Bald Eagle

The Bald Eagle (Haliaeetus leucocephalus), also known in North America as the American Eagle, is a bird of prey found in North America, most recognizable as the national bird of the United States.

The species was on the brink of extinction in the US late in the 20th century, but now has a stable population and is in the process of being removed from the U.S. federal government's list of endangered species.

This sea-eagle gets both its common and scientific names from the distinctive appearance of the adult's head. Bald in the English name is derived from the word piebald, and refers to the white head and tail feathers and their contrast with the darker body. The scientific name is derived from Haliaeetus, New Latin for "sea eagle," (from the Ancient Greek haliaetos) and leucocephalus, Latinized Ancient Greek for "white head", from leukos ("white") and kephale ("head").

Description and systematics
An immature Bald Eagle has speckled brown plumage, the distinctive white head and body developing 2-3 years later, before sexual maturity. This species is distinguishable from the Golden Eagle in that the latter has feathers which extend down the legs. Also, the immature Bald Eagle has more light feathers in the upper arm area, especially around the 'armpit'.

Adult females have an average wingspan of about 7 feet (2.1 meters); adult males have a wingspan of 6 ft 6 in (2 meters). Adult females weigh approximately 12.8 lb (5.8 kg), males weigh 9 lb (4.1 kg). The smallest specimens are those from Florida, where an adult male may barely exceed 5 lb (2.3 kg) and a wingspan of 6 feet (1.8 meters). The largest are the Alaskan birds, where large females may exceed 15.5 lb (7 kg) and have a wingspan of approximately 8 feet (2.4 meters).

The northern birds are the subspecies washingtoniensis, whereas the southern ones belong to the nominate subspecies leucocephalus. They are separated approximately at latitude 38° N, or roughly the latitude of San Francisco; northern birds reach a bit further south on the Atlantic Coast, where they occur south to the Cape Hatteras area. Audubon's type specimen of "Washington's Eagle" - named in honor of George Washington[1] - was apparently an exceptionally large bird, such as are more often found in Alaska; these have been proposed as subspecies alascanus or alascensis, but the variation is clinal and follows Bergmann's Rule.

The Bald Eagle forms a species pair with the Eurasian White-tailed Eagle. These diverged from other Sea Eagles at the beginning of the Early Miocene (c. 10 mya) at latest, possibly - if the most ancient fossil record is correctly assigned to this genus - as early as the Early/Middle Oligocene, some 28 mya (Wink et al. 1996[2]). As in other sea-eagle species pairs, this one consists of a white-headed (the Bald Eagle) and a tan-headed species. They probably diverged in the North Pacific, spreading westwards into Eurasia and eastwards into North America. Like the third northern species, Steller's Sea-eagle, they have yellow talons, beaks and eyes in adults.

Bald Eagles are powerful fliers, and also soar on thermal convection currents.

In the wild, Bald Eagles can live about 20-30 years, and have a maximum life span of approximately 50 years. They generally live longer in captivity, up to 60 years old.

Bald Eagles normally squeak and have a shrill cry, punctuated by grunts. They do not make the "eagle scream" as often shown on the television. What many recognize as the call of this species is actually the call of a Red-tailed Hawk dubbed into the film.

Range, habitat, and restoration
The Bald Eagle's natural range covers most of North America, including most of Canada, all of the continental United States, and northern Mexico. The bird itself is able to live in most of North America's varied habitats from the bayous of Louisiana to the Sonoran desert and the eastern deciduous forests of Quebec and New England. It can be a migratory bird but it also is not unheard of for a nesting pair to overwinter in its breeding area.

Once a common sight in much of the continent, the Bald Eagle may have been severely affected by the use of the pesticide DDT in the mid-twentieth century. The pesticide itself was not lethal to the bird, but it may have made an eagle either sterile or unable to lay healthy eggs: the eagle would ingest the chemical through its food and then lay eggs that were too brittle to withstand the weight of a brooding adult. By the 1950s there were fewer than 500 nesting pairs in the 48 contiguous states of the USA.

However, the role of DDT in the reduction of Bald Eagle numbers in the United States has been questioned. As early as 1921, the journal Ecology reported that bald eagles were threatened with extinction -- 22 years before DDT production even began. According to a report in the National Museum Bulletin, the Bald Eagle reportedly had vanished from New England by 1937 -- 10 years before widespread use of the pesticide.

