Martin Thibault Eric

Vidal Murray

A Potter

Ellie Dyer

Fabrice Brescia

M Thibault
email: thibault@iac.nc

E Vidal

M A Potter

The red-vented bulbul (Pycnonotus cafer): serious pest or understudied invader?

Keywords: Invasive alien bird, Islands, Impact, Biodiversity, Conservation

Recently, debate has flourished about inadequacies in the simplistic ''worst invasive species'' approach and its global scale. Here we investigate the status of the red-vented bulbul (Pycnonotus cafer), an Asian passerine bird. This species has been introduced widely across Pacific islands and is commonly blamed for its impacts on agriculture and biodiversity via dispersal of invasive plant seeds and competition with native fauna. This case study evaluates all available data on the impacts and management of this invasive species and identifies priorities for future research. We reviewed the scientific literature and information from three databases (ABBA, GAVIA, eBird) and highlight that the attention paid to this species by scientists and managers varied considerably between islands and contexts and was globally lower than the attention paid to other species on the IUCN-ISSG list. The red-vented bulbul has now established on 37 islands and in seven continental locations outside its native range. We show that three categories of effects are associated with this species: plant damage, seed dispersal and disturbance of fauna. We compiled lists of 110 plant species consumed, 33 plant species dispersed, and 15 species of bird that this bulbul interacts with. However, these lists were mainly made of opportunistic observations rather than specific assessments. Research outputs that focus on better ways to prevent or quantify the impacts of the red-vented bulbul remain scarce. We found very few references exploring potential positive impacts of this species, and only two examples of management actions undertaken against it. The latter are required to inform management actions, especially on sensitive tropical islands where invasions and dispersal of the red-vented bulbul are ongoing. Our analysis of the literature found no clear support for considering this species to be one of the ''world's worst'' invasive alien species.

contrast to alien birds [START_REF] Pys ˇek | Geographical and taxonomic biases in invasion ecology[END_REF][START_REF] Kumschick | Some alien birds have as severe an impact as the most effectual alien mammals in Europe[END_REF]. Several studies have called for improvements in the way in which impact values of IAS are assessed beyond experts' ''worst'' lists, particularly for bird species [START_REF] Strubbe | Concerns regarding the scientific evidence informing impact risk assessment and management recommendations for invasive birds[END_REF][START_REF] Ricciardi | Progress toward understanding the ecological impacts of nonnative species[END_REF][START_REF] Kumschick | Managing alien bird species: time to move beyond '100 of the worst' lists?[END_REF][START_REF] Saxena | Growing concern and threat of invasive alien species on natural ecosystem and native species[END_REF] and they have stressed that this is vital to better inform management decisions.

The three bird species classified as the world's worst invasive species in the IUCN-ISSG list are the common starling (Sturnus vulgaris), the common myna (Acridotheres tristis), and the red-vented bulbul (Pycnonotus cafer). A recent review of the impact of alien birds on native ecosystems globally [START_REF] Vl | Impact of non-native birds on native ecosystems: a global analysis[END_REF] identified the three species with the highest global impact as being the mallard (Anas platyrhynchos, score = 16), the common myna (score = 13), and the red-whiskered bulbul (Pycnonotus jocusus, score = 10) whereas the global impact score of the red-vented bulbul in this study should be only 4. Recently, [START_REF] Kumschick | Managing alien bird species: time to move beyond '100 of the worst' lists?[END_REF] identified important overlaps in the impacts associated with the common myna and the red-vented bulbul. This raises the question as to whether the red-vented bulbul should be considered as one of the three worst invasive bird species on the planet. Local farmers and environment managers need management frameworks in order to deal with the dispersal/impacts of IAS [START_REF] Blackburn | A proposed unified framework for biological invasions[END_REF]. Biosecurity protocols at frontiers were demonstrated to be the most useful techniques to prevent biological invasions [START_REF] Edelaar | Managing non-native species: don't wait until their impacts are proven[END_REF]. However, controlling a newly established invasive species in a territory depends on economic, ecological and social factors and therefore on specific assessment of these factors at local scales [START_REF] Mack | Biotic invasions: causes, epidemiology, global consequences, and control[END_REF]. A synthesis of management programs toward an alien species offers concrete baselines for managers, and this knowledge also helps understanding how the impacts associated with an invasive species give rise to management operations. It is urgent that we review existing assessments of impacts and management programs implemented against the red-vented bulbul.

We review invasion data to determine the nature and severity of the impacts of this species, whether its impacts are consistent throughout its alien range, whether its status as a major invasive species has led to more research and management programs at local scales, and to assess if its current acknowledged pest

Introduction

Invasive alien species (IAS) are one of the main causes of biodiversity loss (Sala et al. 2000;[START_REF] Keane | Exotic plant invasions and the enemy release hypothesis[END_REF][START_REF] Pereira | Global biodiversity change: the bad, the good, and the unknown[END_REF][START_REF] Gren | Economic development, institutions, and biodiversity loss at the global scale[END_REF], with associated economic impacts [START_REF] Bergman | The economic impact of invasive species to wildlife services'cooperators[END_REF][START_REF] Pimentel | Update on the environmental and economic costs associated with alien-invasive species in the United States[END_REF][START_REF] Pimentel | Biological invasions: economic and environmental costs of alien plant, animal, microbe species[END_REF]) and degradation of ecosystem services [START_REF] Walsh | Invasive species triggers a massive loss of ecosystem services through a trophic cascade[END_REF]. The highly ambitious goal of the 2010 Convention for Biological Diversity, Nagoya, Japan, was to ensure that ''By 2020, IAS and pathways are identified and prioritized, priority species are controlled or eradicated, and measures are in place to manage pathways to prevent their introduction and establishment'' (Secretariat CBD 2010). Concerns about the impacts of IAS have led to the production of several lists of high priority alien species including the ''100 of the World's Worst'' from the IUCN Invasive Species Specialist Group (IUCN-ISSG) [START_REF] Brochier | Alien invasive birds[END_REF][START_REF] Burgiel | Black, white gray lists[END_REF][START_REF] Lowe | of the World's Worst Invasive Alien Species A selection from the Global Invasive Species Database[END_REF]. Such prioritization attempts have incited intense debate among the scientific community on the definition of an invasive species (e.g. [START_REF] Russell | The rise of invasive species denialism[END_REF]. Some considered invasion as a natural phenomenon and compared the prevention of species dispersal as a kind of racism [START_REF] Vale ´ry | Another call for the end of invasion biology[END_REF]. Others saw the observed impacts of alien species as an important challenge for our developing societies [START_REF] Richardson | Misleading criticisms of invasion science: a field guide[END_REF][START_REF] Simberloff | A call for an end to calls for the end of invasion biology[END_REF][START_REF] Blondel | The end of invasion biology: intellectual debate does not equate to nonsensical science[END_REF][START_REF] Pereyra | Revisiting the use of the invasive species concept: an empirical approach[END_REF]. Such debate also applied to species classification methods, as prioritization attempts based on expert assessments is opposed to different classification frameworks based on data analysis and statistics [START_REF] Donlan | Assessing ecological responses to environmental change using statistical models[END_REF][START_REF] Kumschick | A conceptual framework for prioritization of invasive alien species for management according to their impact[END_REF][START_REF] Blackburn | A unified classification of alien species based on the magnitude of their environmental impacts[END_REF][START_REF] Kumschick | Managing alien bird species: time to move beyond '100 of the worst' lists?[END_REF]. In this study, we consider that an alien species expanding its range in a sensitive territory deserves particular attention from both scientists and managers. For their part, scientists must consider the possibility that a species could be harmless in an alien territory and should produce a local assessment of potential issues associated with that species.

Of the terrestrial vertebrates in the IUCN-ISSG list, 14 are mammals, three are birds and only two are reptiles [START_REF] Lowe | of the World's Worst Invasive Alien Species A selection from the Global Invasive Species Database[END_REF]. Unsurprisingly, 10 years after the publication of this ''World's Worst'' list, authors have commented on the imbalance in attention paid by scientists and managers to mammals in status is deserved. We present an updated assessment of an invasive species nearly 110 years after it was first record outside of its native range (Fiji in 1903[START_REF] Watling | Observation on the naturalised distribution of the red-vented bulbul in the Pacific, with special reference to the Fiji islands[END_REF]) and identify priorities for future research.

Methods

Species description

The red-vented bulbul (Pycnonotus cafer Linnaeus, 1766) is a passerine belonging to the family Pycnonotidae. Earlier names include Molpastes haemorrhous J.F. Gmelin, 1789 and Molpastes cafer Baker, 1930. The genus Pycnonotus comprises 47 species [START_REF] Delacour | A revision of the genera and species of the family Pyconotidae (Bulbuls)[END_REF]Dickinson and Dekker 2002), among which the red-vented bulbul is represented by eight different subspecies (Dickinson et al. 2002). The Pacific sub-species is P. c. bengalensis, Blyth 1845 [START_REF] Watling | Observation on the naturalised distribution of the red-vented bulbul in the Pacific, with special reference to the Fiji islands[END_REF].

