Experimentally elevated corticosterone increases song output and complexity in common mynas
Vocalization is an important communication tool that can reflect many aspects of an individual’s internal and external condition. This is especially true for birds. Previous research has shown that bird calls and songs change in response to a variety of potential stressors, although the extent and direction of the changes depend on the nature of the stressor and the environment. Circulating glucocorticoids, such as corticosterone (CORT), often increase in response to stressors and mediate some of the observed changes via alterations of the individual’s physiological state. Chronically high levels of stress or glucocorticoids in adults, and prolonged developmental stress in young, have well-demonstrated negative effects on vocal performance. Acute elevations of CORT often occur as a physiological response to short-term stressors; however, the effects of this elevation on adult vocalizations have not been documented. Here, we experimentally elevated CORT at two different levels using a non-invasive method and examined the effects on the vocal communication of male and female adult common mynas (Acridotheres tristis). CORT elevation temporarily increased song output and some measures of song complexity, while call output decreased. These effects were dosage dependent (higher CORT levels had a stronger effect), most evident forty minutes after ingestion, and some vocal changes were sex-specific. Future studies should investigate whether the changes in vocal performance due to elevated glucocorticoids have consequences for the birds’ behavior, reproductive success, and survival.