Bald eagles thriving in Maine, but health still studied

Marc Payne, co-director of Avian Haven in Freedom, Maine, holds a mature bald eagle in 2009.
Marc Payne, co-director of Avian Haven in Freedom, Maine, holds a mature bald eagle in 2009. Buy Photo
Posted May 27, 2012, at 12 p.m.
Last modified May 27, 2012, at 4:02 p.m.

ELLSWORTH, Maine — Nearly three years after being removed from the state’s list of threatened species, Maine’s bald eagle population appears to be doing well as nests continue to appear in new and sometimes populated areas.

But how, exactly, eagles have fared since their change in status won’t be known until next year when the first detailed aerial surveys since the de-listing are completed.

On May 26, 2009, Gov. John Baldacci signed legislation removing the bald eagle from Maine’s list of threatened species during a special ceremony in Augusta held a short distance from the Kennebec River, where eagles are now a common sight.

At the time, Maine was on track to exceed 500 mating pairs of eagles — more than the combined eagle population in all other states north of the Chesapeake Bay. By comparison, Maine’s eagle population numbered just 20 nesting pairs in 1978.

Formerly, biologists conducted annual aerial surveys to count inhabited eagle nests and to gauge whether nesting pairs successfully reproduced. Those labor-intensive surveys will be conducted every five years now that the eagle is no longer a state-listed threatened species. Bald eagles were removed from the federal endangered species list in 2007.

Charlie Todd, the lead eagle biologist with the Maine Department of Inland Fisheries and Wildlife, said although they won’t know for sure until next year, anecdotal evidence suggests that Maine’s eagle population remains healthy. That’s because he and other biologists are still called upon to check out reports of new nest sites.

“If anything, we have gotten more data in the interim years than I thought we would,” said Todd, who has spent a career working to rebuild eagle populations in the state. “We are finding enough new [nests] year to year without a special effort that it still seems encouraging. It looks like they are still increasing and expanding their range.”

They are even popping up in some relatively populated areas. Students and teachers at Waterville High School, for instance, have a bird’s-eye view of a nest in a tree next to the school. The nest, which is visible from some classrooms with the help of a telescope, was built about 2 years ago and now has several baby eagles, according to news reports.

Although no longer listed as endangered or threatened, eagles are still protected under the federal Bald and Golden Eagle Act. That law prohibits anyone from killing eagles, destroying nests or disturbing the birds to a degree likely to injure the animal, reduce productivity or cause nest abandonment.

Killing an eagle is also a Class D crime in Maine, punishable by up to 364 days in jail and a $2,000 fine. And some development projects near eagle nests still require state or federal review, although the process is less extensive than prior to 2009.

Eagle populations throughout the continental U.S. plummeted during the 1970s due, in large part, to the widespread use of the pesticide DDT, which rendered eagle eggs too brittle to survive. Most of the 20 or so nesting pairs left in Maine in the late 1970s were in coastal areas Down East. Today, they are found throughout the state.

The strong recovery to date does not necessarily mean Maine eagles have a clean bill of health, however. Biologists continue to study toxicity in eagles, especially levels of mercury contamination in the birds.

Many people would likely be surprised to learn that Maine eagles have among the highest mercury concentrations in the country. And Chris DeSorbo, raptor program director at the BioDiversity Research Institute in Gorham, said what’s even more surprising is that eaglets living on pristine-looking Maine lakes are occasionally harboring mercury levels above those found in eaglets near much more polluted developed areas.

DeSorbo stressed that the research is not yet complete. But he suggested that the high mercury levels are likely due to the fact that those areas feature the right natural, environmental conditions for airborne or atmospheric mercury to be converted into a form that readily accumulates in local insects and fish.

As a top predator, eagles then accumulate even higher levels as they eat contaminated fish. The situation seems especially acute on lakes, which are not as readily flushed of contaminants as rivers or coastal areas.

“Clearly, mercury exposure isn’t [threatening] to override the eagles’ population growth because we are seeing strong growth,” DeSorbo said. But mercury contamination could be slowing that growth in some areas, he said.

Other research being conducted by BioDiversity Research Institute and others is also shedding light on the migratory and nesting patterns of Maine’s eagles. DeSorbo said more than 600 eaglets have been fitted with red-colored bands that can be used to identify those individuals.

DeSorbo now receives emails and pictures regularly from bird-watchers and photographers who spotted the banded eagles, which are showing up throughout Maine and New England as well in New York, on Lake Erie and in parts of Canada.

Additionally, some Maine eagles fitted with satellite telemetry devices are reporting their whereabouts to researchers. Of the eight being tracked, three are currently in Maine while the other five are in New Brunswick or Quebec. BRI also operates a webcam on a Maine eagle nest that is popular with viewers.

Todd with DIF&W said his office has been recording about 20 new eagle territories per year since the de-listing. But they will have a better sense of things following next year’s surveys.

“We will take an extra-careful look next year to make sure that we are on track,” Todd said.

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