domain: sde sdv

text:
Cyanecula Svecica

Namnetum Endémico

D E La

Costa Francesa

Implicaciones De Conservación En

E L Contexto

Del Cambio Global

Raphaël Musseau
email: r.musseau@biosphere-environnement.com

Sonia Beslic

Christian Kerbiriou

IMPORTANCE OF INTERTIDAL WETLANDS FOR THE FRENCH COASTAL ENDEMIC BLUETHROAT CYANECULA SVECICA NAMNETUM AND CONSERVATION IMPLICATIONS IN THE CONTEXT OF GLOBAL CHANGES IMPORTANCIA DE LOS HUMEDALES INTERMAREALES PARA EL RUISEÑOR PECHIAZUL

Keywords: coastal zone management, diet, energy expenditure, home range, marshland passerines, moult, trophic resources dieta, gasto energético, gestión de la zona costera, muda, paseriformes de pantanal, rango de hogar, recursos tróficos

Coastal specialised species have naturally restricted distribution areas and may be drastically affected by fragmentation or loss of their habitats due to ongoing changes, such as artificialisation, shoreline erosion, rising water levels or colonisation by invasive species. In this context we characterise the land occupation strategies of a Western Atlantic French coastal endemic bird: the Bluethroat Cyanecula svecica namnetum. Our study focuses on a key period of the life cycle of this species: the post-breeding moult. Capture and recapture sessions in intertidal habitats have allowed us to retrieve 26% of local breeders during their moulting period. The modeling of moult kinetics revealed that moult of flight feathers takes 37-50 days. A radio-tracking survey of moulting birds revealed exploitation by individuals of both the lowest and tallest vegetal formations of intertidal sites and exploitation of small home ranges (0.42-1.34 ha), typical of locations where trophic resources tend to be abundant and predictable. Analyses of droppings highlighted that Coleoptera, Aranea and marine crustaceans (Amphipoda) contributed most of the prey biomass consumed, amphipods being particularly selected by birds in active moult. Our results underline the importance of intertidal wetlands in terms of trophic opportunities to compensate for the energy costs of moult for the Bluethroat. Given the global changes already dramatically affecting coastal habitats, we emphasise that special attention should be given to the conservation of intertidal wetlands for marshland passerines of conservation concern such as the Bluethroat, and that restoration of adjacent coastal terrain is a promising development.

INTRODUCTION

Coastal habitats are currently under various threats. To the context of anthropic pressure must be added such factors as rising sea levels and coastal erosion of shorelines recorded globally. About 70% of the Earth's sandy beach environments are already impacted by erosion dynamics [START_REF] Bird | Coastline changes. A global review[END_REF] and 20-60% of the world's coastal wetlands may disappear during this century due to sea level rise (Titus, 1988;[START_REF] Nicholls | Coastal systems and low-lying areas. Climate Change 2007: Impacts, Adaptation and Vulnerability[END_REF][START_REF] Craft | Forecasting the effects of accelerated sea-level rise on tidal marsh ecosystem services[END_REF]. Erosion can be driven by a local decrease in sediment supply or changes in sea level [START_REF] Feagin | Coastal erosion, global sea-level rise, and the loss of sand dune plant habitats[END_REF]. Erosion results in the displacement of coastal environments, except where there are protective barriers [START_REF] Feagin | Coastal erosion, global sea-level rise, and the loss of sand dune plant habitats[END_REF]. In coastal strips with barriers, including anthropogenic developments (port facilities, dykes, human habitats…), coastal habitat displacement possibilities and areas available for plant and animal communities are reduced [START_REF] Feagin | Coastal erosion, global sea-level rise, and the loss of sand dune plant habitats[END_REF]. Given the physical constraints they face, communities of coastal habitats, such as those of salt marshes, are generally composed of a few specialised species able to cope with periodic exposure to salt water [START_REF] Verberk | Explaining General Patterns in Species Abundance and Distributions[END_REF]. These species have, intrinsically, a restricted distribution area and may be drastically affected by fragmentation or loss of their habitats due to the global changes presently underway.

Within this context, the situation of coastal migratory birds is of particular concern due to their specific habitat requirements and the ongoing changes in habitats they exploit. A global decline of migratory birds has been repeatedly observed [START_REF] Robbins | Population declines in North American birds that migrate to the Neotropics[END_REF]Rappole & McDonald, 1994). The causes of this decline include climate change [START_REF] Both | Climate change and population declines in a long-distance migratory bird[END_REF][START_REF] Saino | Climate warming, ecological mismatch at arrival and population decline in migratory birds[END_REF], degradation of wintering or breeding habitats [START_REF] Robbins | Population declines in North American birds that migrate to the Neotropics[END_REF] and/or loss and fragmentation of stopover sites [START_REF] Hutto | On the importance of stopover sites to migrating birds[END_REF]. Conditions experienced during migration can limit bird breeding populations [START_REF] Newton | Can conditions experienced during migration limit the population levels of birds?[END_REF] and the vital importance of high quality stopover sites along migratory flyways has come to the fore-front of avian conservation [START_REF] Petit | Habitat use by landbirds along nearcticneotropical migration routes: implication for conservation of stopover habitats[END_REF]. For coastal species facing such constraints, sites used for moult are also particularly important. Bird plumage is permanently exposed to alteration agents such as mechanical abrasion [START_REF] Bergman | Why are the wings of Larus f. fuscus so dark?[END_REF][START_REF] Bonser | Melanin and the abrasion resistance of feathers[END_REF][START_REF] Merilä | Fitness and feather wear in the collared flycatcher Ficedula albicollis[END_REF][START_REF] Butler | Are melanized feather barbs stronger?[END_REF], U.V. radiation [START_REF] Bergman | Why are the wings of Larus f. fuscus so dark?[END_REF] or bacterial activity [START_REF] Burtt | Occurence of feather-degrading bacilli in the plumage of birds[END_REF], obliging individuals to replace their feathers regularly. The moult strategy adopted by all adult sedentary passerines breeding in the Western Palearctic, by all short-distance migratory passerines wintering in temperate zones and by some long-distance migrants wintering in equatorial or northern tropical regions, generally involves a complete moult starting immediately after nesting [START_REF] Jenni | Moult and ageing of European passerines[END_REF]. Moult is particularly energy-demanding [START_REF] Lustick | Energy requirement of molt in cowbirds[END_REF][START_REF] Lindström | The energetic cost of feather synthesis is proportional to basal metabolic rate[END_REF][START_REF] Murphy | Energetics and nutrition of moult[END_REF][START_REF] Murphy | Nutritional aspects of avian moult[END_REF] and may conflict with other life cycle events such as reproduction or migration [START_REF] Nilsson | The cost of reproduction: a new link between current reproductive effort and future reproductive success[END_REF][START_REF] Hemborg | Sexual differences in the control of postnuptional moult in the pied flycatcher[END_REF]. Thus, given the energy cost of moult and its potential impact on individual survival, knowledge of a species moult strategies (period, habitats used and trophic resources exploited) is a key element for its conservation.

