Meeting Abstract

P1.137  Saturday, Jan. 4 15:30  The roles of sex, parental care and aggression on testosterone production in eastern bluebirds (Sialia sialis) AMBARDAR, M.*; GRINDSTAFF, J.L.; Oklahoma State University, Stillwater, OK; Oklahoma State University, Stillwater, OK medhavi@okstate.edu

In many animals, the hormone testosterone (T) generally promotes territorial aggression while reducing parental care. In socially monogamous species where both sexes defend the nest, short term elevations in T might facilitate aggression, and thus, the likelihood of successfully defending the nest. Alternatively, T might remain low during aggressive interactions because of the suppressive effects of that hormone on parental care. Because costs associated with aggression and parental care differ between the sexes, there might also be differences across sexes in the relationships between T, aggression, and parental care. We used a wild population of eastern bluebirds (Sialia sialis) to examine how T production differed between sexes during parental and aggressive contexts. We quantified parental care by videotaping feeding behavior by adult bluebirds when nestlings were 5-7 days old. To quantify aggression, we performed simulated territorial intrusions (STIs) using a common nest site competitor, the house sparrow (Passer domesticus) when nestlings were 7-9 days old. Following parental care and STI trials, we collected a blood sample from either the male or female bird to determine circulating levels of T within parental and aggressive contexts. We also performed gonadotropin releasing hormone (GnRH) challenges to test the responsiveness of the hypothalamic-pituitary-gonadal (HPG) axis in male and female bluebirds. The results of this study will provide insight into sex differences in T production during social interactions, and how T relates to the trade-off between aggressive behavior and parental care.