Recovering bald eagles in Maine
Forty years ago, our nation’s symbol was in dire straits.
The bald eagle (Haliaeetus leucocephalus) population had dwindled to such a low number that the iconic species was in danger of extinction—primarily the result of deforestation and extensive pesticide contamination. In Maine, DDT and other chemicals was heavily sprayed to kill the spruce bud worm, which had devastated balsam fir and spruce trees throughout the state.
Residue from these pesticides ran off into lakes and streams, contaminating fish the bird preyed on. Consuming animals with high levels of chemicals had a profound effect on eagle reproduction, causing eagles to lay eggs with shells so thin and brittle they often cracked before hatching. With few chicks hatching by 1976, when aerial surveys began, the state was home to fewer than three dozen individuals.
The 1972 DDT ban helped improve habitat quality for the bald eagle and other species across the U.S. The effort to recover the eagle in Maine was two-fold—understanding the effect of chemical pollution of the species’ prey, and protecting nesting areas to promote hatchling success and population growth.
“It was a state-federal partnership from beginning to end,” says Charlie Todd of the Maine Department of Inland Fisheries and Wildlife, referring to initiatives to recover the bald eagle. “It started with a Section 6 grant under the Endangered Species Act—money to help the state monitor eagles. Maine supplied the manpower.”
First, researchers looked to find whether the eagle, a carrion feeder, could be lured away from contaminated prey with “clean” food—road-killed deer and moose and the carcasses of trapped beavers and raccoons.
Mark McCollough, now a U.S. Fish and Wildlife Service biologist, began working toward an answer during his doctoral studies at the University of Maine in the late 1970s. With funding from Section 6 grants, McCollough’s began his research in Cobscook Bay State Park—home to the last concentration of bald eagles in New England. Here, he set out the bait.
For five years, McCollough furnished a 70-ton banquet of dead animals that game wardens provided. He recorded the action of eagles and forwarded this information, along with eagle band numbers, to the Patuxent Wildlife Research Center in Maryland. The results documented that, rather than the estimated five to 10 percent that lived to be five years old, 70 percent reached adulthood. By the late 1980s, the Maine population was experiencing encouraging growth. … Finish reading this story on our endangered species website!