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Bocher P.,CNRS Coastal and Marine Environment Laboratory | Quaintenne G.,CNRS Coastal and Marine Environment Laboratory | Delaporte P.,Reserve Naturelle Nationale de Moeze Oleron | Goulevant C.,Reserve Naturelle Nationale des Marais dYves | And 2 more authors.
Wader Study Group Bulletin | Year: 2012

The two subspecies of the Red Knot Calidris canutus that occur in Europe during northward and southward migration, islandica and canutus, are only observed simultaneously at a few sites such as the Wadden Sea. Mostly islandica winters on estuarine bays in NW Europe, while canutus go to wintering grounds in W or S Africa. The coasts of France have been described as the main southern limit of the winter distribution of islandica and as providing stopover sites for canutus migrating between the W African coast and breeding grounds in Siberia. Nevertheless, the role and the importance of French sites remain unclear for both subspecies, especially during southward migration. This study updates information on the numbers and the distribution of Red Knots staging or wintering along the coasts of France using International Waterbird Census (IWC) data (counts carried out in Jan, 1976-2010, organised by Wetlands International) and synchronized monthly counts carried out in France's National Nature Reserves during 2000-2010. In recent years, France has supported around 9% (c.35,000 individuals) of the estimated population of islandica in mid-winter. Ninety percent of these birds are concentrated in just six bays, two along the Channel coast and four along coasts of Vendee and Charente-maritime. As intertidal areas are limited along the Mediterranean shore, it does not support Red Knots in winter. Numbers of islandica peak in mid-winter, but significant passage of canutus occurs in May on the central Atlantic coast. Patterns of autumn migration remain unclear and information on occurrence of both subspecies is lacking. Long term trends in site use differ from place to place; this is probably an indication that they are used by birds of different origin and age. Source


Catry T.,University of Lisbon | Lourenco P.M.,University of Lisbon | Lopes R.J.,University of Porto | Bocher P.,CNRS Coastal and Marine Environment Laboratory | And 9 more authors.
Basic and Applied Ecology | Year: 2015

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 be 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) in 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%, n = 185) at Marennes-Oléron 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. Migrationskonnektivität kann als die Wechselrate von Individuen oder Populationen in bestimmten Gebieten zwischen zwei Phasen im Lebenszyklus einer Art definiert werden. Viele Watvögel legen weite Strecken zurück, und während des Zuges zwischen Brut- und Überwinterungsgebieten benötigen sie ein Netzwerk von Feuchtgebieten als Rastplätze, wo Populationen unterschiedlicher Herkunft zusammen kommen. Die Schwierigkeit, solche Populationen zu unterscheiden, stellt ein schwerwiegendes Hindernis für die Bestimmung der Verbindungen zwischen Brut- bzw. Überwinterungsgebieten und den Rastplätzen dar und verhindert außerdem die Bestimmung von demographischen Parametern für einzelne Populationen. Wir testeten, ob -basierend auf den Signaturen der stabilen Kohlenstoff- und Stickstoffisotope in Zehennägeln- lineare Diskriminanzmodelle eingesetzt werden können, um die unterschiedlichen Überwinterungsgebiete von Watvögeln zu identifizieren, die an zwei Rastplätzen entlang des Ostatlantischen Zugweges zusammentrafen. Wir bewerteten außerdem die Fähigkeit dieser Methode, Rückschlüsse auf phänologische Muster der ziehenden Watvögel zuzulassen. Die lineare Diskriminanzanalyse bewährte sich für die meisten Arten gut bei der Unterscheidung von Isotopensignaturen der Vögel aus unterschiedlichen Überwinterungsgebieten (Frankreich, Portugal, Marokko, Mauretanien und Guinea-Bissau). Mehr als 80% (n = 542) der in diesen Gebieten untersuchten überwinternden Individuen konnten korrekt eingeordnet werden. Die Zuordnungsraten der Watvögel, die während des Frühjahrszuges im Mündungsgebiet des Tejo gefangen wurden, waren ebenfalls hoch (96%, n = 323), sie waren aber geringer (40%, n = 185) in der Marennes-Oléron-Bucht (Frankreich) und variierten zwischen den Arten. Ein hoher Anteil von Frühjahrsziehern, die in Portugal und Frankreich gefangen wurden, wurde dem Banc d'Arguin-Nationalpark (Mauretanien) zugeordnet, dem wichtigsten Überwinterungsgebiet des Zugweges. Phänologische Muster von Alpenstrandläufer (Calidris alpina), Sandregenpfeifer (Charadrius hiaticula) und Kiebitzregenpfeifer (Pluvialis squatarola) legten nahe, dass die ersten nordwärts ziehenden Vögel während der zweiten Märzhälfte im Mündungsgebiet des Tejo ankamen, wonach die Spitzenwerte im April oder May erreicht wurden. © 2015 Gesellschaft für Ökologie. Source


Catry T.,University of Lisbon | Lourenco P.M.,University of Lisbon | Lopes R.J.,University of Porto | Bocher P.,CNRS Coastal and Marine Environment Laboratory | And 10 more authors.
Basic and Applied Ecology | Year: 2016

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 be 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) in 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%, n = 185) at Marennes-Oléron 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. © 2015 Gesellschaft für Ökologie. Source


Bocher P.,University of La Rochelle | Quaintenne G.,University of La Rochelle | Robin F.,University of La Rochelle | Doumeret A.,Reserve Naturelle Nationale des Marais dYves | Delaporte P.,Reserve Naturelle Nationale de Moeze Oleron
Journal of Ornithology | Year: 2012

In western Europe, the coasts of Vendée 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. © 2011 Dt. Ornithologen-Gesellschaft e.V. Source

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