequences of rice field post-harvest management practices, and potentially changing for those we have demonstrated in this thesis as being the most beneficial to duck conservation.

"#$%!What could habitat management on rice production sites imply for rice farmers, for society and for decision makers?

For farmers, the main concern when deciding which field management to practice outside the cropping season is the cost of the various management options, so we concluded this PhD work by performing an economic evaluation of these as well as potential ecosystem services. The idea was to associate to our ecological results presented at length above an assessment of the economic balance of ricefield winter flooding.

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We carried out a cost-benefit analysis to evaluate whether winter flooding in France would be economically realistic considering the constraints linked with flooding costs. In fact, contrary to the Spanish area where the Agri-Environmental Schemes "ricefield winter flooding" have been implemented, and where most of the flooding is done passively by gravity, in Camargue water must be actively pumped from the Rhône River and pumping costs constitute a main preoccupation for farmers that have multiple post-harvest options (Article 6, Appendix 3).

In addition to water pumping costs, this analysis was completed considering the market and non-market costs and benefits (i.e., agronomic and environmental benefits) of six different inter crop management sequences (post-harvest scenarios) including the use of different machinery in dry or flooded conditions (Figure 10). This analysis was carried out at both the individual farmer scale and a more macro societal scale. At the individual farmer scale, in addition to the costs of tillage operations and water pumping, waterfowl hunting and savings on pesticides or fertilizers though agronomic benefits were considered. At the macro societal scale, greenhouse gas emissions costs and ecosystem services such as landscape improvement with flooding generating cultural services (ecotourism, birdwatching) were considered. To briefly summarize the results, the current traditional and tolerated burning-ploughing practice barely reaches a financial equilibrium for the farmer (lowest benefits-to-costs ratio, although still above 1), and was associated with greater costs than benefits at the society level (benefits-to-costs ratio < 1). Such a practice hence seems no longer acceptable by society, largely because of greenhouse gas emission costs and the lack of ecosystem benefits that flooded fields can provide. The other scenarios were all economically realistic for both the farmer and society (benefits-to-costs ratios > 1). Harvesting rice in flooded fields was four times more profitable to farmers and more than eight times more profitable for the Camargue society than the traditional burning-ploughing (benefits-to-costs ratios for farmers: 4.15 vs. 1.02; for society: 6.67 vs. 0.78). The sensitivity analysis confirmed the robustness of the above results, since the ranking of the different scenarios generally remained the same even with very large (sometimes unrealistic) changes of the value of the cost or benefit estimates one by one.

The present results suggest that winter flooding in the Camargue is economically viable for individual farmers and is strongly beneficial for the macro society. Although the winter flooding scenarios are economically beneficial to farmers, there may still be some psychological hurdles to overcome (e.g. risk of accident associated with the use of cage-wheel tractors which may flip over). More information of the agricultural community about the possible indirect benefits brought by flooding may help the implementation of this technique. Providing financial incentives to farmers to flood the fields, like in Spain, may however be necessary to initiate winter flooding and allow them realizing the likely benefits of this practice. The benefits-to-costs ratios of winter flooding for society are so high that they would remain well above 1 even if a financial incentive was paid to farmers. Economic valuation of ecosystem services has been advocated by a growing number of environmentalists as a short-term strategy to communicate the value of biodiversity in a language that reflects dominant political and economic views. It can provide complementary insights into sustainable ecosystem management and policy (Turner et al., 2000). However, the association of an economical value to ecological goods and services (direct market goods, non-market goods) is highly critical and should be taken with caution [START_REF] Lant | The tragedy of ecosystem services[END_REF]Gomez-Baggethun and Ruiz-Pérez, 2011). The limits of such an evaluation in our study system have been discussed at the end of Article 6 (Appendix I.1).

For the real implementation of winter flooding at a large scale in Camargue rice fields, spatial analysis should be carried out to determine where in the delta it would be both easier and safer to flood and drain the rice fields. Depending on topography, Camargue farmlands are divided into "highlands" where altitude is greater than one meter, as opposed to "lowlands" (Monier et al., 2009). Rice is grown on the "highlands" in rotation with other cereals (wheat, maize, sorghum) and forage (alfalfa), and in monoculture on the salty, hydromorphic and difficult to drain "lowlands" (Mouret, 2013), where alternative crops are limited by soil salinity (Barbier and Mouret, 1992). In 2011, 8867 hectares (55%) of the cultivated fields of the Camargue Natural Regional Park were "highlands" and 7170 ha (44%) were "lowlands" (unpublished data extracted from land use study of Camargue in 2011, PNRC, 2013a). In the "lowlands", most farmers let water enter their fields from the irrigation network by simple gravity. In the "highlands", farmers must rely on an additional pump. Furthermore, catastrophic rainfall events are not infrequent (last flooding event in 2003) and if the Rhone River, the Vaccarès lagoon or the sea water levels are too high, it is not possible to drain the fields and the system is saturated with water. With climate change, such events may become more frequent. Assessment studies are currently carried out in the Camargue to improve the drainage systems owing to such potential risks of flood in the future (PNRC, 2013b). Potential implementation of rice field winter flooding in the area should be done while considering such water pumping constraints and risk assessments. Some ecological constraints may also potentially have to be considered in the future: in the Ebro Delta many rice fields have actually been kept dry or flooded with sea water over the recent years as a measure against the spread of the exotic apple snail Pomacea insularum, [START_REF] Curcó | Cens hivernal d'ocells aquàtics al delta de l'Ebre[END_REF].

Economics and politics are the main driving factors of European rice production, which represents only 0.5% of the world production (FAOSTAT, 2012). The French production represents 4% of the European total, virtually all in Camargue. It has a low productivity and competitiveness due to relatively inappropriate climatic conditions and lowest access to pesticides compared to biggest and most powerful Spanish and Italian rice productions (C. Thomas, com. pers.). As a consequence, the French rice production is highly fluctuating depending on the national financial incentives and world market prices (Figure 11), which induce rapid changes in economic activity strategies of the Camargue properties and translate into fluctuating Camargue landscapes [START_REF] Picon | L'espace et le temps en Camargue: essai d'écologie sociale[END_REF]. After having been introduced in Camargue after the Second World War, replacing vineyards and a total of 40 000 ha of natural habitats (33 000 ha wetlands, [START_REF] Tamisier | A review of habitat changes in the Camargue: assessment of the effects of the loss of biological diversity on the wintering waterfowl community[END_REF], rice farming collapsed from about 32 000 ha in 1960 to only 4 000 ha by 1980. Support form the E.U. and improvement in the agricultural techniques allowed a recovery of the local rice-farming industry thereafter, which was associated with crop intensification, replacement of manual rice transplanting by mechanized sowing, hedges removal and increase of mean field area. As part of the CAP 2015 reform, a series of Agri-Environment-Climate Schemes (AECS) associated with rice production and aiming to support environment and climatefriendly agricultural practices (e.g. mechanical false seed bed, dry sowing, laser surfacing, ban on straw burning) via financial incentives have been introduced to compensate for the average shortfall in earnings of c.a. 250 Euros/ha compared to the earlier situation (maximum contribution: 369 Euros/ha for two supplementary years of rice production). As a comparison, the promotion of ricefield winter flooding in the Spanish Ramsar sites was through a ca. 60 €/ha incentive through agri-environment schemes, an amount that would seem feasible in Camargue for the next CAP reform (Article 2). However, even in Spain the financial crisis and associated political decisions likely induced the end of the winter flooding incentive to rice farmers in Albufera de Valencia since 2012. Flooding the rice fields may not be regarded as the absolute panacea, as this may be conflicting with concerns and programs on reduction of greenhouse gas emissions (European project tested in France, http://www.greenrice.eu/about-us/, http://www.sostrice.eu/en/ in Spain), except as an alternative to straw burning (Couderc, 2013). It may also counteract efforts to reduce water consumption (http://www.greenrice.eu/about-us/) or promote organic rice farming (Mouret, 2013), as winter flooding implies successive years of rice production (because autumn crops cannot be sown), while organic rice farming often relies on regular and rapid rotation with other crops. However, ricefield winter flooding is in conformity with, or complementary to, most of the concerns and management programs of the European and French rice production organizations: search for alternatives to rice straw burning (Monier et al., 2009 in France; ECORICE-Sustainable management of the rice straw LIFE04 ENV/ES/000184, Albufera de Valencia), reduction of pesticides (National Plan Ecophyto 2018 in France), reduction of soil salinity (rice tolerance to salinity, project France AgriMer, European project NEURICE). In this context, the current rice "crisis" calls for new research, and alternative management such as winter flooding may be supported for both the agronomic and environmental opportunities it could represent, hence opening the way for new income to rice farmers during a difficult period for them. !

IV.4 CONCLUSION: What these results imply -and do not imply-for Camargue land management

This Phd work was focused exclusively on the dabbling duck community using rice fields and on the non-cropping period. We are aware that ducks do not constitute the whole bird community found among ricelands and that the sole post-harvest period does not evaluate the importance of rice production for birds in general [START_REF] Tourenq | Valeurs et fonctions des rizières pour les communautés d'oiseaux d'eau en Camargue[END_REF][START_REF] Toral | Agricultura y Conservación en Doñana: La Importancia del Arrozal para las Aves Acuáticas[END_REF]. During the intercrop period, rice fields have also been shown to be important for other waterbirds such as Black Godwit Limosa limosa (Lourenço and Piersma, 2008;[START_REF] Lourenço | Site selection and resource depletion in Black-tailed Godwits Limosa l. limosa eating rice during northward migration[END_REF], Snipe Gallinago gallinago [START_REF] Beck | Impact of winter management of the Camargue rice fields on the aquatic macroinvertebrates and the common snipe (Gallinago gallinago)[END_REF], White Stork Ciconia ciconia, Eurasian Spoonbill Platalea leucorodia [START_REF] Marti | Atlas de las aves reproductoras de Espana[END_REF] etc, which may not necessary be favoured by the same water levels or post-harvest practices (Toral et al., 2011). While positive for ducks, flooding of rice fields in winter may hence potentially have negative consequences for other birds (Elphick, 2004). In fact, dry rice fields also constitute a suitable habitat for other birds (e.g. raptors, passerines, Elphick, 2004). Wintering crane (Grus grus) numbers have been increasing quickly in the dry rice fields of Camargue over the very last years. We actually performed diurnal and nocturnal surveys of the waterbird community in the rice production area of Doñana in the delta of Guadalquivir in November 2014. Fields with different straw and water management were covered, allowing a broader reflection on the consequences of post-harvest practices for the entire avifauna community, not just waterfowl. These data are still being analysed.

Earlier research in the Camargue, which was conducted across the whole year but limited to diurnal surveys, concluded that bird diversity was lower in rice fields (31 species) than in natural marshes (59 species) (Tourenq et al., 2001). Our results actually show that natural wetlands and flooded rice fields (acting as semi-natural wetlands) are complementary. We do not ignore that winter flooding, although beneficial to ducks, is not necessary the best option for biodiversity in general [START_REF] Tamisier | A review of habitat changes in the Camargue: assessment of the effects of the loss of biological diversity on the wintering waterfowl community[END_REF], see also above). Our aim here was to re-establish the function of duck foraging habitat by appropriate management of harvested rice fields, which could be used by the birds in parallel to more natural habitats. It is also important to note that we are not advocating the conversion of natural marshland into rice

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fields, only a change in the management of existing fields to make these accessible to foraging ducks.

The mutually beneficial option that winter flooding could represent for waterfowl and farmers opens the dialogue and research collaboration between ecologists and agronomists. Agronomists have started to work on new farming strategies in Camargue (e.g., Jaek, 2010;[START_REF] Mouret | Compte rendu d'étude scientifique. Plan d'adaptation de la filière riz (année 5)[END_REF]. These studies however mostly consider the promotion of organic farming in the Camargue. Conversely, how to improve the currently dominant conventional rice farming by integrating agronomical and ecological approaches has received very limited attention so far. The wide introduction of winter flooding could be a strategic way to gain the best from recent knowledge obtained in these two disciplines. In the context of the current rice production problems, actually causing a decline in Camargue rice area, winter flooding may also open the way for new income to rice farmers and contribute to overcome the crisis.

Changes in the Common Agriculture Policy have recently caused the reduction of Camargue ricefield area by one third, inducing two major changes in the landscape: the increase of fallow and the development of dry crops. Some increase in fallow area had already been noticed in the 2011 Camargue land use study (PNRC, 2013a), and is expected to keep on expanding, mostly on salty low altitude lands. These areas may represent a good opportunity for wetland restoration plans. In fact, as for the rice production area of Doñana in the delta of Guadalquivir, the restoration of former rice fields into marsh areas (Mesléard et al., 1995;[START_REF] Muller | Restauration de marais temporaires et de pelouses méso-xériques à partir d'anciennes rizières: Rôle respectif des filtres dans l'assemblage des communautés[END_REF] could complement the maintenance of rice cultivation flooded during winter in other areas. This would seem a more environmentally friendly strategy than the transformation of these abandoned rice fields into cotton (Doñana), tomato fields (Camargue), or solar farms [START_REF] Toral | Agricultura y Conservación en Doñana: La Importancia del Arrozal para las Aves Acuáticas[END_REF].

At the beginning of this PhD, we wondered if sustainable intensification could be possible within European rice fields. We were able to demonstrate that 'win-win' agricultural scenarios for rice producers and waterfowl conservation are possible within these intensive production areas, especially in France. The last step of the adaptive conceptual framework is then to share the results to facilitate learning. Such communication is necessary to bridge the gap between researchers, land managers (including farmers) and decision makers, to confront common and different visions of the landscape [START_REF] Vuillot | Paysages agricoles et biodiversité dans les représentations sociales et les modèles mentaux des agriculteurs. Une approche comparée de quatre régions françaises[END_REF], and to ease practical implementation. This is what we have initiated with key Camargue and European audiences (Appendix III). The results have been well received by farmers, hunters, and conservation managers alike. Due to the iterative nature of the adaptive management cycle, this final "learning" step is also often an important input for the next steps of the project cycle. We hope that the results of this PhD will contribute to increase the conservation value of rice fields while maintaining the economic viability of productive agriculture. ! $+"!

Introduction

Rice cultivation is associated with a range of constraints for farmers. First, the flooding of the ricefield during growth creates favorable conditions for a range of weeds, some of which are pioneer species in temporary wetland ecosystems, meaning that they are very fast-growing and successful in seasonally flooded habitats (e.g. Cyperaceae, Baki et al., 2000;Oerke, 2006;Anders et al., 2008;Rodenburg and Johnson, 2009). Rapid colonization by weeds often limits the quantity of successive years of rice cultivation. As a result, farmers must come to a compromise between regular crop rotation or the heavy use of herbicides, hence largely being prevented from switching to organic farming [START_REF] Palvadeau | Etat des connaissances scientifiques et techniques et perspectives de recherche[END_REF]. Another problem that rice farmers face is the high silica content of rice straw, limiting the use as a compostable biproduct (e.g. wheat straw used as litter for livestock) and requiring farmers to dispose of rice straw without any foreseeable benefit. The simplest method for rice straw disposal is burning, which has long been and is still practiced in many areas (Monier et al., 2009). However, greenhouse gas emissions, air pollution issues caused by fine particles and other problems linked with smoke created by burning fields have led to the ban of this technique in some areas (e.g., California Rice Straw Burning Act 1991 in Anders et al., 2008), calling for alternative practices.

