Direct Benefits and Genetic Costs of Extrapair Paternity for Female American Crows (Corvus brachyrhynchos)

The idea that extrapair paternity (EPP) in birds is part of a mixed reproductive strategy driven primarily by females is controversial. In cooperatively breeding American crows, we compared predictions of four female benefits hypotheses—the genetic diversity, good genes, genetic compatibility, and direct benefits hypotheses—to our predictions if EPP was primarily male driven. We found that genetically diverse broods were not more successful, extrapair young were not in better condition and did not have a higher survival probability, and, contrary to prediction, offspring sired by within‐group extrapair males were more inbred than within‐pair offspring. There was evidence of direct benefits, however: provisioning rate and number of surviving offspring were higher in groups containing within‐group extrapair sires. Females therefore derived no apparent benefits from extragroup extrapair males but both direct benefits and genetic costs from within‐group extrapair males. We suggest that males and females both influence the distribution of EPP in this system.