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Most shorebirds depend on coastal habitats for much of their life cycle. The quality and diversity of feeding areas during the wintering period directly condition their winter survival, subsequent migration, and breeding success. During their wintering in France, shorebirds use intertidal areas for feeding, both in daylight and at night, depending on the availability of mudflats during the tidal cycle. In this context, we studied whether the bar-tailed godwit (Limosa lapponica) shows contrasting foraging behaviors and distributions between day and night in response to differences in visual capacities, prey availability, potential predation risk, and human activities. We carried out a fine-scale GPS tracking of birds at one of their main wintering sites along the French Atlantic coast. We predicted smaller foraging home ranges at night because of limits for godwits to detect prey visually, suggesting more sediment probing and less movement. Godwits used the entire time window when they have access to intertidal areas, but they faithfully selected distinct diurnal and nocturnal feeding areas using a low number of patches. This variability in space use highlights differences in selection of habitats, such as seagrass beds selected by most of the tracked godwits by day and used much less at night. In addition, distinct feeding distributions of monitored birds revealed interindividual variability in habitat selection, even more by night, most likely to reduce intraspecific competition. We therefore urge greater consideration of the night distribution of birds, rarely evaluated in shorebird studies, to define areas and habitats of importance to future management and conservation measures.

The Freshwater Animal Diversity Assessment (FADA) project estimated that freshwater animal species represent 9.5% of the 1.2 million species described. Knowing that freshwater represents only 0.01% of the earth's surface, these wetlands are suitable habitats for a great part of the world's total biodiversity. However, it has been shown that there is a lack of knowledge on these species, including freshwater invertebrates. Nevertheless, they play a key role in the majority of freshwater ecosystems and in their foodweb networks. Freshwater invertebrates are the food resource of many species, such as fish and birds. The knowledge of their morphological, energetic and nutritive characteristics allows a better understanding of their selection by predators (size, energy intake etc.), but also leads to the improvement of wetland management. Although information about freshwater invertebrates exists in literature, they are generally heterogeneous, dispersed and difficult to collect. To facilitate the accessibility of these data and, thus, optimise and accelerate research projects including freshwater invertebrates, we propose a literature review describing 14 morphological and nutritive characteristics (size, dry weight, gross energy, crude protein etc.) for 656 taxa of freshwater invertebrates. This dataset is a review from 104 publications from 1935 to 2020, compiling 14 characteristics when available (size, dry weight, gross energy, crude protein etc.) for 656 taxa of freshwater invertebrates.

International audience; Habitat selection is an important process in birds that influences individual survival and fitness, and ultimately shapes population dynamics. As a consequence, strong selective pressures apply to favor strategies allowing individuals to choose high-quality habitat for foraging while reducing predation risk and competition. In long-distance migratory birds, such as shorebirds, the non-breeding period is considered as a key period of their annual cycle with reported effects on individual survival and subsequent reproduction. Site selection by non-breeding shorebirds should depend on habitat quality for them to ensure survival until the next breeding season. More specifically, birds should distribute in space and time according to their resource availability and specialize on feeding habitats or/and prey to reduce intraspecific competition. To test this hypothesis, we studied Bar-tailed Godwits (Limosa lapponica) at one of their main non-breeding sites along the French coast. We first used GPS tracking to investigate their foraging and roosting home ranges as well as core sampling to define the diversity of available habitats and their quality as feeding resources. We then compared individual habitat selection in relation to feeding home range sizes and benthic macrofauna abundances. Our results provide the first fine scale definition of shorebird movements and distribution along the non-breeding period. We found that godwits showed an extreme fidelity to restricted feeding areas (about 3.4 km2) during winter, with low overlap between individual feeding home ranges. Each bird appeared to mainly use 4–6 of the 11 available foraging habitats, with a specialization on 1 to 2 main habitats and their associated prey. However, our results did not emphasize a clear relationship between home range sizes and the quality of bird feeding sites. This study thus demonstrates the high specialization of individual non-breeding Bar-tailed godwits relying on specific foraging grounds and habitats, with important implications for the conservation of this species.

Migration associations by Eurasian Curlews Numenius arquata are temporary and last for single flight bouts between stopover sites.Migrant shorebirds are known to initiate migration communally, with...

Background: Choosing the appropriate time to depart for spring migration is crucial to achieving a successful subsequent breeding season among migratory bird species. We expected Eurasian Curlews (Numenius arquata) to start their migration during favourable weather conditions and to adjust their flight heights to prevailing wind conditions.Methods: We equipped 23 curlews with Global Positioning System data loggers to record the spatio-temporal patterns of their departure from and arrival at their wintering site in the Wadden Sea, as well as the first part of their migration. We obtained data for 42 curlew migrations over a period of 6 years. Departure and arrival dates were related to 73 meteorological and bird-related predictors using the least absolute shrinkage and selection operator (LASSO) to identify drivers of departure and arrival decisions.Results: Curlews migrated almost exclusively to the western part of Russia for breeding. They left the Wadden Sea mainly during the evening hours from mid- to late April and returned between the end of June and mid-July. There was no difference in departure times between the sexes, but males tended to return from their breeding sites later than females. Flight speeds of the birds increased significantly with increasing tailwind component, suggesting that they timed their migration according to favourable wind conditions. However, curlews left the Wadden Sea during various wind and weather conditions, with significant numbers leaving during headwind conditions, in contrast to the apparent wind-driven start of migration. Curlews migrated at very low altitudes during tailwind conditions, but flew significantly higher during headwind conditions, at altitudes of up to several kilometres. Departure dates varied by Conclusions: Our results suggest that the start of migration in a long-distance migrant mainly depends on the date and is independent of weather conditions. Given the high repeatability of the departure day among subsequent years, this clearly suggests the existence of an internal clock prompting the start of migration. Further insights into the timing of migration in immatures and closely related birds might help us to understand the genetic mechanisms triggering temporal migration patterns.