One alternative practice is to flood the rice fields after harvest. This has proven an efficient means of promoting straw decomposition (review in Pernollet et al., 2015a). Furthermore, some weed seeds have also been shown to loose mass or viability more rapidly in flooded conditions, thereby potentially reducing the need for herbicides (Manley et al., 2005;Fogliatto et al., 2010). Flooding rice fields after harvest also creates vast areas of shallow wetlands. These are artificial habitats, yet they provide very attractive grounds for a large number of wintering waterbirds (Eadie et al., 2008;Pernollet et al., 2015b). The birds could provide additional benefits by themselves further promoting the decomposition of straw by trampling and dabbling (Bird et al., 2000;Brogi et al., 2015) and the consumption of some weed seeds [START_REF] Van Groenigen | Effects of foraging waterfowl in winter flooded rice fields on weed stress and residue decomposition[END_REF], see however Brogi et al., 2015). Summarizing all the above, a recent literature review concluded that the promotion of winter flooding in harvested rice fields would be a win-win strategy by which farmers could support wildlife conservation while also gaining agronomic and other ecosystem service benefits (Pernollet et al., 2015a). A preliminary approach considering potential savings on direct costs suggested winter flooding would be economically beneficial (Manley et al., 1999;2005), but to date a thorough economic evaluation of winter flooding considering all costs of field flooding, tillage operations, savings on nitrogen and pesticides costs, financial incentives or income from hunting, ecotourism or other ecosystem services still had to be carried out and was greatly required (Manley, 2008).

Flooding rice fields during winter may be costly because of the energy required to pump the water. To overcome these costs, subsidies are often given to farmers who undertake winter flooding (e.g. in California, The Nature Conservancy, 2014;in Spain, Pernollet et al., 2015b). In France rice is primarily grown in the Camargue, a vast delta created by the two branches of the Rhône River. Compared to other major waterbird winter quarters in Europe, the Camargue still has extensive areas of natural wetlands. To date only 9% of the Camargue rice fields are flooded in winter compared to 62% in the Ebro delta and Albufera de Valencia, Spain. The post-harvest flooding in the Camargue is mostly for hunting purposes and Camargue farmers receive no financial incentives for flooding (Pernollet et al., 2015b). This may restrict the development of winter flooding of the Camargue rice fields, which is further limited by the fact that Camargue farmers have to pay pumping costs while in other areas (e.g. the Ebro Delta) the fields can be flooded simply by gravity. Therefore the most common practice in the Camargue remains the rapid burning of the straw after harvest, followed by ploughing of the dry fields during winter (75% of the residual rice straw still undergoes burning in Camargue, the remaining 25% mostly being chopped, Monier et al., 2009). Despite the agronomic and environmental benefits potentially brought by post-harvest flooding of rice fields, this will only be implemented by farmers if it is financially acceptable. The aim of the present paper was therefore to conduct a proper cost-benefit analysis of ricefield winter flooding to determine whether this would be an economically feasible option for French rice farmers. We also compared the benefits-to-costs ratio with alternative farming practices during the nongrowing season, including the current burning-ploughing practices (Monier et al., 2009).

Beyond the individual farm, we analysed the potential costs and possible benefits to society, so as to discuss whether financially supporting Camargue rice farmers with public funds to flood their fields during winter would be appropriate.

Methods

Study area

The Camargue delta (43°30'N, 04°30'E) covers about 145,000 ha, of which ca. 15,000 ha are currently cultivated in rice (Parc Naturel Régional de Camargue hereafter PNRC, 2013a).

Water is pumped from the Rhône River and subsequent provision is through a network of canals and channels maintained by specific local organisations (Associations Syndicales Autorisées -ASAs). All farmers pay the ASA for irrigation rights except the farmers located along the river who may use private pumps directly from the Rhône. Farmers that want to flood on the more elevated lands (hereafter high lands, above 1m high, 55% of the total agricultural area) have to use an additional private pump, either a tractor-held pump or private electrical pumps. The fields are most generally dried out during the end of summer to allow harvest in late September or early October, using a drainage network also ran by ASAs. Given that organic farming comprises less than 6% of the cultivated land [START_REF] Palvadeau | Etat des connaissances scientifiques et techniques et perspectives de recherche[END_REF], our analysis was restricted to conventional farms only. Furthermore, the straw management options are similar in organic and conventional farming.

Economic evaluation

We relied on a cost-benefit analysis (CBA), which is based on the economic efficiency criterion, simply measuring whether the total benefits of a particular action are larger than the total costs [START_REF] Hanley | Pricing nature: cost-benefit analysis and environmental policy[END_REF]. Such analyses are becoming increasingly popular with policymakers and have been applied in the context of conservation justification (Turner et al., 2000), conservation controversy [START_REF] Macmillan | Costs and benefits of wild goose conservation in Scotland[END_REF] or in environmental impact assessment such as energy projects [START_REF] Snyder | Ecological and economic cost-benefit analysis of offshore wind energy[END_REF].

We used benefits-to-costs ratios of various selected farming scenarios outside the rice growing season. Compared to alternative approaches such as cost-efficiency analysis or multicriteria analysis, the CBA has the advantage of considering costs and benefits in the same monetary unit [START_REF] Pearce | Analyse coûts-bénéfices et environnement. Développements récents[END_REF].

We first held key informant interviews with agricultural engineers and farmers to identify the most common practices used by Camargue rice farmers to manage their fields from harvest to the beginning of the next growing season. We also identified the most likely alternatives for field use after rice harvest, including winter flooding. For each scenario we listed all potential costs and benefits, separating those experienced by the individual farmer and those for society as a whole (including the farmer, to get a comprehensive balance). For each cost or benefit, we obtained quantitative estimators (expressed in €/ha) from literature searches and data collection from the key informants. The geographic scale of analysis covered the total 11,390 ha of Camargue rice fields within the Camargue Natural Park in 2014 (France AgriMer, unpublished data), and the temporal scale of analysis was limited to the period from harvest to straw incorporation into the soil. All costs and benefits considered hence pertain to one single cultivation cycle and values were adjusted by taking inflation rates into account from the year they were collected to year 2014 (INSEE, 2014: www.insee.fr). A simple ratio of benefits on costs was then computed to evaluate each scenario compared to the current burning-ploughing practice, and a sensitivity analysis was conducted to evaluate the extent to which changes in the parameters would potentially change such evaluation, at the individual farmer and the societal scales (for more methodological details and limits of cost-benefit analysis, refer to [START_REF] Hanley | Pricing nature: cost-benefit analysis and environmental policy[END_REF].

Agricultural scenarios

A total of six inter crop management sequences, called scenarios hereafter, were considered in the analysis, combining the various options available to farmers at each stage from harvest to the end of the winter (Table 1).

In addition to winter flooding we tested only the most common current practices. Harvest was included because whether it is done on dry fields (as most often is the case) or in fields still flooded (practiced only in a few Camargue farms, but largely used in Spain) will profoundly affect the subsequent operations and costs. Straw can either be chopped during harvest, with the addition of a crusher onto the combine harvester itself, or concentrated as swath by the harvester and later burnt. Fields dry at harvest may or may not be subsequently flooded, then potentially drained again. The soil may either be worked deeply (ploughing, only in dry fields) or more superficially (using a cover-crop in dry fields, cage-wheels or rototiller in flooded fields). For each of these sets of practices we then listed the costs and benefits. This encompassed market costs and benefits (those directly costing or bringing money to the farmer, including lost opportunity costs and avoided costs) as well as non-market ones (e.g. environmental damages, ecosystem services, also relevant to society) (see appendices 1 and 2 for full details). Some costs or benefits were not included in the present analysis (indicated by a star in the two appendices). In some cases this was because no quantitative estimate could be found (e.g. yield loss of the cumulated effect of crop lodging and harvest in flooded condition, future costs associated with the degradation of soil structure by ploughing, benefits provided by straw burning in terms of reduction of weeds and rice diseases). Some other items were considered negligible at the present time (risk of overexploitation of water resources, given that water comes from pumping in a very large river very close to its mouth, catastrophic floods due to heavy rains associated with flooded rice fields, given the effective drainage network provided by the ASAs), but could be necessary to consider in the future. Finally, some costs or risks were considered highly unlikely, especially since the analysis was carried out at the scale of one single cultivation year. These elements included the risk of fire associated with the burning of straw and the accident risk to farmers associated with the use of cage-wheel tractors, which may occasionally flip over.

Market costs: irrigation and drainage costs for the farmer

As explained above, irrigation and drainage services and maintenance in the Camargue are provided to rice farmers through a collective system managed by the ASAs. All owners of land within the area of a given ASA have to pay a basic annual fee called "ordinary cost" to contribute to the running of the system (the fees are divided into irrigation and drainage costs as they might not concern the same ASA). Farmers using water to flood their fields pay a second fee termed "exploitation fee". This value depends on the number of hectares to be flooded and the crop to be grown (based on the water needs for each crop). Each ASA determines its own basic and exploitation fees. There are a total of 22 ASAs in the territory of the Camargue Natural Park. Because rice fields are currently flooded mostly during the rice growing period (spring and summer), there is no established value for the cost of winter flooding. This may theoretically be greater given the higher cost of electricity during winter (as prices generally change in November), but farmers may also benefit from cheaper "summer" prices if they were flooding their fields right after harvest (during early October). The analysis was hence conducted using current summer prices, but simulations were made during the sensibility analysis to evaluate the performance of scenarios with field flooding at increased winter pricing. Farmers pay per hectare to be flooded, not per water depth, i.e. volume of water to be pumped. In all simulations, we considered that farmers would pump water only once, after harvest, and would then close the water gates to keep the water in the fields until February. This pumped water would be combined with winter rains (average 58.0 mm across winter, PNRC, 2013b). We used the mean exploitation fees for irrigation (considering that the ordinary role for irrigation is already paid for the previous rice growing period), and the mean ordinary drainage fee over all Camargue ASAs, yielding an average cost of 111.47 €/ha for irrigation and 18.22 €/ha for drainage (raw data, ASAs, unpublished data). In the low lands, most farmers let water enter their fields from the ASA network by simple gravity. In the high lands, farmers must use an additional private pump. Considering this is mostly done using a tractor-held pump (electrical pumps also exist, but the cost of their use was unknown) with a 1800 m 3 /h debit held by a 90 hp tractor using 6 litres of fuel per hour and the need to pump 10,000 m 3 /ha (yielding a ca. 10cm water depth, the ideal depth for foraging ducks), on high lands farmers would pay an additional 24.97 €/ha to flood their fields. Farmers harvesting flooded fields were considered to be able to retain water from the cultivation phase in their fields during the next winter, i.e. would pay no irrigation costs, only the drainage ordinary cost. All scenarios including some degree of flooding include basic drainage fees. The irrigation and drainage costs of each scenario are given in Table 2, separated according to low and high lands. For computing the benefits-to-costs ratios we only considered the high lands and a systematic use of winter drainage, so as not to artificially favour the flooded scenarios by the cheaper irrigation costs of low lands.

Lost opportunity costs for the farmer: fertilization to compensate for nutrient losses to fire

Rice produces ca. 6 tons of dry vegetal matter per ha (seeds excluded), of which 5.1 tons are cut straw, and 0.9 tons (15%) are stalks and roots [START_REF] Mouret | Compte rendu d'étude scientifique. Plan d'adaptation de la filière riz (année 5)[END_REF]. Burning one ton of cut cereal straw leads to the loss of 6 nitrogen units, 2 phosphorus units and 12 potash units, corresponding to 12.9 € of fertilizers to be added for compensation [START_REF] Peloquin | Comment mettre en place un échange paille-fumier (ou autres déjections) ? Chambre d'Agriculture des Deux-Sèvres[END_REF]. Burning the 5.1 tons of straw cut per hectare instead of crushing and incorporating it into the soil would hence force farmers to spend an additional 69.41 €/ha on fertilizers (inflation included).

Non-market costs: Greenhouse Gas Emission costs for the society

The only non-market costs which were considered regular enough to be included into the analysis (see above) were those linked with Greenhouse Gas (GHG) emissions. We considered GHG in the form of CO 2 , CH 4 and N 2 O linked with fuel combustion by machinery use, straw burning, and soil emissions caused by incorporation of straw and flooding of the rice fields. Because they were unknown, we did not consider GHG emissions resulting from energy used by irrigation and drainage pumps of the ASAs (note that many of these are electric). Emissions linked with production, transport, storage and use of fertilizers and pesticides are known to be a major source of GHG emission in agriculture (e.g. Couderc, 2013), but were not considered here as these are used during the rice growing period. We first quantified soil emissions of CO Finally, some CH 4 is also emitted by ricefield soils, especially if flooded, corresponding to 3 kg/ha/day after [START_REF] Roger | L'émission de méthane par les sols : mécanismes, intensité et régulation[END_REF]. This is equivalent to 360 kg CH 4 or equivalent 9 tons of CO 2 over the 120 days of the study period. To summarize, Table 4 shows the total greenhouse gas emissions and their cost value for society under each of the 6 agricultural scenarios. The first set of potential benefits for the farmer is avoided costs, i.e. saved expenses owing to the use of alternative methods. The first of these avoided costs relates to dry organic matter incorporation (either by ploughing, use of cover-crops, rototilling or use of cage wheels). This follows an inverse reasoning compared to losses due to burning the straw described above.

Incorporating one ton of rice straw or stalks corresponds to a saving 12.9 € per ha on fertilizers [START_REF] Peloquin | Comment mettre en place un échange paille-fumier (ou autres déjections) ? Chambre d'Agriculture des Deux-Sèvres[END_REF]. As we have previously mentioned, one hectare of rice produces ca. 6 tons of dry matter [START_REF] Mouret | Compte rendu d'étude scientifique. Plan d'adaptation de la filière riz (année 5)[END_REF]. When straw is burnt only the stalks can be incorporated, reducing dry matter inputs. Considering that this represents approximately 15% of the total dry matter, only one ton of dry matter is incorporated when the fields are burnt. With a 5.5% cumulated inflation rate from 2010, incorporating the residual dry matter from a burnt field (i.e., only stalks and roots) brings a 13.61 € saving per ha. When straw is chopped instead of burnt the entire 6 tons of dry matter can be incorporated, equating to 81.66 € saved on fertilizer costs per hectare.

The second set of potential savings is related to herbicides: first, flooding rice fields during winter is known to reduce some of these weeds, in particular weedy rice (Oryza sativa var.) whose viability is reduced by up to 95% (Fogliatto et al., 2010). Using the guide on weed . Secondly, when farmers can grow several types of crops in their field, crop rotation between rice and wheat (or alfalfa when possible) also constitutes an efficient means of controlling weeds (e.g. [START_REF] Hammond | Aspects techniques, économiques, sociaux, environnementaux. Agriculture biologique-questions posées à la recherche. Riziculture Camarguaise. La durabilité des systèmes de production agricole. Analyse des points de vue des riziculteurs camarguais[END_REF].