The Bluethroat Cyanecula svecica is an Holarctic songbird migratory species of conservation concern in Europe (Tucker & Heath, 2004). This widely distributed passerine is a complex polytypic species with 11 currently acknowledged subspecies distributed in Europe, Asia and Alaska (ten subspecies documented by [START_REF] Cramp | The Birds of the Western Palearctic[END_REF] to which must be added azuricollis, [START_REF] Svensson | Identification guide to European Passerines[END_REF][START_REF] Peiró | A study of migrant and wintering Bluethroats Luscinia svecica in southeastern Spain[END_REF][START_REF] Johnsen | Molecular and phenotypic divergence in the Bluethroat (Luscinia svecica) subspecies complex[END_REF]Arizaga & Alonso, 2015). Some populations have been considered by several authors [START_REF] Huntley | A Climatic Atlas of European Breeding Birds[END_REF] to be under high risk of extinction due to global changes. One subspecies, C. s. namnetum, is endemic to the westernmost Palearctic, with breeding locations restricted to the French Western Atlantic coast (Supplemen-tary Material, appendix 1, Figure A.1) and numbering only 8,000-12,000 pairs (Caupenne et al., 2015). The wintering areas of C. s. namnetum are mainly in Southern Iberia and Northwestern Africa (Arizaga et al., 2015;[START_REF] Arizaga | Breeding origins and pattern of migration of Bluethroats Luscinia svecica wintering from Iberia to Senegal as revealed by stable isotopes[END_REF]Musseau et al., in prep.). The complete moult of adults usually begins in their breeding areas immediately after nesting, starting with primary feathers followed by secondaries, whose moult is completed simultaneously with that of the primaries or slightly later [START_REF] Delany | Ornithology[END_REF][START_REF] Lindström | The energetic cost of feather synthesis is proportional to basal metabolic rate[END_REF]. Moult of the species has been relatively poorly documented. Hence, a research programme was conducted from summer 2012 to summer 2015 to determine the moult strategy of a C. s. namnetum population that breeds in the Gironde Estuary in Southwestern France, in the southern part of the C. s. namnetum breeding range. The work aimed (1) to define moult strategies (moulting grounds period and duration of moult of flight feathers: primaries and secondaries); (2) to determine surfaces and habitats exploited during the moulting period; (3) to characterise the trophic resources exploited by individuals to meet the energy cost of moult and (4) to propose conservation measures for the habitats exploited by birds during the moulting period.

MATHERIAL AND METHODS

Study site

The study was carried out at the Conchemarche Marsh (France, 45° 28' 44" N, 0° 49' 06" W), a 250-ha site on the north bank of the Gironde Estuary (see Supplementary Material, appendix 1, Figure A.1), in the heart of a huge linear coastal ecocomplex of the mesohaline region subjected to tidal influences. This ecocomplex covers approximately 1,500 hectares, is over 25 kilometres in length, and has a width ranging from a few tens of metres to over a kilometre. This large area consists of mudflats, sub-halophilic meadows, reedbeds and numerous flooded depressions created for waterfowl hunting. The site is owned by the Conservatoire du Littoral and managed by the Conservatoire d'Espaces Naturels de Poitou-Charentes. It is composed of habitats of the lowest intertidal zone (including barren mudflats) and low wet vegetation (bulrush-reed beds dominated by Bolboschoenus maritimus that may include patches of Phragmites australis) and habitats of the highest intertidal grounds, including reed beds dominated by Phragmites australis, meadows dominated by Elytrigia acuta and meadows with a mixture of Elytrigia acuta and small reeds.

This area is facing profound changes. In the Gironde Estuary, [START_REF] Sottolichio | Evaluation of the recent morphological evolution of the Gironde estuary through the use of some preliminary synthetic indicators[END_REF] highlighted a maximum turbidity zone migrating continuously towards the upstream portion of the estuary and a significant increase in erosion, with the loss of about 17 km 3 of sediments between 1970 and 1980 and 60 km 3 between 1980 and 1994. Two major phenomena explained these trends: (1) the increased duration of the dry season, affecting fresh water levels in summer with consequent effects on the location of the turbidity maximum zone and (2) the rise in ocean water entering into the estuary (increase between 2.2 and 2.8 mm/year between 1914 and 1996, see details in [START_REF] Eaucéa | Evaluation des impacts du changement climatique sur l'estuaire de la Gironde et prospective a moyen terme, phase 1: analyse des enjeux lies a l[END_REF]. These combined effects generate considerable changes in the area considered in this study. Analyses of satellite photos of the salt marsh ecocomplex comprising the study area (c. 25 km in length) complemented by field surveys, reveal that almost one third (8 km) of the coastline was significantly affected by erosion (see Musseau et al., 2016 and Supplementary Material, appendix 1, Figures A.2 and A.3). This estuary hosts a fairly large Bluethroat population, with up to 20 singing males/10 ha in some areas (Musseau, unpublished data), in dense reedbeds on intertidal mudflats or around flooded depressions created to attract water-fowl. Such densities, combined with the extent of suitable habitat, allow us to consider the Gironde Estuary as one of the most important core areas of the French population of C. s. namnetum. In France, maximum densities are documented in the northern part of the breeding range: 2.6-5 pairs/10 ha in the Guérande saltpans and 5.4-6.6 pairs/10 ha in the Brière marshes (Caupenne et al., 2015).

