JAWOR, Jodie M.*; KETTERSON, Ellen D.; Indiana University; Indiana University: Dominance status influences breeding success in female dark-eyed juncos (Junco hyemalis).

The association between male dominance status and mating success has been well studied in many species. Males of higher dominance status acquire higher quality resources needed for reproduction and higher quality mates. Testosterone influences male aggression, which in turn influences dominance status and later acquisition of resources or mates. The association between dominance status, hormones, and reproductive success in females is less studied. In polygynous species where females breed in groups, higher dominance status confers reproductive advantages, such as exclusive access to paternal care. But for socially monogamous species, the most common avian reproductive strategy, the significance of female dominance status has just begun to receive attention. Here we report findings on female dominance status and reproductive success in dark-eyed juncos (Junco hyemalis), a socially monogamous songbird. We measured body size, condition, and hormone titers in females and formed 22 dyads consisting of 2 females housed in aviaries. We observed dominance status, then introduced a male and assessed male preference and female reproductive status. Twelve trios initiated breeding activity and there was evidence that birds interfered with one another�s reproductive attempts. Female status did not vary with size or condition and males did not prefer dominant females. However, among the trios where breeding occurred, dominance status influenced which female was the breeder. Dominant females were more likely to build nests and lay eggs. We are currently investigating whether dominants and subordinates differed in levels of testosterone and corticosterone, but it appears intrasexual aggression among females can play an important role in pair formation and the maintenance of monogamy. (NSF IBN0216091)