Effects of nutritional restrictions during post-hatching development on adrenocortical function in western scrub-jays ( Aphelocoma californica)

Abstract

Altricial birds grow rapidly during post-hatching period and are developmentally sensitive to variations in food supply. Limited food results in elevated corticosterone levels in chicks of semi-precocial birds but it is not clear whether altricial songbirds show similar adrenocortical stress response to nutritional restrictions during early development. It is also unknown how nutritional stress during early development affects the adrenocortical function later in life in altricial birds which show tremendous variation in the magnitude of adrenocortical stress response. Using western scrub-jays ( Aphelocoma californica), we experimentally demonstrated that moderate food restrictions (65% of ad libitum) during post-hatching development caused significant elevation of baseline corticosterone levels in nest-bound chicks. Compared to controls, 1-year-old scrub-jays that experienced nutritional deficits during post-hatching development also showed a marginally significant trend to have stronger adrenocortical stress response and significantly greater degree of fluctuating asymmetry in bone and feather measurements. Thus, our results demonstrated that developing altricial birds show adrenocortical response to nutritional deficits, which might produce long-term changes in responsiveness of the adrenal system. Our study suggests that baseline corticosterone levels are a good indicator of physiological conditions of developing birds and that individual variance in adrenocortical stress response commonly observed in many species might, at least in part, be explained by environmental conditions during early development. Considering that nutritional restrictions during early development are linked to many permanent changes including impaired cognitive abilities, corticosterone levels in developing young might be a reliable predictor of their future fitness.