Moult of the local breeding population

Given the importance of flight feathers relative to the total feather mass of this species (about 19%, see [START_REF] Lindström | The energetic cost of feather synthesis is proportional to basal metabolic rate[END_REF] we focused our study on primary (PP) and secondary (SS) moult. In order to determine the adult flight feather moult strategy of the local breeding population, ringing sessions were conducted in the study site during breeding and moulting periods. Ringing sessions during breeding periods were conducted from the beginning of April to the first week of July in 2013, 2014 and 2015, before the arrival of migrants (migration of populations breeding on the Atlantic coast mainly occurs between the beginning of August and mid-November, see [START_REF] Correia | Migration strategy of white-spotted bluethroats (Luscinia svecica cyanecula et L.s.namnetum) along the Eastern Atlantic route[END_REF]. Local breeding birds were monitored during the moulting period by summer ringing campaigns from 1 st August to 15 th September 2013 and 15 th July to 12 th September 2014, and 2015, within a 600 m radius of the capture site sampled during the breeding period. These operations aimed: (1) to estimate the ratio of local breeding birds that can be recaptured during the moulting period; and

(2) to study body mass changes of birds captured during the breeding period and recaptured during the moult period. Captures were performed using mistnets (Ecotone® 12 m × 2.50 m, 16 mm mesh, 5 shelves) installed in reedbeds. After capture, birds were aged and sexed according to the criteria detailed by [START_REF] Svensson | Identification guide to European Passerines[END_REF] and ringed. Wing lengths were measured using the flattened straightened method [START_REF] Svensson | Identification guide to European Passerines[END_REF] with a stopped ruler to the nearest 0.5 mm and birds were weighed with an electronic scale to the nearest 0.1 g. Given the relatively small sample size of recaptured birds during the moulting period, we obtained robust statistical standard errors (SE) and confidence intervals (CI) of statistical proportions by analysing datasets using inferential statistic methods. SE and CI were thus calculated using the non-parametric bootstrap resampling method (BRM), consisting of 1,500 random samples taken with replacement from the original dataset of the same size as the original (see details about the method in [START_REF] Efron | Bootstrap methods: another look at the jackknife[END_REF]in Efron &[START_REF] Efron | An introduction to the bootstrap[END_REF]. SE and CI of proportions were calculated using the 'boot' R package [START_REF] Canty | Boot: Bootstrap R (S-Plus) Functions. R package version 1[END_REF], based on methods described by [START_REF] Davison | Bootstrap Methods and Their Applications[END_REF]. For CI, we used the Bias Corrected and accelerated bootstrap method (BCa, detailed by [START_REF] Efron | Better bootstrap confidence intervals[END_REF][START_REF] Preacher | Advantages of Monte Carlo confidence intervals for indirect effects[END_REF][START_REF] Preacher | Advantages of Monte Carlo confidence intervals for indirect effects[END_REF]. Comparisons between breeding season and moult period body masses were done using Fisher-Pitman Permutation Tests (FPPT, Fischer, 1936;[START_REF] Pitman | Significance test wich may be applied to samples from any populations[END_REF], also known as the randomisation test, [START_REF] Manly | Randomization, bootstrap and Monte Carlo methods in biology[END_REF][START_REF] Manly | The Fisher-Pitman permutation test when testing for differences in mean and variance[END_REF], a powerful alternative to the Wilcoxon-Mann-Whitney ranksum test [START_REF] Kaiser | An exact and a Monte Carlo proposal to the Fisher-Pitman permutation tests f paired replicates and for independent samples[END_REF]. Given the nature of our data, we used a paired-samples permutation test, run with the 'EnvStats' R package [START_REF] Millard | EnvStats: An R Package for Environmental Statistics[END_REF] with 10,000 permutations. These statistical analyses were performed using the R software (version 3.2.3, R Development Core Team, 2013).

Flight feather moult chronology of C. s. namnetum

During all mid-July to mid-September ringing sessions, PP and SS feathers were scored for each mist-netted adult bird identified as belonging to C. s. namnetum. Feather scoring followed the method described by [START_REF] Ashmole | The Black Noddy Anous tenuirostris on Ascencion Island[END_REF] with moult score 0 assigned to an old unmoulted feather; 1 to a missing or fully in pin feather; 5 to a new full-grown feather; and 2 to 4 to feathers in intermediate stages. Feather scores were added to determine the overall moult score of flight feathers (see details in Supplementary Material, appendix 2). Global scores for PP and SS combined can thus range from 0 to 160. Given possible captures of C. s. cyanecula migrating through the study site during the post-breeding period, we had to indentify the subspecies of Bluethroat captured. C. s. namnetum is the smallest subspecies, particularly differing from others by wing length [START_REF] Cramp | The Birds of the Western Palearctic[END_REF]. Thus, individual belonging to C. s. namnetum were identified considering the cyanecula wing length inferior limits outlined by [START_REF] Cramp | The Birds of the Western Palearctic[END_REF]. For this, we only considered birds with the longest primary (number 3 ascendant) not growing, i.e. with moult score equal to 0 or 5. Given the nature of such data, fitting a simple linear regression to model moult chronology is inappropriate [START_REF] Underhill | A model for avian primary moult[END_REF] as it gives biased estimates for the start and duration of moult. [START_REF] Underhill | A model for avian primary moult[END_REF] developed models that specifically address the issues of moult data using a likelihood approach. The main issue is that moult has three clearly defined stages (pre-moult, in moult, post-moult), so that moult scores cannot be assumed to be normally distributed.

The duration and start date of moult were estimated using the model defined by [START_REF] Underhill | A model for avian primary moult[END_REF] for type 2 data (individuals in pre-moult, moult and post-moult stages are all equally likely to have been sampled, i.e., sampling probability is independent of moult stage), using the R package 'Moult' [START_REF] Erni | Moult: an R-package to analyse moult in birds[END_REF]. This package runs with moult indexes defined as numerical vectors with values ranged between 0 and 1 (moult not yet started and moult completed). We thus transformed moult scores MS obtained for each sampled birds according to the Ashmole method (ranged from 0 to 100 for PP, 0 to 60 for SS and 0 to 160 for PP + SS) within Models run to estimate duration, means and standard deviations in start dates (days) for moult of primary feathers (PP), secondary feathers (SS) and both tracts (PP + SS) of the Bluethroat population exploiting intertidal wetlands of the Gironde Estuary during the moulting period. Best models are marked in bold. They are defined as the simplest among models separated by a delta AIC (difference between the considered model and the model with the lowest AIC) ≤ 2.

