Extrapair paternity in hooded warblers

We examined the role of extrapair fertilizations (EPFs) in the mating system of the hooded warbler (Wilsonia citrina), a monogamous songbird. DNA fingerprinting revealed that 8 of 17 (47%) females had extrapair young in their first or second brood, and 23 of 78 (29%) nestlings were the result of EPFs. Extrapair young were signifkandy more likely to occur in first broods than in second broods. The proportion of EPFs within a brood was strongly birnodal among broods: nests had 50% or more extrapair young or none. In seven of eight broods where EPFs occurred, an adjacent male neighbor was identified as the actual father. Male-like coloration in females did not reduce the likelihood of having extrapair young. Females with extrapair young did not receive less parental care from their mates. All males who obtained EPFs were mated to fertile females or were feeding offspring at the time they most likely mated with the extrapair female. Our results are consistent with the female control hypothesis, which predicts that females benefit from extrapair copulations (EPCs) and have some control over which males, if any, obtain EPCs. However, we could not reject the alternative hypothesis that some male neighbors are particularly dominant and aggressive during EPC attempts, so females accept these EPCs to minimize costs.