The red-vented bulbul is native to the Indian Subcontinent, Southeast Asia, and Malay Peninsula [START_REF] Long | Introduced birds of the world: The worldwide history, distribution and influence of birds introduced to new environments[END_REF]. It occurs naturally from Eastern Pakistan to southern China and Vietnam, and from Northern India to Sri Lanka. The species also has an historic presence in Bangladesh, Bhutan, Myanmar and Nepal.

Data collection and analysis

We searched for ''Pycnonotus cafer'' and ''red-vented bulbul'' keywords on Google Scholar, Web of Science, ScienceDirect and SpringerLink search engines. We looked for information on impacts primarily, and collected references on pathways of invasion, establishment success, and management. We also visited the websites of the Governments, Environment Ministry, Associations and NGOs for each country where the red-vented bulbul was signaled as present. When our searches failed to find the information we sought, we made direct contact with people who had reported the presence of this species in each country. Most of the documents obtained concerned the red-vented bulbul in its alien range. Those that related to this species in its native range were used to extract information on its biology and ecology in countries of origin. We also compared the number of references obtained by searching for each of the species names listed in the IUCN ''World's Worst'' list in Google Scholar.

In order to update distribution maps, we included records from three international databases. We used the 252 quotations with references from the Global AVian Invasion Atlas Project (GAVIA, [START_REF] Dyer | The global avian invasions atlas-a database of alien bird distributions worldwide[END_REF], 150 sightings from the Atlas of Breeding Birds of Arabia (ABBA, Ornithological Society of the Middle East, Jennings 2010) and 40,152 sightings from the participative eBird database (eBird, [START_REF] Sullivan | eBird: a citizen-based bird observation network in the biological sciences[END_REF]. Maps were designed using the following R software packages: maps (Becker et al. 2015a), mapdata [START_REF] Becker | mapdata: Extra Map Databases. R package version 2[END_REF]mapproj (McIlroy et al. 2015) and maptools [START_REF] Bivand | maptools: Tools for reading hling spatial objects[END_REF].

We classified the reported impacts of the red-vented bulbul into three categories: (1) plant damage; (2) seed dispersal; and (3) disturbance and impact on fauna. We treated each mention of a species-specific plant or animal impact as one ''report''. One published article thus often contained several ''reports'' when listing, for example, species of plants consumed, and the full set of documents potentially contained several reports of impacts on the same species, sometimes at the same location. We chose this index because it facilitates across-taxa comparisons and it is simple to calculate from the large number of references obtained. In addition, the ratio of the number of reports by the number of impacted species provides an informative insight into the attention paid to each impact-category.

Results

Sources of the information

We identified 112 published documents on the redvented bulbul, and obtained comments from seven ornithologists and environment managers about the bulbul from its alien range. The publications comprised 78 academic articles, 15 books, five conference proceedings, five newsletters and nine professional reports. Details about the information obtained are presented in Fig. 1. Among the collected references, 83 addressed the red-vented bulbul in their alien range 74 from islands and nine from continental areas. Three locations (Fiji, Hawaii and French Polynesia) were the focus of 42 documents. We used 12 references that focused on red-vented bulbul in their native range. We also used information from 17 documents dealing with biological invasions at a larger scale. These documents cover a period from 1926 to today, but we focus here on documents from 1975 onwards. The cumulative numbers of publications through time are shown in Fig. 2. A full list of the 112 documents is given in Online Resource 1.

Searching for ''Pycnonotus cafer'' in Google Scholar produced 1370 references. Thus, among the 100 species listed by the IUCN, the red-vented bulbul ranked 11th. In comparison, we found 4880 references for ''Acridotheres tristis'', and 36,500 for ''Sturnus vulgaris'', the two other bird species from the list. Searches for ''Pycnonotus jocosus'' and ''Anas platyrhynchos'' resulted 1300 and 24,300 references respectively.

Pathways of transport and introduction

The red-vented bulbul was first reported in Fiji in *1903 [START_REF] Parham | Birds as pests in Fiji[END_REF], corresponding to the transportation of Indian immigrants from Calcutta harbor to Fiji in the early 1900s [START_REF] Watling | Observation on the naturalised distribution of the red-vented bulbul in the Pacific, with special reference to the Fiji islands[END_REF]. This species was widely used in bird fights in India [START_REF] Ali | Handbook of the birds of India and Pakistan Together with those of Bangladesh Nepal, Bhutan And Sri Lanka[END_REF] because of its aggressive behavior. Over the following century, the red-vented bulbul was introduced into 19 countries and established in 17 of them (Fig. 3). It is now present in at least 37 islands and seven continental locations, and is anticipated to continue its range expansion in several archipelagos. The first recorded year of observation per country is presented in Table 1. Most introductions of the redvented bulbul have been in the Pacific and in the Middle East, but the species was recently recorded in southern Europe (Malaga, Spain) and in North America (Houston, Texas, USA) (Fig. 3). The exact reason for introduction is known for only three locations. The red-vented bulbul was deliberately introduced (1940s) to Tongatapu (Tonga) to control unwanted insects [START_REF] Watling | Observation on the naturalised distribution of the red-vented bulbul in the Pacific, with special reference to the Fiji islands[END_REF]). An American troopship re-routed to Apia took caged birds to Samoa in 1943 instead of New Caledonia that was the intended destination [START_REF] Watling | Observation on the naturalised distribution of the red-vented bulbul in the Pacific, with special reference to the Fiji islands[END_REF], and the species was intentionally released in Noume ´a (New Caledonia) in 1983 by bird dealers to avoid prosecution [START_REF] Gill | Red-vented Bulbuls (Pycnonotus cafer) in New Caledonia[END_REF]. For 10 other locations, bird trade is most often the suspected reason for introduction. Birds were kept in cages and transported by boat or airplane, with accidental or intentional release occurring commonly around harbors, airports and markets. For the Pacific locations, transportation of caged birds and accidental transport of free birds by boat have been the main introduction pathways, with a few records indicating that some introductions have occurred near airports. The redvented bulbul remains abundant in Tahiti (French Polynesia) and is expanding its range in the Polynesian archipelago (T. Ghestemme pers.comm.). In the Middle East, land and air transport of cage birds between markets is implicated. It is not known how the species got to Houston (Texas, USA), Malaga or Corralejo (Spain).

Establishment success

The red vented bulbul is currently considered established in 36 of the 46 locations where it has been historically recorded. Up-to-date information is lacking for three small Pacific islands ('Eua, Savai'i and Ailinglaplap). We found mentions of red-vented bulbuls in Melbourne in 1918 and 1942 [START_REF] Lendon | Bulbuls in Melbourne[END_REF][START_REF] Watling | Observation on the naturalised distribution of the red-vented bulbul in the Pacific, with special reference to the Fiji islands[END_REF]), but the species has not been reported there since and it was recorded as ''Eradicated'' in Australia in the global invasive species database (http://www.issg.org/database). It was observed on five islands in the Hawaii archipelago between 1982 and 1989, but it seems that it failed to establish beyond Oahu [START_REF] Walker | The Red-vented bulbul, Superbird?[END_REF]. It was eradicated from Auckland, New Zealand, in 1955 [START_REF] Watling | Observation on the naturalised distribution of the red-vented bulbul in the Pacific, with special reference to the Fiji islands[END_REF], 3 years after the first observation in 1952 (Turbott 1956).

Recorded impacts

The red-vented bulbul is commonly blamed for three categories of negative impacts, mostly related to its diverse diet that comprises fruits and berries [START_REF] Islam | Red-vented Bulbul (Pycnonotus cafer) Red-whiskered Bulbul (Pycnonotus jocosus)[END_REF][START_REF] Brooks | Ecology, behavior, and reproduction of an introduced population of Red-vented Bulbuls (Pycnonotus cafer) in Houston, Texas[END_REF], and flowers, buds, insects and small reptiles (VanderVelde 2002). We found 165 reports (110 species) of plants that are eaten by the red-vented bulbul. Among these, 50% concerned the degradation of cultivated plants and 35% related to seed dispersal. The remaining 17% (26 species from 17 families) were reports of consumption without consideration of the impacts. In comparison, we found 22 reports of impacts on local fauna in the bulbul's alien range.

Damage to cultivated plants is the most frequently reported impact of the red-vented bulbul in its alien range (Fig. 4), but these studies were conducted in just four locations. In contrast, the publications reporting The impact of the red-vented bulbul appears to be particularly serious on Oahu (Hawaii), where [START_REF] Walker | The Red-vented bulbul, Superbird?[END_REF] reported them consuming several species of fruits, vegetables and flowers, leading to considerable economic losses. The estimated value of the damage to Oahu's Orchid industry in 1 year (1989) was $300,000 (Fox 2011) when the red-vented bulbul together with the Japanese white-eye (Zosterops japonicus) reportedly destroying up to 75% of Hawaiian orchid and anthurium plantations [START_REF] Cummings | Evaluation of methiocarb, ziram, and methyl anthranilate as bird repellents applied to dendrobium orchids[END_REF]. In New

(1) [START_REF] Watling | Observation on the naturalised distribution of the red-vented bulbul in the Pacific, with special reference to the Fiji islands[END_REF], ( 2) [START_REF] Lendon | Bulbuls in Melbourne[END_REF], (3) [START_REF] Carlson | The avifauna of Tonga. Peace Corps, Tonga Cassey P, Blackburn TM, Sol D et al (2004) Global patterns of introduction effort and establishment success in birds[END_REF], ( 4) [START_REF] Dhondt | Bird observations in Western Samoa[END_REF], ( 5) Turbott ( 1956), (6) [START_REF] Clapp | Notes on the birds of Tutuila, American Samoa[END_REF], ( 7) [START_REF] Berger | Red-whiskered and Red-vented bulbuls on Oahu[END_REF], ( 8) [START_REF] Meyer | Status of Miconia calvescens (Melastomaceae), a dominant invasive tree in the society Islands (French Polynesia)[END_REF], (9) [START_REF] Gill | Red-vented Bulbuls (Pycnonotus cafer) in New Caledonia[END_REF], (10)Khamis ( 2010), ( 11) MAAMA ( 2013), ( 12) VanderVelde ( 2002), ( 13 the red-vented bulbul to be a problematic seed disperser come from eight locations (six countries), and faunal impacts are reported for 17 species from 11 locations.

