Male Parental Care and Apparent Monogamy Among Eastern Bluebirds (Sialia sialis)

Abstract

Because 95.5% of breeding eastern bluebirds on study sites in South Carolina were apparently monogamous, I examined hypotheses for the evolution of monogamy. In an effort to assess the effects of male parental care on female reproductive success, males were removed from breeding territories after clutch completion. Experimentally deserted females and control, paired females were matched by age, brood number, habitat type, and study area. No significant differences were found for any measures of reproductive success compared. The hypothesis that parental care by males is necessary for partial reproductive success of females was rejected. This result challenges the notion that parental care by males always positively affects female fitness.