Géraldine Simon

Long-term climatic trend and body size variation in teal Anas crecca

Abstract A general warming of climate in the future may profoundly affect wildlife populations in terms of numbers, distribution and characteristics of the individuals, therefore leading to new challenges in terms of management and conservation. The effects of global warming can already be detected through the analysis of long-term databases, but insights into these processes can also be acquired by studying changes in wildlife populations during periods with clear trends in climatic changes. We analysed ringing data from more than 38,000 teal Anas crecca caught at the Station Biologique de la Tour du Valat in the Camargue, Southern France, between September 1954 and April 1971. Temperature in the Camargue clearly decreased over the ringing period. There was no correlation between average annual body mass and temperature in any age or sex class, nor a significant effect of temperature on the age ratio of the population. In adults, there were more males when average daily maximum winter temperature increased, while the opposite trend was found for juveniles. The clearest pattern we observed was a positive relationship between temperature and wing length of the individuals: in all sex and age classes, birds tended to get smaller as temperature decreased. It is unlikely that this pattern was related to harsh climate affecting teal feather growth. Rather, we hypothesise that climate affected the distribution of the individuals in Europe: as temperature got colder, small birds found it still more difficult to remain in northern areas and increasingly used the Camargue as a refuge. Reversing the observed pattern suggests that a global warming of climate in the future may have profound consequences for the distribution of wintering teal in Europe, as more and more birds will become able to remain in northern areas closer to their breeding grounds.

Differential migration of the sexes cannot be explained by the body size hypothesis in Teal

The “body size hypothesis” predicts that if individuals of a population migrate different distances from the breeding to the wintering grounds, the distance should be related to the differential ability to cope with adverse conditions, with larger individuals wintering further north. Data collected over a 40-year period in Essex, UK and the Camargue, southern France, revealed that the average body mass of Teal ringed in Essex during these years was actually not greater than that of Teal ringed in the Camargue. A higher proportion of males were included in the UK ringing catch than in the French catch, but we found no support for the body size hypothesis to explain such differential migration of the sexes.

Changes in ring recovery rates over the last 50 years: shall we continue to ring ducks?

Although knowledge of ring recovery rate is of crucial importance to establish demographic parameters, such as survival probability, this information is generally unknown for the dabbling ducks. The almost single existing value from the North American Mallard (Anas platyrhynchos) is thus generally applied to other species or geographic areas, even though this assumption may be strongly misleading. In the study reported here, we have relied on a proxy for actual ring recovery rate, namely, the proportion of rings fitted each year that were eventually reported, to test for differences between duck species (Mallard and Teal Anas crecca) and between countries [England (UK) and France] for Teal. Potential trends over time (1952–2005) were also assessed. Ring recovery rate was found to have sharply decreased and at a similar rate over time in both species in France, and in both countries for Teal (e.g. from 22.7% in 1952 to 7.2% in 1992 for the British Teal). Teal rings were, however, reported more frequently than Mallard ones, and Teal rings were more frequently reported in the UK than in France. In recent years, a phone number for reporting the information has been included on the bird mark, with the immediate result of a doubling in the recovery rate in France. Adaptations to current ringing procedures that would improve ring reporting would appear to be necessary in the future if researchers are to keep ringing as a valuable source of information for bird demography studies.

What Type of Lean Ducks Do Hunters Kill? Weakest Local Ones Rather Than Migrants

Abstract An earlier study in western France showed that birds shot around protected areas had a lower body mass than birds remaining in nature reserves, but it was impossible at that time to distinguish whether shot birds were leaner because they were exhausted and ignorant migrants, or whether there was simply a body-condition bias making the leaner individuals of the area more likely to be shot. To test these hypotheses, we used body mass at ringing from close to 5,000 teal Anas crecca in the Camargue, southern France. Distinguishing between ‘resident’ birds recaptured alive in the same protected area at least once during the month following ringing, ‘locally shot birds’ hunted in the Camargue and ‘migrants’ hunted out of the Camargue area during the same period, we could not detect any significant difference between the average body mass of ‘residents’ and ‘migrants’, whereas locally shot birds were generally lighter. This suggests that migration is not the reason why hunters generally shoot lean ducks around nature reserves. Conversely, these results support the idea that some mechanisms, maybe linked to competition and dominance relationships between birds in protected areas, make the leaner teal more likely to get killed by hunters. Whatever the mechanism involved, this pattern suggests that carrying capacity was reached in the protected areas, a situation calling for appropriate habitat management.

