Extinction, colonization, and distribution patterns of common eider populations nesting in a naturally fragmented landscape

Spatial distribution, patchy environments, and population turnover have many fundamental implications for con- servation ecology. Common eider (Somateria mollissima L., 1758) population processes were investigated in Labrador, Canada, between 1998 and 2003. We predicted that local colonies would exhibit population turnover, that extinction would be negatively related to colony and patch size, that colonization would be negatively related to island isolation, and that intraspecific incidence-abundance relationships would be positive. We found that small colonies were prone to extinction, but patch size was not a significant predictor of extinction, nor was colonization related to isolation. The overall observed annual extinction and colonization rates were 0.11 ± 0.02 and 0.41 ± 0.06, respectively, and showed variation across archi- pelagos. At two spatial scales we found that mean colony size was a positive predictor of island occupancy (incidence), and these relationships were maintained across years. Our findings show that common eider colonies in Labrador are dy- namic and have greater turnover rates than previously expected in a species that is considered highly philopatric. Our find- ings support the notion that highly mobile organisms such as migratory birds can exhibit characteristics associated with metapopulation processes.