Mates of Competitive Females: The Relationships between Female Aggression, Mate Quality, and Parental Care

Abstract

Though rarely mate-limited, females in a wide variety of species express traits commonly associated with mate competition in males. Recent research has shown that these competitive traits (ornaments, armaments, and intense aggression) often function in the context of female-female competition for nonsexual reproductive resources and are often positively related to reproductive success. Increased success could occur because competitive females acquire limited ecological resources (nest sites, territories, etc.) or because they pair with high quality males, that is, older, more ornamented, or more parental males. Further, males paired with aggressive/low care females may compensate by increasing their paternal efforts. Here, I examined patterns of social pairing and parental care in free-living dark-eyed juncos (Junco hyemalis), a biparental songbird. I found no detectable relationship between female competitive behavior (aggression) and male quality (age, size, or ornamentation) or male provisioning. Thus, neither of the mate choice hypotheses (females compete for males or males prefer aggressive females) was supported. Instead, these results suggest that females compete for nonsexual resources and mate quality is a secondary consideration. I also found a negative relationship between male and female provisioning rates, suggesting that partners adjust their level of parental effort in response to their partner’s efforts.