Meeting Abstract

P2.163  Monday, Jan. 5  Hormones and life-history trade-offs: how do parental corticosteroid levels correlate with changes in offspring sex ratio in tree swallows (Tachycineta bicolour)? MUNRO, H.*; BONIER, F; LOCKHART, L; MOORE, I; ROBERTSON, R.J.; Queen’s University, Kingston, ON; Queen’s University, Kingston, ON; Queen’s University, Kingston, ON; Virginia Tech, Blacksburg; Queen’s University, Kingston, ON 4hjm3@queensu.ca

Species face many trade offs as a result of resource availability, time, and physical constraints. These trade-offs often manifest themselves in modifications of life-history traits that may be mediated by hormonal signals. Corticosterone (cort), a hormone involved in metabolic function as well as response to stress, may influence these trade offs. Offspring sex ratio biasing in many avian species, including tree swallows (Tachycineta bicolour), has received attention in past years. While occurrence of sex ratio biasing is well documented, the mechanisms underlying this phenomenon remain unknown. Previous studies have suggested a causal relationship between cort and sex ratio biasing. We looked at the relationship between offspring sex ratio in tree swallows and parental baseline cort levels in a box-nesting population at Queens University Biological Station in Ontario, Canada. We will relate both social male and female cort levels to sex ratio of their offspring. We expect that parents with higher cort levels will have female-biased clutches while parents with lower cort levels will have male-biased clutches. A finding of a natural correlation between parental cort levels and offspring sex ratio will provide further support of the potential causal link between cort and sex ratio biasing in birds.