Spring migration dates of teal Anas crecca ringed in the Camargue, southern France

Abstract The policy of the European Commission prohibits hunting of migratory birds while they travel to their breeding grounds. To date, spring migration dates of ducks have mainly been determined using bird counts, but the validity of this sometimes disputed method has never been tested. We used ring-recovery data from close to 9,000 teal Anas crecca ringed in the Camargue, southern France, to determine the onset of spring migration. This method makes it possible to avoid potential biases linked to duck counts, and was used to test the validity of spring migration dates inferred from such counts. Depending on the type of analysis (intra- or inter-annual recoveries), teal appeared to start migrating from the Camargue during the first or second 10-day period of January, with no significant differences between years, and no effect of the birds age or sex. However, when taking potential winter dispersion into account, we suggest that a conservative estimate for the onset of spring migration is the first 10-day period of February. Migration dates inferred from ring-recovery analyses were consistent with earlier results from duck counts, and provide a firm basis for policy making related to hunting. Though ringing data should be preferred when available, our study suggests that determining migration dates from bird counts may be a reliable method for teal, and potentially for other dabbling and diving ducks as well.

The Potential Distance of Highly Pathogenic Avian Influenza Virus Dispersal by Mallard, Common Teal and Eurasian Pochard

Waterbirds represent the major natural reservoir for low pathogenic (LP) avian influenza viruses (AIV). Among the wide diversity of subtypes that have been described, two of them (H5 and H7) may become highly pathogenic (HP) after their introduction into domestic bird populations and cause severe outbreaks, as is the case for HP H5N1 in South-Eastern Asia. Recent experimental studies demonstrated that HP H5N1 AIV infection in ducks does not necessarily have significant pathological effects. These results suggest that wild migratory ducks may asymptomatically carry HP AIV and potentially spread viruses over large geographical distances. In this study, we investigated the potential spreading distance of HP AIV by common teal (Anas crecca), mallard (A. platyrhynchos), and Eurasian pochard (Aythya ferina). Based on capture-mark-recapture method, we characterized their wintering movements from a western Mediterranean wetland (Camargue, South of France) and identified the potential distance and direction of virus dispersal. Such data may be crucial in determining higher-risk areas in the case of HP AIV infection detection in this major wintering quarter, and may serve as a valuable reference for virus outbreaks elsewhere.

Individual quality persists between years: individuals retain body condition from one winter to the next in Teal

AbstractFew studies have considered how body condition changes over time in individual birds, and most of these concerned long-lived breeding birds. We used a large database of Common Teal Anas crecca ringed and recaptured while wintering in the Camargue to study inter-annual persistence in wing length and body condition. Winter body condition may be a major determinant of survival during that season, and may further be related to breeding success. Indices of condition were compared for individual Teal between the moments of ringing and of recapture the following winter, analyzing each sex and age class (adult or juvenile) separately. Wing length was highly repeatable between years, though some limited annual variation was also recorded in adult males. Using scaled mass index as an index of body condition, we observed that condition at ringing was the strongest predictor of body condition at recapture for males and juvenile females, although inter- and intra-annual variation was also significant in most cases. The value of the slope for the relationship between individual body condition indices at ringing and recapture did not differ from 1 for males and for adults, whereas, for juvenile females, the slope was significantly greater than 1, indicating that individual differences in condition became more exaggerated over time. When analyses were repeated using crude body mass instead of a condition index, results were generally similar. Birds recaptured the following winter had a greater body condition at ringing that those that were not recaptured, supporting the hypothesis of a link between winter body condition and return probability. Our results demonstrate the importance of a head start in Teal, given persistent effects of obtaining better condition in the first winter, and suggest specific age and sex effects. They also underline the value of condition indices as a long-term predictor of individual quality in birds, even during the non-breeding season and for such a relatively short-lived species.ZusammenfassungIndividuelle Qualität bleibt von Jahr zu Jahr bestehen: Krickenten behalten ihre individuelle Körperkondition von einem Winter zum nächsten bei Es gibt nur wenige Studien zu zeitlichen Veränderungen der Körperkondition von Vogelindividuen; die meisten von diesen Untersuchungen betreffen zudem langlebige Vogelarten zur Brutzeit. Anhand einer großen Datenmenge von Krickenten Anas crecca, die in ihrem Winterquartier in der Camargue beringt und wiedergefangen wurden, untersuchten wir die Persistenz von Flügellänge und Körperkondition von einem Jahr zum anderen. Die winterliche Körperkondition kann einen Hauptüberlebensfaktor zu dieser Jahreszeit darstellen und darüber hinaus mit dem Bruterfolg zusammenhängen. Es wurden Konditionsindizes für einzelne Krickenten zwischen dem Zeitpunkt der Beringung und dem Wiederfang im darauf folgenden Winter verglichen; dabei wurden Geschlechter und Altersklassen (adult oder juvenil) getrennt analysiert. Die Flügellänge war von einem Jahr zum anderen sehr gut reproduzierbar, obgleich bei den adulten Männchen auch eine gewisse jährliche Variation zu beobachten war. Unter Verwendung des Scaled Mass Index (SMI) als Maß der Körperkondition konnten wir feststellen, dass die Kondition bei der Beringung für Männchen und juvenile Weibchen die besten Voraussagen der Körperkondition beim Wiederfang erlaubte, obwohl die Variation innerhalb und zwischen den Jahren in den meisten Fällen ebenfalls signifikant war. Der Steigungswert für die Beziehung zwischen den individuellen Konditionsindizes bei Beringung und Wiederfang wich bei Männchen und Adulten nicht von 1 ab, für juvenile Weibchen hingegen war die Steigung beträchtlich größer als 1, was darauf hinweist, dass die individuellen Unterschiede in der Kondition im Laufe der Zeit zunahmen. Als die Analysen mit der Rohkörpermasse anstelle eines Konditionsindex wiederholt wurden, waren die Ergebnisse insgesamt ähnlich. Vögel, die im Folgewinter wiedergefangen wurden, hatten bei der Beringung eine bessere Körperkondition als solche, nicht wiedergefangen wurden, was auch die Hypothese eines Zusammenhanges zwischen winterlicher Körperkondition und der Rückkehrwahrscheinlichkeit stützt. Unsere Ergebnisse belegen, wie wichtig ein Konditionsvorsprung für die Krickente in Anbetracht der langfristigen Auswirkungen einer besseren Kondition im ersten Winter ist und deuten auf spezifische Alters- und Geschlechtseinflüsse hin. Außerdem unterstreichen sie den Nutzen von Konditionsindizes zur langfristigen Vorhersage individueller Qualität bei Vögeln, selbst außerhalb der Brutzeit und für solch eine relative kurzlebige Art.

