Meeting Abstract

1.4  Thursday, Jan. 3  Effects of mercury on adrenocortical response and thyroid hormones in tree swallow (Tachycineta bicolor) nestlings WADA, H.*; MCNABB, A.; CRISTOL, D.; HOPKINS, W.; Virginia Polytechnic Institute and State University; Virginia Polytechnic Institute and State University; College of William & Mary; Virginia Polytechnic Institute and State University haruka@vt.edu

Alterations of endocrine systems can be used to identify the effects of sublethal exposure to pollutants such as heavy metals. Mercury (Hg) is known to bioaccumulate, bioamplify, and maternally transfer, making it a significant threat to wildlife. Even at low levels, Hg can retard growth and disrupt reproduction. Little is known about the effect of Hg on endocrine systems in free-living birds, especially nestlings, even though they may be more sensitive than adults. To address this important knowledge gap, we studied tree swallows breeding in a reach of the South River, VA with high levels of Hg contamination. Using nestlings in this area and a nearby reference area, we measured their adrenocortical response to handling and thyroid hormones, thyroxine and triiodothyronine, in three different ages of nestlings: day 3-6, 8-12, and 14+. Regardless of site, all ages had a significant increase in corticosterone in response to handling. Similar to other altricial species, this response increased with age. There was no significant difference in baseline or stress-induced levels between reference and contaminated sites at early ages; however baseline was significantly elevated in contaminated sites by day 14. Stress-induced levels of the same group were also lowered by 55%, resulting in a suppressed response. We are currently analyzing for Hg and thyroid hormone levels in these nestlings, however this study suggests that Hg can affect the hypothalamo-pituitary-adrenal axis in young birds.