JAWOR, Jodie*; RICHARDSON, Jennifer; KETTERSON, Ellen; Indiana University, Bloomington, IN; Indiana University, Bloomington, IN; Indiana University, Bloomington, IN: Do hormones other than testosterone influence intrasexual aggression in female dark-eyed juncos (Junco hyemalis)?

Hormones and aggressive behavior have been widely studied in male birds, but not as widely in females. In some species, female aggression has been linked to increases in testosterone (T), while in others no relationship has been found. Previous research with female dark-eyed juncos (Junco hyemalis) found that experimentally increased T led to increased aggression, but endogenous T did not co-vary with aggression or dominance. Here we investigated whether steroid hormones other than T, estradiol (E2), progesterone (P), or DHEA, increased in females after interacting with a same-sex, conspecific intruder. Thirty females were allowed to establish residence in breeding aviaries and bond with a male. After 48hrs, they were presented with either a female conspecific, or a control heterospecific intruder. Each female was her own control, and the order of presentation of hetero- or conspecific intruders was randomized and occurred one week apart. To compare pre- and post-challenge hormone levels we collected plasma samples prior to and 30min after introductions. Rates of aggression by the resident female were also recorded. Resident female juncos were almost always aggressive towards the conspecific, and were never aggressive to the heterospecific intruder. Hormone assays are currently underway. Hormone levels pre- and post-intrusion will be compared to each other and to rates of aggression. Findings from this research will further our understanding of the hormones influencing female aggression, particularly during the breeding season when selection may have favored a trade-off between hormonally mediated maternal effects and hormones that mediate female aggression.