Site fidelity in breeding Common Eider Somateria mollissima females

Abstract

We studied nest-site and post-nesting feeding site fidelity in a population of Common Eiders Somateria mollissima in North Norway during five consecutive breeding seasons (1986-90). Twenty-five per cent of the females that nested successfully and none of the unsuccessful females returned to the same nest . Whether females nested at the same site was independent of nesting variables other than total clutch loss . Similarly, nest-site fidelity did not result in nesting variables different from those of females which changed their nest-site. In contrast, fidelity to post-nesting feeding sites was very high (92%). Females that showed post-nesting feeding site fidelity did not have a higher rate of nest-site fidelity than than other birds in the population . We therefore contend that in Common Eiders fidelity to a specific nest-site is less important than fidelity to the postnesting feeding site . Going to areas where the female knows that sufficient food can be found is very important for both the female and her brood. In comparison to other duck species with more specific nest-site requirements (cavity-nesting ducks), Common Eiders have a low return rate to previous nest-sites, and we suggest that this reflects a difference in the availability of suitable sites.