Western France is at the crossroads of the migratory routes of two subspecies of black-tailed godwit, Limosa limosa. After leaving Iceland, the godwit L.l. islandica Icelandic black-tailed godwit (IBTG) winters on the coast of western Europe, while the continental black-tailed godwit (CBTG) L.l. limosa can stop in France when migrating between Iberia or Africa and their main breeding grounds in the Netherlands. In this study, we analysed δ15N and δ13C from flight feathers and whole blood throughout the non-breeding period to trace variations in habitat use for both subspecies on the western French coast. Adults and juveniles of IBTG adopt the same feeding habitats as soon as they arrive in the study area, progressively losing the Icelandic freshwater habitat signal, and becoming clearly restricted to marine habitats in winter. Some individuals begin to move locally to freshwater habitats, joining CBTG in a stopover at the end of the wintering period in preparation for northward migration.

International audience; The Eurasian Curlew is an endangered long-lived shorebird breeding in grassland and moorland, with declining numbers across its range due to habitat loss and former hunting. In this context, any additional adult mortality can have a noticeable impact on population dynamics, hence on extinction risk. We report a case of a GPS-tagged individual which track revealed an unusual stopover at the bottom of a wind turbine along its migration route. The curlew rested hours in an unfavourable environment before moving to the adjacent coastal shore, then completed its migration journey the next day. In previous studies, GPS-tags helped to identify death casualties at wind farms, but to our knowledge this is the first detailed report of a non-lethal injury of a tagged animal by a wind turbine, probably by the vortex of rotors. This case alerts on the further potential impacts of wind farm development close to breeding, wintering and stopover sites frequented by Eurasian curlews and other birds. Any wind farm development project should consider the opportunity to avoid, reduce or compensate potential lethal and non-lethal impacts on wildlife.

Precise timing of migration is crucial for animals targeting seasonal resources at locations encountered across their annual cycle. Upon departure, long-distance migrants need to anticipate unknown environmental conditions at their arrival site, and they do so with their internal annual clock. Here, we tested the hypothesis that long-distance migrants synchronize their circannual clock according to the phenology of their environment during the breeding season and therefore adjust their spring departure date according to the conditions encountered at their breeding site the year before. To this end, we used tracking data of Eurasian curlews from different locations and combined movement data with satellite-extracted green-up dates at their breeding site. The spring departure date was better explained by green-up date of the previous year, while arrival date at the breeding site was better explained by latitude and longitude of the breeding site, suggesting that other factors impacted migration timing en route . On a broader temporal scale, our results suggest that long-distance migrants may be able to adjust their migration timing to advancing spring dates in the context of climate change.

SummaryThe Numeniini is a tribe of 13 wader species (Scolopacidae, Charadriiformes) of which seven are Near Threatened or globally threatened, including two Critically Endangered. To help inform conservation management and policy responses, we present the results of an expert assessment of the threats that members of this taxonomic group face across migratory flyways. Most threats are increasing in intensity, particularly in non-breeding areas, where habitat loss resulting from residential and commercial development, aquaculture, mining, transport, disturbance, problematic invasive species, pollution and climate change were regarded as having the greatest detrimental impact. Fewer threats (mining, disturbance, problematic native species and climate change) were identified as widely affecting breeding areas. Numeniini populations face the greatest number of non-breeding threats in the East Asian-Australasian Flyway, especially those associated with coastal reclamation; related threats were also identified across the Central and Atlantic Americas, and East Atlantic flyways. Threats on the breeding grounds were greatest in Central and Atlantic Americas, East Atlantic and West Asian flyways. Three priority actions were associated with monitoring and research: to monitor breeding population trends (which for species breeding in remote areas may best be achieved through surveys at key non-breeding sites), to deploy tracking technologies to identify migratory connectivity, and to monitor land-cover change across breeding and non-breeding areas. Two priority actions were focused on conservation and policy responses: to identify and effectively protect key non-breeding sites across all flyways (particularly in the East Asian- Australasian Flyway), and to implement successful conservation interventions at a sufficient scale across human-dominated landscapes for species’ recovery to be achieved. If implemented urgently, these measures in combination have the potential to alter the current population declines of many Numeniini species and provide a template for the conservation of other groups of threatened species.

International audience; Evaluations of the functioning of benthic marine food webs could be improved by quantifying organic matter fluxes from the meiofauna to higher trophic levels. In this study, we measured the simultaneous ingestion of meiofauna and macrofauna by common dwellers of a tropical intertidal mudflat on the coast of Amazonia. The meiofauna and macrofauna (tanaid) communities of a tropical intertidal mudflat of French Guiana were separately enriched with 15N and 13C, respectively. The enriched preys were then used as tracers during feeding experiments with common predators of different sizes and feeding mechanisms: a Portunidae crab (Callinectes bocourti), a Penaeidae shrimp (Farfantepenaeus subtilis), and a Gobiidae fish (Gobionellus oceanicus). In feeding experiments with all predators except crabs, feeding rates increased with the availability of meiofauna and macrofauna food sources. The ability of consumers to ingest their food selectively was evaluated by calculating the differences in the ratio of macrofauna to meiofauna between the (1) ingested material and (2) that available in the environment. Larger predators showed a higher degree of preferential macrofauna ingestion than smaller predators, consistent with the optimal foraging theory. For large predators, the meiofauna would be important only during early life or in the absence of large food items.

