The bald eagle is not only our nation’s most recognizable natural symbol, and the only eagle found exclusively in North America, it is also the Endangered Species Act’s most prominent success story, and a reminder of how important are the protection of our wildlife, critical habitat and natural resources generally.

Populations of breeding pairs of bald eagles in the lower forty-eight states crashed in the late 1960s to just over 400 pairs, due to hunting, habitat destruction and most prominently, the use of chemical pesticides in agriculture, such as DDT. In a scary process, known as “biomagnification,” bald eagles, being an apex predator at the top on their food chain, and feeding mainly on  fish, occasional small rodents and carrion, in other words, wildlife which had themselves absorbed toxins in various forms ultimately from pesticide-laden vegetation or runoff from agricultural fields, suffer highly concentrated, elevated levels of these toxins, negatively impacting birth and mortality rates. Calcium deficiencies caused by the toxins resulted in the thinning of eggshells, which would collapse under the nesting female’s weight, causing a nosedive in successful eaglet births.

The Endangered Species Act of 1973 was the result of the attention called to these and related problems by wildlife lovers, falconers, hunters and others concerned about the fate of our native species. With the banning of the pesticides most harmful to wildlife in the United States, eagle numbers recovered, with the result that the bald eagle went from “endangered” to “threatened”, and to finally “delisted” in 2007, as mating pairs reached over 11,000 in the lower forty-eight. Eagles were never as threatened in Alaska and British Columbia, and Alaska still has about 80% of the World’s bald eagles.  Many raptors joined in the recovery, due to the banning of these pesticides, most notably, the peregrine falcon.

Of course, the problem with pesticides is far from over, as most folks don’t realize that the sale of these pesticides was banned by the EPA in the U.S., and later in many other western nations, but they are still being used in Africa, Asia  and South America. DDT is said to help fight malaria in third world nations, and Swainsons Hawks, which nest on the Canadian-American prairies, remain on the endangered species list, because they winter on the Argentine Pampas, where Swainsons die-offs from an inexpensive but lethal pesticide, monocrotophos, were still a problem in the late nineties.

There is also a downside to “delisting,” as it opens formerly protected critical habitat to development and some of the very pressures that contributed to the decline of the eagle in the first place.

Adirondack comeback

Bald eagles disappeared from the Adirondacks by the early sixties, but in 1981, Peter Nye, an eagle biologist and leader of the Endangered Species Unit of the New York Department of Environmental Conservation, traveled to Alaska on a mission to repopulate the Adirondacks with bald eagles. Alaska has four times as many eagles as the rest of the country, so Nye’s mission, in a process known as “hacking,” was to take wild eaglets mature enough to care for themselves and just about ready to fly, transport them to New York, build nests protected from climbing predators like  fishers, gray fox and black bears, and release them in a remote area, unvisited by people, in the hopes that the eagles would begin breeding, nesting and repopulating New York.

A logical place to release them was Follensby Pond, a remote wilderness area of over 14,000 acres, once home to bald eagles, and the site of a famous get together in 1858 known as the “Philosophers Camp”, which was organized by painter William James Stillman, and included poet and essayist Ralph Waldo Emerson, poet and diplomat James Russell Lowell and paleontologist, geologist and all around naturalist, Louis Agassiz.

The owners of the Follensby Wilderness, John and Bird McCormick, sold the property to the Nature Conservancy in 2008, on the condition that the Nature Conservancy work with New York State to ensure that the Wilderness remains wild, and inaccessible to the public, at least for the foreseeable future. It is here that Nye hacked the eagles, with the result that there are today in 2020 probably 24 nesting pairs of eagles in the Adirondacks, and over 200 pairs in New York State. Way to go, Pete!

Nesting habits

Bald eagles are usually monogamous, and a mating pair will use the same nest every year, like a home owner, constantly tweaking it and adding to it, with the result that bald eagle nests can measure ten feet wide and ten feet thick, weigh up to a ton and are the largest nests of any bird, aided by the fact that eagles can begin mating by their fourth or fifth year, and can live over thirty years. The record size nest is two and a half tons, but some nests eventually collapse under their own weight, and a new nest has to be constructed. The nest of our oldest non-flighted bald eagle at the Adirondack Wildlife Refuge, Sylvia, was blown down in a Pacific storm while she was still a fledgling, resulting in the permanent disabling which resulted in her living with us. Her two male siblings were successfully rehabbed and released.

Nests are typically located very high in old growth conifer or hardwood trees, ranging from only twenty feet above water when the tree’s trunk is in the water, to 125 feet high when the tree is on land , protruding above smaller trees, and within two miles of large bodies of both salt and fresh water, with most within sight of open water. All else being equal, for example, the potential for scavenging deer and other carrion, and for kleptoparasitism, stealing fish from ospreys or carrion from other scavengers, a nesting pair will generally require a lake of at least four or five square miles in order to make a living.

Eagles nest and breed earlier than other raptors, with the female laying one to four eggs in sequence between mid February and mid March, depending on climate and latitude, with hatching between mid April and early May, and branching and fledging late June to early July. As with some other raptors, older and larger siblings, those which hatch first may monopolize more food from its parents, by pushing younger siblings out of the nest. Eaglets grow quickly, gaining up to six ounces per day, beginning to flap their wings at 8 weeks, fledging between 8 to 14 weeks, and finally leaving the nest area about 8 weeks after fledging. 

Current threats

The number one killer of the bald eagle in America today is lead poisoning, which the eagles pick up while scavenging the remains of game, mainly white tailed deer taken by hunters using lead based bullets, which shatter on impact, sending lead shards into flesh, often away from the path of the bullet. This is a problem easily solved by having hunters switch to solid ammunition, such as copper, but the NRA sees this as an attempt to take your weapons. 

That’s like saying that when the state mandates seat belt use, that is an attempt to take your car, but such is the ridiculous logic employed in polarized political debate today. No one is saying don’t hunt, just change the type of ammunition you use. States like California have made this argument academic, by banning the use of lead ammunition, just as many states have banned the use of lead sinkers, which can be mistaken for pebbles and swallowed as aids in digestion by loons and other waterfowl.

Part two of two-part series. Click here for part 1.

Top photo courtesy of Steve Hall, Adirondack Wildlife Refuge. Photo by Trish Marki shows Wendy Hall of Adirondack Wildlife Refuge working with a bald eagle which was caught in a leg hold trap near Stillwater. Pastel of Eagle Man carrying an ambassador eagle by Wendy Hall.