Abmigration, the switch between flyways, is thought to be frequent in dabbling ducks, and supposedly results from high female philopatry combined with winter pairing: a male pairing in winter with a female from another flyway may follow her to her breeding area and thus abmigrate. On this basis, the frequency of abmigration should be much higher amongst males than amongst females, should increase with time since ringing, and be higher if environmental conditions force birds from different flyways into the same geographical area in winter (in this case the Iberian peninsula in the case of cold spells). Analysing more than 9000 recoveries of Teal ringed in the Camargue, southern France, showed that even with the most conservative flyway definition, 15% of Camargue (Mediterranean flyway) individuals (both males and females) were subsequently recovered in the North‐west European flyway. Moving a flyway boundary closer to the Camargue (i.e. to the south‐east) increased this percentage to c. 32%. None of the predicted patterns were supported by the data: there was no systematic sex difference in abmigration rate; abmigration showed no consistent increase with time from ringing, and was not significantly more frequent after cold spells. These results suggest that there is permeability between these two flyways for all classes of individuals, which might better be considered as a continuum. This should be taken into account in the development of management and conservation policies for Teal in Europe.

Although it is today accepted that population viability analyses are needed at a meta-population level for most species, usually only single populations are monitored in the context of management and conservation programmes. This paper outlines a fairly general and easy-to-implement approach based on counts and capture-recapture data that allow the dynamics of single populations to be assessed even when they are highly connected to other populations. This approach was motivated by a study of the French population of the slender-billed gull Larus genei, which experienced a sharp population increase in the 1980s and 1990s, suggesting that the species was not at risk of extinction. However, several recently raised concerns indicate that the observed population increase is unlikely to have been achieved uniquely by an intrinsic growth rate. We estimated local adult survival probability at 0.81 (0.79-0.83), which is considerably lower than that of other gull species of comparable size. Moreover, local fecundity observed in slender-billed gulls [0.66 (0.47-0.85)] is lower than that observed in similar species. Massive reproduction failures and the low demographic parameters observed could be caused by chick exposure to aerial and terrestrial predation, leading to permanent emigration. Unrealistically high demographic parameter values would be needed to generate the observed local population increase. The results of our study indicate that connections with other neighbouring populations are responsible for the local population dynamics, and that about 10% of the individuals may be immigrants into this local population annually. However, our results suggest that the population of the slender-billed gull may be stable at the west Mediterranean scale. The high annual fluctuations of population size observed at a larger scale also highlight the necessity for coordinated international action to protect a maximum of potential breeding sites in order to protect the species. bs_bs_banner Animal Conservation. Print

Repeated association between subsets of individuals is a common feature of species living in social groups. Because colonial breeding, an extreme case of group living, is associated with certain group behaviour, colonial species are interesting study models to explore the occurrence of social bonds between individuals. As colonial species are usually highly philopatric, disentangling the fidelity to a breeding site from the fidelity to a group of individuals is challenging. Slender-billed gull, Chroicocephalus genei, colonies, however, relocate almost yearly. This behaviour makes it possible to study individual associations over several years, i.e. associations between individuals breeding in the same colony in more than 1 year. To quantify and identify the mechanisms that favour repeated individual associations across years, we analysed data from 14 years of observations of 953 individually marked gulls. Our results showed that some individuals repeatedly bred together across breeding seasons despite the colony moving every year. The probability of an individual selecting a colony increased with an increase in the number of birds that had bred in the same colony as that individual the previous year and not the overall number at the colony. However, we found yearly variation in group tenacity levels and that colony breeding failure favoured splitting of the groups. We also found that association rates rapidly decreased across years but stayed higher than random associations during 2 consecutive years after the first observations. Moreover, over the entire study period, we plotted a bipartite network and found that all colonies and individuals in the population were fully connected. This study reveals group tenacity across years in a colonial bird. Evolutionary pressures as well as the mechanisms favouring social bond persistence across years in colonial birds, however, need further research.

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