Interspecific brood parasitism by the Common Eider Somateria mollissima at Er Valant Island, Brittany, France

Interspecific brood parasitism (IBP) involves individuals of one species leaving the incubation and rearing of their brood to another species, while conspecific brood parasitism (CBP) involves a female laying its eggs in the nest of another of the same species (Robert &amp Sorci 2001 Lyon &amp Eadie 2008). CBP is a common reproductive tactic in Anatidae, found in 46% of species including the Common Eider Somateria mollissima (Yom-Tov 2001), while IBP is infrequent in precocial species such as Anatidae (Robertson 1998).