A new exploratory approach to the study of the spatio-temporal distribution of ring recoveries: the example of Teal (Anas crecca) ringed in Camargue, Southern France

We use a new method called “product kernel estimator” to explore the spatial and temporal distribution of 9,114 recoveries of Teal (Anas crecca) ringed in Camargue, southern France, and recovered over the whole of Europe. This method allows exploration of the changes in time of the probability density to recover a ringed bird over a grid covering the study area. We thus identified two migration corridors for this species to the north and south of the Alps, whereas earlier analyses mostly suggested a southern route from Camargue, especially in spring. The northern route seems to be used to a greater extent in autumn than in spring, indicating a frequent abmigration (animals switching from one corridor to the other). Moreover, migration of the population seems faster in spring than in autumn. The simultaneous presence of Teal recoveries in many distinct geographical areas in spring is consistent with the idea that these ducks are not limited by their migratory speed in spring, nor do they wait until favorable environmental conditions before colonizing their breeding areas.

A test of the wintering strategy hypothesis with teal (Anas crecca) ringed in the Camargue, southern France.

Body mass changes in wintering ducks have been considered as the consequence of their “wintering strategy”, i.e. low mass after autumn migration, active foraging leading to body mass restoration, then pairing leading to low body mass again. This pattern is supported by weights of hunter-killed birds, but this is not enough to rule out potential alternative hypotheses linked to the existence of different populations with different body masses. The use of data collected at ringing and subsequent recaptures of known birds demonstrates that teal (Anas crecca) gain and lose body mass from September to March.

Comparing the migration of Eurasian Teal Anas crecca from two main wintering areas of Western Europe: A long‐term study from Essex, England, and the Camargue, France

MATTHIEU GUILLEMAIN1*, RICHARD HEARN2, ROY KING2, MICHEL GAUTHIER-CLERC3, GERALDINE SIMON3 and ALAIN CAIZERGUES4 1Office National de la Chasse et de la Faune Sauvage, CNERA Avifaune Migratrice, La Tour du Valat, Le Sambuc, 13200 Arles, France 2Wildfowl & Wetlands Trust, Slimbridge, Gloucester GL2 7BT, UK 3Centre de Recherche de la Tour du Valat, Le Sambuc, 13200 Arles, France 4Office National de la Chasse et de la Faune Sauvage, CNERA Avifaune Migratrice, 39 Bd. Albert Einstein, CS42355, 44323 Nantes,Cedex 3, France