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A team of partners is keeping tabs on the health of bald eagles like this one in a nest in Michigan (U.S. Fish and Wildlife Service photo by Jeremy N. Moore)

A team of partners is keeping tabs on the health of bald eagles like this one in a nest in Michigan (U.S. Fish and Wildlife Service photo by Jeremy N. Moore)

Partners Study Bald Eagles to Gauge Great Lakes Region’s Environmental Health

By Jeremy N. Moore
Contaminants Biologist
East Lansing Field Office

High up in the trees above Shiawassee National Wildlife Refuge, in east central Michigan, biologists gently remove a 52-day-old bald eagle chick from its nest.  The eaglet is carefully banded, weighed and measured, and samples taken of its blood and feathers, before it is returned to its nest to be tended by its parents.

Six years after the bald eagle was declared recovered and removed from the list of threatened and endangered species, a team of partners continues to monitor the species’ status.  In Michigan, this work not only focuses on the numbers – how many pairs of eagles, the number of nesting attempts, how many eaglets hatch – but the health of the birds as well.  Biologists here are closely watching for signs of the contaminants that originally forced eagles to the brink of extinction and threatened the health of their environment.

As a top predator, the bald eagle accumulates contaminants from the prey it consumes.  Because bald eagles are susceptible to problems caused by some types of contaminants, biologists use them as a sentinel species.  The observations and data acquired through continued monitoring allow resource managers a glimpse into bald eagle and ecosystem health.

Today, the Service’s East Lansing Field Office coordinates monitoring efforts in Michigan through support from the Great Lakes Restoration Initiative.  Among the key partners in the monitoring effort are University of Maryland, which runs the program and provides supplies and field crews; Michigan Department of Environmental Quality, which funds the program; Michigan Department of Natural Resources, which flies survey routes; and Michigan State University, which trains field crews.  Volunteers also play an important role.

Because bald eagles feed primarily on fish, biologists can analyze blood and feather samples to gain information on water quality.  Contaminants such as DDT, PCBs and mercury can be detected and pose risks to eagles, fish and other wildlife where detected.  The information can then be used to establish acceptable levels of contaminant discharge and to prioritize clean-up efforts.  The data is also used to focus clean-up efforts in Areas of Concern – those sites around the Great Lakes that are most affected by toxic substances.

Michigan’s bald eagle population has rebounded dramatically from lows in the early 1960s.  In 1961, there were 52 occupied territories (meaning a pair of eagles was present), and 21 pairs produced a total of 34 eaglets.  In 2012, the state had 684 occupied territories, with 457 pairs producing 718 eaglets.

The bald eagle recovered primarily because the United States banned the use of DDT, a pesticide that resulted in thin eggshells and failed nests; and the passage of the Endangered Species Act which coordinated recovery efforts and focused attention on the plight of imperiled species.

Today, bald eagles remain protected by the Bald and Golden Eagle Protection Act and the Migratory Bird Treaty Act.  Continued monitoring by the Service, state and tribal partners and other organizations are aimed at ensuring the nation’s symbol continues to thrive.

See the links below for even more on eagle monitoring efforts:

See images of biologists banding bald eagles in Michigan at: and find out more about the Midwest’s bald eagle population at 



Last updated: August 12, 2013