Cowbirds use conspecific social information to detect host nests in the wild

Recent work shows that hosts of avian brood parasites use social information to increase egg rejection rates, but fewer studies explore how parasites themselves use such information to detect host nests in the wild. To determine whether wild Brown‐headed Cowbirds Molothrus ater use social information to detect host nests, we measured how individual cowbirds interacted with decoy nests when presented alongside calling experimental cowbird models or control Mourning Dove Zenaida macroura models, and whether females interacted with these decoy nests more than males (because females are the parasitizing sex). We found that cowbirds interacted with decoy nests in the presence of a conspecific cowbird model, but entirely ignored the nests in the presence of a heterospecific dove model, and that females approached decoy nests more than males. Our findings suggest that wild cowbirds use conspecific social information to detect host nests.