[Modelos para estimar la duración, las medias y desviaciones en las fechas de comienzo (en días) de la muda de plumas primarias (PP), secundarias (SS) y ambas (PP + SS) de la población de ruiseñor pechiazul que explota los humedales intermareales del estuario de la Gironda durante el periodo de muda. Los mejores modelos están marcados en negrita. Estos se definen como los modelos más simples de entre aquellos separados por un incremento delta (la diferencia entre el modelo bajo escrutinio y el modelo con el menor AIC) de the 0-1 interval. In order to ensure the independence of individual observations, only one datum per bird and per year was used. In cases of intra-annual recapture, we decided to keep one single datum. To select data among several recaptures, we used the following rules: (1) if MS = 0 or 0 < MS < 1, we chose the MS value corresponding to active moult (i.e. 0 < MS < 1);

(2) if MS = 0 for several capture occasions, we used the more recent data; (3) if MS = 1, for several capture occasions, we used the oldest data; (4) if 0 < MS < 1 for several capture occasions, we used the MS value closest to 1. We ran a total of eight models to estimate the mean start date and duration of moult, testing a sex effect on mean start, duration and standard deviation (see Table 1). The selection of the most plausible models was based on the Akaike Information Criterion (AIC, Burnham & Anderson, 2002), with selection, among models with delta AIC < 2 relative to the model with the lowest AIC, following criteria defined by [START_REF] Arnold | Uninformative parameters and model selection using Akaike's Information Criterion[END_REF].

Determination of home range exploited by adult moulting birds

During August 2014 and 2015, we fitted a total of 16 adults during the moult of their PP or SS (eight birds per year, 12 males and four females) with radio transmitters (see details in Supplementary Material, appendix 3). Birds equipped with radio tags were radio-tracked daily, from one hour before sunrise and for five hours, in order to obtain, to the fullest extent possible, one location every 15 minutes for each monitored bird. Each bird was radiotracked until we obtained a flattening of the curve representing the number of locations (x-axis) versus the surface explored by birds (y-axis) (see example in Supplementary Material, appendix 4, Figure A.7).

For home range analysis, locations recorded on the day of tag fitting were removed from the data set to avoid potential behavioural biases that might be related to stress of capture or to an adjustment period inherent to carrying the radio tag equipment. Ranges exploited by monitored birds were estimated by calculating kernels, defined as the most accurate estimators of surfaces used by animals [START_REF] Worton | Kernel methods for estimating the utilisation distribution in home range studies[END_REF]. We used the 95% kernel (K95, [START_REF] Worton | Kernel methods for estimating the utilisation distribution in home range studies[END_REF] to define the global home range of the birds monitored, the estimator most often used to calculate the total home range of animals (e.g. [START_REF] Mcloughlin | Effect of spatial differences in habitat on home ranges of grizzly bears[END_REF][START_REF] Bender | Annual and seasonal habitat use of Columbian black-tailed deer in urban Vancouver, Washington[END_REF][START_REF] Prange | Influences of anthropogenic resources on raccoon (Procyon lotor) movements and spatial distribution[END_REF][START_REF] Kauhala | Home ranges and densities of medium-sized carnivores in south-east Finland, with special reference to rabies spread[END_REF][START_REF] Drygala | Habitat use of the raccoon dog (Nyctereutes procyonoides) in north-eastern Germany[END_REF][START_REF] Palphramand | Spatial organization and behaviour of badgers (Meles meles) in a moderate-density population[END_REF]. Areas with high occupancy (high density of locations, i.e. core areas), which corresponded to the areas actually exploited by birds, were calculated using the 50% kernel (K50), considered a good estimator of core areas (e.g. [START_REF] Okarma | Home ranges of wolves in Bialowieża primeval forest, Poland, compared with other Eurasian populations[END_REF][START_REF] Baghli | Home ranges and movement patterns in a vulnerable polecat Mustela putorius population[END_REF][START_REF] Dahl | Distinct seasonal habitat selection by annually sedentary mountain hares (Lepus timidus) in the boreal forest of Sweden[END_REF][START_REF] Elmeros | Home range of the badger (Meles meles) in a heterogenous landscape in Denmark[END_REF]. For each tracked bird we calculated a habitat selectivity index. We chose to use the Jacobs index [START_REF] Jacobs | Quantitative measurement of food selection. A modification of the forage ratio and Ivlev's electivity index[END_REF], a selection / rejection index of habitats taking into account the habitat availability in each area exploited by birds. This index (D) is calculated according to the formula D = (r -p) / (r + p -2rp) where r is the proportion of locations in a given habitat and p the proportion of the same habitat in the range explored by each considered bird. Given that we had a large data set for each sampled birds (on average more than 60 locations per individuals radio-tracked, see 'results'), and a relatively high tracking accuracy (estimated to be about 5 metres), we chose to calculate the Jacobs index using r as the proportion of locations in a given habitat (instead of, for instance, the percentage of habitats in the core areas, see possible methods reviewed in [START_REF] Kauhala | Estimating habitat selection of badgers -a test between different methods[END_REF]. The range explored by birds has been calculated with the Minimum Convex Polygons (MCP) method described by [START_REF] Mohr | Table of equivalent populations of North American small mammals[END_REF] and discussed by [START_REF] Harris | Homerange analysis using radio-tracking data -a review of problems and techniques particularly as applied to the study of mammals[END_REF], since MCPs may reflect the available area for individuals more neutrally than K95 (MCPs more exactly cover the area where the animals move, and avoid attributing more weight to some areas than to others, see [START_REF] Harris | Homerange analysis using radio-tracking data -a review of problems and techniques particularly as applied to the study of mammals[END_REF][START_REF] Kauhala | Estimating habitat selection of badgers -a test between different methods[END_REF]. Calculation of Jacobs indexes were done using habitat mapping, identifying five main types of intertidal habitats of the study site: (1) barren mudflats mixed with small ground water bodies (with channels or temporary pools);

(2) bulrush-reed beds: vegetal formations dominated by Bolboschoenus maritimus that may include patches of Phragmites australis;

(3) pure reedbeds dominated by Phragmites australis; (4) pure meadows dominated by Elytrigia acuta and ( 5) meadows with a mixture of Elytrigia acuta and small Phragmites australis. All home range analyses were performed using the 'Ranges 8 v. 2.16' software (Anatrack Ltd., [START_REF] Kenward | Ranges 8. For the analysis of tracking of location data[END_REF], see example of analysis in Supplementary Material, appendix 4, Figure A.8).

