Habitat selection, dispersal and population dynamics in seabirds: response to environmental variability at different spatial scales.
BOULINIER, Thierry1, McCOY, Karen2, TVERAA, Torkild3, 1 CNRS-CEFE, Montpellier, France2 CNRS-IRD, Montpellier, France3 NINA, Tromsoe, Norway
ABSTRACT- Habitat selection and dispersal behaviour of individuals are key processes for the understanding of the response of subdivided populations to the variability of the environment at different spatial scales. Processes involved at various scales may nevertheless differ. Available methodological approaches and data may also differ. Using a replicated field experiment at a small spatial scale and a population genetic approach at larger scales, we investigated the dispersal ecology of seabirds. At small spatial scales, detailed observations had suggested that individuals use the reproductive performance of conspecifics as a source of public information on breeding patch quality, but no experimental study investigated how information gathering behaviours can determine dispersal and recruitment decisions in colonial birds. In such species, local factors affecting breeding success, such as predation and ectoparasitism, may lead to spatially heterogeneous, but temporally predictable, habitat patches. By manipulating the breeding success of focal individuals and the one of their neighbours on a series of cliffs within a large breeding colony of the Black-legged kittiwake (Rissa tridacyla), it was possible to assess the effect of the performance of conspecifics on individual decisions. Local attendance of breeders and prospectors was affected by information conveyed by conspecifics, which in turn resulted in differential site fidelity and recruitment the year after. To investigate the potential dispersal and movement of individuals among colonies at larger spatial scales, we used polymorphic neutral genetic markers in two seabird species (the kittiwake and the Common guillemot Uria aalge) and their ectoparasitic tick Ixodes uriae. The low levels of population genetic structure found for the seabirds suggest that gene flow occurs even at large scales, but the population structure found for their parasite shows that movements of prospecting individuals, which can disperse the tick among colonies only within a breeding season, are limited in space. Such results help understanding the role of dispersal in the response of population to environmental change at different scales.
Key words: dispersal, habitat selection, Rissa tridactyka, population structure
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