Microphytobenthos (MPB) from intertidal mudflats are key primary producers at the land-ocean interface. MPB can be more productive than phytoplankton and sustain both benthic and pelagic higher trophic levels. The objective of this study is to assess the contribution of light, mud temperature, and gastropod Peringia ulvae grazing pressure in shaping the seasonal MPB dynamics on the Brouage mudflat (NW France). We use a physical-biological coupled model applied to the sediment first centimeter for the year 2008. The simulated data compare to observations including time-coincident remotely sensed and in situ data. The model suggests a MPB annual cycle characterized by a main spring bloom, a biomass depression in summer, and a moderate fall bloom. In early spring, high simulated photosynthetic rates due to mud surface temperature (MST) values close to the MPB temperature optimum for photosynthesis and to increasing solar irradiance trigger the onset of the MPB spring bloom. After the bloom, high MST values lead to synoptic events when MPB thermo-inhibition (39.5 % of summer) and limitation by P. ulvae grazing (8.7 % of summer) superimpose. During these synoptic events of thermo-inhibition and grazing combination, 14 % of the simulated annual MPB primary production is channeled towards the P. ulvae secondary production through ingestion. The model suggests that such a combined effect is highly linked to the MPB biomass depression in summer. The model ability to infer on biotic and abiotic mechanisms driving the seasonal MPB dynamics could open the door to a new assessment of the export flux of biogenic matter at the land-ocean interface and, more generally, of the contribution of productive intertidal biofilms to the coastal carbon cycle.

International audience; Given the lack of background data on essential and non-essential trace elements in invertebrates and fish known to be the predominant prey of marine mammals and seabirds breeding at the Kerguelen Islands, this study intends to provide these results of great influence for predators in higher trophic levels. To this end, plankton organisms (9 species/4 phyla), mollusks (2 bivalves and 2 squid species) and fishes (8 benthic and 10 pelagic species) from Kerguelen waters were analysed for cadmium (Cd), copper (Cu), mercury (Hg), and zinc (Zn). Individual concentrations of non-essential elements (particularly Cd) showed larger variation in comparison with essential ones due to homeostasis. Cd ranged over 4 orders of magnitude; however, Hg ranged only 1, without significant correlation to trophic level. Instead, ecological parameters (benthic/mesopelagic habitat and feeding ecology) showed a more important influence on the results. Concerning seashore organisms, bivalves collected inside the Gulf of Morbihan had higher Cd concentrations compared to those from the Kerguelen shelf, suggesting a local source of Cd, such as runoff water from bird colonies. Comparison with literature showed metal concentrations in invertebrates and fishes from Kerguelen Islands somewhat lower than in the Antarctic area, with Hg prevailing in benthic species and Cd in pelagic ones. In contrast to Hg, Cd values of squids, jellyfish and the amphipod Themisto gaudichaudii were significantly higher than all other species. Finally, top predators foraging in this area that can be subject to potentially high Hg and Cd exposure through their diet at Kerguelen are reviewed.

International audience; A new species, Monokalliapseudes guianae, is described from French Guianese estuaries. It is distinguishable from its only congener most notably by lacking an exopodite on pereopod 1 and by the nature of the basal article of the uropod. The inner distal corner of the basal article is only slightly produced and lacks a rounded lobe. The bases of pereopods 2 and 3 lack numerous long setae. Sexual dimorphism is observed in the antennule, cheliped, and pereopod 1. Depending on size, males can exhibit two forms of chelae. A new diagnosis is presented for the genus Monokalliapseudes.

The extreme dynamics of the Amazonian coast and associated mudbanks raises questions about their unknown resistant infauna. In order to fill the gap, we investigated the seasonal variations of species composition, abundance and population structure of Tanaidacea in two dynamic mudbanks near the coast of French Guiana. Despite the low species richness recorded for this taxon, the very high densities and biomass of tanaids constituted a potential plentiful trophic resource for many coastal species, such as shorebirds, fish, shrimps, and crabs. The estuarine habitat at Sinnamary presented more tanaid species than the bare marine mudflat at Awala-Yalimapo. All species showed strong female-biased sex ratios and differed in range of total length and stage of maturity. The species with smaller body size with sexual maturity occurring at an earlier stage were dominant and widely distributed. Pore water salinity and predator pressure may be considered key factors driving seasonal variations of tanaid abundance and population structure. This study gives a novel insight into the macrobenthos communities along the highly dynamic Amazonian coast.

