Extrapair paternity in hooded warblers

We examined the role of extrapair fertilizations (EPFs) in themating system of the hooded warbler (Wilsonia citrina), a monogamoussongbird. DNA fingerprinting revealed that 8 of 17 (47%) femaleshad extrapair young in their first or second brood, and 23 of78 (29%) nestlings were the result of EPFs. Extrapair youngwere signifkandy more likely to occur in first broods than insecond broods. The proportion of EPFs within a brood was stronglybirnodal among broods: nests had 50% or more extrapair youngor none. In seven of eight broods where EPFs occurred, an adjacentmale neighbor was identified as the actual father. Male-likecoloration in females did not reduce the likelihood of havingextrapair young. Females with extrapair young did not receiveless parental care from their mates. All males who obtainedEPFs were mated to fertile females or were feeding offspringat 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, obtainEPCs. However, we could not reject the alternative hypothesisthat some male neighbors are particularly dominant and aggressiveduring EPC attempts, so females accept these EPCs to minimizecosts.