Comparing demographic parameters for philopatric and immigrant individuals in a long-lived bird adapted to unstable habitats

Abstract

Theoretical models about the benefits of philopatry predict that immigrant fitness can be higher, lower or similar to that of philopatrics depending on habitat heterogeneity, dispersal costs, distance between patches or population densities. In this study, we compared transience rates, local survival and recruitment among philopatric and immigrant individuals of Audouin's gull Larus audouinii, a long-lived bird with high dispersal capacities. Several previous studies have shown that these capacities were probably the result of adaptation to unstable and highly discrete habitats; hence, we tested the hypothesis that fitness components for philopatrics and immigrants were similar. During 1988-2006, ca. 27,800 chicks were marked in 31 colonies in the western Mediterranean metapopulation, and more than 52,000 resightings were made in a single, high-quality colony, to estimate local demographic parameters by capture-recapture analyses. Results suggest that, even though parameters related to site-tenacity (e.g. recapture rates) were higher for philopatrics than for immigrants, survival and recruitment were fundamentally similar. Small differences between philopatrics and immigrants were probably influenced by a highly suitable habitat at the study site, which reduced dispersal costs for immigrants; furthermore, the similarities in most fitness components were also probably the result of a life-history strategy of a species living in unpredictable, unstable habitats with high emigration rates among local populations, and with a relatively low cost of dispersal.

When to stay, when to disperse and where to go: survival and dispersal patterns in a spatially structured seabird population

“…This, together with the increase in dispersal from the large Ebro Delta colony, may explain the increasing colonization rates (> 90% relative to the existing and extinct patches, unpubl.) of new patches in recent years (Oro et al 2011). In our study system, the mean breeding success of the recipient patch was not a significant driver of habitat choice and settlement for dispersing breeders and this may confirm the unreliability of breeding success as indicator of habitat quality in systems where local productivity is unpredictable (Doligez et al 2003, Parejo et al 2006).…”

Some Clouds Have a Silver Lining: Paradoxes of Anthropogenic Perturbations from Study Cases on Long-Lived Social Birds

“…The life-history traits of flamingos have evolved in ephemeral habitats such as the Etosha desert where birds have bred in only 27.5% of the last 40 years when rainfall has been high enough to ensure protection against terrestrial predators and to satisfy energy demands for breeding [42]. Species evolving in these type of habitats may be more adaptable to abrupt changes brought about by human activities (see also [12]). Finally, the three species involved are all birds with excellent dispersal abilities.…”

“…The organisms evolving in habitats that historically have been most affected by natural perturbations (e.g. flooding or wildfires) and that are dependent on new habitats appearing after perturbations may eventually turn out to be more resilient to anthropogenic perturbations [1], [12].…”

Demography and dispersal of juvenile and adult Brown-headed Cowbirds (Molothrus ater) in the eastern Sierra Nevada, California, estimated using multistate models

“…Quantifying survival and dispersal can also provide insights into connectivity among populations and how such patterns, in turn, relate to social and ecological factors (Pärn et al 2009, Dale and Steifetten 2011, Oro et al 2011. This is especially true if done separately for individuals of different ages and sexes, because they likely experience different selective pressures that influence both survival and dispersal (Greenwood and Harvey 1982).…”