In tropical South America, the mudflats of the Amazonian coast are unique because of their large size and unrivaled migration dynamics. On Guiana’s coast, macrofaunal communities are believed to be well-adapted to these dynamic conditions. In this study, the benthic macrofauna was sampled in April 2012 in the Awala-Yalimapo region of western French Guiana and at two sites in Suriname: Warappa Kreek and Bigi Pan. These sites are found 800, 920, and 1140 km from the Amazon delta, respectively. The richness, diversity, and densities of the macrofaunal communities in these mudflats are here described for the first time. Only 38 operational taxonomic units (OTUs) were recorded, among which two species were common and widely distributed: the tanaid crustacean Halmyrapseudes spaansi and the polychaete Sigambra grubii; the former represented 84% of all individuals collected, with densities reaching up to 73,000 individuals m−2. Most of the OTUs consisted of relatively small individuals (

In this study, we describe food availability and diet selection of the Red Knot Calidris canutus islandica wintering in three estuarine bays on the French Channel coast. We examined whether the distribution of birds is related to the density and availability of high quality prey. Results indicate strong seasonal and inter-annual variation in the abundance of birds and considerable variation in prey-item abundance and diet selection depending upon site. At Mont Saint-Michel Bay, the prey community was dominated by Baltic Tellins, Macoma balthica. As expected from their high meat-to-shell ratio, Macoma contributed more than 90% of the diet. Most of the cockles, Cerastoderma edule were too large and their quality too low to be preyed upon. Less than 100 km away, in Saint-Brieuc Bay, Red Knots mainly selected the Thin Tellin Tellina tenuis. Although Tellina are a lower quality prey than Macoma, they occurred at a high density and in some winters might explain why the number of Red Knots exceeds those at Mont ...

Summary. Coastal shorebird species overlap at many wintering sites or migratory stopovers. However, each species is morphologically and physiologically specialised for reducing competition for space, time or habitat. A species can encompass several populations, sometimes designated as subspecies. Differences between populations, ages and sexes within the same species can also lead to segregation between individuals in a foraging area. In this study, we explored the non-breeding spatial and temporal overlap between two subspecies of the black-tailed godwit Limosa limosa on the central Atlantic coast of France (the Pertuis Charentais). The proportions of individuals of each sex and each age within the populations were assessed to explore differences in the wintering distribution. The subspecies L.l. islandica winters in the area from July to March whereas the subspecies L.l. limosa may stopover in the area during south- and northward migration. The two subspecies occasionally overlap at some sites just afte...

Species with known long-term changes in abundance and distribution enable exploring the role of newly accessible sites in population regulation. In Western Europe, the Black-tailed Godwit Limosa limosa islandica is one of the few wintering shorebirds with increasing populations. The French coasts comprise a major wintering site within its global wintering area, with several thousand individuals at some sites. Nevertheless, the role and importance of French sites in general distribution patterns of the species remain unclear, especially as its hunting was legal there until 2008. In contrast, recent increases in protected areas in France (from 4,000 ha in 1973 to 28,000 ha in 2005) offer new safe sites and suitable habitats for the species. In this study, we assessed the numbers and distribution of Black-tailed Godwits along the coasts of Western France. The main wintering sites in France are progressively occupied from August, reaching peak occupation in late autumn or early winter although few of the ten sites listed showed similar patterns of monthly variations in the distribution of Godwit numbers. France welcomes c. 28% of the total L. l. islandica population in mid-winter over the period 2003–2007. Numbers declined steadily from the base year (1977) until 1991, then progressively increased, reaching a maximum in 2010 (c. 27,000 individuals). The creation of Nature Reserves throughout the 1990s probably contributed to the increasing number of Godwits in France, with new accessible sites visited and occupied intensively during the period of population increase. The clearly contrasting phenologies between the British Isles and France suggest that most of the individuals first arrive in the United Kingdom after the breeding season, and then some of the birds move to southern sites in either France or Iberia, while very few birds fly directly to France from Iceland.

In expanding populations, individuals may increasingly be forced to use sites of relatively low quality. This process, named the "buffer effect," was previously described for the Black-tailed Godwit (Limosa limosa islandica) in its use of nonbreeding sites in Great Britain and of breeding areas in Iceland. On the basis of diet analyses from droppings and stable isotopes, we describe a new case for the expanding French wintering population of the Black-tailed Godwit, an expansion accompanied by a drastic change in feeding strategy. In the 1990s, Black-tailed Godwits started using intertidal mudflats at Ile de Re, where they eat the rhizomes of seagrass (Zostera noltii) rather than the customary shellfish (Macoma balthica) eaten at both the preferred (initial) site (Aiguillon Bay) and the area occupied last (Yves to Marennes-Oleron bays). Individually color-marked godwits appeared faithful to both diet type and site, suggesting a cost of a change of strategy. This represents a first case of rhizome-feeding in shorebirds, and it exemplifies a case of carnivorous birds occupying a new site shifting to herbivory.

Migratory connectivity can be defined as the flux of individuals or populations among areas between stages of an animal's life cycle. Many shorebird species perform long-distance migrations and while moving between breeding and wintering grounds, they depend on a network of intermediate wetlands (stopover sites) where populations of different origins extensively overlap. The difficulty to discriminate such populations represents a serious obstacle to the identification of the links between breeding or wintering areas and stopover sites, and also precludes the estimation of demographic parameters for each population. In this study, we test if linear discriminant models based on stable carbon and nitrogen isotope ratios in toenails can he used to identify populations of several shorebird species of different wintering origins overlapping at two stopover sites of the East Atlantic Flyway. In addition, we evaluate the ability of this approach to infer migratory phenological patterns of shorebirds. Linear discriminant analyses performed overall well in distinguishing the isotopic signals of birds from wintering areas (in France, Portugal, Morocco, Mauritania and Guinea-Bissau) most species, correctly classifying over 80% (n = 542) of all wintering individuals sampled at these areas. Assignment rates of shorebirds captured during spring migration were also high (96%, n=323) at the Tejo estuary, Portugal, but lower (40%, 0 = 185) at Marennes-Oleron Bay in France, and also differed among species. A large proportion of spring migrants captured in Portugal and France were assigned to Banc d' Arguin in Mauritania, the most important wintering area in the flyway. Phenological patterns derived for dunlins (Calidris alpina), common ringed plovers (Charadrius hiaticula) and grey plovers (Pluvialis squatarola) suggest that the first northward migrants started arriving at the Tejo estuary during the second half of March, with peaking numbers occurring during April or May.