Diet of moulting birds

The diet of adult birds during the moulting period was assessed from droppings collected by putting the captured birds for a few minutes in plastic-bottomed cloth bird bags. Identifiable chitinous fragments were counted in each sample to estimate the minimum number of individuals of each taxonomic group (e.g for insects, seven legs were counted as two individuals). This method can potentially induce bias because small or soft-bodied prey are less easily detected. However, for several insectivorous passerines Davies (1977aDavies ( & 1977b) ) found a strong correlation between prey remnants in droppings and the composition of the true diet. In addition to the number of prey items per dropping and to the occurrence of the different taxa, we assessed prey biomass using predictive models based on the relationship between the body length and mass of the invertebrate groups involved. For terrestrial arthropods we used models defined by [START_REF] Ganihar | Biomass estimates of terrestrial arthropods based on body length[END_REF] and for marine arthropods (Amphipoda) we used the model defined by [START_REF] Lastra | Processing of allochthonous macrophyte subsidies by sandy beach consumers: estimates of feeding rates and impacts on food resources[END_REF] for the genus Talitrus. Mean prey lengths were determined using a large number of samples collected in the study site or in French coastal Atlantic wetlands with the same ecological features (see details in Supplementary Material, appendix 5). To evaluate sample size representativeness, we used species accumulation curves (modeled with the R package 'Vegan', function 'specaccum', Oksanen et al., 2013, see details in Supplementary Material, appendix 5) which allowed us to assess the expected (mean) species richness for a certain number of sampled sites or individuals. For taxa representing more than 5% of the prey abundance, we used a Generalized Linear Model (GLM) to test potential variations of different prey abundances over time (12 periods of five days: pentads, from 15 th July to 10 th September), the age effect (juveniles vs adults) and the moult effect of PP and SS. Effects of these explanatory variables were tested using a type-II analysis-of-variance with an F-test [START_REF] Shaw | Anova for Unbalanced Data: An Overview[END_REF]. According to the nature of the data (counts) we ran models using a Poisson error distribution with a log link (Crawley, 2009). Due to the relatively small sample size to test the moult effect of PP and SS (28 individuals in active moult and 11 individual not in moult) we used a Robust Generalized Linear Model (R package 'Robust', Carroll & Pederson, 1993). All statistical analyses were performed using the R software (R Development Core Team, 2013).

RESULTS

Moult conditions of the local breeding population

Of a total of 31 birds ringed during the breeding period (22 males and nine females ringed between 23 April and 7 July), eight birds (six males and two females) were recaptured in August or in September over an area extending up to 600 m around the capture location. During the moulting period, birds were recaptured only once each, between 24 th August and 6 th September. The recapture rate was estimated at 25.98 ± 0.08% (95% CI = 9.68%-38.71%). The eight birds recaptured during the moulting period had an average moult score of 142.38 ± 8.34 (possible maximum 160), whereas they had been caught during the breeding period with a zero moult score (worn plumage). Differences between the body masses of birds measured during the breeding period and again during the end of the moulting period were not significant (paired-samples permutation test: P = 0.37).

Moult chronology of C. s. namnetum

Between mid-July and mid-September, 105 moult sheets of birds in active moult of flight feathers (PP and / or SS, corresponding to 63 males and 33 females) were completed. Five males and four females were captured over two different years. Models tend to highlight an increase in moult duration when SS are included in the analyses, with different sex effects (see Tables 1 andTable 2). Extreme values of the models retained (average values including SE for models M3 and M5, with sex effect for mean start in both models, see Table 1 andTable 2) allowed us to estimate for moult of PP and SS combined: (1) for females a mean start date between 19 th and 25 th July and a duration of 37-47 days; (2) for males, a mean start date between 12 th and 18 th July and a duration of 43-50 days. Figure1 represents a summary of model M4, run for PP and SS added with sex effect for moult duration, start date and standard de-viation of start date. [Puntuaciones de muda totales de ruiseñores pechiazules de acuerdo a la fecha. Machos = triángulos, hembras = círculos. Línea negra = trayectoria de muda para todas las aves (modelo 1), línea de puntos = machos (modelo 4), línea discontinua = hembras (modelo 4).]

Home range and habitats exploited by moulting birds

A total of 16 moulting birds were successfully monitored (eight from 16 th July to 23 rd August 2014 and eight from 16 th July to 19 th August 2015). The mean tracking duration of monitored birds was 4.44 ± 0.20 days (excluding the first monitoring day, see details in Supplementary Material, appendix 4). A total of 993 locations (distributed over an area of 60.57 ha) were recorded. This corresponds to an average of 62.06 ± 2.36 locations analysable for each sampled bird. The average K95 was 2.74 ± 0.79 ha (95% CI = 1.55-5.01). Core areas (K50) were estimated at 0.71 ± 0.20 ha (95% CI = 0.42-1.34). Among the five habitats identified in the study site, means of Jacobs indexes revealed that pure reedbed (in the highest part of the intertidal zone) and bulrush-reed beds (in the lowest part of the intertidal zone) are the selected habitats most exploited, whereas meadows mixed with reedbeds, barren mudflats, small ground water bodies and pure meadows are clearly avoided (Table 3).

Diet during the moulting period

We collected a total of 138 droppings (67 in 2012; 48 in 2014 and 23 in 2015). We collected samples from young birds and adults in moult (of PP or SS) or not in moult (before or after moult of PP or SS). This allowed us to test the effects of age or flight feather moult on diet. The samples collected comprised 99 from first year birds, 28 from adult birds in moult and 11 from adult birds captured before or after their moult. On average, each dropping contained 4.85 ± 0.37 prey items. The use of species accumulation curves showed that from 18 samples, each additional sample provided fewer than 1% of new taxa (very small differences in sample size were detected according to bird age or period, see Supplementary Material, appendix 5). In terms of abundance and occurrence, ants (Hymenoptera, Formicidae) were the most represented prey in droppings (ants comprised 40.66% of identified prey and were found in 51.45% of the droppings analysed, see results Table 4). In more than one third of the samples collected, we found Coleoptera (in 41.30% of the droppings analysed), Amphipoda (Orchestia gammarellus or Talitrus saltator, 36.96%), Diptera (36.23%) and Araneae (35.51%) (see details in Table 4). Coleoptera, Aranea and Amphipoda contributed more to the arthropod biomass consumed among taxa representing over 5% of the prey identified in the droppings analysed (respectively39.87%, 22.52% and 21.48%, see Table 4). Finally, in terms of abundance, we detected no significant variation between age classes (first year birds vs adults) and only one significant seasonal variation (for Coleoptera). However, we detected several differences between the diet of birds in flight feather moult and those in which moult had either not started or had been completed (see de-tails in Table 4). Formicidae and Amphipo-da were found significantly more often in fae-ces of moulting birds, while Cicadellidae and Araneae appeared more often in droppings of non-moulting birds. Marine crustaceans (Amphipoda) represented 21.44 ± 0.12% of the consumed biomass for birds sam-pled during moult of flight feathers vs 12.84 ± 0.10% for birds sampled before or after moult. TABLE 3 Mean selection / rejection indexes (Jacobs indexes) of the 16 birds radiotracked in the Gironde Estuary during moult of flight feathers.

