Uncovering sources of variation in female sociality: Implications for the development of social preferences in female cowbirds (Molothrus ater)

The purpose of this study was to investigate variation in female cowbird (Molothrus ater) sociality. We studied four captive flocks of brown-headed cowbirds, two composed of adult females and juvenile males and two composed of juvenile females and juvenile males. From September through December, we documented sociality using affiliation measures. From the outset, we found large age differences: juvenile females interacted more with each other and with males than did adult females. We conducted perturbations of flock composition to examine the differences between juvenile and adult females. When adult females were mixed with juvenile females and juvenile males, the adult females adopted the behavior of the juvenile females, with both becoming more interactive with males. The perturbations did not appear to be a consequence of juvenile male social behavior. The results are significant as they show a special role for juvenile females to regulate male-female interactions, which in turn affect vocal and social ontogeny as well as reproductive success.