International audience; The case study of Yves Bay (Pertuis Charentais, France) highlighted links between environmental gradients (i.e. sediment characteristics and emersion time) and prey distribution and availability for the two most numerous shorebird species overwintering in Yves Bay: the red knot Calidris canutus and the dunlin Calidris alpina. Two hundred and fifty-two stations were sampled on a predetermined 250 m regular grid covering the intertidal mudflats of this major wintering site in France for east-Atlantic migratory shorebirds. The distribution of principal benthic species abundance and biomass was modelled along two environmental gradients: sediment structure (particularly pronounced north–south sand-mud gradient) and emersion time. The effect of emersion time combined with sedimentary structure strongly explained abundances and biomasses of the main prey for C. canutus and C. alpina in the bay (Cerastoderma edule, Hydrobia ulvae, Macoma balthica, Scrobicularia plana, and Nephtys hombergii). This study highlighted prey species-specific spatial segregation/overlapping as well as spatial interferences in the trophic niche of the two shorebirds.

International audience; This study investigated sub-lethal effects and detoxification processes activated in free-ranging Red Knots (Calidris canutus) from the Pertuis Charentais on the Atlantic coast of France, and compared the results with previous data obtained on another shorebird species, the Black-tailed Godwit (Limosa limosa). The concentrations of 13 trace elements (Ag, As, Cd, Co, Cr, Cu, Fe, Hg, Mn, Ni, Pb, Se, Zn) were assessed in the liver, kidneys, muscle and feathers. Stable isotope analyses of carbon and nitrogen were carried out to determine whether differences in diet explained variations in elemental uptake. The mRNA expression of relevant genes (cytochrome c oxidase 1, acetyl-CoA carboxylase, superoxide dismutase Cu/Zn and Mn, catalase, metallothionein, malic enzyme), antioxidant enzyme activities (catalase, glutathione peroxidase (GPx), superoxide dismutase), and metallothionein (MT) levels were investigated to shed light on trace element detoxification and toxic effects. Although Red Knots were characterized by elevated As and Se concentrations which were potentially toxic, most elements were usually below toxicity threshold levels. The results strongly suggested a dietary specialization of Red Knots, with individuals feeding on higher trophic status prey experiencing higher As, Hg and Se burdens. Red knots and Godwits also showed discrepancies in elemental accumulation and detoxification processes. Higher As and Se concentrations in Red Knots enhanced catalase gene expression and enzyme activity, while Godwits had higher Ag, Cu, Fe and Zn levels and showed higher MT production and GPx activity. The results strongly suggest that detoxification pathways are essentially trace element- and species-specific.

International audience; Trace elements concentrations (Ag, As, Cd, Co, Cr, Cu, Fe, Hg, Mn, Ni, Pb, Se, Zn) were investigated in the liver, kidneys, muscle and feathers of 31 black-tailed godwits (Limosa limosa) accidentally killed during catches by mist net in the Pertuis Charentais, Atlantic coast of France. Analyses of carbon and nitrogen stable isotope ratios were carried out in liver, muscle and feathers in order to elucidate dietary patterns and to determine whether differences in diet explained the variation in elemental uptake. This study also aimed to have a preliminary assessment of sub-lethal effects triggered by trace elements through the investigation of gene expressions by quantitative real-time PCR, antioxidant enzyme activities (catalase, superoxide dismutase, glutathione peroxidase), and metallothionein (MT) levels. The results showed that Cr and Ni concentrations in tissues of adults were lower than in juveniles in part because adults may have eliminated these trace elements through moulting. Except for Cd and Ni, trace element concentrations were negatively correlated to the body mass of godwits. Ag, As, Hg and Se concentrations were positively linked with the trophic position of birds. The diet could be considered as a fundamental route of exposure for these elements demonstrating therefore the qualitative linkage between dietary habits of godwits and their contaminant concentrations. Our results strongly suggest that even though trace elements concentrations were mostly below toxicity threshold level, the elevated concentrations of As, Ag, Cd, Cu, Fe and Se may however trigger sub-lethal effects. Trace elements appear to enhance expression of genes involved in oxidative stress defence, which indicates the production of reactive oxygen species. Moreover, birds with the highest concentrations appeared to have an increased mitochondrial metabolism suggesting that the fight against trace element toxicity requires additional energetic needs notably to produce detoxification mechanisms such as metallothioneins.

