Male parental care, female reproductive success, and extrapair paternity

Birds differ considerably in the degree of male parental care, and it has b een suggested that interspecific variation in extrapair paternity is determ ined by the relative importance of benefits to females from male parental c are and good genes from extrapair sires. I estimated the relationship betwe en extrapair paternity and the importance of male parental care for female reproductive success mainly based on male removal studies, using a comparat ive approach. The reduction in female reproductive success caused by the ab sence of a male mate was positively correlated with the male contribution t o feeding offspring. The frequency of extrapair paternity was negatively re lated to the reduction in female reproductive success caused by the absence of a mate. This was also the case when potentially confounding variables s uch as developmental mode of offspring and sexual dichromatism were conside red. A high frequency of extrapair paternity occurs particularly in bird sp ecies in which males play a minor role in offspring provisioning and in whi ch attractive males provide relatively little parental care. Bird species w ith frequent extrapair paternity thus appear to he those in which direct fi tness benefits from male care are small, females can readily compensate for the absence of male care, and indirect fitness benefits from extrapair sir es are important.