Plant damage

The red-vented bulbul has been reported to cause damage to at least 52 plant species ( 2010). Conversely, the red-vented bulbul is not considered an agricultural pest in Fiji [START_REF] Watling | The Bulbul gets a clean bill[END_REF], nor in Houston (Texas, USA) where it was found to consume mainly introduced tropical plant species [START_REF] Brooks | Ecology, behavior, and reproduction of an introduced population of Red-vented Bulbuls (Pycnonotus cafer) in Houston, Texas[END_REF].

Seed dispersal

We found 56 mentions of problematic seed dispersal by the red-vented bulbul (Table 2) from six countries inside its alien range. The red-vented bulbul is able to spread the seeds of at least 33 plant species from 25 families. Among these species, 30% are considered alien (10 species) and 42% invasive (14 species) in the alien locations. We found records of only one endemic (Coprosma taitensis, Tahiti) and eightFdeso native species that are spread by this bird [START_REF] Spotswood | An invasive tree alters the structure of seed dispersal networks between birds and plants in French Polynesia[END_REF].

The red-vented bulbul is considered a major vector of the invasive tree Miconia calvescens in Tahiti [START_REF] Meyer | Status of Miconia calvescens (Melastomaceae), a dominant invasive tree in the society Islands (French Polynesia)[END_REF] and can potentially disperse seven other alien plant species in French Polynesia including Lantana camara [START_REF] Spotswood | An invasive tree alters the structure of seed dispersal networks between birds and plants in French Polynesia[END_REF][START_REF] Spotswood | Preference for an invasive fruit trumps fruit abundance in selection by an introduced bird in the Society Islands, French Polynesia[END_REF]. Its ability to disperse Miconia and Lantana is not unique to the red-vented bulbul, and many other species, both alien and native, also disperse seeds of these plants, and the propensity of the red-vented bulbul to disperse seeds of these plants varies from island to island. For example, the introduced silvereye (Zosterops lateralis) also disperses these seeds in Tahiti, but in Moorea the endemic fruit dove (Ptilinopus purpuralis) disperses seeds of these alien plants. In Fiji, the redvented bulbul contributes to the spread of primary colonist weeds [START_REF] Watling | The Bulbul gets a clean bill[END_REF]. In New Caledonia, the red-vented bulbul is suspected of spreading seeds of another invasive species: Schinus terebinthifolius, as it A report corresponds to one mention in one reference. Endemic plants occurred at one location only, native plants are indigenous to the location but also present elsewhere, alien species were introduced in the corresponding location and invasive plants are alien species with negative impacts at the current location is often observed feeding on fruits [START_REF] Spotswood | An invasive tree alters the structure of seed dispersal networks between birds and plants in French Polynesia[END_REF][START_REF] Thouzeau-Fonseca | Contribution a `la gestion d'un oiseau introduit envahissant en Nouvelle-Cale ´donie, le bulbul a `ventre rouge (Pycnonotus cafer L.): e ´tude des modalite ´s de pie ´geage et du comportement alimentaire en milieu naturel. IAC Production, Paita, Nouvelle-Cale ´donie Trail PW[END_REF].

Disturbance and impact on fauna

The list of animal species reported to be impacted by the red-vented bulbul is presented in Table 3. The list comprises 15 species of bird, one reptile and one insect. Only one study addressed the issue of how the aggressive behavior of the red-vented bulbul affected the other bird species [START_REF] Pernetta | the introduced and native terrestrial vertebrates of Fiji[END_REF].

On Oahu (Hawaii), direct predation of the monarch butterfly (Danaus plexippus) by the red-vented bulbul led to an induced color selection against the orange morph in the monarch [START_REF] Stimson | Predator Induced Color Polymorphism in Danaus plexippus L (Lepidoptera, Nymphalidae) in Hawaii[END_REF]. After 10 years, the same authors reported a predation transfer to the larvae, leading to an overall decline in abundance of the butterfly [START_REF] Stimson | Decline in the frequency of the white morph of the monarch butterfly (Danaus plexippus plexippus L., Nymphalidae) on Oahu, Hawaii[END_REF]. In Tahiti, red-vented bulbuls are considered a threat to the Tahiti monarch (Pomarea nigra), an endemic and critically endangered passerine, through competition for nest sites and territory [START_REF] Blanvillain | Impact of introduced birds on the recovery of the Tahiti Flycatcher (Pomarea nigra), a critically endangered forest bird of Tahiti[END_REF]. 2011), ( 4) [START_REF] Clunie | Red-vented Bulbul uses Vanikoro Broadbill nest[END_REF], (5) [START_REF] Pernetta | the introduced and native terrestrial vertebrates of Fiji[END_REF], (6) Sherman and Fall ( 2010), ( 7) Khamis ( 2010), ( 8) Kahn ( 1993), ( 9) [START_REF] Azin | Occurrence of the Redvented Bulbul Pycnonotus cafer on Kish Island, Northeastern Persian Gulf, Iran[END_REF], ( 10) Gregory ( 2005), ( 11) [START_REF] Nation | Birds New to Qatar[END_REF], (12) [START_REF] Hannecart | Trade, transport and trouble: managing invasive species pathways in an era of globalization[END_REF] In Fiji, several authors have reported red-vented bulbuls displaying aggressive behavior and competition for food resources towards other passerine species [START_REF] Clunie | Red-vented Bulbul uses Vanikoro Broadbill nest[END_REF][START_REF] Pernetta | the introduced and native terrestrial vertebrates of Fiji[END_REF][START_REF] Williams | 100 alien invaders[END_REF]. However, [START_REF] Watling | The Bulbul gets a clean bill[END_REF] suspected that the observed confinement of native bird species to forest was mainly due to habitat loss rather than the aggressive behavior of the red-vented bulbul in Fiji. On Tutuila (American Samoa), [START_REF] Sherman | Observations on feeding frequencies among native and exotic birds and fruit bats at Erythrina variegata and Dysoxylum trees on American Samoa[END_REF] observed that bulbuls competed for access to food resources with two passerine species. Finally, insect and skink predation by red-vented bulbuls is mentioned in several studies [START_REF] Vandervelde | The Red-vented bulbul has come to Micronesia[END_REF][START_REF] Walker | The Red-vented bulbul, Superbird?[END_REF][START_REF] Brooks | Ecology, behavior, and reproduction of an introduced population of Red-vented Bulbuls (Pycnonotus cafer) in Houston, Texas[END_REF]). In the Middle East, crossbreeding between the exotic red-vented bulbul and the three closely related native species (white-cheeked bulbul, P. leucogenys; the white-eared bulbul (P. leucotis) and the yellow-vented bulbul, P. xanthopygos) is often reported as a potential threat for native bulbuls [START_REF] Khan | The introduced but naturalized avifauna of the United Arab Emirates[END_REF][START_REF] Nation | Birds New to Qatar[END_REF][START_REF] Gregory | The birds of the State of Kuwait[END_REF][START_REF] Azin | Occurrence of the Redvented Bulbul Pycnonotus cafer on Kish Island, Northeastern Persian Gulf, Iran[END_REF][START_REF] Khamis | Alien species in Bahrain the overseen threats[END_REF].

Dispersal of neither endo-nor ecto-parasites by redvented bulbul is well documented in its alien range (Table 4). In its native range, the red-vented bulbul is known to host Isospora spp. [START_REF] Boughton | Avian hosts of the genus Isospora (Coccidiida)[END_REF], Menacanthus eurysternus [START_REF] Price | The Menacanthus eurysternus Complex (Mallophaga: menoponidae) of the Passeriformes and Piciformes (Aves)[END_REF], Bruelia guldum and Sturnidoecus guldum [START_REF] Ansari | Studies on ischnoceran Mallophaga infesting birds in the Panjab[END_REF]) and Pteroherpus pycnonoti (Constantinescu et al., unpublished).

In 1996, [START_REF] Jarvi | Detection of avian malaria (Plasmodium spp.) in native land birds of American Samoa[END_REF] detected no avian malaria (Plasmodium spp.) in blood smears, and [START_REF] Atkinson | Hematozoa of forest birds in American Samoa-evidence for a diverse, indigenous parasite fauna from the South Pacific[END_REF] found no evidence of Plasmodium, Trypanosoma, Atoxoplasma or microfilaria. Redvented bulbuls in Tahiti, however, have been found to carry the zoonotic disease Chlamydia sp. [START_REF] Blanvillain | Mission d'enque ˆte sur la contamination de l'avifaune par salmonella enteritidis et d'autre pathoge `nes des volailles[END_REF].

