The eagle is perhaps one of the most iconic and intricately woven symbols associated with the United States of America. Printed on currency and even official documents and forms, the eagle is an enduring image of the strength and independence we associate with this country.
North America is home to two species of eagles: the bald eagle (Haliaeetus leucocephalus) and the golden eagle (Aquila chrysaetos). Both are majestic birds of prey with wingspans that range from 6 to 8 feet, with body lengths varying between 3 and 3-1/2 feet. Females are larger than males in both species, and often have a slightly longer wingspan. Females of either species weigh between 8 and 15 pounds, while males weigh between 6 and 10 pounds. Their size – second only to the California condor – makes them unmistakable in flight compared to the much smaller raptors such as hawks, falcons or owls.
The populations of both the bald and golden eagle have seen dramatic changes since the time of the colonists’ arrival in America. It would be impossible to get an accurate estimate from the time period, but there is some speculation that anywhere from 50,000 to 150,000 breeding pairs lived in the lower 48 states.
The application of DDT (dichloro-diphenyl-trichloroethane) in the U.S. from 1940 to 1950 – used primarily to control malaria, typhus and other human diseases transmitted through insects – caused bald eagle populations to plummet to an all-time low of 487 nesting pairs in 1963.
It was determined that DDT alters the calcium metabolism in female eagles which prevents them from creating a hard shell for their eggs. The thin shells were easily cracked, which led to egg loss in the nest. Bald eagles suffered a higher rate of decline than the golden eagle because fish – which is their primary source of food – built up high levels of DDT in their systems. Golden eagles were less susceptible to the DDT because their main food source is small mammals, which were not subjected to the same high levels of DDT. DDT being a large factor in the eagle’s decline, shooting, trapping, poisoning, and lack of prey also factored into the population decrease for both species.
As early as 1940, the dwindling numbers of eagles compelled Congress to pass the Bald Eagle Protection Act, which outlawed the killing and disturbing of bald eagles as well as possession of eagle parts such as feathers, eggs and nests. The law was modified in 1962 to include golden eagles. Legal protection continued with the Endangered Species Preservation Act of 1966, and later the amendment of 1978 listing the eagle under the Endangered Species Act of 1973. In 1972 in what many feel was the most important regulation in the eagles recovery, DDT was banned for most uses in the United States.
According to the National Wildlife Federation, the first discussion about using the bald eagle as a symbol of our nation took place shortly after the signing of the Declaration of Independence on July 4, 1776. The Continental Congress appointed a committee made up of Thomas Jefferson, John Adams and Benjamin Franklin to select a design for the national seal.
All three of the founding fathers had contrasting ideas about the design, and none included the bald eagle. The Congress wasn’t impressed with any of them either, so they turned to Philadelphia artist William Barton. His design originally incorporated the golden eagle. Although they liked the design, the golden eagle could also be found in European nations. Wanting to be free of any association with the crown, the lawmakers requested that the eagle be changed to the American bald eagle. On June 20, 1782, the national seal we know today was approved by the federal lawmakers.
With its distinctive white head, brown body and white tail, the bald eagle is easily identified. Breeding pairs of bald eagles can be found in every U.S. state except Hawaii. They prefer areas around coasts, rivers and lakes that have plentiful fish. Alaska contains the highest breeding population of eagles, but they are also found in high numbers throughout Canada, the Pacific Northwest and along the Mississippi River. Florida is home to a large population of breeding pairs during winter when eagles migrate from colder climates.
Bald eagles are noted for their opportunistic feeding habits. While they are very adept at hunting from a high perch and swooping down to catch their prey, they are not averse to scavenging carrion or road kill. They are also notorious for stealing food from other birds of prey, such as the osprey, harassing them until they drop their catch. Besides fish, eagles will feed on small mammals, shore birds and ducks.
Eagles don’t reach maturity until they are 4 to 5 years old, and they are known to mate for life. If a mate dies, the surviving eagle will usually find another mate. The nest is usually placed in a tree located very high off the ground. Nests are built by both sexes and contain mounds of sticks and are lined with small branches, twigs, grass and other fine material. Nests are often reused and added to for years becoming quite large.
Eagles in the northern regions nest in the spring months, often in May and June and sometimes as early as February, while eagles in the south nest in the winter months. Bald eagles will lay one to three eggs, and incubation is between 34 and 36 days. Both parents remain with the hatchlings for the first 2 weeks and bring food to the nest to feed the young. The fledglings begin flying at about 10 to 12 weeks of age and remain with their parents for another month or so.
The average lifespan for a bald eagle is 20 years in the wild, but there are records of captive eagles living up to 48 years.
While they don’t have the privilege of adorning any currency here in the U.S., golden eagles are no less majestic and impressive than the bald eagle. The golden eagle is the national bird of Mexico, and their image is seen on many flags around the world. Native American tribes particularly admired and honored the strength and courage of the golden eagle. They wore eagle feathers on ceremonial dress and regarded the power of the eagle to be both mystical and much desired.
Golden eagle adults are brown with a tawny color on the back of the head and neck with a light band visible across the tail. Their range encompasses most of western North America and as far north as Alaska. They're also found in Mexico, Asia, northern Africa and Europe. In the western U.S., populations are estimated at around 10,000 birds with up to 30,000 across all of North America.
Although the golden eagle will not turn down a meal of carrion, it prefers to hunt. Their diet is made up mostly of small mammals, including anything from small squirrels to jackrabbits. They have also been noted to take small deer or antelope on occasion, and they’ll hunt game birds such as grouse and pheasant. Golden eagles are opportunistic and will dine on anything from snakes and lizards to big insects.
Golden eagles reach maturity at 4 to 5 years of age and will remain in mating pairs for life. Unlike the bald eagle, golden eagles prefer to nest on cliff faces or rocky ledges, but they will occasionally nest in a tall tree or other tall structure, such as windmills or telephone poles. Golden eagles will return to the same nest for years. Nests are built similarly to those made by bald eagles with twigs and soft materials.
Golden eagles lay between one and four eggs, usually in the spring with an incubation between 41 and 45 days. The female remains with the young most of the time, and the male does the majority of the hunting. Fledglings take their first flight between 9 and 10 weeks after hatching. The average lifespan of the golden eagle is up to 25 years in the wild and may reach 50 in captivity.
With populations for both of these amazing birds increasing, you can still continue to support their numbers by leaving plenty of habitat for them on your property. Tall trees near water sources are prime real estate, and they’ll help you out when it comes to keeping small critters and rodents in check.
New nests are often about 5 feet across and can weigh a half ton. As eagles continue to add to the nest over several years, they can span as wide as 10 feet and weigh as much as 2 tons.
The well-known call of the bald eagle often heard in movies is actually the call of a red-tailed hawk. Listen to their call at the Audubon Field Guide.
Eagles can spot fish in the water and field mice from several hundred feet in the air.
Tim Nephew is a freelance writer living in Minnesota, where he owns and maintains 80 acres for wildlife to enjoy.
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