Using feathers to assess risk of mercury and selenium to bald eagle reproduction in the Great Lakes region

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Abstract

Mercury (Hg) and selenium (Se) concentrations were determined in feathers of nestling and adult bald eagles (Haliaeetus leucocephalus) in the Great Lakes region, 1985–1989. Relationships between concentrations and two measures of reproduction, productivity and nesting success, were examined. Hg and Se were detected in all feathers analyzed. A maximum concentration of 66 mg/kg Hg was found in adult feathers in the upper peninsula of Michigan. The geometric means of Hg in adult feathers for sample areas were: interior lower peninsula of Michigan, 21 mg/kg; interior upper peninsula of Michigan, 21 mg/kg; Lake Superior, 22 mg/kg; Lakes Michigan and Huron, 20 mg/kg; and Lake Erie, 13 mg/kg. The geometric means of Hg in nestling feathers for sample areas were: interior lower peninsula of Michigan, 8.8 mg/kg; interior upper peninsula of Michigan, 8.1 mg/kg; Lake Superior, 8.7 mg/kg; Lakes Michigan and Huron, 8.0 mg/kg; Lake Erie, 3.7 mg/kg; and Voyageurs National Park, 20 mg/kg. Se concentrations were not significantly different across regions or between adult and nestling feathers, and Se concentrations ranged from 0.8 to 3.2 mg/kg.

No significant relationships between adult or nestling feather concentrations and either measure of reproduction, productivity or nesting success, was found for either Hg or Se. It was concluded that neither Hg nor Se concentrations are currently affecting bald eagle reproduction in the Great Lakes region.