MICHIGAN WILDLIFE CONTAMINANT TREND MONITORING Nestling Bald Eagle Mercury Report: Spatial Trends

The bald eagle (Haliaeetus leucocephalus) is a widely distributed bird of prey throughout Michigan. It has been extensively studied and is susceptible to the effects of environmental contaminants. As a long-lived apex predator, the species is exposed to the effects of biomagnification, and analysis of tissue samples can produce valuable information about organisms positioned lower in the food chain. In addition, bald eagles are territorial nesters; therefore, nestlings provide a representation of the contaminant levels of the local environment. Mercury (Hg) can have negative effects on the environment, and feathers of exposed bald eagles have been analyzed to monitor Hg levels. Nestling bald eagle feather samples were collected throughout the state of Michigan from 1986 to 2012 and analyzed for concentrations of elemental Hg. Data were used to evaluate spatial and temporal trends of Hg throughout the state of Michigan. Results show that Hg decreased from 1986 to 2008 with a slight increase between 2009 and 2012. Overall, remediation has positively affected the Great Lakes region. However, with changing climate, land-use practices, and human population trends, management strategies should be planned cautiously, particularly in Michigan’s Upper Peninsula and Lake Superior shoreline.