In western Europe, the coasts of Vendee and Charente-Maritime on the central Atlantic shoreline of France constitute the most southern wintering site for the Red Knot Calidris canutus islandica, welcoming around 37,000 individuals each winter, and also represent a key stopover area for C. c. canutus (up to 60,000 individuals) between Africa and the Wadden Sea in spring. Nevertheless, the origin of the birds in France arriving in the autumn is unclear, considering that the first islandica start to appear for wintering while canutus could use the same sites as a stopover on their migration route to Africa. We used biometric data from birds caught between 1983 and 2008 to assess the origin of Red Knot staging and wintering in France, and we also investigated the age structure of Red Knot groups during three distinctive periods of their biological cycle: autumn migration, wintering and spring migration. This first assessment was completed by data analysis of ring recoveries over a period of 44 years and isotopic ratio signatures of feathers. The obtained results were in conformity with the general patterns of distribution throughout the year and the timing of migration of both subspecies in Europe as described in previous reviews. Nevertheless, this study highlights two unknown features for both subspecies in this part of their European area distributions. First, a very large predominance of juveniles was recorded at the expense of an extreme rarity of adults in autumn and early winter. We prove the presence of canutus-knots among these juveniles, even with staging later in the autumn and the possibility of wintering there for some of them. Although the Atlantic coast of France welcomes only 9% of the population of islandica-knots wintering in Europe, this network of estuarine bays could represent a crucial strategic area for juveniles. The place could constitute a liberated area for islandica juveniles coming later than adults already settled in northern sites. It offers the possibility for canutus to migrate south on distance-limited stages in order to experiment with the flyway and refuel to join the traditional African wintering grounds.

Numerous animals move vast distances through media with stochastic dynamic properties. Avian migrants must cope with variable wind speeds and directions en route , which potentially jeopardize fine-tuned migration routes and itineraries. We show how unpredictable winds affect flight times and the use of an intermediate staging site by red knots ( Calidris canutus canutus ) migrating from west Africa to the central north Siberian breeding areas via the German Wadden Sea. A dynamic migration model incorporating wind conditions during flight shows that flight durations between Mauritania and the Wadden Sea vary between 2 and 8 days. The number of birds counted at the only known intermediate staging site on the French Atlantic coast was strongly positively correlated with simulated flight times. In addition, particularly light-weight birds occurred at this location. These independent results support the idea that stochastic wind conditions are the main driver of the use of this intermediate stopover site as an emergency staging area. Because of the ubiquity of stochastically varying media, we expect such emergency habitats to exist in many other migratory systems, both airborne and oceanic. Our model provides a tool to quantify the effect of winds and currents en route .

Burrowing bivalves are associated with particular sediment types within sedimentary systems. The degree to which bivalve sediment associations are repeatable across systems has seldom been investigated. To investigate whether such repeatability exists across tidal flats, we compared adult and juvenile distributions of 3 bivalve species (Cerastoderma edule, Scrobicularia plana, Macoma balthica) across 6 European tidal flats. Across systems, the adult bivalves showed fairly repeatable distributions, with C. edule occurring in sandy sediments and AT balthica and S, plana occurring in muddy sediments. Exceptions were observed in systems composed primarily of muddy sediments (Aiguillon Bay and Marennes-Oleron Bay) and the Dutch Wadden Sea. Interestingly, juveniles and adults of C. edule and S. plana showed similar distributions across systems, M. balthica juveniles and adults showed habitat separation in 3 of the 6 studied systems; in 2 of these, it has been shown previously that juvenile M. balthica settle in mud at high tidal levels and migrate to lower sandier flats later in life. The high occurrence of juvenile M. balthica towards high sandy flats in Mont Saint-Michel Bay suggests that juveniles might choose high tidal fiats rather than muddy sediments per se. A repeatable association in adults and juveniles with respect to sediment could Suggest that juveniles actively settle in the proximity of the adults and/or that juveniles settling away from the adults incur a higher mortality due to either predation, physiological stress, or other factors.

In expanding populations, individuals may gradually be constrained to use new sites with non-optimal quality habitats. On the coast of Western Europe, the Black-tailed Godwit Limosa limosa islandica, breeding in Iceland, is one of the rare shorebird species with an increasing population trend. The coast of France hosts 28 % of this population in mid-winter, with the remainder of the population wintering in the British Isles or in the Iberian Peninsula. Unlike godwits in Britain and Ireland, they are distributed among a small number of sites across France and are concentrated in high numbers at each. The Pertuis Charentais hosts up to 65 % of the Black-tailed Godwits recorded nationally (ca 18 000 individuals). In this study, we describe how prey selection and feeding strategies in intertidal areas are linked to site selection at the local scale and could explain the distribution of birds during the non-breeding period. The selection of site and prey species by godwits was studied by describing the diet and food supply of the species in six feeding areas at four local wintering sites. In the Pertuis, it has been confirmed that they have expanded into a herbivorous niche at newly established wintering sites on Ré Island where they feed on the seagrass Zostera noltii. The species remains strictly carnivorous at continental sites, where it forages actively on the bivalve Macoma balthica. Within sites, godwits target the most profitable preys. With the exception of human disturbances, the distribution of individuals within the Pertuis seems to be determined by the distribution, abundance and accessibility of only two prey species among a large array of macrofaunal species., Sélection des sites et des proies par les Barges à queue noire Limosa limosa islandica s’alimentant sur les herbiers de zoostères et les vasières du centre de la côte atlantique française. Dans une population en expansion, certains individus sont voués à explorer et exploiter de nouveaux habitats de moindre qualité. Sur la façade ouest européenne, la Barge à queue noire Limosa limosa islandica, qui se reproduit exclusivement en Islande, est l’une des rares espèces de limicoles avec une tendance démographique positive. Les côtes françaises accueillent 28 % de la population au milieu de l’hiver, le reste se distribuant sur les îles britanniques et la péninsule ibérique. Contrairement à la Grande Bretagne et l’Irlande, la population française se concentre sur un nombre restreint de sites mais avec de fortes concentrations. Les Pertuis Charentais accueillent plus de 65 % de la population nationale (ca 18 000 individus). Dans cette étude, nous décrivons comment la sélection des proies et les stratégies d’alimentation en milieux intertidaux sont liées à la sélection des sites à l’échelle locale and peuvent expliquer la distribution des oiseaux en période de non reproduction. La sélection des sites et des espèces-proies par les barges a été étudiée par la description du régime alimentaire et de la ressource trophique sur six zones d’alimentation sur les quatre principaux sites hivernages. Dans les Pertuis Charentais, il a été confirmé que ces barges occupent une niche écologique herbivore sur le nouveau site d’hivernage de l’île de Ré, où elles s’alimentent de Zostères naines Zostera noltii. La barge garde un régime carnivore sur les sites continentaux, où elle s’alimente principalement du bivalve Macoma balthica. Sur ces sites, les barges ciblent la proie la plus rentable. À l’exception du dérangement humain, la distribution des individus dans les Pertuis Charentais semble être déterminée par la distribution, l’abondance et l’accessibilité de seulement deux espèces-proies parmi un large éventail d’espèces benthiques., Robin Frédéric,Meunier Francis,Corre Frédéric,Joyeux Emmanuel,Cayatte Marie-Laure,Delaporte Philippe,Lemesle Jean-Christophe,Pineau Philippe,Bocher Pierrick. Site and prey selection by wintering Black-tailed Godwit Limosa limosa islandica feeding on seagrass beds and bare mudflats on the central Atlantic coast of France. In: Revue d'Écologie (La Terre et La Vie), tome 70, n°2, 2015. pp. 134-147.

