Meeting Abstract
Glucocorticoid hormones play an essential role in responding to stressors, as well as in mediating important behavioral and physiological traits. Moderate to long-term elevations in circulating glucocorticoids, like those seen in the context of chronic stress, are known to impair reproduction. However, it is not clear whether brief acute increases in glucocorticoids – like those observed during the course of a normal stress response – also influence reproductive behavior or success. A multi-year analysis in tree swallows (Tachycineta bicolor) indicates that variation in the magnitude of the glucocorticoid stress response strongly predicts reproductive success: females that mount stronger responses to a standardized restraint stressor during incubation later fledge fewer and smaller young. To assess whether these links are causal we experimentally induced a brief, acute glucocorticoid response of varying magnitude in free-living tree swallows, and measured the immediate and longer-term effects on parental behavior and physiology, as well as nestling phenotype and survival. The results of these studies have implications for understanding the evolution and regulation of the stress response, and for determining whether brief exposure to passing stressors can have lasting impacts on phenotype and fitness.