In our case crop rotation was assumed to be possible only and implemented always following the dry scenarios 1 and 2. According to CFR (2011), such crop rotation would impact a wider range of weeds than only weedy rice, corresponding to a savings of 225 € on herbicides per ha. , 2005). Here we only considered the two such incentives of the last CAP revision that can be received by rice farmers for practices implemented outside the crop-growing season. Measure "Couver16" supports the incorporation of rice straw (owing to the likely benefits in terms of reduced need for fertilizers and absence of air pollution with straw combustion). This measure is contracted for a three-year time period. Measure "Irrig09" is contracted for two additional years of rice cultivation and supports flooded crops (rice). In our study, all scenarios with winter flooding (which impose a subsequent flooded crop owing to the inability to implant a dry crop such as winter wheat), i.e. scenarios 3-6, were considered to receive a 44.76 € incentive per hectare with measure "Irrig09". All scenarios where straw is chopped and later incorporated (2, 4, 5 and 6) were considered eligible to "Couver 16", i.e. would receive 180.74 €/ha. Scenarios where straw is chopped and incorporated, in fields that are also flooded (i.e. scenarios 4-6), were considered to receive 225.50 €/ha as they combine the benefits from both measures. The most common practice,burning-ploughing (scenario 1) is the only scenario that is not entitled to any Agri-Environment-Climate Schemes.

2.4.7. Hunting in rice fields: market benefits and provisioning + cultural ecosystem services for farmers Tamisier and Dehorter (1999) estimated that a minimum of 100,000 ducks are shot annually by hunters in the Camargue on a total area of 27,000 ha, hence an average of 3.7 ducks/ha/year. Flooded rice fields are among the habitats where such wildfowling activity occurs (e.g., Tamisier and Dehorter, 1999;Mathevet, 2000). Considering a market cost of 5.85 € per Mallard (Anas platarhynchos) in 2014 (Au gibier de France website, http://www.gibierdefrance.com/tarifs-gibier/colvert/, accessed on May 2015), the most commonly hunted duck, hunting would represent an ecosystem provisioning service corresponding to 21.65 €/ha on avoided food costs.

The enjoyment obtained by hunters from wildfowling over flooded rice fields also represents a (non-market) benefit to society and so to the farmer as an own lobby. This was evaluated at 46.65 €/ha by [START_REF] Calvet | Rapport d'étude scientifique du projet : combien coûte la Camargue ? Rapport de recherche Fondation MAVA[END_REF], (corrected for inflation to 2014), and is embedded as a cultural ecosystem services in the ecosystem services provided by flooded rice fields to the society described in the next section. The French law attributes the right to hunt to the owner of the land. However, such rights can then be transferred to someone else, either for free or for a given agreed hunting right lease. A survey conducted by Mathevet (2000) concluded that All those three potential benefits from hunting were considered at the scale of the farmer (not society) while computing the benefits-to-costs ratios.

Winter flooding: ecosystem services to the farmer

For the farmer, flooding the fields during winter can bring ecosystem benefits in the form of buffer against floods which amount to 15.16 €/ha after [START_REF] Calvet | Rapport d'étude scientifique du projet : combien coûte la Camargue ? Rapport de recherche Fondation MAVA[END_REF].

Winter flooding: ecosystem services to society

Besides the potential ecosystem services provided by flooded rice fields in terms of habitat for wildfowling or agronomic+environmental benefits to the farmer, artificial wetlands also provide services to society in terms of 1) support for biodiversity, 2) water quality, and 3) aesthetical landscape value.

Sensitivity analysis

For the sensitivity analysis, the costs and benefits were lumped into higher-order categories, with values varying from -99% (avoiding -100% which would have prevented computation of some ratios) to +200% before re-computing the benefits-to-costs ratios of each of the 6 agricultural scenarios. These higher-order categories were: 1) "Farming costs", comprising salary, fuel and fixed costs, 2) Irrigation+drainage costs, 3) GHG costs, 4) Agrienvironmental incentives, 5) "Hunting income" (comprising food provisioning from hunted game, cultural benefits from hunting enjoyment, and hunting leases), and 6) Ecosystem services (all those listed in the section above, except those from recreational hunting, which were considered above only at the farmer level). In all cases the simulations were calculated separately for the individual farmer and for society (including the farmer). The ranking of the scenarios according to their benefits-to-costs ratio was then evaluated.

Results

The total costs, total benefits and benefits-to-costs ratio of each scenario are presented separately for the individual farmer and the whole society, including the farmer (Table 5).

For the farmer, all possible scenarios were economically profitable given that the benefits outweighed the costs (B/C ratios > 1) in all cases. The current burning-ploughing scenario had the lowest benefits-to-costs ratio, while the most beneficial scenario was when the rice was harvested in flooded fields and the chopped straw was later incorporated with a rototiller. The benefits-to-costs ratio was consistently lower for the scenarios where straw was burnt instead of chopped.

The results were somewhat different when the situation was considered from the society's point of view. First, the burning-ploughing scenario was unsustainable given that costs outweighed benefits (B/C ratio = 0.78). All other scenarios were strongly beneficial, with benefits more than twice to almost seven times greater than costs. Scenarios with flooding yielded the greatest benefits-to-costs ratios and the most beneficial scenario was harvesting in flooded fields. Scenarios with burning instead of chopping of straw were generally less beneficial. It should be noted that the ratios were generally greater for society than for the farmer, which was mostly due to the ecosystem services provide to society by the flooding of fields.

Table 5 Total benefits, total costs and benefits-to-costs ratios (B/C) of each agricultural scenario, when considering the individual farmer or society as a whole (including the farmer).

Changing the value of the costs or the benefits in the sensitivity analysis confirmed the robustness of the above results. Although the benefits-to-costs ratios of the various scenarios were sometimes very different from the initial situation, the ranking of the agricultural options, evaluated from such ratios, was generally conserved except for extreme simulations (virtual disappearance or close to 200% increase of some parameters). Globally speaking harvests in flooded fields were consistently the most profitable option, for both individual farmers and the society (Fig. 1, Fig. 2). Chopping-incorporation (scenario 2), for which farmers pay little costs apart from salaries, fuel and fixed costs, became the most profitable option when such farming costs were reduced, reaching benefits-to-costs ratios as high as 236 when farming costs were reduced by 99%. However, farming costs had to be reduced by close to 90% before this scenario became more profitable than harvesting in flooded fields. The ranking of the various options otherwise remained globally similar across the sensitivity analysis (Fig. 1).

Scenarios

Increasing the irrigation+drainage costs did not change the ranking of the scenarios for the individual farmer. Yet reducing costs by as little as 20% made most scenarios with flooding more profitable than any dry scenarios. For society, conversely, reducing the costs of irrigation and drainage did not lead to a changes in the ranking of the scenarios, because flooding scenarios were already more profitable in the initial situation. Conversely, increasing the cost of water more than ca. 100% lead to some flooded scenarios becoming less beneficial than dry ones, albeit harvest in flooded fields (when there were no irrigation costs) always remained the best option (Fig. 1).

The cost of greenhouse gas emissions was not considered for individual farmers, thus they were not affected by changes in this parameter. For society, the initial ranking of the scenarios was maintained if the costs of greenhouse gas emissions were reduced. The three best scenarios (those with flooding and chopping instead of burning of the straw) remained the same with up to a 200% increase in such costs (Fig. 1).

Reducing the current agri-environmental incentives did not change the order of the scenarios for farmers. Increasing incentives by ca. 50% lead to scenarios 4 and 5 (chopping-flooding) to become more beneficial than chopping-dry incorporation. For society, changing the value of the agri-environmental incentives changed the magnitude of the difference between the ratios of some scenarios, but the ranking of these remained the same (Fig. 2).

The benefits from hunting are linked with the flooding of fields in our analysis. Reducing the potential income from hunting favoured dry scenarios, while increasing such income promoted the flooded scenarios. With an increase in hunting income greater than 70% all flooded scenarios became more profitable than dry ones for the individual farmer. The income from hunting had to be reduced to almost zero for chopping-dry incorporation (scenario 2) to become the best option for the individual farmer. For society, the flooded scenarios remained the best option even with no income from hunting, with the exception of scenario 3 (burningflooding-incorporation) when hunting income was reduced by more than 70% (Fig. 2).

The pattern for changes in ecosystem services for society was similar as for hunting: all flooded scenarios greatly benefited from increases in non-market income, but this did not change the ranking of the scenarios compared to the initial situation where they were already more profitable than dry scenarios. Individual farmers were affected only marginally by changes in the ecosystem services, since this only relied to the agronomic+ecosystem services of flooding (i.e. 15.16 €/ha in the initial situation; Fig. 2).

Discussion

Worldwide research has repeatedly highlighted the ecological and agronomical benefits that can be expected from flooding rice fields during the intercrop season (reviews in Manley, 2008 for the U.S., in Elphick et al., 2010aor Pernollet et al., 2015a for a worldwide perspective). However, all of these studies recommend that a precise economic evaluation of such waterfowl-friendly management should be compared to other post-harvest practices in each rice production region. The present study suggests that winter flooding in the Camargue (France) is economically viable for individual farmers as it increases savings on fertilizers and pesticides, and the farmers can benefit from agri-environmental incentives and income from waterfowl hunting. This practice is even more beneficial for the macro society as a wide array of ecosystems services is associated with winter flooding. The sensitivity analysis suggested such results were robust against wide variations in the value of costs and benefits considered here.

The farmer's point of view

The results of the benefits-to-costs ratio analyses were straightforward when considering the individual farmer's point of view: all scenarios were profitable (benefits-to-costs ratios > 1), but the traditional burning-ploughing had the lowest ratio, while harvesting rice in flooded fields had the best ratio by saving pumping costs. Apart from fees to be paid to ASAs for pumping water in and out of the fields and the cost of pumping water with a tractor-held pump for high lands, the other costs to the farmer were similar among all scenarios considered (Appendix 1). Conversely, the benefits were massively increased with flooded scenarios, owing especially to current agri-environmental incentives and the income from waterfowl hunting that farmer could receive.

The costs of flooding and the use of agricultural machinery are well studied by agronomists and clearly perceived by farmers as well as probably the possible benefits from hunting lease. Conversely, the possible benefits from savings on tillage requirements or fertilizers and pesticides in some post-harvest practices are poorly evaluated, and hence not really considered by farmers worldwide in their economic balance (see however Manley et al., 2005). This could explain why the most common practice in Camargue (burning-ploughing) is actually the least beneficial of the scenarios we tested.

The costs of flooding are known to vary greatly between rice production regions depending on flooding systems: either by pumping such as in California, Texas or Camargue, by gravity such as in the Mississippi Valley, the Delta del Ebro, the Albulfera de Valencia or the Pô Valley, or by winter rain concentration such as in some parts of Portugal or Japan (Shimada et al., 2000;Anders et al. 2008;Lourenço and Piersma, 2009;Pernollet et al., 2015b). In the Camargue, we chose to evaluate such flooding costs as the mean exploitation fee of irrigation and the mean ordinary fee for drainage over all ASAs. We assumed that the fields would be flooded directly after harvest, in October and hence maintain summer electricity prices. This water input, when combined with winter rains, should be enough to maintain the fields flooded until the beginning of February (corresponding to the end of hunting season and before the initiation of the new cultivation cycle). The situation may be different if farmers had to regularly re-flood their fields throughout the winter, which would be associated with greater electricity costs. Finally, it should be kept in mind that we considered an average situation, while owing to specific ASA decisions, the cost of flooding actually varies greatly between sub-regions of the Camargue (min=16.68€/ha, max=180.66€/ha for exploitation irrigation fees and min=0.09€/ha and max=88.57€/ha for ordinary drainage fees, ASAs, unpublished data). Relying on winter flooding would hence be much cheaper for some Camargue farmers than others; however, the sensitivity analysis showed that even profoundly changing the irrigation+drainage costs had little effect on the ranking of the different agricultural scenarios for the farmer. Agricultural market costs are well known in the rice production systems, mainly concentrating on the cultivation period (e.g. Technical report of [START_REF] Livezey | Characteristics and Production Costs of U.S. Rice Farms[END_REF] but also for the intercrop period (e.g. Brouder and Hill, 1995and Horwath and van Kessel, 2001in Anders et al. 2008;Bird et al., 2000;[START_REF] Hill | The California rice cropping system: agronomic and natural resource issues for long-term sustainability[END_REF]. However, potential savings on fertilizers or pesticides made possible by particular post-harvest practices are less evaluated and, as explained above, probably not considered by farmers. [START_REF] Muzzi | Winter floods offer duck habitat and crop savings[END_REF] and then Manley (1999) and Manley et al. (2005) made an important step in this direction in the U.S. by estimating the possible savings on direct tillage requirement costs, but very little information is available on herbicide and fertilizer savings linked with improved straw and weed decomposition in flooded and non-burnt fields.

The potential income from waterfowl hunting largely contributed to the high benefits-to-costs ratios of flooded scenarios for farmers, and is also recognised as an important business in Camargue private estates (e.g. Mathevet, 2000). The majority of American and European rice farmers that flood their fields after harvest do so to attract ducks for leisure hunting purposes (Elphick et al., 2010b), generating about 4.4 million euros in lease income annually in Camargue (Mathevet and Mesléard, 2002), and representing an economy of about $86.8 million in the US (equivalent to 76.5 million Euros, [START_REF] Grado | Economic impacts of waterfowl hunting in Mississippi derived from a state-based mail survey[END_REF]. In the case where farmers or landowners do not want to promote wildfowl hunting, this could be replaced by any alternative activity (e.g. ecotourism or birdwatching: Kerlinger, 1993 in Eadie et al., 2008) yielding a minimum income of ca. 85 €/ha in Camargue (20% of estimated income from hunting, under which the sensitivity analysis suggests some dry scenarios become more profitable than the flooded ones). Furthermore, farmers could capitalize on additional income opportunities (not considered in the present CBA) from managing fields in a "waterfowlfriendly way" and advertising this by marketing products with a special mark and at higher prices. Such products already exist in other countries, sometimes focusing on other species: Spanish Ebro Delta organic rice, http://www.rietvell.com/, "CheolwanCrane Rice," in Korea, "Ibis Rice" in Cambodia, http://www.wildlifefriendlyorg/ ibis-rice (in Elphick et al., 2010c).

The society's point of view

The analysis of the benefits-to-costs ratios for society provided somewhat different results than for the single farmer. Non-market costs and benefits, especially those linked with greenhouse gas emissions or ecosystem services, profoundly changed the ratios and strongly increased the advantages associated with winter flooding. Conversely, the current burningploughing no longer appeared as a sustainable option when considered from the society's stand point instead of the individual farmer's point of view.

