Eagles in Yellowstone National Park
The Bald Eagle and Golden Eagle are the only two species of eagle in Yellowstone. Both birds are raptors and carnivores, seeking a diet of fish, waterfowl, rodents and small mammals. They also scavenge from the carcasses of large animals such as elk and bison.
The Golden Eagle and the Bald Eagle are perfectly built for hunting. They have very sharp vision and can spot small animals in the grass from up to a mile away. Eagles can see in much finer detail than humans can. The eyes of an eagle have five times as many light-sensitive cells than the eyes of humans. Eagles are also equipped with sharp, curved talons used for grasping prey. Their hooked beaks are used to tear food apart.
Bald Eagle (Haliaeetus Leucocephalus)
The Bald Eagle is a very large bird, and stands about 30-45 inches tall with a wingspan of up to 81 inches. Females are 25 percent larger than males and weigh approximately 12 pounds. Males weigh about nine pounds.
Male and female bald eagles have identical plumage coloration. Adults over five 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 their under parts. Their head and tail will whiten with each molt as they reach adulthood. A bald eagle’s tail is moderately long and slightly wedge-shaped. The bird’s beak, feet, and irises are bright yellow.
Bald eagles are mainly found perched in the trees near Yellowstone Lake, Hayden Valley and Gardner and Madison Rivers. In the summer, Bald Eagles are often found in close association with water, however they can be found venturing over mountain meadows and even the summits of mountain peaks on occasion. Their summertime prey is primarily fish and waterfowl.
Although some adult bald eagles will winter in the park, most migrate to lower elevations. During the winter months, habitat for Bald Eagles often centers around ungulate (elk, antelope, bison) winter ranges and watercourses free of ice…look for them, sometimes in groups of five or six along the Yellowstone River north of the park. Carrion and waterfowl are the primary foods for the Bald Eagles in the winter.
Bald Eagles are sexually mature at four or five years of age. When they are old enough to breed, they often return to the area where they were born. Bald Eagles mate for life except if one member of a pair dies or disappears, the other will choose a new mate. A pair which has repeatedly failed in breeding attempts may split and look for new mates.
Bald Eagle courtship involves elaborate calls and flight displays. The flight includes swoops, chases, and cartwheels, in which they fly high, lock talons, and free fall, separating just before hitting the ground.
Nesting usually begins in late February to mid-March. A bald eagle’s nest is the largest of any bird in North America; it is used repeatedly over many years and with new material added each year it may eventually be as large as 13 feet deep,8 feet across and weigh one ton! The nest is built out of branches and is usually located in trees near water.
Eagles produce between one and three eggs per year, but it is rare for all three chicks to successfully fly. Both the male and female take turns incubating the eggs. The other parent will hunt for food or look for nesting material. The eggs average about 2.9 inches. long and have a breadth of 2.2 inches. Eagle chicks hatch in late March-early April, while fledglings leave the nest somewhere between late June and late July depending on the elevation of the nest.
Bald Eagles: Past and Present
The Bald Eagle was classified as an endangered species under the Endangered Species Act in 1973. It is estimated that in the early 1700s, the bald eagle population was between 300,000–500,000. By the 1950s there were only 412 nesting pairs in the 48 contiguous states of the U.S.
The Bald Eagle was severely affected in the mid-20th century by a variety of factors, among them thinning of egg shells, attributed to the use of the pesticide DDT. The chemical itself was not lethal to the adult bird, but it interfered with the bird's calcium metabolism, and actually made them either sterile or unable to lay healthy eggs. Female eagles laid eggs that were too brittle to withstand the weight of a brooding adult, making it nearly impossible to produce young.
Other factors in Bald Eagle population reductions were a widespread loss of suitable habitat, and illegal shooting of young and adult bald eagles. In 1984, the National Wildlife Federation listed hunting, power line electrocution, and collisions in flight as the leading causes of eagle deaths. Bald Eagle populations have also been negatively affected by oil, lead, and mercury pollution.
