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Factors that influence individual and colony spacing are still not well understood in many organisms. Common eiders (Somateria mollissima (L. 1758)) nest on coastal islands and forage in intertidal and shallow subtidal waters. We considered several biotic and abiotic factors, their interactions, and how these might influence the distribution of eider col- onies at several spatial scales in Labrador, Canada. At the island level, nest abundance was not related to intertidal prey density. At the 104 km 2 grid scale, eider nest abundance and the coefficient of dispersion (CD; the variance to mean ratio of colony size or grid cell, where CD indicates population dispersion) were negatively related to the number of islands. Spring ice cover was positively related to the number of islands but was negatively related to eider nest abundance and to CD. Ice cover - abundance and ice cover - CD were significant at two spatial scales (104 and 455 km 2 , respectively), but other relationships were weaker at the larger spatial scale. We hypothesize that during the spring, archipelagos with many islands trap ice, providing terrestrial predators access to nesting islands by acting as bridges and that increased predation reduces habitat quality causing nesting eiders to disperse. Our findings suggest that eiders respond to landscape features, including ice cover, a feature that is being influenced by climate change. Resume ´ : Les facteurs qui influencent l'espacement des individus et des colonies restent encore mal connus chez de nom- breux organismes. Les eiders aduvet (Somateria mollissima (L. 1758)) nichent sur des oles cotieres et se nourrissent dans la region intertidale et les eaux peu profondes de la zone subtidale. Nous avons examineplusieurs facteurs biotiques et abiotiques et leurs interactions afin de voir comment ils peuvent influencer la repartition de colonies d'eiders adifferentes echelles spatiales au Labrador, Canada. Al'echelle des oles, la densitedes nids n'est pas relieeala densitedes proies de la zone intertidale. Al'echelle d'une grille de 104 km 2 , l'abondance des nids d'eiders et le coefficient de dispersion (CD

Spatial distribution, patchy environments, and population turnover have many fundamental implications for conservation 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 archipelagos. 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 dynamic and have greater turnover rates than previously expected in a species that is considered highly philopatric. Our findings support the notion that highly mobile organisms such as migratory birds can exhibit characteristics associated with metapopulation processes.