Corticosterone secretion in response to adult alarm calls in American Kestrels

Abstract

Abstract Many nestlings respond to alarm calls with anti-predator behavior, but their physiological responses to such calls are poorly understood. Alarm calls could stimulate increased secretion of corticosterone to mobilize energy reserves in anticipation of an interaction with a predator. However, elevated corticosterone levels can be costly to nestlings because they induce catabolic reactions at a time when the birds are engaged in anabolic processes. Thus, there may be constraints on the secretion of corticosterone if the catabolic costs outweigh the behavioral benefits. Furthermore, many studies use baseline corticosterone levels as a correlate of body condition, and if nestlings respond hormonally when they hear alarm calls rather than when they are first handled by (or catch sight of) an investigator, then determination of baseline hormone levels would be difficult. To investigate this phenomenon, we broadcast taped calls of either adult conspecific alarm calls or songs of heterospecifics to 15–20 ...