With climate change, the question of GHG emissions continuously gains in importance in societal and individual decisions. Because rice is cultivated in water, this crop is known as a CH4-emitting culture, which is gaining attention in Europe (http://www.sostrice.eu/en/ and http://www.greenrice.eu/about-us/). Flooding rice fields during winter may be detrimental in terms of greenhouse gas emission, but based on our calculations, burning the straw would produce GHG than chopped scenarios. On the other hand, a recent study suggested that postharvest agricultural practices aimed at reducing GHG emissions could be detrimental to waterbirds (see [START_REF] Sesser | Waterbird Response to Practices Aimed at Reducing Greenhouse Gas Emissions from Rice Fields in The Sacramento Valley[END_REF]. There is therefore a potential conflict of interest between flooding for waterfowl and keeping the fields dry to avoid GHG emissions. This conflicting point of view should be further studied. The potential benefits from the various scenarios at the society level, mostly linked with the ecosystem services provided by flooded fields, could be quantified thanks to earlier works by [START_REF] Calvet | Rapport d'étude scientifique du projet : combien coûte la Camargue ? Rapport de recherche Fondation MAVA[END_REF], who estimated the willingness to pay by visitors for such Camargue landscape. This willingness to pay by tourists was used as a mean to evaluate the aesthetical landscape value of the study area and generated the greatest values in our analysis. Such evaluations, which are mostly based on people interviews, has been highly criticized in the past and should be treated with caution. Despite this criticism, we maintained this data in our analysis given that this was the only data of this type available to us and the sensitivity analysis suggested that best scenario remained the same even without any such ecosystem service benefits.

We did identify some costs and benefits to farmers that we could not quantify, and hence these elements were not included in the analyses. Two potential problems that are frequently put forward by farmers as the reason for not flooding the land are the fear that this could prevent early preparation of the fields for the next crop season and the risk of deadly accidents involving cage-wheels, as the tractors may flip over. The successful implementation of winter flooding in North America and Spain partially eliminates the first hypothesis. The latter appears to be a psychological hurdle rather than a real potential. While this has repeatedly happened in Camargue in the past, the modern tractors are generally heavier and have a cabin and/or roll-cages, so the risk of flipping over is reduced. Furthermore, incorporation of straw in flooded fields can now also be done using a rototiller (a new south-korean machinery recently introduced in Camargue and largely used in Spain) rather than cage-wheels, eliminating such risks.

One major benefit from rice cultivation in Camargue is its desalination effect since fields are continuously flooded during the rice growing season, allowing farmers to grow wheat or other highly profitable crops in future crop rotations (Mañosa i Rifé, 1997). Flooding the fields during winter could further contribute to the desalination of the fields, but we were unable to quantify this potential benefit.

At the level of society, some other costs were identified but could not be estimated. Some of these costs included the risk of fire on natural features when burning the straw, uncontrolled flooding from heavy rains in autumn associated with already flooded rice fields and the risk of overexploitation of the water resource if all of the Camargue rice fields were flooded. As explained in the Methods section, the likelihood of the former two events is very low at the scale of one single intercrop season, as considered here. The risk of overexploiting the water resources is negligible in the current Camargue system where water is pumped from the Rhône, one of the main rivers in France with a high debit, close to the river mouth. The situation may be different in other regions using winter flooding, such as in California or in southern Spain, where water supply is limited and competition for water may arise between natural wetlands and irrigated fields (Pernollet at al., 2015a). Nevertheless, it should be kept in mind that things may change in the future if the river debit decreases in the alpine tributaries due to decreased snow pack and glaciers. In this case, a salt wedge could move upstream from the Rhône mouth, increasing the salt levels in the river and making the water inappropriate for agricultural irrigation (e.g. [START_REF] Chauvelon | A story of water, salt and sediments: constraints for adaptive management in the River Rhone delta. In: Deltas: landforms, ecosystems and human activities[END_REF]. Similarly, catastrophic rainfall events linked with climate change may also induce more frequent floods. Assessment studies are currently carried out in the Camargue to improve the drainage systems owing to such potential risks of flood in the future (PNRC, 2013b). Taking into consideration climate change, spatial analyses should be carried out to determine where in the delta it would be both easier and safer to flood and drain the rice fields. Admittedly, the benefits-to-costs ratio analysis as practiced here may be adequate to analyse current or temporary processes, but it is poorly suited for predicting the outcome of different practices over the long term in a changing environment. To better take into account the future effects of potential climate, agricultural or politic changes, a proper modelling approach such would be more appropriate.

For the time being and for the purpose of the present study, which was limited to assessing the best scenarios for one intercrop period in the short-term, the benefits-to-costs ratios does seem to be a valuable approach. The sensitivity analyses at both the individual farmer and the society scale highlighted the robustness of the results, since the ranking of the scenarios remained consistent across changing values of the costs and benefits.

Conclusion: implications and prospect

The actual and traditional burning-ploughing practice barely reaches a financial equilibrium for the farmer and was associated with great costs than benefits at the society level (benefitsto-costs ratio < 1). This was linked with the scenario providing none of the ecosystem services that flooded fields can bring, while simultaneously being associated with both high agronomic costs to farmers (in terms of fertilizers to compensate losses to fire) and high non-market costs through greenhouse gas emissions for society. Burning the straw is only tolerated through derogation in Camargue. Once this derogation ends, the farmers will be required to switch to other means of straw disposal (like in California, California Rice Straw Burning Act 1991 in Anders et al., 2008)). The present results suggest that chopping and later incorporating or flooding+incorporating the straw is economically feasible for the individual farmer and preferable from a societal point of view.

The current analysis shows that it would be economically feasible for rice farmers to implement winter flooding in the Camargue, even if farmers have to pump water from the river to flood the fields. Raising awareness and providing information to the agricultural community about the possible benefits brought by flooding may help promote the implementation of this technique, yet there may still be some psychological hurdles to overcome. Among flooded scenarios, keeping water from the rice growing season until postharvest, with harvest in flooded fields, appears like the most beneficial option, since this relieves farmers from paying additional irrigation costs. According to the information that we were able to obtain, only one rice farmer in the Camargue is currently harvesting in flooded fields, making it difficult to determine exact agronomic outcomes within this specific geographic region. In particular, keeping the fields flooded during summer and early autumn may increase the risk of crop lodging, or may cause the straw to remain greener and hence more difficult to decompose (Thomas C., CFR, com. pers.). We hence recommend introducing the flooding of harvested fields in Camargue rice farms, but also that such fields be simultaneously studied and monitored by agronomists to better assess the later consequences in terms of crop yield and other agricultural issues. One way to do so could be to promote exchanges with Spanish agronomists and farmers that already have more than 15 years of experience in harvesting, rototiller use and weed management in winter flooded conditions. Another low-cost procedure that should be explored is the passive harvest of rain through improving water retention (e.g. in Japan, Shimada et al., 2000;in Portugal, Lourenço and Piersma, 2009). With an average of 58.0 mm rain between October and February and a maximum of 90.6 mm in October (1977( -2006( , PNRC, 2013b)), rainfall could provide the minimum suitable water depth of 5 cm for dabbling ducks during winter in the Camargue (with the exception of particularly windy winters). Although these scenarios are already beneficial to farmers, it may be useful to provide financial incentives to farmers in order to promote winter flooding, while still having benefitsto-costs ratios well above 1 for the general public. Diverse ways of payments are already implemented to promote winter flooding of rice fields in the U.S. and in Japan by the federal government (Eadie et al., 2008;[START_REF] Natuhara | Ecosystem services by paddy fields as substitutes of natural wetlands in Japan[END_REF] and some NGO funds are also used through reverse auctions (BirdReturns Project, The Nature Conservancy, 2014). In Europe, Spanish rice farmers of the Ebro Delta and Albufera de Valencia can apply for ca. 60 €/ha through agri-environment schemes to flood their fields for a minimum of 3.5 to 4 months during winter, resulting in the creation of an immense artificial wetlands available to waterfowl in these RAMSAR sites (Albufera, Law: RD 4/ 2001 andRD 708/2002, Ebro Delta: Council Regulation (EC) No 1257/1999 in Pernollet et al., 2015b). In both regions, as in the Pô valley in Italy where harvested rice fields are kept dry during winter, flooding costs are lower than in the Camargue since water comes to the fields by simple gravity (Pernollet et al., 2015b).

CBA can be a useful tool for decision-making in a given area and for a given time period, but it does not provide universal results applicable to every situations. The results regarding the potential feasibility of winter flooding in Camargue were clear-cut, and may apply to other similar rice cultivation systems; however, a nuanced approach of the CBA which weighs the site-specific costs and benefits of winter flooding is necessary for further comparisons [START_REF] Boyer | Évaluation économique de biens et services environnementaux par la méthode du transfert de bénéfices[END_REF].

INTRODUCTION

Winter flooding has been identified as the best waterfowl-friendly management in post-harvest ricefields in the U.S., providing mutual benefits to wintering ducks through its direct translation into foraging grounds, and to farmers through improved straw decomposition rate and weed seeds reduction.

We tested for such mutual relationship in Europe via 4 distinct studies. Seed depletion rate was highly dependent on initial seed density, and was greater with ploughing (stat not shown). • !" #$%&$''("$"!)*+,)*-)."/"0)*%",(&(!)1%"%2,)3%%"(*"(*4%,*)" " " 56789:;"."52$1%"-,$"<2%&-%""4$,($=(1("" (*>(!$"?%'1()"(1"*2?%,)">("$*$-,%" (*4%,*$1("3,%&%*@""*%11%"0)*%",(&(!)1%" %2,)3%%A" 823%,B!(%"(*." " C"D(&$(%"(*"$&!(2E$"(*"(*4%,*)" " C"D(&$(%""$11$'$-%"(*"(*4%,*)" """""""""""""""""""""""""""""""""""""""""""""" C"F)*%"2?(>%"*$-

  '($!)*(!+,-./0123/41!#1!56.471++/12!! 38/1.813!14!4189./:-13!#-!+;.<-1#68!! ! ! 7($)*($=!*>!?=&@!A=!%,1BC%=!#CBDC(*%=!<;/;E!! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!A=!%,-@&D$!;'&F*>@=!5&G(*D(&B=!A=!%,6.8H3! !!!!!!!!!!!!!!!!!!!!!!!!!!!=D!A>!#$)*(D=I=@D!1?)JB=?!A=!%*!4C>(!A>!0*%*D! ! ! 3)$B&*%&D$K!1BC%CG&=E!1'C%>D&C@E!2=??C>(B=?!<$@$D&L>=?E!7*%$CM&C%CG&=! !%=!NO!H$'(&=(!N"PQ!A='*@D!%=!R>(S!BCI)C?$!A=!

  %&!'(&!)*'+*,&!-(#*#&!.+,+/0&!1%*!+*2(,#!,+3(/!4!.$,#/(!.$%/+,#!! "!.(%5!1%*!&(!/(0/(&&(,#!+-/6&!'+!#(2-7#(!! "!.(%5!1%*!&$,#!,8&!-(,0+,#!.(##(!#96&(! "!2(&!0(%5!-(#*#&!:$%#&!0(!;(22(&<!=(+,,(##(!(#!=(+,,(!! "!2(&!-+/(,#&<!>!$,!*/+!+%!:$%#!0%!2$,0(!?! "!@'+%0*$<!-$/1%(!#$0$!(&$!)+'*$!'+!-(,+Plusieurs collaborations ont eu une part active dans ce travail:

I. 1

 1 Agroecosystems as integrated elements of the landscape I.2 Relevance of the Ricefield-Duck model I.3 Agriculture intensification and farmland bird decline in Europe: food resources matter for seed-eating birds I.4 From science to policy to science: implementation of Agri-environment schemes during the winter period II. Ducks and rice in the French Camargue landscape: the structure and aims of this thesis II.1 Rice farming and general duck conservation II.2 Rice farming landscapes and post-harvest practices beneficial to ducks II.3 Waterfowl-friendly management providing ecosystem services to farmers II.4 Economic valuation of winter flooding in Camargue III. Schematic overview of the PhD thesis $%What could habitat management on rice production sites imply for rice farmers, for society and for decision makers? 183 IV.4 CONCLUSION What these results imply -and do not imply -for Camargue land management

  (ex : Anders et al, 2008 et Tableau 2 de l'Article 1).

  ; Camargue pour les sarcelles: Guillemain et al., 2015a, Annexe I.2) et des changements de distribution (Californie, vallée de Sacramento, Fleskes et al., 2005) pourraient être observés. La mise à disposition de champs inondés pourrait non seulement se traduire par une utilisation ponctuelle ou saisonnière de ces champs par les canards pendant un hiver donné, mais une tradition d'hivernage forte pourrait également se développer dans ces habitats (Guillemain et al., 2015a, Annexe I.2) et donc se traduire par une amélioration de la dynamique des populations plutôt que la simple satisfaction temporaire des besoins énergétiques des oiseaux. En effet les tendances démographiques ont augmenté après la mise en place de la MAE « inondation hivernale des rizières » en Espagne (Article 2).

  al., 2015a, Guillemain et al., 2015b, Annexes I.2 et I.3). Nous ignorons dans quelle mesure l'inondation hivernale des rizières en Camargue, quartier d'hiver situé très au sud de l'aire de répartition de beaucoup d'espèces d'Anatidés, pourrait compenser les conséquences du changement climatique.

Figure 1 .

 1 Figure 1. Impacts of farm and landscape management on the flow of ecosystem services and disservices to and from agroecosystems (reproduced from Power, 2010).

Figure 2 .

 2 Figure 2. Changes in arable land management that might influence plant, insect and bird populations. The most relevant drivers are highlighted by shading (reproduced from Robinson and Sutherland, 2002 with kind permission from Journal of Applied Ecology).

Figure 3 .

 3 Figure 3. Processes acting to limit the distribution of individuals within certain parts of the potential habitat spectrum (wide bar at the top) (reproduced from Fuller, 2012 with kind permission from Cambridge University Press).

  introduction of an AES ''ricefield winter-flooding'' in Spanish sites translated into greater local duck numbers? (Article 2) -Do the post-harvest practices influence the availability of seed resources in rice fields?

Figure 4 .

 4 Figure 4. The agricultural-wetland mosaic landscape of Camargue in 2011 (by A. Guelmani from the PNCRC database, PNRC, 2013a).

Figure 4 .

 4 Figure 4. Day roosts and nocturnal foraging grounds of wintering ducks, together forming their functional units (Reproduced from Guillemain and Elmberg, 2014 with kind permission from Bloomsbury publishing).

  Winter flooding is an effective organic management to control rice weeds through the increase of seed deterioration (Article 4) -Ducks attracted in flooded post-harvest rice fields benefit to farmers through the reduction of weed seed bank by foraging and the reduction of stalks by trampling (Article 5) The main issues addressed were: % -Does overwinter seed deterioration rate differ between rice and weed species, and depending on whether fields are kept dry or flooded? (Article 4) -Is seed quality well conserved in flooded ricefield conditions, and hence represents a valuable food stock to wintering ducks throughout the season? (Article 4) -Can ducks foraging in flooded post-harvest rice fields significantly reduce the number of standing stalks? (Article 5) -Can ducks foraging in flooded post-harvest rice fields significantly reduce the weed seed bank? (Article 5)

-

  Winter flooding in Camargue is economically realistic for the farmer (Article 6) -Winter flooding in Camargue is economically realistic for the local society (Article 6) The main issues addressed were: -What are the market and non-market costs and benefits of different inter crop management sequences (post-harvest scenarios) for the farmer in Camargue? (Article 6) -What are the market and non-market costs and benefits of different inter crop management sequences (post-harvest scenarios) for the local society? (Article 6) -Do the benefits of rice field winter flooding outweigh the costs for Camargue farmers? for the general Camargue society?

