Experimental effects of early-life corticosterone on the hypothalamic-pituitary-adrenal axis and pre-migratory behaviour in a wild songbird
Although laboratory studies have shown that chronic exposure to elevated glucocorticoids during development has profound effects on animals, we still have a poor understanding of the consequences of early-life stress on wild individuals. In an island population of Savannah sparrows (Passerculus sandwichensis), I examined multiple hypotheses to explain how elevated corticosterone exposure during the nestling period influenced both hypothalamic-pituitary-adrenal (HPA) axis function and the subsequent movement and survival of young after they fledged the nest. Corticosterone-treated nestlings had higher baseline corticosterone levels and lower stress reactivity than untreated individuals, and were more sensitive to inclement weather. Corticosterone-treated individuals also had higher rates of temporary emigration outside of the study site than sham or controls. My results provide support for both the ceiling hypothesis and CORT-activity hypothesis, and highlight the importance of tracking individuals across multiple life stages to understand how early life events carry-over to influence both physiology and behaviour.