Meeting Abstract
The dampened hormonal stress responses in neonates is thought to be an adaptive response against the damaging effects of exposure to chronically high concentrations of glucocorticoids, such as retarded growth. Glucocorticoids facilitate the mobilization of stored energy but can also promote anabolic processes in specific contexts. Understanding the development of the glucocorticoid stress response and when and how glucocorticoids affect growth are important for predicting how growing animals will respond to perturbations. We investigated the development of the hormonal stress response and the relationship between endogenous corticosterone (Cort) and growth in the lance-tailed manakin (Chiroxiphia lanceolata). We subjected 11-day-old nestlings and adult manakins to a standardized capture and restraint protocol to measure baseline and stress-induced levels of Cort post-capture. We found that nestlings had an attenuated stress-response and faster negative feedback compared to adults. We also compared concentrations of Cort to mass and skeletal growth. Baseline concentrations had an inverted U-shaped relationship with both mass and structural growth. Stress-induced concentrations had a negative relationship with structural growth but did not affect mass. These results demonstrate the importance of validating the timing of stress series protocols in developing young independent of those used for adults. Further, Cort appears to facilitate growth at low concentrations, while overall mass is buffered against the negative effects of high concentrations of Cort at the expense of structural growth. This is likely important for altricial avian species, as they rely on fast structural growth, particularly of wings, to minimize predation risk in the nest.
