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.
Townsend
Andrea K
AK
Fuller Evolutionary Biology Program, Cornell Lab of Ornithology, Cornell University, Ithaca, New York 14850, USA. at256@cornell.edu
Clark
Anne B
AB
McGowan
Kevin J
KJ
D000818:Animals; D046368:Crows / Q000235:genetics / Q000502:physiology*; D005260:Female; D008297:Male; D012726:Sexual Behavior, Animal / Q000502:physiology*