Behavioral and physiological responses of wild-caught European starlings (Sturnus vulgaris) to a minor, rapid change in ambient temperature.

Free-ranging animals continuously adjust to changes in their environment. The stress response, typified by increases in heart rate and glucocorticoids, is an important physiological response regulating these changes. This study investigated heart rate, corticosterone and behavioral responses of European starlings (Sturnus vulgaris) to a rapid 30min decrease in temperature using an air-conditioning unit. Ten wild-caught birds were divided into pairs and exposed to four different trials. Three trials were controls: undisturbed birds; exposing birds to only the noise of the air-conditioning unit; and exposing the birds to 20°C airflow. For the experimental trial birds were exposed to 12°C air, leading to a rapid but modest 3°C drop in ambient temperature inside the birdcages. Heart rate and behavior were recorded before and during trials, while blood samples were collected before and after each trial for corticosterone measurements. Cooling, but none of the control conditions, induced an increase in heart rate and corticosterone. Additionally, cooling led to an increase in perch hopping and feather ruffling. We conclude that minor changes in temperature can elicit a stress response in European starlings, which suggests that this may be an important mechanism by which animals cope with minor rapid environmental changes.