Meeting Abstract

35.1  Wednesday, Jan. 5  The stress of parenthood? Relationships between reproductive investment and glucocorticoid concentrations in Tree Swallows BONIER, F*; MOORE, IT; Queen’s University; Virginia Tech bonierf@queensu.ca

Glucocorticoid, or stress hormone, concentrations may reflect the level of environmental challenges confronting an individual. In general, elevated glucocorticoids are thought to indicate an individual in trouble – possibly in poor condition, experiencing a challenging environment, and with reduced relative fitness. But what if the most significant environmental challenge facing an individual is the challenge of parenthood? We predicted that in female Tree Swallows (Tachycineta bicolor), those investing the most in reproduction would have the highest baseline glucocorticoid levels and that experimental manipulation of reproductive effort would correspondingly increase or decrease glucocorticoids. We present results of four years of correlative analyses of relationships between glucocorticoids and reproductive investment in free-ranging Tree Swallows, along with preliminary results of the effects of brood size manipulation on glucocorticoids. Our findings suggest that in some cases, those individuals with the highest glucocorticoid concentrations are those with the greatest investment in reproduction, translating into higher relative fitness for individuals that can withstand the stress of parenthood.