Delayed effect of early-life corticosterone treatment on adult anti-predator behavior in a common passerine.

Acute, short-term effects of early-life stress and associated glucocorticoid upregulation on behavior are widely documented across vertebrates. However, the persistence and severity of these effects are largely unknown, especially through the adult stage and in wild species. Here, we investigate long-term effects of experimental post-natal increases in a circulating glucocorticoid on antipredator behavior in wild house sparrows (Passer domesticus) tested in captivity. We manipulate circulating corticosterone concentration in wild, free-living nestlings, transfer fledglings to captivity, and test juveniles and adults for two measures of antipredator behavior: evasiveness during a direct human encounter, and propensity to escape from a risky environment. We find no effect of early-life stress hormone manipulation on escape behavior, but a delayed effect on evasive behavior: evasive behavior was depressed in adults but not juveniles, and influenced by current body condition. These results highlight the importance of state-behavior interactions and life stage in assessing long-term effects of early-life stress, and provide rare evidence for delayed effects of early-life stress to adults of a wild avian species.