Secondary reproductive strategies in Pacific black brant (Branta bernicla nigricans)

Abstract

Waterfowl are known to use secondary reproductive strategies, both extra-pair copulations and intraspecific brood parasitism, to increase fitness. We used five polymorphic microsatellite loci to determine extra-pair paternity and nest parasitism in 30 nests of Pacific Black Brant geese (Branta bernicla nigricans) containing 108 offspring. Fourteen of the 30 nests contained offspring that were not genetically related to one or both of the attending adults: 6.5% (7/108) of the offspring resulted from extra-pair copulations (EPC); 13.9% (15/108) of the offspring resulted from intraspecific brood parasitism (IBP). All offspring resulting from EPCs were produced during the peak period of nest initiation. Adult females hosting parasitic eggs were significantly older than non-hosts. After accounting for eggs resulting from IBPs in the calculated clutch size, clutches containing IBPs were significantly smaller than unparasitized clutches. Our data indicate that secondary strategies represent an important component of reproductive effort in Black Brant.