Biodiversity Research Institute
Biodiversity Research Institute
Show menu Hide menu
Raptors: Contaminants Monitoring
Raptors: Contaminants Monitoring

Mercury in New York State Bald Eagles

Over the past decade, research by BRI staff and our collaborators has shown that Bald Eagles in Maine and other states in the Northeastern U.S. are exposed to high levels of mercury through their diet. Researchers in New York State have documented elevated levels of mercury in air, fish, and wildlife throughout New York State, particularly in New York’s Catskill region. However, questions remained about exposure in Bald Eagles. Bald Eagles sit at the top of the food web, and as a result, they tend to accumulate contaminants like mercury if the toxin is present in the aquatic environment.


What We Studied

Initiated by a grant from The Nature Conservancy, scientists at BRI partnered with biologists at the New York State Department of Environmental Conservation to evaluate mercury exposure in New York’s Bald Eagle population. We sampled blood and feathers from Bald Eagle nestlings and evaluated these samples for mercury. We also evaluated mercury accumulation in adults by collecting feathers found at nests and analyzing them for mercury. Lastly, we compared mercury concentrations in eagle tissues to those in local fish at Bald Eagle nesting lakes.

What We Found: Study Highlights

This study revealed contaminant risks for Bald Eagles throughout the state; we determined that Bald Eagles nesting in the Catskill region of New York State had elevated mercury levels. Findings from this research support growing concerns that the Catskill region is a “biological mercury hotspot” —a region associated with elevated concerns for mercury exposure and impacts.

Other findings include:

  1. Bald Eagle chicks in the Catskill region had mercury levels most similar to chicks sampled in areas associated with significant mercury pollution, such as some Maine lakes and a mercury mine in British Columbia, Canada.
  2. One-third of the adult Bald Eagles sampled in the Catskill region and one-quarter of those sampled statewide had accumulated mercury in their bodies at levels associated with harmful effects in other fish-eating birds such as Common Loons.
  3. In the Catskill region, high mercury levels in Bald Eagle chicks were often found at sites where predator fish such as smallmouth bass, brown trout, and walleye also had high mercury levels.

Significance to Policy

Efforts to document contaminant exposure and evaluate risks to wildlife are a prerequisite step in informing the general public, environmental agencies, and decision makers about environmental concerns that have potential to impact wildlife and ecosystem health. This research helped demonstrate a need for continued efforts to document mercury exposure in other wildlife throughout New York State, particularly in the Catskills region of New York State. The resulting accumulation of fish and wildlife research has helped promote a need for more comprehensive mercury monitoring in this and other regions where mercury contamination may be of concern to wildlife.


Project Links

DeSorbo, C. R., Burgess, N. M., Nye, P. E., Loukmas, J. J., Brant, H. A., Burton, M. E. H., Persico, C. P. & Evers, D. C. (2020). Bald eagle mercury exposure varies with region and site elevation in New York, USA. Ecotoxicology, 1-15.

DeSorbo, C. R., P. Nye, J. J. Loukmas, and D. C. Evers. 2008. Assessing mercury exposure and spatial patterns in adult and nestling bald eagles in New York State, with an emphasis on the Catskill region. Report no. 2007-09 submitted to The Nature Conservancy, New York State.

Photo Credits: Photo of Adult Bald Eagles tend their nestling. © Virginia Gumm and Daniel Poleschook
Biodiversity Research Institute