International audience; Concentrations of cadmium, mercury, copper and zinc were measured in muscle, kidney and liver tissues and in the main prey of five species of zooplankton-eating petrels: blue petrel (Halobaena caerulea), thin-billed (Pachyptila belcheri) and Antarctic (P. desolata) prions, and South Georgian (Pelecanoides georgicus) and common (Pelecanoides urinatrix) diving petrels. Since some of these species are closely related species with respect to body size, timing ofmoult and life span, their diet has been examined to evaluate its influence on heavy-metal bioaccumulation. Inter-specific differences were significant for Hg concentrations in the liver and for Zn concentrations in both liver and kidney tissues. Blue petrels exhibited the highest Hg concentrations in the liver (3.9±2.02 lg.g)1 wet weight). No significant differences were found in Cd concentrations between species. Exposure to heavy metals through the most important prey species in the diet during the breeding period was evaluated. The most evident result was the influence of fish prey on Hg levels. Although crustacean species exhibit different cadmium concentrations, the diet composition does not appear to be discriminant for Cd bioaccumulation within the small petrel community at Kerguelen.

The food and feeding ecology of the blue petrel Halobaena caerulea was investigated over 4 consecutive chick-rearing periods at Iles Kerguelen. In all years, blue petrels fed on a large diversity of crustaceans and fish, with a small proportion of squid and other organisms. Crustaceans ranked first by number (98%) and second by reconstituted mass (37%). The hyperiid Themisto gaudichaudii and the euphausiid Thysanoessa sp. were the dominant prey items, accounting each for 42% by number, and for 12 and 4% by mass of the diet, respectively. Other important crustacean prey were the Antarctic krill Euphausia superba (2% by number and 10% by mass) and the large shrimp Pasiphaea scotiae ( 1000 km from the breeding colonies, but blue petrels also foraged on their way back to Iles Kerguelen from these distant foraging grounds to feed their chicks. A comparison of the stable carbon and nitrogen isotopic compositions of chick and adult feathers reveals that adult blue petrels fed at the same trophic level during the chick-rearing and moulting period, and that they renew their flight feathers in Antarctic waters.

The food and feeding ecology of the 2 closely related species of prions Pachyptila belcheri and P. desolata was investigated over 3 consecutive chick-rearing periods at Iles Kerguelen, the only place where they nest sympatrically in large numbers. In all years, the 2 prion species fed on crustaceans, with a small proportion of mesopelagic fish and squid. The hyperiid amphipod Themisto gaudichaudii was consistently the dominant prey item, accounting for 76 and 70% by number, and 57 and 57% by reconstituted mass of the diet of P. belcheri and P. desolata, respectively. Prions, how- ever, were segregated by feeding on different euphausiids, P. belcheri on Thysanoessa sp. (18% by number and 16% by mass) and P. desolata on Euphausia vallentini (9% by number and 15% by mass). P. desolata also caught more small prey such as copepods (9 vs 1000 km from the breeding colonies, during the chick-rearing period. The stable-carbon and -nitrogen isotopic compositions of chick feathers were identical in both species, indicating no important trophic segregation during the breeding period, when adult birds are central-place foragers. The ratios were, however, different in adult feathers, suggesting moulting in Antarctic waters for P. belcheri and in subtropical waters for P. desolata, i.e. in distinct foraging areas when birds are not constrained to return to the colonies.

