Mercury concentrations in blood and feathers of nestling Bald Eagles in coastal and inland Virginia

Abstract

Background: Mercury (Hg) and methylmercury are widely considered significant issues for wildlife, and in particular, piscivorous birds due to their widespread availability and neurotoxic properties. Whereas a substantial number of studies of Hg contamination of Bald Eagles (Haliaeetus leucocephalus) have been conducted throughout the east coast of the United States, little has been done that directly addresses Hg contamination in Bald Eagles in Virginia, particularly the inland population. Methods: We collected blood and feather samples from nestling Bald Eagles in the coastal plain, piedmont, and western regions of Virginia in an effort to determine which areas of the state were more likely to contain populations showing evidence of Hg toxicity. We analyzed the samples for total Hg using a Milestone DMA-80. Results: Samples collected from individuals located in the coastal region exhibited low concentrations of Hg compared to those further inland located on freshwater rivers and reservoirs. Samples collected from the inland population exhibited levels in some areas that are approaching what may be considered to be sub-lethal to avian health (blood: mean 0.324 mg/kg, SE = 0.13, range = 0.06-0.97 mg/kg; feather: mean = 8.433 mg/kg, SE = 0.3, range = 3.811-21.14 mg/kg). Conclusions: Even after accounting for known point-sources of Hg, the inland eagle population in Virginia is susceptible to concentrations of Hg that are significantly higher than their coastal counterparts. Moreover, several locations besides those currently known to be impacted by point-sources are exhibiting concentrations that are approaching a sub-lethal level.