Figure 5 .

 5 Figure 5. Schematic overview of the three major chapters of the thesis and the articles they contain.

Figure A. 1 .Figure A. 2 .

 12 Figure A.1. Rice cover (ha) in the main production areas in year 2011 (data after FAO-STAT, 2013).

Figure 7 .

 7 Figure 7. Nocturnal duck densities in rice fields as a function of distance to the nearest potential roosting site in Camargue (France, blue dots) and in Doñana (Spain, red dots). Extracted from Appendix II.2.

  Distance to the potential nearest roosting site (km) Duck Density (Ducks/ha) Distance to the potential nearest roosting site (km) Duck Density (Ducks/ha) Distance to the nearest potential roosting site (km)

5

  / to test the effectiveness of the ricefield "Winter Flooding" Agri-Environmental Scheme and consider its implementation at the European flyway scale.In Europe, environment-friendly practices are supported by Agri-Environment Schemes (AES) implemented through the Common Agricultural Policy. The European Community often lacks the factual data necessary to implement these recommendations, as well as scientific assessment of the efficiency of current schemes. AES have been implemented in Spanish ricefield areas at the beginning of the 2000s to promote winter flooding (Albufera, Law: RD 4/2001 and RD 708/2002, Ebro Delta: Council Regulation (EC) No 1257/1999), and Article 2 proves that such AES have positively influenced duck population trends. Promoting such schemes more widely across the European rice production areas could make a big difference in terms of waterfowl habitat quality at the scale of their wintering range, as was done for instance in California.Collectively, the articles of Chapter II therefore show that waterfowl conservation would greatly benefit from a wider implementation of winter flooding of harvested rice fields, with potential consequences ranging from a changed nocturnal distribution of the birds locally to a broader redistribution at the flyway scale. The next chapter in turn considers the possible agronomic consequences of winter use of the flooded fields by ducks from the point of view of the rice farmers.

Figure 1 .

 1 Figure 1. Map of the Camargue showing the 11 rice farms where soil samples were collected during winter seasons 2012-13 and 2013-2014 (points). Eight of these were also visited during winter 2013-2014 for nocturnal waterfowl surveys (open circles) (a black and white version is available). !

!

  Function lmer of package lme4(Bates et al. 2014) and a Gaussian distribution were used for the analyses of seed availability. Seed densities per core (kg/ha -rice and weed seeds considered separately) were log-transformed to get model residuals closer to normal distribution. Several transformations were tested on the seed depletion rate, but the log-

Figure 2 .

 2 Figure 2. Average rice and weed seed densities (black and grey columns, respectively) in the 52 Camargue rice fields surveyed three times a season over two winter seasons (2012-2013, n = 16 and 2013-2014, n = 36). Vertical bars represent standard errors. The horizontal dashed line at 50 kg/ha represents the theoretical Giving-Up Density below which waterfowl should cease foraging in rice fields, after Reinecke et al. (1989) and Geer et al. (2009).

  ) + Years of rice +Farming type + Log(Weed seed density) x Years of rice + Years of rice x Farming type! 6seed density) + Years of rice +Straw + Log(Weed seed density) x Years of rice ! 6seed density) + Years of rice +Farming type + Straw + Years of rice x Farming type ! 8seed density) + Years of rice + Farming type + Straw + Log(Weed seed density) x Years of rice ! 8seed density) + Years of rice +Farming type + Straw + Years of rice x Farming type + Log(Weed seed density) x Years of rice ! 9

Figure 3 .

 3 Figure3. Average rice and weed depletion rates (proportion of change per day) for each agricultural practice in the 52 studied Camargue rice fields for winter2012-2013 (n = 16) and 2013-2014 (n = 36). The figure represents the minimum, the first quartile, the median, the third quartile, and the maximum. Post-hoc Tukey tests at P < 0.05 indicated that depletion rates of rice were greater in plowed fields than in stubble fields or fields with no agricultural treatments ("None"). There were no significant differences between the other treatments (see text).

  2 % ± 2.0 SE, 0.7 % ± 0.4 SE and 0.1 % ± 0.03 SE, respectively). Unidentified dabbling ducks comprised 9.0 % ± 3.4 SE of the 16,347 individual detections. Mean densities of each duck species are shown in Fig.4.

Figure 4 .

 4 Figure 4. Weekly average densities of duck observed per species in the 46 rice fields surveyed for nocturnal duck use over the winter 2013-2014, and weekly proportion of all study fields flooded (dotted line). "Other" includes Gadwall, Northern Shoveler and Common Shelduck, Error bars represent standard errors. ! ! ! !

Figure 8 .

 8 Figure 8. Integration of agronomic values and wildlife conservation in ricelands (reproduced from Eadie et al. 2008, with kind permission from S. Manley). In red colour the elements that were studied in this chapter.

  considered with a binomial error structure, including the same fixed and random factors as above.

  barnyardgrass and sea clubrush seeds lost an average of 40.

!!Fig. 1

 1 Fig.1Predicted percentages of mass remaining for seeds of cultivated rice and three main rice weeds (weedy rice, barnyardgrass, sea clubrush) computed from estimated remaining seed mass by the best selected model (cf. Table1), after being left in dry ricefield substrate or submerged in flooded ricefield substrate during the winter of 2014-2015, in microcosms positioned in a greenhouse at the Tour du Valat Research Center, Camargue, Southern France. Samples (2g of seeds initially) were weighted at day 58 (T2) and day 123 (T3, vertical lines). The effects of the control treatment (water only, with no substrate in trays) did not significantly differ from flooded (see text) and are therefore not represented.

Fig. 2

 2 Fig.2Predicted energetic density per gram of seeds of cultivated rice and three main rice weeds (weedy rice, barnyardgrass, sea clubrush) computed from estimated energy density change from the best selected model (cf. Table2). Values from samples kept in dry ricefield substrate or submerged in flooded ricefield substrate during the winter 2014-2015, in microcosms positioned in a greenhouse at the Tour du Valat Research Center, Camargue, Southern France. Samples at time T2 and T3 were extracted from the experiment at day 58 and day 123 (vertical lines). The effects of the control treatment (water only, with no substrate in trays) did not significantly differ from flooded (see text) and are therefore not represented.

  3% [89.6-97.1] at T1 to a mean of 60.

  ., Burns E.,[START_REF] Van Groenigen | Effects of foraging waterfowl in winter flooded rice fields on weed stress and residue decomposition[END_REF]. Effects of foraging waterfowl in winter flooded rice fields on weed stress and residue decomposition. Agriculture, EcosystemsEnvironment, 95,[289][290][291][292][293][294][295][296]

  potentially compensate for the consequences of climate change and birds increasingly staying in northern areas outside the breeding season.

Figure 9 .

 9 Figure 9. Forager flowcharts in SWAMP: main program loop flowchart (left) and agent step flowchart (right) (reproduced from Miller, 2014 with king permission from SAGE Publications).

Figure 10 .

 10 Figure 10. Post-harvest options in rice fields.

Figure 11 .

 11 Figure11. Changes in rice field cover in Camargue and agricultural practices: production is highly dependent upon the political and economical contexts (graphic built from unpublished data of J-C.Mouret, 2008 and France AgriMer, 2014).

Fig. 1 .Fig. 2 .

 12 Fig. 1. Effects of changing the value of costs to the individual farmer or society on the benefits-to-costs ratios of the six agricultural scenarios during the intercropping period in Camargue rice fields.

  Flooded scenarios were economically feasible for farmers and highly beneficial to society.

  , Pintail observed in the ricefields in Camargue Mallard, Shoveler, Wigeon commonly observed in Doñana DUCK DENSITIES potential nearest roosting site (km) Duck Density (Ducks/ha) High concentration of ducks in Camargue in the few flooded ricefields compare to Doñana. Ducks potentially fly much more from their diurnal roosting to their nocturnal foraging site in Doñana than in Camargue. Camargue: More ducks in flooded ricefields Claire A. Pernollet, François Cavallo, Michel Gauthier-Clerc, Jordi Figuerola, Andy J. Green, Matthieu Guillemain Email: claire.pernollet@oncfs.gouv.fr Camargue Doñana Ducks~ Straw Management ** + Nearest Roost ** (0.90 positive) Stubble -Mudflat -1.44 ** DIURNAL SURVEY IN ALL HABITATS Camargue : Nov 2013 to Feb 2014, 51 fields in 9 farms surveyed, survey repeated weekly. Doñana : Nov 2014, 136 fields surveyed, 25 transects, 3 transects per night, 2 to 5 fields in each transect.

  Guelmami A., Green A.J., Curcó Masip A., Dies B., Bogliani G., Tesio F., Brogi A., Gauthier-Clerc M., Guillemain M. (sous presse). A comparison of wintering duck numbers among European rice production areas with contrasting flooding regimes. Biological Conservation 186, 214-224. DOI : 10.1016/j.biocon.2015.03.019.Flooding ricefields after harvest would therefore provide nocturnal foraging habitats to ducks, and also bring agronomic benefits in terms of increased straw decomposition and reduction of the weed seed bank. Winter flooding of ricefields in Europe would hence benefit both farmers and wintering waterfowl, and should be promoted by adequate agro-environmental policy wherever possible.

2. 2 ) 2 .!

 22 Ducks are more numerous in flooded ricefieldsWinter flooding did not significantly affect seed depletion rate AND makes seeds available for wintering ducks even only with rain At natural or agro-ecological densities, ducks had a very clear effect on the standing straw stalks participating to straw decomposition while they did not have any effect on the seed bank. the species with the biggest degradation whatever the ricefield condition was. Winter ricefield flooding is known to act as biological weed control for wild rice. 2015. Quina importància tenen els arrossars inundats a l'hivern per a les anàtides a Europa? Soldó 44. Informatiu del Parc Natural del Delta de l'Ebre. parcsnaturals.gencat.cat/ca/delta-ebre/coneix-nos/centre-(in Catalan). Tesio F., Nobile S., Pernollet C.A. 2015. La sommersione invernale può mettere d'accordo risicoltori, anatre, ambientalisti e birdwatchers! Natura e montagna. Anno LXII -2, 7-11 (in Italian) Popularization leaftlet in French, Spanish and Italian for farmers on the results of Article Popularization leaftlet in French on the results of Article 5. SAVOIR PLUS SUR LE PROJET Claire Pernollet (doctorante : claire.pernollet@oncfs.gouv.fr) 04.90.97.29.88 Matthieu Guillemain (ingénieur : matthieu.guillemain@oncfs.gouv.fr) 04.90.97.28.79La sommersione invernale offre un grande vantaggio alle anatre. Sarebbe interessante poter applicare questa tecnica lungo tutto il canale di migrazione, cominciando dalle zone o dalla maggior parte delle zone umide naturali che sono state distrutte, come nel caso della piena del delta del Po' in Italia (allagamento facile sfruttando la gravità). Attualmente è in corso un analisi costi/benefici per il territorio della Camargue. Questo studio mira ad esaminare se questa pratica è applicabile e economicamente accetabile. !"#$%&' ()#**#+#,&$-.''/$0&"$#*&'/$'12".3#'4'*&'#$#-"&'/$0&"$#*/'' !!"#!!!!!!!!!!!!!!!$%#!!!!!!!!!!!!!!!!!!&'%#! 5'6/7#/&'#**#+#-&'/$'/$0&"$.' 689:;9<=>' ' ()#??.$@#$A#'@&**&'#$#-"&'/$0&"$#*/'' B'*&+#-#'3.7/C0#,&$-&'#**#'3"&7&$A#' @&**&'A.$&'2,/@&'/$'7&$7.'*#"+.D' ' ;77/#''#**#'7.,,#''@&**&'A.$&'2,/@&' $#-2"#*/'&'@&**&'"/7#/&'#**#+##!!!!!!!!!!!!!!!$%#!!!!!!!!!!!!!!!!!!&'%#! 5'6/7#/&'#**#+#-&'/$'/$0&"$.

"

  %"$$&%.&#B%"#,*#'&)*#:2(+*##*#(,#):2*%&# +(#%(1"(*#/"%("#)&.*/&,2*).*#"#1*0&)+"# +*,#$"*1*A#?)#&%+()*#+*0%*10*).*#+(# 0&)1*%/"'(&)*#3#="2"%-:*#8CD7<#E#F;%&# 8G@7<#E#H,;:B*%"#8IJ7<#E#K"/(*#8G7<#E# L*%0*,,(#8I7<A#PER MAGGIORI INFORMAZIONI SUL PROGETTO Claire Pernollet (dottoranda: claire.pernollet@oncfs.gouv.fr) 04.90.97.29.88 Matthieu Guillemain (dottore : matthieu.guillemain@oncfs.gouv.fr) 04.90.97.28.79 # Impact des canards hivernants sur les chaumes de la paille et sur la banque de graines adventices EN SAVOIR PLUS SUR LE PROJET Claire Pernollet (doctorante : claire.pernollet@oncfs.gouv.fr) 04.90.97.29.88 Matthieu Guillemain (ingénieur :matthieu.guillemain@oncfs.gouv.fr) 04.90.97.28.79 Anne Brogi (master : anne.brogi@gmail.com) 06.95.96.61.08 Heureux soient les fêlés car ils laisseront passer la lumière" Michel Audiard Sung to the tune / A chanter sur l'air de "My Girl" of Nirvana My duck, my duck, don't lie to me Tell me where did you sleep last night In the pound, in the marshfrom here His head was found in a close montille But his body never was found My duck, my duck, don't lie to me Tell me where did you sleep last night In the pound, in the marsh, Where the hunters never hunt I'm going to count…my duck My duck, my duck, where will you go I'm going where the cold wind blows In the pound, in the marsh, Where the hunters never hunt I'm going to look for my duck Chanson écrite par Mailis, David, Elvin, Anne B, Anne L, Radka.

  in Cahiers Agriculture, the BirdReturns project by The Nature Conservancy or the project CORINAT (Coltivazione Riso Naturale in Italy) (42 references). % -Grey literature from ornithologist group specialists (Duck Specialist Group; NEOORN Bulletin Board for Ornithologists working with Neotropical Birds, etc…) as well as external experts from institutions such as BirdLife International, Wetlands International, Wildfowl and Wetlands Trust, Durrell Wildlife Conservation Trust, Doñana Biological Station-CSIC, USGS or Mississippi State University, among others.

Table A .

 A 1 Duck species that have been classified as rice pest in the literature. Table A.2 Agronomic benefits of winter flooding and foraging by wild or farm ducks. Read also Long et al. (2013) for more details. Table A.3 Duck species known to breed in ricelands.