Positive impacts

Red vented bulbuls feed on a variety of native plant species (Trail 1994;[START_REF] Sherman | Observations on feeding frequencies among native and exotic birds and fruit bats at Erythrina variegata and Dysoxylum trees on American Samoa[END_REF], and dispersal of native seeds is the only service that has been explored in the bulbul's alien range [START_REF] Spotswood | An invasive tree alters the structure of seed dispersal networks between birds and plants in French Polynesia[END_REF]. Interestingly, in a village-scale survey led by [START_REF] Daigneault | Invasive species management in the Pacific using survey data and benefit-cost analysis[END_REF] in Viti Levu (Fiji), 47% of the respondents reported that the red-vented bulbul was good for their community and highlighted three main reasons. First, the bulbul was effective at insect control. Second, the bulbul reduced mongoose attacks on chickens. Third, village focus groups responded that red-vented bulbuls were occasionally eaten by villagers.

Management

The red-vented bulbul is considered an invasive species and environmental pest under the law in Australia (Tasmanian government 2010), Fiji (Minister of Primary Industries 1985), French Polynesia (Direction de l'environnement de la Polyne ´sie Franc ¸aise 2016), Hawaii (Division of Forestry and Wildlife 2014), New Caledonia (Direction du De ´veloppement Economique et de l'Environnement 2008; Direction de l'ENVironnement de la Province Sud 2016), New Zealand (Ministry of Primary Industries 2017), South Africa (Department of Environmental Affairs 2016) and Spain (Ministerio de Agricultura, Alimentacion y Medio Ambiante 2013). In these countries, transportation, trade or possession of this species is forbidden, and hunting is authorized. We found no mention of this species as a pest or invasive species in other countries.

We found only three examples of management action taken against the red-vented bulbul in its alien range. The first one is the successful eradication program implemented in New Zealand between 1952[START_REF] Parham | Birds as pests in Fiji[END_REF](Turbott 1956). This program allowed the early detection and shooting of bulbuls thanks to a [START_REF] Boughton | Avian hosts of the genus Isospora (Coccidiida)[END_REF], ( 2) [START_REF] Price | The Menacanthus eurysternus Complex (Mallophaga: menoponidae) of the Passeriformes and Piciformes (Aves)[END_REF], (3) Ansari ( 1957), (4) [START_REF] Atkinson | Hematozoa of forest birds in American Samoa-evidence for a diverse, indigenous parasite fauna from the South Pacific[END_REF], ( 5) [START_REF] Jarvi | Detection of avian malaria (Plasmodium spp.) in native land birds of American Samoa[END_REF], ( 6) [START_REF] Blanvillain | Mission d'enque ˆte sur la contamination de l'avifaune par salmonella enteritidis et d'autre pathoge `nes des volailles[END_REF] whiskered bulbul could have been included in the IUCN list in the same way as suggested in [START_REF] Vl | Impact of non-native birds on native ecosystems: a global analysis[END_REF]. This reflects the heterogeneity in the attention paid to this ''world's worst invasive species''. In fact, more than half of the information we obtained came from just three island locations: Fiji, where the species was first transported; Hawaii, where it was responsible for huge economic losses; and French Polynesia, where it was considered to contribute to pressures on endemic biodiversity. Dispersal of the red-vented bulbul is strongly linked to human activities, as is the case for other bird species [START_REF] Cassey | (ed) Biological invasions in changing ecosystems: vectors, ecological impacts, management and predictions[END_REF]. In Assam in the north-east of India, bulbul fights were part of a traditional and religious annual celebration until this was banned in January 2016. Wild bulbuls were trapped, kept in cages and prepared for the fights, and finally released if they won [START_REF] Shalet | India: Guwahati High Court stays bulbul fight, protests errupt in Assam[END_REF]. The long and close relationship with humans led to the transportation of caged birds across the Pacific Ocean by Indian migrants from the early 20th century, first by boat, and then by airplane from the 1950s, certainly fostered the bulbul expansion (Hulme 2009). This was also a key period for invasion biology, with the publication of the Elton's book (1958) marking the start of an increasing scientific interest in this field. While we found just eight references to this species between 1926 and 1966, 15 were published between 1967 and 1978. This species is still sold in local markets in several countries of the Arabic Peninsula (J. Babbington pers.com.), and bird trade remains the suspected principal vector of redvented bulbul in this region. Precise historical data are lacking regarding the propagule pressure, exact pathways of introduction, and dates associated with each introduction event, and we found very few records of this species being introduced but failing to establish. Globally, the establishment success recorded from Pacific islands to the USA or Europe suggests a better latitudinal plasticity of this species toward climate than expected when looking at the native distribution only. Moreover, its populations are considered to be selfsustaining or increasing in most of the tropical islands to which it has been introduced. Conversely, in most of the alien continental areas, population trends are considered steady or decreasing (ABBA database, Jennings 2004). This global pattern is consistent with the finding of Cassey et al. (2004) who showed that without consideration of the propagule pressure, reward associated with a call for information and led to an announcement of eradication in 1955 [START_REF] Watling | Observation on the naturalised distribution of the red-vented bulbul in the Pacific, with special reference to the Fiji islands[END_REF]. This management strategy remains in place in New Zealand and it helped prevent establishment following two more recent introduction events (September 2006 andFebruary 2013).

Second, a cage test conducted in Hawaii on bird repellant showed that Ziram, Methiocarb and Methyl anthranilate reduced the consumption of treated papaya mash by red-vented bulbuls [START_REF] Cummings | Evaluation of methiocarb, ziram, and methyl anthranilate as bird repellents applied to dendrobium orchids[END_REF]. In an open-field test, the same authors showed that Methiocarb significantly reduced damages on orchids.

The third location where management actions have been implemented against the red-vented bubul is the island of Tahiti in French Polynesia. In Tahiti, a management program that was not focused on redvented bulbul management specifically, but rather on Tahiti monarch conservation, aimed to control alien birds. Pilot control campaigns were implemented twice, in 2012 and 2013 [START_REF] Saavedra | First control campaign for Common myna and Red vented bulbul on Tahiti[END_REF][START_REF] Saavedra | Second control campaign for Common myna and Red vented bulbul on Tahiti. Internal Report[END_REF], against the red vented-bulbul and the common myna. These actions resulted in 1035 red-vented bulbuls being trapped in 2012, and 849 in 2013 and led to an increase in the breeding success of the Tahiti monarch [START_REF] Saavedra | Second control campaign for Common myna and Red vented bulbul on Tahiti. Internal Report[END_REF]. Elsewhere in the French Polynesia archipelago, bulbul removal programs are in progress in Bora-Bora, Makatea and Nuku Hiva, three islands where the species is still rare but that are located near uninvaded parts of the archipelago.

In Fiji, a recent cost-benefit analysis of controlling the red-vented bulbul recommended ''taking no action against the bulbul until such time as other benefits and or means of control have been field tested'' [START_REF] Daigneault | Invasive species management in the Pacific using survey data and benefit-cost analysis[END_REF].

Discussion

The red-vented bulbul is still expanding its range into islands and continental areas across a wide geographic range between latitudes 22°N and 36°S. The number of references associated with this species outside its native range is also growing, but remains low compared to other species listed in the IUCN ''100 world's worst list''. As an example, searching for ''Acridotheres tristis'' in Google Scholar results in a four times larger output than the keywords ''Pycnonotus cafer''. Based on this metric, the mallard and the red-islands are significantly associated with introduction success and increased geographical range in birds.

