Yellowstone Bald Eagle (Haliaeetus leucocephalus)
Bald Eagles are again a common site along the rivers and lakes of the Greater Yellowstone Region, and they always bring a thrill to my tour and wildlife safari guests whenever they set their eyes on one of these magnificent birds. The bald eagle holds a position in the pecking order that parallels that of the grizzly. Of all the birds in the park, visitors are most interested in spotting this photogenic species. The Yellowstone/Grand Teton area is now home to one of largest populations of eagles in the continental United States They can be found along the lakes and rivers of Yellowstone where they perch in trees watching for fish. The Yellowstone Plateau, Snake River, Yellowstone Lake, and headwaters of the Madison River are prime spotting areas for this spectacular bird.
The Bald Eagle was officially declared the National Emblem of the United States by the Second Continental Congress in 1782. It was selected by the U.S.A.'s founding fathers because it is a species unique to North America. Ben Franklin wanted the wild turkey to be the national bird, because he thought the eagle was of bad moral character as it was a scavenger. The Bald Eagle has since become the living symbol of the U.S.A.'s freedoms, spirit and pursuit of excellence. Its image and symbolism have played a significant role in American art, folklore, music, and architecture.
The bald eagle (Haliaeetus leucocephalus) is a member of the sea and fish eagle group. A translation of the scientific name of the Bald Eagle means "white-headed sea eagle." They live near large bodies of open water such as lakes, marshes, seacoasts and rivers, where there are plenty of fish to eat and tall trees for nesting and roosting. Its natural domain is from Alaska to Baja, California, and from Maine to Florida. Bald Eagles that reside in the northern U. S. and Canada migrate to the warmer southern climates of the U. S. during the winter to obtain easier access to food, especially fish. Some Bald Eagles that reside in the southern U. S. migrate slightly north during the hot summer months. They are in every state except Hawaii. Bald Eagles use a specific territory for nesting, winter-feeding or a year-round residence.
They are very large birds, they stand about 30-45 inches tall, their wing span may reach up to 7 feet depending on the individual Adults over 5 years old have a white head, neck, and tail, dark brown to black body and yellow bill. Immature eagles are brown with whitish wing linings and blotches on bellies. Their head and tail will whiten with each molt as they reach maturity. Nesting usually begins in late February to mid-March. Eagle chicks hatch from the large platform tree nest in late March-early April, while fledglings leave the nest somewhere between late June and late July depending on the elevation of the nest.
When nesting, eagles lay two to three eggs sometime after February to mid-April. Both adults incubate the eggs, which hatch in 34 to 36 days. At birth, eaglets are immobile, downy, have their eyes open, and are completely dependent upon their parents for food. When 10–14 weeks old, they can fly from the nest.
As winter approaches, immature and sub-adult eagles typically leave the park. Winter habitat for those Bald Eagles that stay often centers on elk and bison winter ranges and watercourses free from ice. Carrion and waterfowl are the primary food items taken by Bald Eagles in the winter. Fish can be taken as a winter food item but are not as easily available as in the summer due to the icing of lakes and rivers.
Once an eagle spots a fish swimming or floating near the surface of the water, it approaches its prey in a shallow glide and snatches the fish out of the water with a quick swipe of its talons. You can often see them gliding in circles above the water then abruptly hovering while getting a fix on a fish before the dive. Bald eagles are capable of seeing fish in the water from several hundred feet above, while soaring, gliding, or in flapping flight. This is quite an extraordinary feat, since most fish are counter-shaded, meaning they are darker on top and thus harder to see from above.
Bald eagles also steal food from other bald eagles and ospreys. Ospreys are much better fishermen, but their smaller size prevents them from defending their catch from the larger eagles. Chasing another raptor is usually enough to persuade it to drop its kill, but occasionally bald eagles will attack them. A bald eagle's lifting power is about 4 pounds.
There is no single cause for the decline in the bald eagle population. When Europeans first arrived on this continent, bald eagles were fairly common. As the human population grew, the eagle population declined. The food supplies for eagles decreased, because the people hunted, and fished over a broad area. Essentially, eagles and humans competed for the same food, and humans, with weapons at their disposal, had the advantage. As the human population expanded westward, the natural habitat of the eagles was compromised, leaving them fewer places to nest and hunt, which caused the population of bald eagles to decline sharply by the late 1800s.
By the 1930s, people became aware of the diminishing bald eagle population, and in 1940 the Bald Eagle Act was passed. This reduced the harassment by humans, and eagle populations began to recover. However, simultaneously DDT and other pesticides began to be widely used. Pesticides sprayed on plants were eaten by small animals, which were later consumed by birds of prey. The DDT poison harmed both the adult birds and the eggs that they laid. The eggshells became too thin to withstand the incubation period, and were often crushed. Eggs that were not crushed during incubation often did not hatch, due to high levels of DDT and its derivatives. Large quantities of DDT were discovered in the fatty tissues and gonads of dead bald eagles, which might have caused them to become infertile.
In 1995, the U.S. Fish and Wildlife Service delisted the Bald Eagle from endangered to threaten due to significant population gains made over the previous three decades. Though off the endangered species list, it will continue to be strongly protected by federal law under a series of actions designed to govern management of eagles,
A Bald Eagle management plan objective for the greater Yellowstone ecosystem is to have 62 breeding pairs produce an average of 53 young each year. Current population figures indicate there are 34 eagle nests that produced 26 eaglets in 2007.