			!"#$%&'()*(#'%+!,&()('+!&(-#'.+/0(1(23!4(!5/6&'7#%+5/( !"#$%&'()*(#'%+!,&()('+!&(-#'.+/0(1(23!4(!5/6&'7#%+5/( !"#$%&'()*(#'%+!,&()('+!&(-#'.+/0(1(23!4(!5/6&'7#%+5/(
	nis	Waterfowl	Red rice seeds decreased 97% in fields	Arkansas, Smith and
	Indian Spot-billed Golden apple Rice-duck farming South Asia	Sundar and Subramanya, 2010 CH 4 emissions decreased by 44.2% China, Huang et al., 2003 heavily infested with red rice and Sullivan, 1980 Golden apple snail density reduced > Japan, Teo, 2001
	Duck snail	Japan, China, India, Pakistan for early rice and 40.7% for late rice Lane, 1998 adjacent to a wildlife area with large 80%
	A. poecilorhyncha Pomacea	numbers of ducks
	Species Gadwall A. stepera canaliculata Species	Country/Region South Asia Lower N 2 0 emission rates and 22% Sundar and Subramanya, 2010 References lower global warming potential in China, Zhang et al., 2008 Dendrocygna White-faced Whistling Duck foraged Venezuela, Bruzual and Anas platyrhynchos Predator of apple snail Japan, Yusa et al., 2006 Country/Region References
	White-faced Whistling Duck Dendrocygna viduata Red-billed duck A. erythrorhyncha Agronomic variable Treatment South Africa Tanzania Senegal, Mali Cameroon Argentina, Colombia, Nicaragua, Surinam, Uruguay, and Venezuela Tanzania Madagascar Results Straw decomposition Winter flooding Straw biomass decreased 43-68% Petrie and Petrie, 1998 in Kear, 2005 Katondo, 1996 Tréca, 1992 Katondo, 1996 Roch and Newton, 1863 in Phillips, 1923 Localisation, Source MAV, Manley et al., 2005 fields with ducks and organic fertilizers than fields with ducks and chemical fertilizers viduata Anas fulvigula for Oryza perennis and Cyperus rotundus Mottled Duck found to consume red Bruzual, 1983 in Kear, 2005 Arkansas, McAtee, 1918 in Planthopper and leafhopper Rice-duck farming Brown planthopper outbreaks China, Qin et al., 2011 Fulvous Whistling Duck Louisiana, USA Hohman et al., 1996 controlled by altering its spatial Dendrocygna bicolor Cuba Mugica, 1993 in Pierluissi, 2010 distribution patterns and ecological Argentina and Brazil Don Pablo Ranch Project, 2012 niche characteristics + those of its De Grazio, 1978 De Grazio and Besser, 1970 in de Grazio, 1978 Fulvous Whistling Duck D. bicolor Louisiana, Florida, and Texas, USA Venezuela Argentina Cameroon Mugica, 1993; Hohman et al., 1996 Flincklinger and King, 1972 in Stafford et al., 2010 Blue-winged Teal A. discors Suriname, Guyana Arkansas, USA Grist and Lever, 1969 in de Grazio, Phillips, 1923 Yellow-billed Pintail A. georgica Argentina De Grazio, 1978 Ferreyra et al., 2009 Mottled Duck Arkansas, USA McAtee, 1918 in Phillips, 1923 Winter flooding +Wild Waterfowl Straw decomposition in flooded fields with waterfowl more than twice greater Straw biomass decreased 27-41% in flooded fields, 72-76% in flooded fields with waterfowl California, Van Groenigen et al., 2003 California, Bird et al., 2000 Nitrogen leakage reduced 5-7% by the presence of fish and ducks in rice paddies; N 2 O emissions lower in fields with ducks (51.4 kg N.ha -1 ) and fish China, Cheng-fang et al., rice Phillips, 1923 natural enemies Black-bellied Whistling South Texas, USA Bourne, 1981 2008 Barnyard grass /Millet Anas platyrhynchos Rice, Echinochloa crus-galli, and Glyceria declinata consumed by Portugal, Rodrigues and Ferreira, 1993 Number of planthopper and Duck Guyana China, Yu et al., 2008 D. autumnalis leafhopper decreased 65% 12 days (52.6 kg N.ha -1 ) than conventional fields (55 kg N.ha -1 ) Echinochloa spp. wintering mallard 11% of total volume of seeds eaten by Rodrigues et al., 2002 after ducks released, 79% after 42 Lesser Whistling Duck India Sundar and Subramanya, 2010 days D. javanica Arkansas, Forsyth, 1965 Meanley and Meanley, 1959 in Czech and Parsons, 2002 Bruzual and Bruzual, 1983 Gomez-Dallmeier and Cringan, 1990 in A. fulvigula Grey Teal A. gracilis Australia Taylor and Schultz, 2010 Stalks reduction increased with duck densities France, Brogi et al., 2015 Weed seeds Winter flooding Wild Waterfowl Weed biomass reduced 24-83% Growing season weed biomass decreased > 50% following a winter Mississippi, Manley et al., 2005 Mallards, third most consumed seed after rice and acorns Leafhopper, planthopper and rice bug populations significantly lower Bangladesh, Hossain et al., West Indian Whistling Cuba Acosta et al., 2010 2005 Duck California, Van Groenigen et al., 2003 17% of total volume of seeds D. arborea Arkansas, Wright, 1959 Kear et al, 2005 Ferreyra et al., 2009 De Grazio, 1978 Lesser Whistling Duck D. javanica South Asia Pacific Black Duck A. superciliosa New Guinea, New South Wales Grist and Lever, 1969 in de Grazio, Nutrient cycling/ Nutrient conservation/ Winter Flooding Crop N uptake increased 26% Soil and nutrients conservation, runoff California, Eagle et al., 2001 in Anders et al., 2008 MAV, Manley, 1999 in Rice-duck farming with ducks in flooded rice fields Weed biomass reduced 84% after farm duck trampling and 98% after farm China, Zhang et al., 2009 Anas consumed by Mallards, second after rice Rice, Echinochloa sp., Scirpus France, Brochet et al., 2012 Rice blast disease Rice-duck farming Diseased hill rate, diseased plant rate China, Xue et al., 2009 Mallard California, USA McLandress et al., 1996 in and disease index of rice sheath blight Anas platyrhynchos Pierluissi, 2010 better controlled by rice-duck farming Italy Fasola and Ruiz, 1996 than by treatment with pesticides Ali and Ripley, 1987 in Sundar and Subramanya, 2010 Black-bellied Whistling Duck D. autumnalis Guyana Gray Teal A. giberrifrons New South Wales, Australia Grist and Lever, 1969 in de Grazio, Water quality Wild Waterfowl water quality improved Residual 15N decreased 83%-89% Anders et al., 2008 California, Van Diepen et duck trampling + grazing Weeds decreased 68% and 98% after China, Yu et al., 2008 platyrhynchos/ Anas crecca maritimus, and Potamogeton pusillus seeds four most important food items in diet of Mallard and Teal Rice blast controlled, 57% of Cinnamon Teal California, USA Taft and Elphick, 2007 China, Zhen et al., 2007 A. cyanoptera outbreaks prevented Bourne, 1981 Knob-billed Duck Sarkidiornis melanotos South Asia Tanzania Senegal Sundar and Subramanya, 2010 Katondo, 1996 Tréca, 1992 Rice-duck farming Return of C, N and P into paddy soils al., 2004 China, Fan, 2012 15 and 45 days of duck release Weed growth reduced 96% and weed China, Zhen et al., 2007 Dendrocygna autumnalis Millet, Echinochloa sp. and Paspalum sp. most important food items to Mottled Duck Louisiana, USA Durham and Afton, 2003 in Guyana, Bourne, 1981 A. fulvigula Pierluissi, 2010
	Whistling tree duck D. arcuata Wood Duck Aix sponsa A. poecilorhyncha Indian Spot-billed Duck New Guinea MAV, USA Japan increased by 20%, 56% and 379% Grist and Lever, 1969 in de Grazio, 1978 Stafford et al., 2010 Total N, P and K increased 85-506%, China, Quan et al., 2008 variety decreased Weed vegetation reduced up to 90% Bangladesh, Hossain et al., Black-bellied Whistling Duck after rice Fujioka et al., 2010
	Spotted tree duck D. guttata Rosy-billed Pochards Netta peposaca Dendrocygna New Guinea Argentina bicolor A. superciliosa Pacific Black Duck Australia 201-870% and 43-109% Soil organic matter, total N, available Grist and Lever, 1969 in de Grazio, 1978 Ferreyra et al., 2009 China, Zhi-hui et al., 2004 Weeds reduced 99% 2005 China, Yu et al., 2004 Aquatic earthworms Oligochaeta and wild millet seeds Echinochloa sp. most important food items for Fulvous Louisiana, Hohman et al., 1996 Taylor and Schultz, 2010
	Mallard Anas platarhynchos Brazilian Teal Amazonetta Common Shelduck Weedy rice Winter Rice-duck farming South Asia/Japan Bulgaria USA Brazil N, P and K increased 11-29%, 3-15%, Sundar and Subramanya, 2010; Lane, 1998 Weed biomass reduced 52-58% Philippines, Cagauan, 1997 whistling ducks Europe Longoni, 2010 Ferreyra et al., 2009 6-10%, 4-10% and 23-27% Weedy rice seed viability 90% in Korea, Baek and Chung, Tadorna tadorna Young millet controlled by foraging Grist and Lever, 1969 in de Grazio, 1978 Phillips, 1923 Northern Pintail A. acuta South Asia Senegal/Mali USA Sundar and Subramanya, 2010 Tréca, 1992 Phillips, 1923 brasiliensis Maned Duck Chenotta jubata New South Wales, Australia Grist and Lever, 1969 in de Grazio, Greenhouse gasses: Rice-duck farming CH 4 emissions 6.7% lower when chemical fertilizer used together with ducks China, Zhang et al., 2011 Oryza sativa flooding/Freezing unflooded paddies, 61% in flooded 2012 farming ducks during early summer Japan, Tojo et al., 2007 Red-crested Pochard Europe Longoni, 2010 paddies, 78% after freezing treatment Algae/Aquatic Rice-duck farming Algae and aquatic animal biomasses Netta rufina China, Wang et al., 2006 CH 4 /N 2 O CH 4 reduced 19.3-19.6% China, Zhan et al., 2011 Winter flooding Weedy rice seed viability at the end of winter reduced by 95% in flooded fields, 26-77% in unflooded fields Italy, Fogliatto et al., 2010 organisms reduced, increased biodiversity index N. peposaca value Rosy-Billed Pochard Argentina and Brazil Don Pablo Ranch Project, 2012
	Garganey A. querquedula Invertebrates Red rice Oryza punctata/peren	South Asia, India Senegal/Mali Rice-duck farming Number of arthropod individuals and Sundar and Subramanya, 2010 Hume and Marshall, 1879 in Phillips, 1923 Tréca, 1981 in Tréca, 1992 China, Xiang et al., 2006 China, Zhong et al., 2011 CH 4 emissions of no-tillage areas with ducks 25% lower than without ducks, and 40.5% lower than conventional-tillage areas without ducks Winter flooding Red rice + other weed infestations reduced biodiversity index values higher USA, Street and Bollich, Diversity of aquatic organisms lower Japan, Yamazaki et al., 2003 2004
	! ! !			"&! "'! "(!

!"#$%&'()*(#'%+!,&()('+!&(-#'.+/0(1(23!4(!5/6&'7#%+5/( ! "$! !"#$%&'()*(#'%+!,&()('+!&(-#'.+/0(1(23!4(!5/6&'7#%+5/( ! "%! SUPPLEMENTARY INFORMATION: Article 1 !"#$%&'()*(#'%+!,&()('+!&(-#'.+/0(1(23!4(!5/6&'7#%+5/( ! ")! SUPPLEMENTARY INFORMATION: Article 1 ! CHAPTER II.

INFLUENCE OF POST- HARVEST PRACTICES ON SEED AVAILABILITY AND DUCK USE

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	!"#
	Agronomics	Wildlife Conservation
	Harvest
	Management	Food	& Shorebirds
	Straw Management	Resources Habitat	Other Grain Consumers
	Pest Management	Suitability	Decomposition & Sprouting
	Crop
	Rotation
		Modified part of a scheme after Eadie et al. 2008

!

""!

Article 3: Seed Availability and Waterfowl Use of Rice fields in Camargue (France): the Role of Post-harvest Practices

  Winter flooding did not significantly affect seed depletion rate, but was the main determinant of nocturnal duck use of the fields (flooded: 23.5 ducks/ha ± 2.3 SE, unflooded: 0.3 ± 0.1 SE). Duck numbers were lower in burned fields than in chopped or disked fields. One hectare of Camargue ricefield could support an average of 45 mallard-sized ducks per hectare per day for the entire wintering season (i.e. 5,373 duck-use days/ha, (DUDs/ha)) given initial post-harvest seed densities. Harvested rice fields have a great potential as nocturnal foraging habitat for wintering ducks in the Camargue. The present study suggests that plowing should be avoided and flooding promoted to better allow ducks to use of these fields.!

	Pernollet C.A., Cavallo F., Simpson D., Gauthier-Clerc M.,
	Guillemain M.
	Under revision in Journal of Wildlife Management
	KEY WORDS food resources, nocturnal surveys, post-harvest management, rice, waterfowl,
	winter flooding.

ABSTRACT

European rice fields provide potential nocturnal foraging habitat to waterfowl during winter. Agricultural practices may influence seed availability and accessibility, thereby influencing the extent to which ducks use this managed habitat. To assess the potential influence of postharvest stubble-management practices on waste rice and weed seed densities, and to evaluate the link of the latter with nocturnal duck abundance, a large-scale experiment was conducted in rice fields of the Camargue, France. Different post-harvest treatments (flooding, burning, chopping, disking, ploughing and their combinations) were tested. The quantity of available seeds was assessed three times across the winter season, from harvest in late October to departure of the wintering ducks in early February, over two winters

(2012/13-2013/2014)

. Nocturnal duck use of these fields was monitored during the second year. Initial post-harvest rice and weed seed densities were positively correlated and highly variable (average: rice seeds: 350 kg/ha ± 58 SE; weed seeds: 142 kg/ha ± 21 SE). Mean seed availability was not dependent on straw management procedure (burning, chopping or disking). Average rice density decreased by 89% and weed seed density by 69 % between harvest and late winter. Seed depletion rate was highly dependent on initial seed density, and was greatest in plowed fields. ! !"#$%&'(8*(#'%+!,&(<*($56%9"#'7&6%($'#!%+!&6(1(6&&2(#7#+,#:+,+%;(1(23!4(36&( ! $$(! Around 12% of the Earth's land area is covered by farmlands (FAO

  We used Log-transformed seed density because we expected seed density to influence bird use following a log-normal relationship(cf. Anteau et al. 2011).All statistical tests were performed using R version 3.1.3 (R Core Team 2013). Data are presented as mean ± standard error (SE) throughout the paper. ! We evaluated carrying capacity (DUDs) of Camargue rice fields immediately following harvest for two scenarios -the actual, where 9% of rice fields are winter flooded(Pernollet et al. 2015), and a hypothetical, where all rice fields are winter flooded. For the latter we calculated possible DUDs as the total available energy in the area (available food [g dry mass] times the metabolizable energy of this food [kcal/g dry mass]) divided by the daily energy requirements of an individual bird [kcal/day/duck]. DUD was calculated based on the total initial density of rice and the main three weed seeds (red rice Oryza sativa var.