International audience; In ecological systems, it is necessary to describe the trophic niches of species and their segregation or overlap to understand the distribution of species in the community. In oceanic systems, the community structure of top predators such as seabird communities has been well documented with many studies in several biogeographical areas. But for coastal habitats, very few investigations on the trophic structure have been carried out in avian communities. In this study, the trophic resource partitioning was investigated on eight of the most abundant species of a shorebird community on the central Atlantic coast of France. Our work comprised a comprehensive sample of birds with different ecomorphogical patterns and data on their main prey to encompass potential sources of overlap and segregation in this community. We examined the stable carbon (δ13C) and nitrogen (δ15N) isotopic composition of blood to investigate the trophic structure (1) on a temporal scale by comparing migration and wintering periods; (2) on a spatial scale through inter-site comparisons; and (3) on the community level within groups of phylogenetically related species. Diets appeared different in several cases between periods, between sites and between juveniles and adults for the same sites. A clear trophic partitioning was established with four functional groups of predators in winter inside the community. The Grey Plover, the Bar-tailed Godwit, the Curlew and a majority of the dunlins were worms-eater mainly feeding on Nereis diversicolor or Nephtys hombergii Two species were predominantly deposit-suspensivorous mollusc-eaters, including the Red Knot and the Black-tailed Godwit feeding mainly on Macoma balthica. The Oystercatcher fed mainly on suspensivorous molluscs like Cerastodrema edule and two species including the Redshank and some dunlins adopted opportunistic behaviours feeding on mudflat and/or in marshes.

International audience; This study investigated the link between trace element concentrations and respective diets of two shorebird species present in the Pertuis Charentais, Atlantic coast of France: the Dunlin (Calidris alpina) and Redshank (Tringa totanus). Trace elements concentrations (Ag, As, Cd, Co, Cr, Cu, Fe, Hg, Mn, Ni, Pb, Se, Zn) were investigated in the liver, kidney, muscle and feathers of 28 dunlins and 15 redshanks accidentally dead during catches by mist net. Analyses of carbon and nitrogen stable isotope ratios were carried out in liver, muscle and feathers to determine whether differences in diet explained the variations in elemental levels. These results were compared to previous data obtained on two other shorebird species present on the same sites: the Black-tailed Godwit (Limosa limosa) and Red Knot (Calidris canutus). This study demonstrated that shorebirds of the Pertuis Charentais were characterized by differential trace element bioaccumulation. Arsenic and Se concentrations were elevated in red knots and dunlins, whereas redshanks displayed higher Cd concentrations in internal tissues. These trace element bioaccumulation discrepancies could mainly come from divergences of trophic habits between shorebirds. Species with the highest trophic position displayed the highest Hg concentrations in the liver, muscle and feathers demonstrating therefore the biomagnification potential of this metal, as opposed to Cd and Pb. The same trend was observed in muscle and feathers for Se and only in feathers for As. These data highlighted the need to study several tissues to obtain a full comprehension of trace element exposure and pathways especially for long-distance migrating species using various habitats and sites.

International audience; Comparing food samples from diving and surface-feeding seabirds breeding in the Golfe du Morbihan at Kerguelen Islands to concurrent net samples caught within the predator foraging range, we evaluated the functional importance of the hyperiid amphipod Themisto gaudichaudii in the subantarctic pelagic ecosystem during the summer months. T. gaudichaudii occurred in high densities (up to 61 individuals m-3) in the water column, being more abundant within islands in the western part of the gulf than at open gulf and shelf stations. The amphipod was a major prey of all seabird species investigated except the South Georgian diving petrel, accounting for 39, 80, 68, 59 and 46% of the total number of prey of blue petrels, thin-billed prions, Antarctic prions, common diving petrels and southern rockhopper penguins, respectively. The length-frequency distribution of T. gaudichaudii was similar between the 2 diving species, which fed on 1 large size class of adult individuals, whereas the 3 surface-feeding seabirds preyed upon 2 size classes but in different proportions. Juveniles and adults T. gaudichaudii were equally important in the diet of blue petrels, whereas juveniles and adults predominated in the food of thin-billed and Antarctic prions, respectively. Comparison of T. gaudichaudii found in nets and food samples together with observations at sea indicated that common diving petrels and southern rockhopper penguins fed in the close vicinity of the colonies in the Golfe du Morbihan, whereas blue petrels, and thin-billed and Antarctic prions mainly preyed upon amphipods outside the sampled area. Our study shows that T. gaudichaudii is an important local component of the macrozooplankton community and the main prey for planktivorous seabirds inhabiting the Kerguelen archipelago. In certain areas of the subantarctic zone, it therefore has a trophic role similar to that of Antarctic krill Euphausia superba further south, in Antarctic waters.

Maximum dive depths of common diving petrels Pelecanoides urinatrix were measured monthly over > 1 year, from January 1995 to February 1996, with miniature gauges attached to the birds at Mayes Island, Kerguelen Archipelago. Overall, maximum dive depths of 347 diving petrels averaged 31 ± 6 m (range: 8–64 m), with a mode at 30–35 m. Mean maximum dive depths differed significantly over the study period. The lowest value (22 ± 8 m) was obtained in winter and it was associated with euphausiid crustaceans, suggesting a change in foraging behaviour associated with a shift in the main prey consumed. During the breeding season, birds fed mainly upon the hyperiid amphipod Themisto gaudichaudii (66% of the total number of prey), followed by the large carnivorous copepod Paraeuchaeta antarctica (15%) and zoea larvae of the crab Halicarcinus planatus (13%). Comparison of the diving capabilities of diving petrels (genus Pelecanoides) with those of other diving seabirds suggests that, relative to body mass, diving petrels can dive deeper than penguins and also possibly than alcids, and are thus the most proficient divers among birds.