Male parental care, female reproductive success, and extrapair paternity

Abstract

Birds differ considerably in the degree of male parental care, and it has been suggested that interspecific variation in extrapair paternity is determined by the relative importance of benefits to females from male parental care and good genes from extrapair sires. I estimated the relationship between extrapair paternity and the importance of male parental care for female reproductive success mainly based on male removal studies, using a comparative approach. The reduction in female reproductive success caused by the absence of a male mate was positively correlated with the male contribution to feeding offspring. The frequency of extrapair paternity was negatively related to the reduction in female reproductive success caused by the absence of a mate. This was also the case when potentially confounding variables such as developmental mode of offspring and sexual dichromatism were considered. A high frequency of extrapair paternity occurs particularly in bird species in which males play a minor role in offspring provisioning and in which attractive males provide relatively little parental care. Bird species with frequent extrapair paternity thus appear to be those in which direct fitness benefits from male care are small, females can readily compensate for the absence of male care, and indirect fitness benefits from extrapair sires are important.