In 1995, the Bald Eagle was down-listed from endangered to threatened because of evidence of significant population growth. DDT had been banned for a number of years and while certain specific populations were not completely recovered (the Bald Eagles of the Great Lakes region are still exposed to heavy metal contamination and struggle with habitat loss), the Bald Eagle population of Yellowstone Park had soared. By 2003, 32 pairs of Bald Eagles were found in Yellowstone Park — more than ever recorded before.
Bald Eagles were removed from the U.S. Fish and Wildlife Service Threatened List on June 28, 2007.
Golden Eagle (Aquila Chrysaetos)
Golden Eagles vary in the size from 26–40 inches with a wingspan range of 59–95 inches. An adult’s weight range is from 5.5-15.5 pounds, with females weighing one-fourth to one-third more than the male birds. The Golden Eagle has a longer tail but smaller head, bill, and neck than the Bald Eagle.
The plumage colors of a Golden Eagle vary from black-brown to dark brown, with a striking golden-buff crown and nape. The upper wings have an irregular lighter area. Immature birds have a duller more mottled appearance than the adults and they have a white-banded tail and a white patch at the carpal joint, which gradually disappears with every molt. Full adult plumage is reached in the fifth year.
The golden eagle is primarily a mountain bird which feeds on rabbits and large rodents such as prairie dogs and ground squirrels and sometimes on birds, martens and foxes. During the winter months when prey is scarce, Golden Eagles scavenge on carrion to supplement their diet. Sometimes when no carrion is available golden eagles will hunt down owls, hawks, falcons, and large ungulates.
Like Bald Eagles, Golden Eagles usually mate for life. The pair build several eyries (nest sites) in trees within their territory and use them alternately for several years. The nests consist of heavy tree branches which they line with grass when in use and which can get as large as 6.6 feet in diameter and 3.3 feet in height.
The female lays two black eggs anytime between January and September. Incubation starts immediately after the first egg is laid and after about 45 days the young hatch. The eaglets are entirely white and are fed for fifty days before they are able to make their first flight attempts and eat on their own.
Golden Eagles invest much time and effort in bringing up their young; once able to hunt on their own, most Golden Eagles survive many years, but mortality even among first-born nestlings is much higher, in particular in the first weeks after hatching. In most cases only the older chick survives, because it has a few days' advantage in growth and consequently wins most squabbles over food.
Eagles in Native American Myths and Legends
The Bald Eagle is a sacred bird in Native North American cultures, and its feathers, like those of the Golden Eagle, are central to many religious and spiritual customs. Eagles are considered spiritual messengers between gods and humans. Eagle feathers are often used in traditional ceremonies, particularly in the construction of regalia worn and as a part of fans, bustles and head dresses.
The Lakota give an eagle feather as a symbol of honor to a person who achieves a task. In modern times, it may be given on an event such as a graduation from college. The Pawnee considered eagles as symbols of fertility because their nests are built high off the ground and because they fiercely protect their young. The Kwakwaka’wakw scatter eagle down to welcome important guests.
During the Sun Dance, which is practiced by many Plains Indian peoples, eagle symbols are dominant. An eagle nest is represented by the fork of the lodge where the dance is held. A whistle is made from the wing bone of an eagle and is used during the course of the dance. A medicine man can direct his eagle feather fan towards the people who seek to be healed. The medicine man touches the fan to the center pole and then to the patient, in order to transmit power from the pole to the patient. The fan is then held up toward the sky, so that the eagle may carry the prayers for the sick to the Creator.
One legend tells of a time when the world was new and the Creator made all the birds. He colored their feathers like a bouquet of flowers. The Creator then gave each bird a distinct song to sing. The Creator instructed the birds to greet each new day with a chorus of their songs. Of all the birds, the Creator chose the Eagle to be the leader.
It was told the Eagle flies the highest and sees the furthest of all creatures. The Eagle is a messenger to the Creator. During the Four Sacred Rituals an eagle feather is worn as a hair decoration. To wear or to hold an eagle feather causes the Creator to take immediate notice. With the eagle feather the Creator is honored in the highest. When one receives an eagle feather that person is being acknowledged with gratitude, with love, and with ultimate respect.
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