Interest in introduced red-vented bulbuls grew rapidly in response to the considerable damage it caused on orchid production on Oahu, Hawaii, following its arrival in 1966. However, except for a few mentions of the cost associated with this issue [START_REF] Cummings | Evaluation of methiocarb, ziram, and methyl anthranilate as bird repellents applied to dendrobium orchids[END_REF]Fox 2011), all references that reported damage to plant production referred only to species lists, inducing a lack in quantitative data on this impact category [START_REF] Vl | Impact of non-native birds on native ecosystems: a global analysis[END_REF]. Impact scores attributed to the red-vented bulbul in the study of [START_REF] Vl | Impact of non-native birds on native ecosystems: a global analysis[END_REF] were based on the two other impact categories. Seeds dispersal was demonstrated in three studies that explored the dispersal pattern of invasive plants such as M. calvescence. But these studies were all conducted in French Polynesia, and concluded that seed dispersal networks are complex and the interactions between native and alien plants and birds depend on both the frugivore community and on the relative abundance of available fruit [START_REF] Spotswood | An invasive tree alters the structure of seed dispersal networks between birds and plants in French Polynesia[END_REF]. Negative impacts through competition also gain mention in three studies. Particularly, the aggressive behavior of red-vented bulbul was reported in Fiji and French Polynesia. In Tahiti, its aggressiveness toward adults of Tahiti monarchs (P. nigra) combined with predation by black rats (Rattus rattus) has contributed substantially to the decline in abundance of the critically endangered monarch species [START_REF] Thibault | Understanding the decline and extinction of monarchs (Aves) in Polynesian Islands[END_REF]. However, the same author reported that the main cause of the Tahiti monarch decline was predation by the black rat. The red-vented bulbul was blamed as a strong competitor because of its aggressive behavior, but rats, cats, and other bird species such as the common myna are also recognized as chick predators or nest competitors [START_REF] Blanvillain | Impact of introduced birds on the recovery of the Tahiti Flycatcher (Pomarea nigra), a critically endangered forest bird of Tahiti[END_REF][START_REF] Ghestemme | Impact of introduced birds on Tahiti Monarch[END_REF]). According to [START_REF] Saavedra | First control campaign for Common myna and Red vented bulbul on Tahiti[END_REF], the combined effects of the myna and red-vented bulbul were responsible for 35% of the nest failing of the Tahiti Monarch in 2012. Except for observed hybridization with its native cousins from the Pycnonotidae family in the Middle-East [START_REF] Khan | The introduced but naturalized avifauna of the United Arab Emirates[END_REF][START_REF] Nation | Birds New to Qatar[END_REF], there are no reported impacts of red-vented bulbuls in continental areas [START_REF] Khamis | Alien species in Bahrain the overseen threats[END_REF][START_REF] Brooks | Ecology, behavior, and reproduction of an introduced population of Red-vented Bulbuls (Pycnonotus cafer) in Houston, Texas[END_REF]. However, we reported some other potential impacts of the red-vented bulbul such as predation, hybridization, and dispersal of ecto-and endoparasites that were not included in any previous impact scoring attempts. This highlights a large knowledge gap about how the inter-specific behavior of the red-vented bulbul impacts other species. Therefore, we believe that the role of the red-vented bulbul in the decline of plant or animal species is still to be demonstrated, or at least quantified, as has been done for other major invasive bird species such as the common myna [START_REF] Lowe | Do common mynas significantly compete with native birds in urban environments?[END_REF].

Moreover, positive effects or ecosystem services brought by introduced red-vented bulbuls have been poorly studied in its alien range, but may compensate to some degree for noxious impacts at the local scale [START_REF] Daigneault | Invasive species management in the Pacific using survey data and benefit-cost analysis[END_REF]. Studies conducted in the bulbul native range confirmed part of this assessment. For example, it was shown that the bulbul was effective at insect control, including eating the widespread and highly polyphagous agricultural pest Helicoverpa armigera [START_REF] Rana | Evaluation of birds as predators of insect pests infesting cauliflower[END_REF][START_REF] Rana | Studies on the role of insectivorous birds in managing insect pests of cabbage (Brassica oleracea var capitata L.)[END_REF]. By doing so, they improved curd and seed yields of cauliflower. The bulbul was also found to be an efficient pollinator of Erythrina variegata in India [START_REF] Raju | Passerine bird-pollinationand fruiting behavior in Erythrina variegate L. (Fabaceae) in the Eastern Ghats, India[END_REF]). Finally, an anti-predator response strategy that relies on eavesdropping of the bulbul's alarm call may also benefit other species such as Emoia cyanurea, a species of skink that is widespread throughout Pacific islands [START_REF] Fuong | Heterospecific alarm call eavesdropping in nonvocal, white-bellied copper-striped skinks, Emoia cyanura[END_REF]). These few examples suggest that positive impacts may partly counterbalance the three categories of negative impacts attributed to the red-vented bulbul depending on the environment where the species occur.

For this reason, local-scale surveys led by [START_REF] Daigneault | Invasive species management in the Pacific using survey data and benefit-cost analysis[END_REF] are crucial to inform local farmers and environment managers. We found few published studies dealing with the local management of the red-vented bulbul in its alien range. One is the biosecurity protocol currently in place in New Zealand [START_REF] Watling | Observation on the naturalised distribution of the red-vented bulbul in the Pacific, with special reference to the Fiji islands[END_REF]) that illustrates the efficiency of locally preventing alien species introductions on reducing their dispersal [START_REF] Edelaar | Managing non-native species: don't wait until their impacts are proven[END_REF]. A test of bird repellents on Hawaiian orchids and papaya production demonstrated the efficiency of three chemicals [START_REF] Cummings | Evaluation of methiocarb, ziram, and methyl anthranilate as bird repellents applied to dendrobium orchids[END_REF]. In their study exploring the efficiency of bird repellent methods in the bulbul native range, [START_REF] Patyal | Damage potential and abundance of avian fauna associated with grapes in Indian Mid Hills of Himachal Pradesh[END_REF] highlighted nets as the most efficient methods although it can be costly to implement on large orchards. In their overview of birds impacts on Indian agriculture, [START_REF] Kale | Damage to agricultural yield due to farmland birds, present repelling techniques and its impacts: an insight from the Indian perspective[END_REF] reviewed the existing repellant techniques used against birds including the biodiversity and plant production being from tropical islands, but even here the bulbul's reported impacts are heterogeneous and typically non-specific. This work reveal that the red-vented bulbul remains highly understudied considering its invasive and pest status. The species' long and close associations with people in its native range and subsequent transportation around the world as a cage-bird, coupled with its competitive foraging behavior [START_REF] Sherman | Observations on feeding frequencies among native and exotic birds and fruit bats at Erythrina variegata and Dysoxylum trees on American Samoa[END_REF], have surely contributed to its presence among the UICN-ISSG list of the world's worst invasive species, but this may well be overstated. Detailed and specific knowledge of this bulbul's impacts and the threats it poses is essential, and [START_REF] Kumschick | Managing alien bird species: time to move beyond '100 of the worst' lists?[END_REF] recently insisted on the need for such information to inform the construction of global prioritization lists. In comparison, the red-whiskered bulbul or the mallard, for example, apparently attracted a more attention from both scientists and managers.

In conclusion, we found few references on the redvented bulbul, reflecting a less attention paid by scientists to this species compared to the other world's worst invasive species. The consideration of its negative impacts is largely influenced by few island locations whereas it is considered elsewhere as harmless, which prevent us from considering the bulbul as an absolute pest. Negative impacts led to the implementation of management programs in only one country and crop protection methods exist but are not necessarily used by local communities. Therefore, we suggest that the redvented may not always be a dangerous pest. red-vented bulbul, and underlined two main limits to their use being (1) social and ecological issues associated with killing birds and (2) danger of most chemical repellants for the biodiversity. This suggest that preventing damages of the red-vented bulbul on plants is feasible and that the investment intensity and the method used mostly depends on local communities. On the other hand, preventing impacts on seed dispersal and native fauna will rely on bird control programs and we found no feedbacks of such operations from the red-vented bulbul alien range yet. Results of the control programs currently in course in French Polynesia will certainly contribute to fill this gap [START_REF] Saavedra | Second control campaign for Common myna and Red vented bulbul on Tahiti. Internal Report[END_REF]. In comparison, 13 eradication programs were conducted on islands against the common Myna and two against the red-whiskered bulbul that were mostly successful [START_REF] Diise | The database of island invasive species eradications, developed by Island Conservation[END_REF]. Thus, more research is needed in the countries were the bulbul was introduced to evaluate threats associated with this species and guide adapted management strategies. Priority should be given to captive and field assessments of its diet and foraging ecology in its alien range. This would allow more accurate determination of the range of resources it uses and its prey [START_REF] Bhatt | Foraging ecology of Red-vented Bulbul Pycnonotus cafer in Haridwar, India[END_REF], its role in seed dispersal [START_REF] Spotswood | An invasive tree alters the structure of seed dispersal networks between birds and plants in French Polynesia[END_REF], and its interspecific relationships [START_REF] Bates | Foraging behaviour and habitat partitioning in sympatric invasive birds in French Polynesia[END_REF].

Management strategies often rely on rigorous expert assessment and are mostly ''restricted only to species for which there is already some suspicion of a threat, often an agricultural one'' [START_REF] Simberloff | Confronting introduced species: a form of xenophobia?[END_REF]. Even for suspected pests, risk assessment is often based on ''anecdotal observations relating to small areas only'' rather than direct scientific research [START_REF] Strubbe | Concerns regarding the scientific evidence informing impact risk assessment and management recommendations for invasive birds[END_REF]. The alien range of the redvented bulbul, mostly consisting of tropical islands, could have also contributed to the negative reputation of the bird as island ecosystems are especially sensitive to the arrival of alien species [START_REF] Sax | Species invasions and extinction: the future of native biodiversity on islands[END_REF][START_REF] Tershy | The importance of islands for the protection of biological and linguistic diversity[END_REF]. The high endemicity and naivety of insular species accentuates their vulnerability [START_REF] Gerard | Knocking on Heaven's door: are novel invaders necessarily facing naı ¨ve native species on islands?[END_REF][START_REF] Walsh | Exotic species richness and native species endemism increase the impact of exotic species on islands[END_REF]. This sensitivity of tropical islands towards alien species may also be reinforced with the risk that a newly established population becomes a stepping stone for further introduction events through shortdistance colonization [START_REF] Gillespie | Long-distance dispersal: a framework for hypothesis testing[END_REF]. The information we present here supports this claim, with most reported impacts of red-vented bulbul on

Fig. 1

 1 Fig.1Sources of the collected information. The ''General information'' scope refers to documents dealing with invasion biology at a global scale

Fig. 3

 3 Fig. 3 Native and alien range of the red vented bulbul

  )[START_REF] Azin | Occurrence of the Redvented Bulbul Pycnonotus cafer on Kish Island, Northeastern Persian Gulf, Iran[END_REF], (14)Nation et al. (1997), (15) Pederson and Aspinall (2015), (16)[START_REF] Gregory | The birds of the State of Kuwait[END_REF], (17) J. Eriksen com.pers., (18) J. Babbington com.pers, (19)[START_REF] Brooks | Ecology, behavior, and reproduction of an introduced population of Red-vented Bulbuls (Pycnonotus cafer) in Houston, Texas[END_REF] M.Thibault et al.

