Response of parasitically laying goldeneyes to experimental nest predation

Conspecific brood parasitism (CBP) has been identified as an integral life history component in birds. Recent empirical and theoretical studies suggest that nest predation is an important ecological factor affecting the occurrence and evolution of CBP; however, behavioural responses of parasites to nest predation remain unexplored. Here we report on a field experiment addressing the ability of parasitically laying common goldeneye, Bucephala clangula, females to respond to nest predation, based either on their own experience or on public information. Females that started parasitic laying in a nest and afterwards experienced partial clutch predation stopped laying in the nest. However, nests that faced partial clutch predation earlier in the season were not avoided by other parasitically laying females later in the season; these later-laying females had not themselves experienced the partial clutch predation in the nest. Hence, considering within-season responses to nest predation, a parasite uses its own experience, rather than public information, in laying decisions and nest choice. The rate of parasitic laying in the experimental nests decreased from the first to the last year of the experiment. Because the experimental nests never produced a successful clutch, this finding suggests that parasites used information on the ever-failing nature of the nests and avoided laying in them. Our results offer new experimental evidence to support the hypothesis that safety and success of nest sites play important roles in CBP.