Dietary restriction causes chronic elevation of corticosterone and enhances stress response in red-legged kittiwake chicks

Release of corticosterone in hungry kittiwake chicks facilitates begging an d allows them to restore depleted energy reserves by increasing parental fo od provisioning. However, in order to avoid detrimental effects of chronic elevation of corticosterone, chicks might suppress adrenocortical activity in response to prolonged food shortages. In this study we examined temporal dynamics of corticosterone release in red-legged kittiwake (Rissa breviros tris) chicks exposed to prolonged restrictions in energy content and/or nut ritional quality (low versus high lipid content) of their food. Starting at the age of 15 days, chicks were fed either high- or low-lipid fish at 40%, 65%, and 100% of ad libitum energy intake. Body mass measurements and base line plasma samples were taken on a weekly basis after beginning of the tre atment. After 3 weeks of treatment, chicks were exposed to a standardized a cute handling and restraint stress protocol, where in addition to a baselin e sample, three plasma samples were taken at intervals up to 50 min. We fou nd that food-restricted chicks had lower body mass, chronically (during 23 weeks) elevated baseline and higher acute stress-induced levels of corticos terone compared to chicks fed ad libitum. Low lipid content of food further exacerbated these effects. An increase in baseline levels of corticosteron e was observed within a week after energy requirements of food-restricted c hicks exceeded their daily energy intake. A tendency for suppression of adr enocortical activity was observed in treatments fed low-lipid diets only at the end of the experiment. We suggest that nest-bound chicks, if food-stre ssed, might suffer deleterious effects of chronic elevation of corticostero ne.