Fig. 4

 4 Fig. 4 Representation of the three impact categories associated with the redvented bulbul Pycnonotus cafer. Each axis corresponds to one category and represents the number of reports, species and location

Table 1

 1 The current alien distribution of the red-vented bulbul Pycnonotus cafer, year of first observation (Y.F.O), number of colonized islands, current introduction success, status, range

	trend, and associated references. (?) Scarce (??) Common
	(???) Very common

Table 2

 2

	) belong-
	ing to 25 families with 67% (35 species) being food
	plants and 33% (17 species) being ornamental plant
	species. The full list of damaged and dispersed plant

Table 2

 2 Numbers of plant species reported as damaged, dispersed or just consumed by the red-vented bulbul Pycnonotus cafer in the literature and corresponding number of reports

	Impact	Status	Species	Reports
	Damage		52	81
		Food plant	35	61
		Ornamental plant	17	20
	Seeds dispersal		33	56
		Endemic	1	1
		Native	8	11
		Alien	10	16
		Invasive	14	28
	Consumption only		25	28
	Total		110	165

Table 3

 3 List of animal species reported as being impacted by the red-vented bulbul Pycnonotus cafer, with associated locations, inter-specific relationship, reported impact, method and references

	Species	Countries	Islands	Inter-specific	Reported	Method	References
				relationship	impact
	Insects
	Danaus plexippus	H	O'ahu	Predation	Decline	Indirect Obs. (1)
	Birds
	Pomarea nigra	PF	Tahiti	Competition	Decline	Direct Obs.	(2)
	Lamprolia victoriae	FJ	Vanua Levu	Competition	Decline	Hypothesis	(3)
	Myiagra vanikorensis FJ	Viti Levu	Aggressivity/competition Nest	Monitoring	(4), (5)
					parasitism
	Lalage maculosa	FJ	Viti Levu	Aggressivity	NA	Monitoring	(5)
	Acridotheres tristis	FJ	Viti Levu	Aggressivity	NA	Monitoring	(5)
	Acridotheres fuscus	FJ	Viti Levu	Aggressivity	NA	Monitoring	(5)
	Zosterops lateralis	FJ	Viti Levu	Aggressivity	NA	Monitoring	(5)
	Amandava amandava FJ	Viti Levu	Aggressivity	NA	Monitoring	(5)
	Streptopelia chinensis FJ	Viti Levu	Aggressivity	NA	Monitoring	(5)
	Foulehaio	FJ, AS	Viti Levu;	Aggressivity/competition NA	Monitoring	(5), (6)
	carnunculata		Tutuila
	Myzomela cardinalis	AS	Tutuila	Aggressivity/competition NA	Direct Obs.	(6)
	Pycnonotus	AE, BH		Cross-breeding	Setrile	Obs./	(7), (8)
	leucogenys				hybrids	Hypothesis
	Pycnonotus leucotis	KW, QA,	Kish Island	Cross-breeding	NA	Obs./	(9), (10), (11)
		IR				Hypothesis
	Pycnonotus	UAE		Cross-breeding	NA	Obs./	(8)
	xanthopygos					Hypothesis
	Zosterops xantochroa NC	Grande-Terre	Competition	NA	Hypothesis	(12)
	Reptile
	Hemidactylus frenatus NC	Grande-Terre	Predation	NA	Direct. Obs	Pers. Obs.

H Hawaii, PF French Polynesia, FJ Fiji, AS American Samoa, AE United Arab Emirates, BH Bahrain, KW Kuwait, QA Quatar, IR Iran, NC New Caledonia (1) Stimson and Berman 1990, (2) Thibault et al. (2002), (3) Williams (

Table 4 P

 4 Parasite load of the red-vented bulbul Pycnonotus cafer in the literature

	Type	Species	Host	References
	Ecto-	Isospora sp.	Yes	(1)
		Menacanthus Eurysternus	Yes	(2)
		Bruelia guldum	Yes	(3)
		Sturnidoecus guldum	Yes	(3)
	Endo-	Plasmodium sp.	No	(4), (5)
		Trypanosoma sp.	No	(4)
		Atoxoplasma sp.	No	(4)
		Chlamydia sp.	Yes	(6)
	Ecto-(Ectoparasites) corresponds to parasites livig outside of
	the animal body. Conversely Endo-(Endoparasites)
	corresponds to parasites living inside the animal body
	(1)

The red-vented bulbul (Pycnonotus cafer)

Acknowledgements We thank the Global Avian Invasions Atlas program, the eBird community and the Ornithological Society of the Middle East for giving access to parts of their databases. Thanks to T. Ghestemme, J. Babbington, J. Eriksen, M. Pope, N. Morris, J. Buchan and M. Jennings for their assistance while summarizing information from the Middle East.

Compliance with ethical standards

Conflict of interest The authors state that they have no conflict of interest.


Hala Mortada
email: hala.mortada@lix.polytechnique.fr

Tatiana Prosvirnova
email: prosvirnova@lix.polytechnique.fr

Antoine Rauzy
email: antoine.rauzy@ecp.fr

Safety Assessment of an Electrical System with AltaRica 3.0

Keywords: AltaRica3.0, Complex systems, Reliability, Modeling, Safety

This article presents the high level, modeling language Al-taRica 3.0 through the safety assessment of an electrical system. It shows how, starting from a purely structural model, several variants can be derived.Two of them target a compilation into Fault Trees and two others target a compilation into Markov chains. Experimental results are reported to show that each of these variants has its own interest. It also advocates that this approach made of successive derivation of variants is a solid ground to build a modeling methodology onto.

Introduction

The increasing complexity of industrial systems calls for the development of sophisticated engineering tools. This is indeed true for all engineering disciplines, but especially for safety and reliability engineering. Experience shows that traditional modeling formalisms such as Fault Trees, Petri nets or Markov processes do not allow a smooth integration of risk analysis within the overall development process. These analysis require both considerable time and expertise. The specialization and the lack of model's structures make it difficult to share models amongst stakeholders, to maintain them throughout the life-cycle of the systems, and to reuse them from one project to another.

The AltaRica modeling language ([1], [START_REF] Rauzy | Modes automata and their compilation into fault trees[END_REF]) has been created at the end of the nineties to tackle these problems. AltaRica makes it possible to design highlevel models with a structure that is very close to the functional or the physical architecture of the system under study. Its constructions allow models to be structured into a hierarchy of reusable components. It is also possible to associate graphical representations to these components in order to make models visually close to Process and Instrumentation Diagrams. The formal semantics of AltaRica allowed the development of a versatile set of processing tools such as compilers into Fault Trees ( [START_REF] Rauzy | Modes automata and their compilation into fault trees[END_REF]), model-checkers ( [START_REF] Griffault | The mec 5 model-checker[END_REF]) or stochastic simulators ( [START_REF] Khuu | Contribution à l'accélération de la simulation stochastique sur des modèles AltaRica Data Flow[END_REF]). A large number of successful industrial experiments with the language have been reported (see e.g. [START_REF] Humbert | Deriving safety software requirements from an altarica system model[END_REF], [START_REF] Quayzin | Performance modeling of a surveillance mission[END_REF], [START_REF] Sghairi | Distributed and reconfigurable architecture for flight control system[END_REF], [START_REF] Chaudemar | Altarica and event-b models for operational safety analysis: Unmanned aerial vehicle case study[END_REF] and [START_REF] Adeline | Toward a methodology for the altarica modelling of multi-physical systems[END_REF]). Despite its quality, AltaRica faced two issues of very different natures. First, systems with instant feedback's loops turned out to be hard to handle. Second, constructs of model's structuring were not fully satisfying. AltaRica 3.0 [START_REF] Prosvirnova | The altarica 3.0 project for model-based safety assessment[END_REF] is a new version of the language that has been designed to tackle these two issues. Regarding model structuring, AltaRica 3.0 implements the prototype-oriented paradigm [START_REF] Noble | Prototype-Based Programming: Concepts, Languages and Applications[END_REF]. This paradigm fits well with the level of abstraction reliability and safety analysis stand at. Regarding mathematical foundations, AltaRica 3.0 is based on Guarded Transition Systems (GTS) [START_REF] Rauzy | Guarded transition systems: A new states/events formalism for reliability studies[END_REF]. GTS combine the advantages of state/event formalisms such as Petri nets and combinatorial formalisms such as block diagrams. This combination is necessary to model system patterns namely cold redundancies, cascading failures or remote interactions.