, Echinochloa spp., and Bolboschoenus maritimus) multiplied by their respective metabolizable energy contents: 3.34 kcal/g for rice and red rice (true metabolizable energy,

Reinecke et al. 1989

), 2.75 kcal/g for Echinochloa spp. (true metabolizable energy,

Checkett et al. 2002

) and 3.12 kcal/g for Bolboschoenus maritimus (considering a 70% assimilation efficiency and total !"#$%&'(8*(#'%+!,&(<*($56%9"#'7&6%($'#!%+!&6(1(6&&2(#7#+,#:+,+%;(1(23!4(36&( ! $%%! energy density,

  in weed seed density was observed in fields where straw was burned, chopped or disked (Table7). In contrast to what was observed for rice grains, in fields where straw was burned there were not significantly more weed seeds in the burned rows than unburned rows (log(weed seed density)~straw.fac+(1|field.fac)+(1|farm.fac), P=!0.53).

!"#$%&'(8*(#'%+!,&(<*($56%9"#'7&6%($'#!%+!&6(1(6&&2(#7#+,#:+,+%;(1(23!4(36&( ! $%'!

Table 2 .

 2 Candidate models, numbers of parameters (K), Akaike's Information Criterion (AIC), difference from lowest AIC value (∆ AIC), and Akaike model weight (w i ) used to determine what influences Log(mean rice seed density per core sample) in rice fields during early winter (immediately following harvest) for winters 2012-2013 and 2013-2014 in Camargue, France. Log(Weed seed density) (kg/ha) in the same core sample, Years of rice = number of consecutive years this field had already been cultivated in rice, Farming type = conventional vs. organic, Straw = method of straw disposal (burning, chopping, disking) and possible interactions. Random factors: Year = winters 2012-2013 vs. 2013-2014, Field number and Farm identity.

	Parameters!	K!	AIC!	∆AIC! w i !
	Log(Weed seed density) + Years of rice!	2! 2516.51!	0.00!	0.38!
	Log(Weed seed density) + Years of rice + Log(Weed seed density) x Years of rice!	3! 2518.33!	1.82!	0.15!
	Log(Weed seed density) + Years of rice + Farming type!	4! 2518.35!	1.84!	0.15!
	Log(Weed seed density) + Years of rice + Farming type + Years of rice x Farming type!	5! 2519.77!	3.26!	0.07!
	Log(Weed seed density) + Years of rice + Straw !	5! 2519.85!	3.34!	0.07!
	Log(Weed seed density) + Years of rice +Farming type+ Log(Weed seed density) x Years of rice!	5! 2520.21!	3.70!	0.06!
	Log(Weed seed density) + Years of rice + Farming type + Straw !	7! 2521.46!	4.95!	0.03!
	Log(Weed seed density

Table 3 .

 3 Candidate models, numbers of parameters (K), Akaike's Information Criterion (AIC), difference from lowest AIC value (∆ AIC), and Akaike model weight (w i ) used to determine what influences Log(mean weed seed density per core sample) in rice fields during early winter (immediately following harvest) for winters2012-2013 and 2013-2014 in Camargue, France. Log(Rice seed density) (kg/ha) in the same core sample, Years of rice = number of consecutive years this field had already been cultivated in rice, Farming type = conventional vs. organic, Straw = method of straw disposal (burning, chopping, disking) and possible interactions. Random factors: Year = winters 2012-2013 vs. 2013-2014, Field number and Farm identity. !

	Parameters

!

$%)!

Date of the duck nocturnal survey

  Candidate models, numbers of parameters (K), Akaike's Information Criterion (AIC), difference from lowest AIC value (∆ AIC), and Akaike model weight (w i ) used to determine what influences weed depletion rate during winters 2012-2013 and 2013-2014 in Camargue, France. Period = early to mid-winter or mid-to late winter; Seed density = average density of seeds (rice + weed) per field at the beginning of the corresponding time period; Practice = the agricultural practice applied during that period, i.e., partially-disked, disked, plowed, none; and Flooding = winter flooding vs. no flooding. Random factors: Year = winter[START_REF] Fuller | Birds and habitat: relationships in changing landscapes[END_REF]-2013 vs. 2013- 2014, Field number and Farm identity.

	%=>?@(B*!Parameters				K	AIC	∆AIC	wi
	Seed density + Practice + Flooding		7	-682.46	0.00	0.20
	Seed density			1	-682.35	0.11	0.19
	Seed density + Period			3	-682.34	0.12	0.19
	Seed density+ Practice		5	-681.58	0.89	0.13
	Seed density + Flooding		3	-680.60	1.86	0.08
	Seed density + Practice + Flooding + Period	9	-680.52	1.94	0.08
	Seed density + Period + Flooding		5	-680.45	2.02	0.07
	Seed density + Practice + Flooding		7	-679.58	2.89	0.05
	Practice + Period			6	-676.17	6.29	0.01
	Practice + Period + Flooding		8	-675.43	7.03	0.01
	Period				2	-675.07	7.39	0.00
	Period + Flooding			4	-673.14	9.32	0.00
	Mallard	Teal	Non Identified	Others	Pintail	Proportion of study fields flooded

Table 7 .

 7 Mean number of ducks per ricefield during the survey week depending on water levels over the winter 2013-2014 in Camargue, France. Vertical bars represent standard errors. Columns with different letters differed significantly after post hoc Tukey tests. Model-averaged parameter estimates, standard-errors and 95% confidence intervals of the variables present in models with ∆ AIC <2 to explain rice and weed seed initial density values immediately following harvest, rice and weed seed depletion rates in the post-harvest rice fields in the Camargue, winter 2012-2013 and 2013-2014, and duck numbers counted in the post-harvest rice fields in the Camargue, winter 2013-2014.

	Parameters	K	AIC	∆AIC	wi
	Water Level + Straw	10	877.44	0.00 0.35!
	Water Level + Straw + Roost	11	878.54	1.11 0.20
	Water Level + Roost	6	879.03	1.60 0.16
	Water Level + Straw + Log (Seed density)	11	879.16	1.73 0.15
	Water Level + Straw + Log (Seed density) + Roost	12	880.50	3.06 0.08
	Water Level + Log (Seed density) + Roost	7	881.03	3.59 0.06
	Water Level	5	884.66	7.23 0.01
	Water Level + Log (Seed density)	6	886.63	9.19 0.00
	Straw + Roost	6	929.28	51.84 0.00
	Straw	5	929.67	52.23 0.00
	Straw + Log (Seed density)	6	931.12	53.68 0.00
	Straw + Log (Seed density) + Roost	7	931.65	54.21 0.00
	Roost	1	947.32	69.88 0.00
	Log (Seed density) + Roost	2	949.17	71.74 0.00
	Log (Seed density)	1	949.49	72.06 0.35

%=>?@(C* Candidate models, numbers of parameters (K), Akaike's Information Criterion (AIC) difference from lowest AIC value (Delta AIC), and Akaike model weight (w i ) used to determine what influenced the number of ducks counted in post-harvest rice fields across winters 2013--2014, Camargue, France. Water level = dry, rain, low, middle, high water level; Straw = method of straw disposal (burning, chopping, chopping -disking, disking, plowing); Roost = Distance (km) to the nearest potential roosting site; Log (Seed density) = Log(seed density, rice + weed seed density, kg/ha) in the field. Random factors: Week of survey, Field number and Farm identity.

  (66 to 672 kg/ha), and exceeds the ca. 250 kg/ha reported byAmano et al. (2004, 2006 in Stafford et al. 2010) in Japan. The weed seed density we recorded greatly exceeds the 3.1-7.4 kg/ha calculated byManley et al. (2004) for the MAV, and the 4-44 kg/ha fromEadie et al. (2008), in which data was assessed from all relevant US studies. Intensive mechanical and chemical weed control in North American rice fields is considered to generally limit weed seeds to less than 50 kg/ha(Stafford et al. 2010). However, in France where access to pesticides are more limited than in the US and in other neighbouring Mediterranean countries, less effective weed control measures such as crop rotation and/or mechanical control take a greater role in curbing weed growth, and weed incursions are generally more severe as a result. Previous European studies incorporated comparatively low sampling efforts (fewer cores and study sites), and reported significantly lower seed density (rice and weeds) estimations than that of the present study (210 kg/ha seeds in Camargue(Tamisier and Dehorter 1999) and 240 kg/ha in Doñana, Spain[START_REF] Toral | Agricultura y Conservación en Doñana: La Importancia del Arrozal para las Aves Acuáticas[END_REF]) vs a total of 492 kg/ha in the present study). ! Rice and weed seed densities were positively correlated, which is contrary to the general expectation that weedy fields generate lower rice yields (e.g.Oerke 2006

		!"#$%&'(8*(#'%+!,&(<*($56%9"#'7&6%($'#!%+!&6(1(6&&2(#7#+,#:+,+%;(1(23!4(36&(
	!	$&%!

(134 to >600 kg/ha) and

Stafford et al. (2010)

!"#$%&'(8*(#'%+!,&(<*($56%9"#'7&6%($'#!%+!&6(1(6&&2(#7#+,#:+,+%;(1(23!4(36&(

  where farmers receive financial incentives to flood their fields from the European Commission (Agri-Environmental Schemes;Pernollet et al. 2015). ! Spatial distribution of rice seed between and within fields, for example in burned and unburned rows of burned fields, may profoundly influence duck foraging efficiency, but has gone largely unstudied. More direct field research on duck foraging behaviour under various flooding and straw disposal treatments and through winter as seed stocks are depleted (e.g.[START_REF] Rutka | Waste rice depletion by waterfowl wintering in the Mississippi Alluvial Valley[END_REF]) would be useful to better gauge the influence of the various post-harvest practices. Such studies would also provide more precise parameters for energetic models (e.g., TRUEMET:Petrie et al. 2014, ECCs: Beatty et al. 2015), and spatially explicit individualbased behavioural models (e.g. SWAMP:Miller et al. 2014), improve the prediction of movement and use of the fields by wintering ducks, and allow testing of different scenarios of winter ricefield flooding or reduction in area cultivated under rice.The rice industry in Camargue (France) is highly reactive to changes in the political sphere, as will likely be noted following revision of the EU Common Agricultural Policy 2015, when specific financial support to rice production has been suppressed. As a result a reduction of ca. 30% of the rice area has already been recorded in the Camargue between 2012 and 2015 and a replacement with dry crops such as wheat or vegetables is observed which can be detrimental for waterbirds (C.

	LITERATURE CITED
	Amano, T., K. Ushiyama, G. Fujita, and H. Higuchi. 2006. Foraging patch selection and
	departure by non-omniscient foragers: a field example in White-fronted Geese. Ethology
	112:544-553.

!

$&(! A.

Pernollet, unpub. data)

. In Camargue, water to flood rice fields is pumped from the Rhône River and the associated costs are too high for flooding to be feasible without support or financial assistance. Financial support of winter flooding of rice fields through Agri-Environmental Schemes, or at least passive flooding through rainwater retention, should be promoted in Camargue and throughout the wintering range of European waterfowl

(Pernollet et al. 2015)

to provide ample foraging grounds where necessary (such as in the Camargue,

Brochet et al. 2009)

.

ACKNOWLEDGMENTS

C.P PhD project is financially supported by the Centre de Recherche de la Tour du Valat and an ONCFS PhD grant. We especially thank the following rice farmers: Mr. Vezzetti, Mr. Bon, Mr. Mégias, Mr. Callet, Mr. Daujat, Mr. Vadon, Mr. Mandrolini, Mr. Grand, Mr. Plagne, Mr. Gauthier, Mr. Grossi and Mr. Roche, who granted access to their fields and provided information concerning field history and practices. We are grateful for the assistance received from some Tour du Valat staff during nocturnal duck surveys and for the kind help of eight students and volunteers in the core sieving process (M. Longine, J. Fauchet, R. Laroche, B. Marie-Catherine, M. Mahut, L. Belfort, D. Simpson, L. Gili). We appreciated the guidance of O. Pineau, F. Mesléard, J.-C. Mouret and Juan Lozano. O.Devineau and F. Mesléard provided constructive comments on a previous draft of the manuscript. Anders, M. M., K. Van Kessel, and J. M.

Eadie. 2008

. Agronomic impacts of winter wetland and waterfowl management in ricelands. Conservation in Ricelands of North America. In: Manley, S.W. (Eds), Conservation in ricelands of North America. The Rice

Foundation, Stuttgart, Arkansas,

  mallards on straw inBird et al. (2001). Here we used experimental tests to study seed degradation by water in greenhouse microocosms and to assess stalk trampling and seed consumption by ducks penned in a ricefield.

		!"#$%&'(<*(#0'5/5.+!(:&/&-+%6(5-(D+/%&'(-,552+/0(1(23!4(36&(
	Agronomics	Wildlife Conservation
	Harvest Management	Food		Waterfowl & Shorebirds
	Straw Management	Resources Habitat	Other Grain Consumers
	Pest Management	Suitability	Decomposition & Sprouting
	Crop
	Rotation
		Wildlife Abundance & Diversity
		Nutrients	Weeds & Disease	Straw Decomposition
	Yield
		Modified part of a scheme after Eadie et al. 2008
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Table 1

 1 Model selection to evaluate the influence of the species (rice, weedy rice, barnyardgrass, sea clubrush), treatment (non-flooded, flooded, control), period (T2, T3) and species*treatment on seed mass across the winter 2014-2015, in microcosms positioned in a greenhouse at the Tour du Valat Research Center, Camargue, Southern France. Numbers of parameters (K), Akaike's Information Criterion (AIC), difference from lowest AIC value (∆ AIC), and model weight (wi) are provided for plausible model sets involving the main effects and key interaction. Random factor: replicate (i.e. tray) ID.

Table 4

 4 Energy loss across the season for 4 seed species under a flooded or dry treatment during the winter 2014-2015, in microcosms positioned in a greenhouse at the Tour du Valat Research Center, Camargue, Southern France. Energy densities and remaining proportions of initial seed biomass are the predicted values from the best models of tables 1 and 2. Seeds were collected for analysis after 123 days of experiment.

		Energy density per	Energy density per	Remaining proportion	Final energy	Gross energy loss
		gram seed at the	gram seed at the	of initial seed	available at the end of the	through the winter
		beginning of the	end of the winter	biomass at the end of	winter from an initial
		winter (kJ/g)	(kJ/g)	the winter	1gram seed (kJ)
	Rice dry	16.5	17.0	0.538	9.146	62.3%
	Rice flooded	16.5	17.8	0.376	6.693	59.4%
	Weedy rice dry	16.9	17.0	0.734	12.478	26.2%
	Weedy rice flooded	16.9	17.8	0.547	9.737	42.4%
	Barnyardgrass dry	18.3	18.5	0.621	11.489	37.2%
	Barnyardgrass flooded	18.3	19.3	0.567	10.943	40.2%
	Sea clubrush dry	19.7	20.0	0.765	15.30	22.3%
	Sea clubrush flooded	19.7	20.0	0.747	14.94	24.2%

, Appendix I.2, I.3).

