Differential responses to related hosts by nesting and non-nesting parasites in a brood-parasitic duck

Host-parasite relatedness may facilitate the evolution of conspecific brood parasitism (CBP), but empirical support for this contention remains inconclusive. One reason for this disparity may relate to the diversity of parasitic tactics, a key distinguishing feature being whether the parasite has a nest of her own. Previous work suggests that parasites without nests of their own may be of inferior phenotypic quality, but due to difficulties in identifying these parasitic individuals, little is known about their host selection criteria. We used high-resolution molecular maternity tests to assign parasitic offspring to known parasites with and without their own nests in a population of Barrow’s goldeneyes (Bucephala islandica). We determined whether parasite nesting status, host-parasite relatedness, and distance between host and parasite nests affected the probability of parasitizing a host and the number of eggs laid per host. We also investigated whether nesting parasites, conventional...