[Índices medios de selección / rechazo (índices de Jacobs) de 16 aves controladas por radio-seguimiento en el estuario de la Gironda durante la muda de plumas de vuelo.] Faunistic groups found in faecal samples from Bluethroats during the post-breeding period at the Gironde Estuary: number of individuals found in samples, occurrence frequency (in %), proportion of total biomass and factors influencing the relative prey abundance (age: yearlings vs adults; period: pentads between 15 th July and 10 th September; moult effect: birds in active moult vs birds before or after moult).

Habitat

[Grupos faunísticos encontrados en muestras fecales de ruiseñor pechiazul durante el periodo posreproductor en el estuario de la Gironda: número de individuos encontrados en las muestras, frecuencia de aparición (en %), proporción de la biomasa total y los factores que influyen en la abundancia relativa de presas (edad: juveniles vs adultos antes o después de la muda; periodo: péntadas entre el 15 de julio y el 10 de septiembre; efecto de la muda: aves en muda activa vs aves antes o después de la muda).]

DISCUSSION

Moultconditions of the local breeding population

Moult is one of the most energy-consuming events in the avian life cycle [START_REF] Newton | Moult and plumage[END_REF]. In the Bluethroat, the pre-moult basal metabolic rate averages 39.7 ± 9.1 KJ / day but reaches 83.8 ± 16.7 KJ / day during the most intensive part of the moulting period (i.e. an increase of 111% over the basal metabolic rate, [START_REF] Lindström | The energetic cost of feather synthesis is proportional to basal metabolic rate[END_REF]. During the moulting period we recaptured about a quarter of birds ringed during the breeding season and detected potentially quite important movements in moulting birds: on 22 th August 2013 we captured an individual with a moult score of 154 that had been ringed on 10 th August 2016, three kilometres North of our ringing station. These movements illustrate the incomplete detection of birds that must be considered in addition to the bias due to the sampling method (trapping). Given this incomplete detection, the recapture rate between the breeding and moulting periods appears rather high, and suggests that most breeding birds, if not all, remain to moult in the same location where they nested, as documented by [START_REF] Cramp | The Birds of the Western Palearctic[END_REF]. For C. s. namnetum, this finding is supported by the feather condition of adults captured during fall migration at stopover sites south of the taxon's breeding grounds: at wetlands on the French/Spanish border, where all captured adults have fresh flight feathers (Fontanilles & Arizaga, pers. comm.). [START_REF] Lindström | The energetic cost of feather synthesis is proportional to basal metabolic rate[END_REF] highlighted that at the end of the moult period (in optimal captive conditions with high availability of trophic resources) body mass tends to be equivalent to that measured before moult and that birds tend to have a high fat score. In our study, comparison between body mass of local breeders measured before moult and towards the end of moult period (with an average moult score of 142.38) revealed no significant difference. Despite the small sample size, this highlights that birds that remain in intertidal wetlands can moult as well as in captivity with unlimited trophic resources and can easily meet the energy costs of moult.

Moult chronology of C. s. namnetum

Moult of flight feathers took 37-50 days, with a significant difference in mean start date depending on sex revealed in the two models selected: males starting to moult about one week before females. This trend is reported by different authors for different species (e.g: Blue Tit Cyanistes caeruleus, [START_REF] Svensson | The trade-off between molt and parental care: a sexual conflict in the blue tit?[END_REF]Collared Flycatcher Ficedula albicollis, Hemborg & Merilä, 1999). This sexual difference could be due to the much greater energy expenditure during the breeding season by females than by males (due to egglaying, incubation and chick brooding combined, see [START_REF] Svensson | The trade-off between molt and parental care: a sexual conflict in the blue tit?[END_REF]. Another explanation can be extra-pair fertilisations (well documented in the Bluethroat, see [START_REF] Johnsen | Ecological constraints on extra-pair paternity in the Bluethroat[END_REF] which may induce a lower investment in parental care by males than by females [START_REF] Svensson | The trade-off between molt and parental care: a sexual conflict in the blue tit?[END_REF]. The mean moult start dates (corresponding to the beginning of primary moult: 16 th July for males and 22 th July for females) are relatively similar to results obtained for C. s. cyanecula (21 st July ± 4.1 days for a captive sample; 19 th July ± 2.7 days for a wild population, [START_REF] Lindström | The energetic cost of feather synthesis is proportional to basal metabolic rate[END_REF]. In contrast, primary moult duration in the present study differed significantly from moult duration measured by [START_REF] Lindström | The energetic cost of feather synthesis is proportional to basal metabolic rate[END_REF]: 37.48 ± 1.92 days for males and females in our study, vs 54 ± 6.9 days for the captive population studied by [START_REF] Lindström | The energetic cost of feather synthesis is proportional to basal metabolic rate[END_REF]. This could be because in wild birds captivity is known to potentially affect the activity of the hypothalamic-pituitary-adrenal axis [START_REF] Dickens | Stress, captivity, and reproduction in a wild bird species[END_REF], a gland complexs constituting a major part of the neuroendocrine system controlling reactions to stress and regulating many body processes, including digestion, the immune system and energy storage.

