The Effect of Mercury on Baseline Corticosterone in a Breeding Songbird
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Although songbirds accumulate mercury at rates equivalent to better-studied aquatic avian species, effects of mercury bioaccumulation in songbirds remain understudied. Little is known about the effects of mercury on endocrine physiology, but recent evidence indicates that mercury may disrupt the function of the hypothalamic–pituitary–adrenal axis. Both field-based correlational studies and a recent dosing experiment suggest that mercury exposure alters levels of the primary avian stress hormone, CORT. We sampled zebra finches that had been dosed with 0, 0.5, or 1.0 ppm dietary methylmercury for baseline CORT twice; once during pairing and once after successfully fledging young. Circulating levels of CORT were not significantly affected by mercury exposure. However, our findings indicate potentially important differences in CORT responses between the sexes when exposed to environmentally relevant doses of mercury across the nesting cycle.
KeywordsCorticosterone Endocrine disruption Mercury Stress Zebra finch
Funding for this research was provided by a grant from E.I. DuPont de Nemours and Company and the Williamsburg Bird Club. Research was completed with oversight from the South River Science Team, which is a collaboration of state and federal agencies, academic institutions, and environmental interests. We thank Matthias Leu, John Swaddle, Margaret Whitney, Catherine Lewis, Kenton Buck, Amanda Bessler, Stephanie Apple, Joanna Weeks, and Eliza Spear.
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