  Considering that the Camargue is among the more southerly wintering sites in Europe, we ignore to what extent ricefield

Table 2

 2 Basic market costs to farmers under the various agricultural scenarios (the numbers in parentheses correspond to the activities in Table1). Values provided in Euros per hectare during the post-harvest period (October through February), computed fromDelmotte (2011) and[START_REF] Pérès | Coûts prévisionnels indicatifs des matériels agricoles[END_REF] for the salary, fuel and fixed costs with correction for inflation. Costs for high lands were used for benefits-to-costs ratios calculation.

	Scenarios	Salary costs	Fuel costs	Irrigation and drainage costs Low High	Fixed costs Low High	Total costs Low High
				lands	lands	lands	lands	lands	lands
	Burning -ploughing (1)	30.39	51.97	-	-	82.77	82.77	165.13 165.13
	Chopping -cover-crop (2)	25.18	39.13	-	-	84.45	84.45	148.76 148.76
	Burning -
	flooding -cage-wheels -	39.69	37.63	129.69 161.32	67.8	109.05 274.81 347.69
	drainage (3)
	Chopping -
	flooding -drainage -	34.49	58.18	129.69 161.32	96.17	137.42 318.53 391.41
	ploughing (4)
	Chopping -
	flooding -rototiller -	30.98	43.83	129.69 161.32	89.95	131.2	294.45 367.33
	drainage (5)
	Harvest in
	water -
	chopping -	30.98	43.83	18.22	18.22	100.03 100.03 193.06 193.06
	rototiller -
	drainage (6)

  2 , CH 4 and N 2 O. We calculated the global warming impact based on CO 2 equivalencies of CH 4 and N 2 O using the ratios provided by the Intergovernmental Panel on Climate Change (IPCC, 2006), i.e. 25 tons equivalent CO 2 for 1 ton CH 4 and 298 tons CO 2 for 1 ton N 2 O. The economic value of such emissions was then estimated, considering a 7 € cost per ton of CO 2 as implemented by the French Ministry of Economy and Finances (2014).

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Table 3

 3 shows the greenhouse gas emissions caused by fuel use of each specific machinery for the work carried out on one hectare of rice fields. GHG emissions from straw burning were taken fromCouderc (2013) for conventional rice farming: 9,313 kg CO 2 /ha, 16.6 kg CH 4 /ha and 0.43 kg N 2 O/ha, which represents a total equivalent to 9.9 tons of CO 2 /ha. Some N 2 O is emitted by the soil following nitrification-denitrification of the dry organic matter if it is incorporated. Considering that rice cultivation produces 6 tons of dry organic matter per hectare (see above), 85% of such matter may be incorporated when a plough, cover crop, rototiller or wheel cages are used after chopping (i.e. not burning) straw[START_REF] Doublet | ClimAgri : Guide méthodologique et des facteurs d'émission[END_REF], rice crop residuals contain 0.7% nitrogen[START_REF] Doublet | ClimAgri : Guide méthodologique et des facteurs d'émission[END_REF], 1% of such nitrogen would be emitted by soils as N-N 2O (IPCC, 2006) and the correction factor from N-N 2 O to N 2 O is 44/28[START_REF] Doublet | ClimAgri : Guide méthodologique et des facteurs d'émission[END_REF], 0.00066 tons N 2 O would be emitted by soils per ha, corresponding to an equivalent of 0.197 tons CO 2 if all stalks, roots and straw were incorporated to the soil. When the straw is burnt and only stalks and roots are incorporated, this value would fall to 0.00011 tons N 2 O emitted by soils per ha, corresponding to an equivalent of 0.033 tons of CO 2 .

Table 3

 3 Greenhouse gas emissions associated with the use of each tool during the harvest and post-harvest periods.

	Machinery	Fuel
		consumption
		(l/

ha) 3 CO 2 emission (kg/ha) 4 CH 4 emission (kg/ha) 4 N 2 O emission (kg/ha) 4 Equivalent CO 2 (t/ha)

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	Combined harvester 1	24	64.08	0.00364	0.00127	0.064
	Crusher 2	7	18.69	0.00106	0.000371	0.019
	Cover-crop	11	29.37	0.00167	0.000583	0.029
	Plough	31.25	83.43	0.00475	0.00165	0.084
	Cage-wheels	16	42.72	0.00243	0.000848	0.043
	Rototiller	16	42.72	0.00243	0.000848	0.043
	Private irrigation pump	33.3	88.91	0.00506	0.00176	0.089
	1 Fuel use considered equivalent for combined harvester used in flooded and dry fields.
	² Additional fuel use when a crusher is fixed to the back of the combined harvester.
	3 From Delmotte (2011)
	4 using 2.67kg CO2, 0.000153kg CH4 and 0.0000532kg N2O per litre of fuel burnt (van Kempen, 2010; EnviroConsult, 2011)
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Table 4

 4 Greenhouse gas emissions under the six agricultural scenarios (the numbers in parentheses correspond to the activities in Table1) and their equivalent cost to society (see text for details of the calculations).

	Scenarios	CO 2	CH 4	N 2 O	Equivalent	Societal cost
		emission	emission	emission	CO 2	(€/ha)
		(kg/ha)	(kg/ha)	(kg/ha)	(t/ha)
	Burning -ploughing (1)	9460.51	16.60	0.54	10	70
	Chopping -cover-crop (2)	112.14	0.0063	0.66	0.31	2.17
	Burning -
	flooding -cage-wheels -	9508.71	376.60	0.54	19.10	133.70
	drainage (3)
	Chopping -
	flooding -drainage -	255.11	360	0.67	9.45	66.15
	ploughing (4)
	Chopping -
	flooding -rototiller -	214.40	360	0.66	9.41	65.87
	drainage (5)
	Harvest in water
	-chopping -rototiller -	125.49	360	0.66	9.32	65.24
	drainage (6)
	2.4.5. Avoided costs: reduced need for fertilizers and herbicides for the farmer

  limitation prepared by the French Rice Organisation (Centre Français du Riz, CFR, 2011), corrected with a 3.4% cumulated inflation rate from 2011 to 2014, 95% reduction of weedy rice seed stocks would correspond to a savings of 52.90 € per hectare (including the costs associated with the purchase and application of herbicides)

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  The French government and the European Union jointly support environment and climatefriendly agricultural practices via financial incentives called Agri-Environment-Climate Schemes, contracted by farmers and implemented through the Common Agricultural Policy (CAP) (EC Directorate General for Agriculture and Rural Development

	2.4.6. Market benefits: Agri-environmental schemes for the farmer

  the mean income from hunting in the sampled hunting estates was 1,839 French Francs per hectare per year which, including cumulated inflation rates, equates to 358.43 €/ha in 2014.

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  Through a meta-analysis of Mediterranean wetland data,[START_REF] Calvet | Rapport d'étude scientifique du projet : combien coûte la Camargue ? Rapport de recherche Fondation MAVA[END_REF] see also[START_REF] Brander | The empirics of wetlands valuation: a comprehensive summary and a meta-analysis of the literature[END_REF] provided estimates which, corrected for inflation until 2014, amount to 5.83 €/ha for support to biodiversity and 17.49 €/ha for water amelioration.[START_REF] Calvet | Rapport d'étude scientifique du projet : combien coûte la Camargue ? Rapport de recherche Fondation MAVA[END_REF] estimated that the willing to pay by visitors of the Camargue, used as a means to evaluate the aesthetical landscape value, was equivalent to 16.09 € per visit as of year 2014. Considering that 5.3 million individuals visit the Camargue, of which 12% do so during winter (PNRC, 2013c), and that 11,390 ha were cultivated in rice in 2014 (France AgriMer, unpublished data), the total willingness to pay by visitors for such landscapes would be (16.09*5,300,000*0.12)/11,390 = 898.44 €/ha. Combined with the other ecosystem services above the total benefit provided to society by flooded rice fields is 921.76 €/ha.

Par exemple, les conditions climatiques à l'intérieur de la serre peuvent avoir été différentes de celles dans les champs, ce qui pourrait avoir affecté les taux de dégradation des graines (Article 4). Pour aller au bout de la logique de l'expérience sous serre, celle-ci pourrait être étendue en incluant les phases de germination et d'émergence des plantules. La biomasse des plantules pourrait également être mesurée en plein champ, afin d'évaluer si l'inondation hivernale des rizières pourrait être un moyen de contrôle biologique des adventices au-delà du stade de fin d'hiver. Le test expérimental avec les canards devait également être mené sur une période de temps limitée pour des contraintes évidentes liées à l'utilisation d'oiseaux dans des enclos. Nous avons simulé la présence d'une faible densité de canards pendant tout un hiver à l'aide de nombreux oiseaux dans un petit enclos sur une courte période de temps. Cela nous a empêché de mesurer à proprement parler la décomposition de la paille sur plusieurs mois, et seule la submersion des chaumes a été considérée (Article 5). Ces études, qui fournissent déjà des résultats intéressants, pourraient être améliorées par des expériences complémentaires.

includes insurance, amortization and storage costs ² values for high lands, where the pumping costs are greater * not quantified in the present study

includes insurance, amortization and storage costs * not quantified in the present study

ACKNOWLEDGMENTS

We especially thank Mr. Vezzetti Mr. Bon and Mr. Callet, the rice farmers, who granted access to their fields for seed and substrate collection. We are grateful for the assistance received from Pierre Rivier, Pierre Hebert and Nicole Yavercovsky who helped for the setting-up of the experiments and the laboratory analyses, and Mark Petrie and John Eadie for sending us information on similar studies in the U.S.. C.P PhD project is financially supported by the Centre de Recherche de la Tour du Valat and an ONCFS PhD grant.

Acknowledgements

We would like to thank Hélène Rey-Valette, and Christian Poncet for their support and comments during the preparation of this work, as well as Jean-Marc Barbier and Lisa Ernoul for valuable help with the former version of the manuscript. We also thank the many people who answered our questions throughout the study or provided valuable data: Olivier Pineau, Anis Guelmami, Marie Suet and Coralie Beltrame from Tour du Valat, Vincent Couderc, Jean-Claude Mouret and Jean-Marc Barbier from UMR-Innovation and INRA Montpellier, Stéphanie Cavé from SMGAS du pays d'Arles, Marie Granier and Anne Vadon from the Camargue Regional Natural Parc, Bertrand Mazel from the French Rice Farmers' Union, Cyril Thomas from the Centre Français du Riz, Gilbert Lannes from Cirad and the farmers who took part in CP PhD study. This PhD work is financially supported by the Centre de Recherche de la Tour du Valat and an ONCFS PhD grant. !""#$%&'#()!%%&*&+$!,)"!"#-()!-*&',#).)'+(*/0#$#1&*)!$!,2(&() ! "#%! ) ! "#"! ! "&+!

II. LIST OF POPULAR COMMUNICATIONS

n'auraient pas pu être réalisés sans un soutien de la Tour du Valat qui m'a offert le gîte, le couvert et This dissertation concludes a 3-years doctoral work at the Centre de Recherche de la Tour du Valat (, under the supervision of Dr. Matthieu Guillemain (ONCFS) and Dr. Michel Gauthier-Clerc (Associate researcher at Tour du Valat, current director of the Garenne Zoo, Switzerland), and in collaboration with numerous other scientists. I worked for the Migratory Bird Unit of the Office National de la Chasse Doñana, Spain, during November 2014, under the supervision of Dr. Andrew Green and Dr. the Wildlife, Fish, and Conservation Biology Faculty of the research, and to reinforce professional links to prepare future research after the PhD. projects we have started to implement during this PhD, and plan to develop further in the near future. These data are still being analysed, so that the results are therefore not included in the current thesis.

The core of my research was financially supported by the Centre de Recherche de la Tour du Valat and an ONCFS PhD grant. Part of the United States internship was financed by a scholarship for international mobility from the SIBAGHE (current GAIA) doctoral school, Montpellier University,

The outcomes of these training periods do not properly appear in the current manuscript. These are

Appendix II. [START_REF]A0,$?05+'0$GL'0H$(,)$(5&0[END_REF] The costs for salary and fuel were calculated using data provided by the INRA Montpellier UMR Innovation database, which is largely based on Delmotte (2011), and fixed costs for each practice were calculated using information provided by the Bureau de Coordination du Machinisme Agricole [START_REF] Pérès | Coûts prévisionnels indicatifs des matériels agricoles[END_REF]. The latter include the machinery insurance and storage costs as well as the depreciation rate of the machinery. Note that such fixed costs were not available for cage-wheels and private pumps, and were hence not considered here. Fixed costs included 500 hours of use per ha per year for tractors and a minimum of 200 hours per ha per year for the other equipment [START_REF] Pérès | Coûts prévisionnels indicatifs des matériels agricoles[END_REF]. Because tractors may be used for other activities during other parts of the year than our study period (e.g. to sow rice or spread fertilizers during spring) the value used here may be slightly overestimated since we were only interested in the harvest+intercrop period, but the bias should be relatively similar among all scenarios considered here. The values of salary, fuel and fixed costs for each scenario are provided in Table 2.

Appendix 1. Costs associated with the six agricultural scenarios (the numbers in parentheses correspond to the activities in Table 1). Crosses indicate costs known to exist but not quantified in the present analysis.

Burningploughing (1)

Choppingcover-crop ( 2 Appendix 2. Benefits associated with the six agricultural scenarios (the numbers in parentheses correspond to the activities in Table 1). Crosses show benefits known to exist but not quantified in the present analysis.

Burningploughing (1)

Choppingcover-crop ( 2

NOCTURNAL USE OF RICEFIELDS BY DUCKS IN TWO MAJOR WINTER QUARTERS OF WESTERN EUROPE

ABSTRACT

Cultivated systems dominate the Earth and represent both a threat and an opportunity for the conservation of biodiversity. Some agricultural practices can simultaneously allow abundant food production and some protection of the environment. Winter flooding of rice fields has been identified as a habitat management with potential advantages for both wintering ducks and farmers in Asia and North America. Through a set of empirical and experimental studies, we tested if similar benefits could be expected in Europe. The mean number of wintering ducks in five major rice production regions of Western Europe is positively related with the total wetland area (natural wetlands plus flooded rice fields), suggesting complementarities between these habitats for waterfowl conservation. Applying a variety of agricultural practices to 50 harvested rice fields in Camargue (France), we demonstrate the existence of vast amounts of duck food resources (ca. 500 kg/ha of rice and weed seeds remaining on the ground after harvest). Seed availability greatly decreases across the winter (-89% for rice seed mass and -69% for weeds), seed depletion being accentuated by ploughing. Winter flooding is the main determinant of nocturnal use of the fields by wintering ducks (on average 24 and. 0.3 ducks/ha in flooded and unflooded fields, respectively). In return, experiments show that waterfowl foraging in flooded rice fields enhance straw stalks reduction, but do not significantly reduce the weed seed bank. A cost-benefit analysis was eventually carried out to evaluate whether winter flooding in France would be economically realistic considering agronomic and environmental constraints and advantages. Harvesting rice in flooded fields is four times more profitable to farmers and more than eight times more profitable for the Camargue society than the traditional burning-ploughing (benefits-to-costs ratios for farmers: 4.15 vs. 1.02; for society: 6.67 vs. 0.78). Promoting winter flooding of rice fields in Europe would benefit both farmers and wintering ducks. In Camargue, in addition to be economically realistic for farmers, this practice is strongly desirable from an environmental conservation point of view, and should therefore be promoted.