Home ranges of moulting birds

Habitats particularly selected by moulting birds monitored during our study: bulrushreed beds (plant formations dominated by Bolboschoenus maritimus and Phragmites australis) or pure reedbeds, are similar to habitats exploited by first-year birds during autumn migration in the Jaizubia Estuary (North-Western Spain), where the main habitats occupied by Bluethroats are reedbeds and tidal flats with areas essentially devoid of vegetation and areas with low halophytic herbaceous vegetation subject to tidal influences (see [START_REF] Arizaga | Spatial behaviour and habitat use of first-year Bluethroats Luscinia svecica stopping over at coastal marshes during the autumn migration period[END_REF]. The home range areas exploited by moulting birds (K95: 2.74 ± 0.79 ha) are also quite similar tothose of Bluethroats in the Jaizubia Estuary: averaging around 2 ha (ranging from 0.55 ± 0.18 ha to 2.37 ± 0.30 ha, depending on tide: spring tide or neap tide) and location of the habitats exploited: lower marshes or upper marshes [START_REF] Arizaga | Spatial behaviour and habitat use of first-year Bluethroats Luscinia svecica stopping over at coastal marshes during the autumn migration period[END_REF]. These results are also quite similar to those obtained for breeding Bluethroats in the Marais du Mes (South Brittany, France), where territories of breeding males covered on average 1.7 ha (range 0.5-2.4 ha), and were home range size of birds were smaller in diversified landscapes composed of tidal creeks and salt marsh patches and larger in landscapes dominated by water ponds (see [START_REF] Godet | Bluethroats Luscinia svecica namnetum offset landscape constraints by expanding their home range[END_REF]. Such results confirm the high trophic potential of intertidal coastal marshes exploitable by Bluethroats, particularly for meeting the energy costs of moult. [START_REF] Chernetsov | Spatial behaviour of some nocturnal passerine migrants duringstopovers[END_REF] have demonstrated the relationship between spatial behaviour of migrants at stopover sites and food distribution. When the abundance of trophic resources is unpredictable, birds tend to exploit large home ranges [START_REF] Chernetsov | Movement patterns of European reed warblers Acrocephalus scirpaceus and sedge warblers A. schoenobaenus before and during autumn migration[END_REF][START_REF] Fransson | When and where to refuel before crossing the Sahara desert -extended stopover and migratory fuelling in first-year garden warblers Sylvia borin[END_REF], whereas when food availability is more predictable, birds tend to exploit small home ranges [START_REF] Bibby | Foraging behaviour of migrant pied flycatchers, Ficedula hypoleuca, on temporary territories[END_REF][START_REF] Chernetsov | Contrasting spatial behaviour of two long-distance passerine migrants at spring stopovers[END_REF].

Diet of moulting birds

In term of abundance and occurrence, the diet identified in our study emphasises the importance of Hymenoptera, Diptera, Coleoptera, Araneae, Amphipoda and Hemiptera. These six Arthropod taxa represent over 90% of prey consumed. In addition, moulting birds appeared to feed more on ants and Amphipoda. Our results are relatively similar to the diet of L. s. cyanecula studied in reedbeds at a sewage treatment facility in South-west Poland, whose authors particularly highlighted the importance of Coleoptera among the relatively small number of taxa exploited (see [START_REF] Orłowski | Partial dietary segregation between adult and nestling Bluethroats Luscinia svecica[END_REF]. The main difference our study reveals is the importance of marine crustaceans (Amphipoda) which represent 9% of the prey identified in our samples and about a quarter of the biomass consumed by moulting birds. Amphipoda have also been widely identified in the diet L. s namnetum chicks in the Guérande saltpans (South Brittany, France, see [START_REF] Allano | Premières données sur le régime alimentaire des jeunes gorgebleues (Luscinia sve-cica namnetum, Mayaud) au nid dans un marais salant exploité (Guérande, Loire Atlantique)[END_REF]. This unusual kind of prey for a songbird species suggests the specific advantages that the local namnetum subspecies may obtain by exploiting intertidal wetlands. Amphipoda are among the most abundant taxa of salt marsh invertebrates [START_REF] Pétillon | Evaluating the success of managed realignment for the restoration of salt marshes: Lessons from invertebrate communities[END_REF] and are known for their high nutritional value [START_REF] Parsons | The cultivation of marine amphipods and their use as food for young salmonids[END_REF][START_REF] Baeza-Rojano | Nutritional analysis of freshwater and marine amphipods from the Strait of Gibraltar and potential aquaculture applications[END_REF].

Conservation implications

Our results reveal the importance of the trophic resources exploitable in intertidal wetlands by Bluethroats during their moult, a particularly energy-demanding event. These resources appear particularly important for populations breeding along the Atlantic coast and thus for the namnetum subspecies. The namnetum subspecies breeds in limited and fragmented sites along the Atlantic coastline, where several important breeding sites in coastal marshes are already subject to global changes resulting in rising water levels and coastal erosion. Our study reveals in particular the high proportion of breeding birds that remain to moult in the intertidal zone, but the origin of all the moulting birds remains unknown and intertidal areas can probably also accommodate birds originating from locations more or less distant from the coast. In the Guérande saltpans (South Brittany, France) [START_REF] Eybert | La Gorgebleue[END_REF] have reported movements of birds that nest in the saltpans gathering in the peripheral reedbeds of the marsh ecocomplex during moult of flight feathers. Given the high level of trophic resources exploitable by Bluethroats in intertidal wetlands, such gatherings of moulting birds are also highly likely along the Atlantic coastal fringes.

Throughout its life cycle, C. s. namnetum depends on mainly Atlantic coastal marshes located across relatively a restricted geographical area (Arizaga et al., 2015). The importance of Atlantic wetlands has also been highlighted for European species of conservation concern in Europe, such as the Aquatic Warbler (Acrocephalus paludicola, [START_REF] Musseau | Ecology of Aquatic Warblers Acro-cephalus paludicola in a fall stopover area on the Atlantic coast of France[END_REF]. Unfortunately, these habitats tend to be widely vulnerable to global changes. Between 2000 and 2015, along the 8 km of the most eroded part of the mesohaline region of the Gironde Estuary, an average retreat of the coastline exceeding 35 m has been highlighted and gentle shore gradients have progressively become steep slopes with the loss of about 50% of the lowest intertidal vegetal formations, exploited by such species as the Bluethroat and Aquatic Warbler during moult or migration (see [START_REF] Musseau | L'érosion des Zones humides estuariennes[END_REF].

In addition to local erosion issues noted in such areas as the Gironde Estuary, global sea level rise (26-82 cm expected by the end of the century; IPCC, 2013) threatens the future of ecological functions enabled by the large part of the Atlantic intertidal wetlands that have no possibility of retreating naturally inland because of human infrastructures, such as dykes and roads.