AltaRica 3.0 comes with a variety of assessment tools. In this article, we show how, starting from the same root model, different variants can be obtained by successive refinements: a first series targeting a compilation into Fault Trees and a second one targeting a compilation into Markov chains. Each of these variants capture a particular aspect of the system under study. We advocate that this approach made of successive derivation of variants is a solid ground to build a modeling methodology onto.

The remainder of this article is organized as follows. Section 2 presents the electrical system that is used as a red-wire example throughout the paper. Section 3 discusses how to describe the architecture of the system with a purely structural model. Section 4 proposes a first variant of this structural model which targets a compilation into Fault Trees. Section 5 presents a second variant which targets a compilation into Markov Chains. Finally, section 6 concludes this article.

Red Wire Example

Figure 1 shows a simple electrical system with cascade redundancies borrowed from [START_REF] Bouissou | A new formalism that combines advantages of fault-trees and markov models: Boolean logic-driven markov processes[END_REF] (we present it here with some additional complexity).

In a normal operating mode, the busbar BB is powered by the grid GR either through line 1 or through line 2. Each line is made of an upper circuit breaker CBUi, a transformer TRi and a lower circuit breaker CBDi. The two lines are in cold redundancy: Let's assume for instance that line 1 was working and that it failed either because one of the circuit breakers CBU1 or CBD1 failed, or because the transformer failed. In this case, the line 2 is attempted to start. This requires opening the circuit breaker CBD1 (if possible/necessary) and closing the circuit breakers of line 2. Since line 2 was out of service, the circuit breaker CBD2 was necessarily open.

If both lines fail, the diesel generator DG is expected to function, which requires closing the circuit breaker CB3. Circuit breakers may fail to open and to close on demand. The diesel generator may fail on demand as well. The grid GR may be lost either because of an internal failure or because of a short circuit in the transformer TRi followed by a failure to open the corresponding circuit breaker CBUi.

The two transformers are subject to a common cause failure. There is a limited repair crew that can work on only two components at a time. After maintenance, the components are as good as new, but may be badly reconfigured.

Fig. 1. A small electrical system

The problem is to estimate the reliability and the availability of this system. This example is small but concentrates on a number of modeling difficulties (warm redundancies, on demand failures, short-circuit propagation, common cause failures, limited resources), due to its multi-domains aspects.

Describing the Architecture of the System

The first step in analyzing a system consists of describing its functional and physical architecture. Figure 1 describes a possible decomposition of our electrical system. This decomposition deserves three important remarks.

First, it mixes functional and physical aspects. In fact, due to the small size of the example, only basic blocks (leaves of the decomposition) represent physical components. The others represent functions. We could consider functional and physical architectures separately. However, considering both in the same diagram simplifies things here. Moreover, it matches better with the usual way of designing models for safety and dependability analysis. Note also that at this step, we do not consider interactions between components.

Second, the underlying structure of this decomposition is not a tree, but a directed acyclic graph for the external power supply is shared between Line 1 and Line 2. As we shall see, this has very important consequences in terms of structuring constructs. Third, the system embeds five circuit breakers and two transformers. We can assume that the circuit breakers on the one hand, the transformers on the other hand are all the same. From a modeling point of view, it means that we need to be able to define generic components and to instantiate them in different places in our model. On the contrary, components like "Primary Power Supply", "Backup Power Supply" and "Busbar Power Supply" are specific to that particular system. The structure of the AltaRica 3.0 model that reflects this architecture is sketched in Figure 2. In AltaRica 3.0, components are represented by means of blocks. Blocks contain variables, events, transitions, and everything necessary to describe their behavior. At this step, the behavioral part is still empty. Blocks can also contain other blocks and form hierarchies. The block "BusbarPowerSupply" contains two blocks: "PrimaryPowerSupply" and "BackupPowerSupply". "Bus-barPowerSupply" is the parent block of "PrimaryPowerSupply" and an ancestor of "CBU1". Objects defined in a block are visible in all its ancestors. For instance, if the class "CircuitBreaker" defines an event "failToOpen", the instantiation of this event in "CBU1" is visible in the block "BusbarPowerSupply" through the dot notation, i.e. "PrimaryPowerSupply.Line1.CBU1.failToOpen".

An instance "GR" of the class "Grid" is declared in the block "PrimaryPower-Supply". It is convenient to be able to refer to it as "GR" as if it was declared in "Line1". This is the purpose of the "embeds" clause. This clause makes it clear that "GR" is part of "Line1", even if it is probably shared with some sibling blocks.

Classes in AltaRica 3.0 are similar to classes in object-oriented programming languages (see e.g. [START_REF] Meyer | Object-Oriented Software Construction[END_REF], [START_REF] Abadi | A Theory of Objects[END_REF] for conceptual presentations of the object-oriented paradigm). A class is a block that can be instantiated, i.e. copied, elsewhere in the model. There are several differences however between blocks and classes. AltaRica 3.0 makes a clear distinction between "on-the-shelf", stabilized knowledge, for which classes are used, from the model itself, i.e. the implicit main block and all its descendants. Such a distinction has been conceptualized in C-K-theory ( [START_REF] Hatchuel | C-k design theory: An advanced formulation[END_REF]). The implicit main block can be seen as the sandbox in which the analyst is designing his model. Declaring a class is in some sense creating another sandbox. Amongst other consequences, this means that it is neither possible to refer in a class to an object which is declared outside of the class, nor to declare a class inside another one or in a block. A class may of course contain blocks and instances of other classes up to the condition that this introduces no circular definition (recursive data types are not allowed in AltaRica 3.0). To summarize, AltaRica 3.0 borrows concepts to both object-oriented programming and prototype-oriented programming [START_REF] Noble | Prototype-Based Programming: Concepts, Languages and Applications[END_REF] -blocks can be seen as prototypes -so to provide the analyst with powerful structuring constructs that are well suited for the level of abstraction of safety analysis. We shall consider first a very simple model, close to a block diagram, in which basic blocks have a (Boolean) input, a (Boolean) output and an internal state (WORKING or FAILED). This basic block changes its state, from WORKING to FAILED, when the event "failure" occurs. The diagram for the whole system is pictured in Figure 4.

The AltaRica code for the diagram (with the architecture defined in the previous section) is sketched in Figure 5. The class "NonRepairableComponent" declares a state variable "s" and two Boolean flow variables: "inFlow" and "out-Flow". "s" takes its value in the domain "ComponentState" and is initially set to WORKING. "inFlow" and "outFlow" are (at least conceptually) reset to false after each transition firing. Their default value is false. The class also declares the event "failure" which is associated with an exponential probability distribution of parameter "lambda". This parameter has the value "1.0e-4" unless stated otherwise.

After the declaration part, which consists in declaring flow and state variables, events and parameters, comes the behavioral part. This behavioral part itself includes transitions and assertions. In our example, there is only one transition and one assertion. The transition is labeled with the event "failure" and can be read as follows. The event "failure" can occur when the condition "s == WORKING" is satisfied. The firing of the transition gives the value FAILED to the variable "s".

The assertion describes the action to be performed to stabilize the system after each transition firing (and in the initial state). In our example, the variable "outFlow" takes the value true if "s" is equal to WORKING and "inFlow" is true, and false otherwise. In the initial state, all components are working, so the value true propagates from the input flow of the grid "GR" to the output flow of the system. If the circuit breaker "CBU2" fails, then the value false propagates from the output flow of "CBU2" to the output flow of the Line 2.

It would be possible to copy-paste the declaration of "NonRepairableComponent" in the declaration of the basic components of our model ("Grid", "Cir-cuitBreaker", etc.). However, AltaRica 3.0 is an object-oriented language and thus provides a much more elegant way to obtain the same result: inheritance. It suffices to declare that the class "Grid" inherits from class "NonRepairableComponent". This is done in the code of Figure 5. In the class "Grid" the default value of the input flow is set to "true". This change makes the grid a source block. The remainder of the model consists in plugging inputs and outputs of the components in order to build the system. Note that the resulting model is not just a flat block diagram, but a hierarchical one. The compilation of this model into Fault Trees is performed according to the principle defined in [START_REF] Rauzy | Modes automata and their compilation into fault trees[END_REF]. The idea is to build a Fault Tree such that:

-The basic events of this Fault Tree are the events of the AltaRica model. -There is (at least) an intermediate event for each pair (variable, value) of the AltaRica model.

-For each minimal cutset of the Fault Tree rooted by an intermediate event (variable, value), there exists at least one sequence of transitions in the AltaRica model labeled with events of the cutset that ends up in a state where this variable takes this value. Moreover, this sequence is minimal in the sense that no strict subset of the minimal cutsets can label a sequence of transitions ending up in a state where this variable takes this value.

For technical reasons, the Fault Trees generated by the AltaRica compiler are quite different from those an analyst would write by hand. The minimal cutsets are however the expected ones. For instance, the minimal cutsets for the target "(BusbarPowerSupply.outFlow, false)", i.e. the busbar is not powered, with our first model are as follows.