Two measures to maintain the ecological functions of intertidal wetlands along the Atlantic coastline seem worth considering. Reclaimed lands may be returned to nature (depolderisation), compensating for losses of intertidal wetlands. Also new wetlands may be created behind the dykes of agricultural polders. This latter measure can offer the possibility of developing large wet vegetated pools or ditches between fields (for instance with extensive organic grazing), connected to marine waters and partly or fully subject to tidal influence by means of water regulation systems. Such management of inshore coastal areas could guarantee the long-term conservation of an important part of the trophic webs threatened by the global changes affecting the lowest intertidal lands. This solution, allowing the maintenance and the development of a specific agricultural sector with high added value products, and the development of ecosystem services provided by wetlands (such as water purification), is probably the best alternative to compensate for intertidal wetland losses, and would gain wide public acceptance more easily than full depolderisation. This management option highlights the key role of farming policies on inshore coastal areas to ensure the future of intertidal wetlands and to conserve such species as C. s. namnetum whose habitats may be dramatically and suddenly impacted by local and/or global factors. Such management logistics also highlight the key responsibilities of environmental and agricultural governance for the conservation of coastal habitats threatened by global changes.

  FIG. 2.-Total moultscores of Bluethroatsversusdate. Triangles= males, circles =females. Blackline= moult trajectories for all birds (model 1), dotted line = males (model 4), dashed line = females (model 4).[Puntuaciones de muda totales de ruiseñores pechiazules de acuerdo a la fecha. Machos = triángulos, hembras = círculos. Línea negra = trayectoria de muda para todas las aves (modelo 1), línea de puntos = machos (modelo 4), línea discontinua = hembras (modelo 4).]

  bed D = 0.20 ± 0.13 -0.08 -0.45 Meadows mixed with reedbed D = -0.18 ± 0.10 -0.35 -0.05 Barren mudflats and small ground water bodies D = -0.35 ± 0.10 -0.55 --0

TABLE 1

 1

  AIC ≤ 2.]

	Model	Duration|start|SD	No. of parameters	AIC PP (delta AIC)	AIC SS (delta AIC)	AIC PP&SS (delta AIC)
	M1	1|1|1	3	57.67 (6.28)	58.07 (4.72)	5.94 (8.65)
	M2	Sex|1|1	4	57.61 (6.23)	59.47 (6.13)	7.15 (9.86)
	M3	Sex|Sex|1	5	52.64 (1.26)	53.35 (0.00)	-1.30 (1.40)
	M4	Sex|Sex|Sex	6	52.71 (1.32)	55.30 (1.95)	-2.07 (0.64)
	M5	1|Sex|Sex	5	51.38 (0.00)	56.41 (3.07)	-2.71 (0.00)
	M6	1|1|Sex	4	55.36 (3.98)	59.83 (6.49)	2.09 (4.80)
	M7	1|Sex|1	4	51.67 (0.29)	55.00 (1.65)	0.37 (3.08)
	M8	Sex|1|Sex	5	55.68 (4.30)	61.05 (7.70)	2.22 (4.93)

TABLE 2

 2 Duration (days), start date and standard deviation of start date (days) for moult of primary feathers (PP), secondary feathers (SS) and both tracts (PP + SS) obtained from the different selectable models tested for the Bluethroat population exploiting intertidal wetlands of the Gironde Estuary.

	[Duración en días, fecha de comienzo y desviación típica de la fecha de comienzo (en días) de la muda
	de primarias (PP), secundarias (SS) y de ambos tractos (PP+SS) obtenidos de los diferentes modelos
	construidos para la población de ruiseñor pechiazul que explota los humedales intermareales del estuario
	de la Gironda.]
		Duration (SE)	Start (SE)	SD in start (SE)
	M7 PP
	Females	37.48 (1.92)	July 22 th (1.70)	7.83 (2.44)
	Males	37.48 (1.92)	July 16 th (1.86)	7.83 (2.44)
	M7 SS
	Females	34.09 (2.23)	July 31 th (2.07)	8.16 (2.49)
	Males	34.09 (2.23)	July 27 th (2.05)	8.16 (2.49)
	M5 PP&SS
	Females	44.77 (1.70)	July 21 th (1.83)	9.52 (3.68)
	Males	44.77 (1.70)	July 16 th (1.89)	6.45 (2.07)
	M3 PP&SS
	Females	39.54 (2.84)	July 23 th (1.90)	7.34 (2.15)
	Males	46.26 (3.46)	July 15 th (2.50)	7.34 (2.15)

ACKNOWLEDGEMENTES._Ringing sessions and the radio-tracking scheme were conducted with the authorisation of the Centre de Recherchessur la Biologie des Populations d'Oiseaux (CRBPO / Muséum National d'Histoire Naturelle).Access to the study site has been allowed by the owner and the manager of the sites: Conservatoiredu Littoral and Conservatoire d'Espaces Naturels de Poitou-Charentes. This study received the financialsupport of the Conseil Départemental de la Charente-Maritime, the EDF Foundation, the Conservatoire du Littoral and the Grand Port Maritime de Bordeaux. For their help during this work we particularly thank: Estelle Kerbiriou (Conseil Général de la Charente-Maritime), Olivier Dehorter, Frédéric Jiguet and Pierre-Yves Henry (CRBPO / Muséum National d'Histoire Naturelle), Thomas Hérault (Conservatoire Régional d'Espaces Naturels de Poitou-Charentes), Pascal Cavallin (Conservatoire du Littoral), Jérôme Baron (SMIDDEST), Estelle Gironnet and Emilie Savoie (Parc de l'Estuaire), Régine Boisseau, Patricia Brenner and Dominique Marion (Ferme de la Gravelle), José Gallego, Sophie Musseau, Mathis Vérité, Alain Lelong, Eric Blanchet and all residents of the Foyer Occupationnel de Saint-Genis de Saintonge (ADEI 17). We are grateful to all who assisted us during the radio-tracking and ringing sessions, especially: Valentine Herrmann, Jade Bruxaux, William Gonzalez, Charly Souc, Mathilde Bertrand, Célia Sineau, Leila Kilota, and all the assistants (interns and volunteers) we have been fortunate to have throughout this project. Finally, we thank Nick Casey (Anatrack Ltd) for his valuable advice on the 'Range 8' software, Birgit Erni (University of Cape Town) for her kind assistance with the 'Moult'R package, Robert Smith and John Allen for the thorough re-reading of this paper and Juan Arizaga and an anonymous reviewer who provided valuable comments that helped us to improve this work.

SUPPLEMENTARY ELECTRONIC MATERIAL

Additional supporting information may be found in the on-line version for this article. See volume 64(2) on www.ardeola.