Taking into Account Common Cause Failures

We shall now design a second model in order to take into account the common cause failure of the two transformers (due for instance to fire propagation). To do so, we have to model that transformers fail simultaneously when the common cause failure occurs. AltaRica provides powerful synchronization mechanisms to make transitions simultaneous. The idea is to create an event "CCF" and a transition at the first common ancestor of the two transformers, i.e. "Prima-ryPowerSupply". The new code for the "PrimaryPowerSupply" is sketched in Figure 6. The operator & synchronizes the transitions "failure" defined for each transformer. The operator & is associative and commutative. Any number of transitions can be thus synchronized. To fire the synchronizing transition, at least one of the synchronized transitions must be fireable. If the synchronizing transition is fired, then all the possible synchronized transitions are fired simultaneously. The modality ? indicates that the corresponding synchronized transition is not mandatory to fire the synchronizing transition. The modality ! indicates that the corresponding transition is mandatory.

Note that the synchronized transitions continue to exist independently of the synchronizing transition. It is possible to hide transitions by means of a special clause "hide". Our second model has the following two additional minimal cutsets. PrimaryPowerSupply.CCF, BackupPowerSupply.DG.failure PrimaryPowerSupply.CCF, BackupPowerSupply.CB3.failure block PrimaryPowerSupply ... event CCF (delay = exponential(lambdaCCF)); parameter Real lambdaCCF = 1.0e-5; ... transition CCF: ?Line1.TR1.failure & ?Line2.TR2.failure; assertion ... end Fig. 6. Synchronization mechanism to model the Common Cause Failures

Targeting Compilation into Markov Chains

In this section we consider repairs of components, reconfigurations and limited resources. First, we assume that there is an unlimited number of repairers. Then, we refine our model to take into account a limited number of repairers. Both models are compiled into Markov chains.

Unlimited Number of Repairers

All components are repairable. The AltaRica code in this case is similar to the one of the "NonRepairableComponent" (see Figure 5), except that a new event "repair", the corresponding parameter mu and the corresponding transition are added to the previous model. Instead of the "NonRepairableComponent", the classes "Transformer" and "Grid" of this model, will inherit from a "Repairable-Component".

The on demand failures of the circuit breakers and the diesel generator are also considered. The automata describing the behavior of the diesel generator, the transformer, the grid and the circuit breakers are figured in 7 and 8. The solid lines correspond to the stochastic transitions, whereas the dashes correspond to the immediate ones.

Figure 9 represents the AltaRica 3.0 model of the spare component corresponding to the left automaton depicted in Figure 7. Transitions "stop", "start" and "failureOnDemand" are immediate (their delays are equal to 0). When the state variable "s" is equal to STANDBY and the flow variable "demanded" is true, the event "start" may occur with the probability "1-gamma" and the event "failureOnDemand" may occur with the probability "gamma". The values of the probabilities are given through the attribute "expectation".

In this example, we also take into consideration the short circuit case (see the automaton in the right hand side of the Figure 8). For the transformer, the event failure is considered as a short circuit, that will propagate into the whole line and make it instantly fail. If the short circuit is in the "Grid", the whole "Primary Power Supply" system will eventually fail, inducing the spare block (the "Backup Power Supply" system) to take over. The structure of the whole The semantics of AltaRica 3.0 are a Kripke structure (a reachability graph) with nodes defined by variable assignments (i.e. variables and their values) and edges defined by transitions and labeled by events. If the delays associated to the events are exponentially distributed, then the reachability graph can be interpreted as a continuous time Markov chain. In the case when the graph contains immediate transitions, they are just collapsed using the fact that an exponential delay with rate λ followed by an immediate transition of probability p is equivalent to a transition with an exponential delay of rate pλ. The generated Markov Chain contains 7270 states and 24679 transitions. The tool XMRK calculates the unavailability for different mission times. For λ = 10 -4 , γ = 10 -3 and µ = 10 -1 , the probabilities are represented in Figure 12.

Limited Number of Repairers

In this part, we consider the case of a limited number of repairers, namely lower than the number of failures. Counter to the previous model, in order for a repair to take place, the repairer should be available and not used by another component. In this case, some changes in the behavior of the system take place. We will not only be interested in the "repair" transition, but also in the time it starts and ends at. Therefore, the "repair" transition is replaced by a whole set of transitions: startRepair and endRepair (see for example the automaton in the right hand side of the Figure 8). Besides, a new class called "RepairCrew" that defines when a job can start is added to the previous model (see Figure 10).

The transitions "startRepair" and "startJob", as well as "endRepair" and "endJob" are synchronized using the operator & as shown in Figure 11.

Compared to the definition of the common cause failure (see Figure 6), here the modality ! is used in the synchronization, which means that both synchronized events should be fireable to be able to fire the synchronizing transitions. In this example, the synchronized events are hidden explicitly using the clause "hide". In order to make the results more interesting, two numbers of repairers n = 1 and n = 3 are considered. This will allow us to compare the two graphs of unavailability. The same parameters mentioned in the first subsection are used here as well. The Markov Chain consists of 29332 states and 98010 transitions. The graph in Figure 12 shows indeed that the unavailability is lower when the number of repairers is bigger, and even lower when it is unlimited.

Conclusion

In this paper we showed, using an electrical system as a red-wire example, how AltaRica 3.0 can be used to model complex phenomena. A purely structural model was designed. Then, we derived four variants from it: two of them targeting a compilation into Fault Trees and two others targeting a compilation into Markov chains. Each variant, or subset of variants, was tailored for a particular assessment tool, i.e. to capture a particular aspect of the system under study. Based on this experience (and several others we have performed), we are convinced that this approach, consisting of deriving models by means of successive refinements, is a solid ground to build a modeling methodology. The calculations to be performed are actually very resource consuming. Therefore, a model is always a trade-off between the accuracy of the description and the ability to perform calculations. Refining a model in successive variants is a good way to seek a good trade-off. Moreover, the trade-off depends on the characteristics of the system to be observed. Therefore, different tools must be applied. As a consequence, the refinement process should not be linear, but rather have a tree-like structure.

Fig. 2 .

 2 Fig. 2. Architecture of the Busbar Power Supply System

Fig. 3 .

 3 Fig. 3. Structure of the AltaRica 3.0 Model for the Electrical System (partial view)

Fig. 4 .

 4 Fig. 4. A Block Diagram for the electric supply system

Fig. 5 .

 5 Fig. 5. A simple model targeting a compilation into Fault Trees (partial view)

  GR.failure DG.failure GR.failure CB3.failure CBU1.failure CBU2.failure DG.failure CBU1.failure TR2.failure DG.failure CBU1.failure CBU2.failure CB3.failure TR1.failure CBD2.failure DG.failure CBU1.failure CBD2.failure CB3.failure TR1.failure CBU2.failure DG.failure CBU1.failure CBD2.failure DG.failure TR1.failure CBU2.failure CB3.failure CBD1.failure CBU2.failure DG.failure TR1.failure TR2.failure CB3.failure CBU1.failure TR2.failure CB3.failure TR1.failure CBD2.failure CB3.failure CBD1.failure CBU2.failure CB3.failure TR1.failure TR2.failure DG.failure CBD1.failure CBD2.failure DG.failure CBD1.failure TR2.failure CB3.failure CBD1.failure CBD2.failure CB3.failure CBD1.failure TR2.failure DG.failure

Fig. 7 .Fig. 8 .

 78 Fig. 7. Two automata describing the behavior of the Diesel Generator and the Transformer

domain

  SpareComponentState { STANDBY, WORKING, FAILED } class SpareComponent Boolean s (init = WORKING); Boolean demanded, inFlow, outFlow (reset = false); event failure (delay = exponential(lambda)); event repair (delay = exponential(mu)); event start (delay = 0, expectation = 1 -gamma); event failureOnDemand (delay = 0, expectation = gamma); event stop(delay = 0); parameter Real lambda = 0.0001; parameter Real mu = 0.1; parameter Real gamma = 0.001; transition failure: s == WORKING -> s := FAILED; repair: s == FAILED -> s := STANDBY; start: s == STANDBY and demanded -> s := WORKING; failureOnDemand: s == STANDBY and demanded -> s := FAILED; stop: s == WORKING and not demanded -> s := STANDBY; assertion outFlow := s == WORKING and inFlow; end

Fig. 9 .

 9 Fig. 9. AltaRica 3.0 model of a spare component (Diesel generator)

Fig. 12 .

 12 Fig. 12. Unavailability for a different number of repairers

  PPS GR startRepair, PPS GR endRepair; ... transition PPS GR startRepair: !R.startJob & !PrimaryPowerSupply.GR.startRepair; PPS GR endRepair: !R.endJob & !PrimaryPowerSupply.GR.endRepair; hide R.startJob, PrimaryPowerSupply.GR.startRepair; hide R.endJob, PrimaryPowerSupply.GR.endRepair; ... end Fig. 11. A model targeting a compilation into Markov Chains (partial view)

	class RepairCrew
	Integer numberOfBusyRep (init = 0);
	parameter Integer totalNumberOfRepairers = 1;
	event startJob, endJob;
	transition
	startJob: numberOfBusyRep < totalNumberOfRep ->
	numberOfBusyRep := numberOfBusyRep + 1;
	endJob: numberOfBusyRep > 0 ->
	numberOfBusyRep := numberOfBusyRep -1;
	end
	Fig. 10. AltaRica model of the Repair Crew
	block BusbarPowerSupply
	RepairCrew R;
	block PrimaryPowerSupply
	...
	end
	block BackupPowerSupplySystem
	...
	end
	event