But by 1960, 20 years after the Bald Eagle Protection Act and at the peak of DDT use, the Audubon Society reported counting 25% more eagles than in its pre-1941 census. U.S. Forest Service studies reported an increase in nesting Bald Eagle productivity from 51 in 1964 to 107 in 1970, according to the 1970 Annual Report on Bald Eagle Status.

The U.S. Fish and Wildlife Service attributed bald eagle population reductions to a "widespread loss of suitable habitat," but noted that "illegal shooting continues to be the leading cause of direct mortality in both adult and immature bald eagles," according to a 1978 report in the Endangered Species Tech Bulletin.

A 1984 National Wildlife Federation publication listed hunting, power line electrocution, collisions in flight and poisoning from eating ducks containing lead shot as the leading causes of eagle deaths.

U.S. Fish and Wildlife Service biologists fed large doses of DDT to captive Bald Eagles for 112 days and concluded that "DDT residues encountered by eagles in the environment would not adversely affect eagles or their eggs," according to a 1966 report published in the "Transcripts of 31st North America Wildlife Conference."

The Fish and Wildlife Service examined every Bald Eagle found dead in the U.S. between 1961-1977 (266 birds) and reported no adverse effects caused by DDT or its residues.

A 1970 study published in Pesticides Monitoring Journal reported that DDT residues in bird egg shells were not correlated with thinning. Numerous other feeding studies on caged birds indicate that DDT isn't associated with egg shell thinning.

In the few studies claiming to implicate DDT as the cause of thinning, the birds were fed diets that were either low in calcium, included other known egg shell-thinning substances, or that contained levels of DDT far in excess of levels that would be found in the environment -- and even then, the massive doses produced much less thinning than what had been found in egg shells in the wild.

Other potential causes of thin bird egg shells that have been reported in the scientific literature include: oil, lead, mercury, stress from noise, fear, excitement or disease, age, bird size (larger birds produce thicker shells), dehydration, temperature, decreased light, human and predator intrusion, restraint and nutrient deficiencies.

Currently it is still slowly but steadily recovering its numbers; Organizations like the Fraternal Order of Eagles which carry the Eagle as their emblem, have helped the American Bald Eagle on its recovery, by supporting other groups that rescue and preserve the Eagles and their habitat. The Bald Eagle can be found in growing concentrations throughout the United States and Canada, particularly near large bodies of water. The U.S. state with the largest resident population is Alaska; out of the estimated 70,000 Bald Eagles on Earth, half live there.

Bald Eagles will also congregate in certain locations in Winter. From November until February, between one and two thousand birds winter in Squamish, BC, about halfway between Vancouver and Whistler. The birds primarily sit along the Squamish and Cheekamus Rivers and feed on salmon spawning in the area. There are numerous viewing spots where numerous birds can easily be seen, and Float tours on rafts down the rivers are available from Canadian Outback Adventures.

Permits are required to keep this species in captivity (e-CFR 1974). As a rule, the Bald Eagle is a poor choice for public shows, being timid, prone to becoming highly stressed, and unpredictable in nature. As remarked above, they can be long-lived in captivity if key demands are met, but do not breed well even under the best conditions. The only Bald Eagle to be born outside North America hatched on May 3, 2006 in Magdeburg Zoo, Germany.

Reproduction

Bald Eagles build huge nests out of branches, usually in large trees near water. The nest may stretch as large as eight feet across and weigh up to a ton (907kg). When breeding where there are no trees, the Bald Eagle will nest on the ground.

Eagles that are old enough to breed often return to the area where they were born. An adult looking for a site is likely to select a spot that contains other breeding Bald Eagles.

Bald Eagles are sexually mature at 4 or 5 years old. 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 sitting on the eggs. The other parent will hunt for food or look for nest material.

Diet

The Bald Eagle's diet is varied, including carrion, fish, smaller birds, rodents, and sometimes food scavenged or stolen from campsites and picnics. Most prey is quite a bit smaller than the eagle, but rare predatory attacks on large birds such as the Snow Goose, the Great Blue Heron or even swans have been recorded. Also, fairly large salmon and trout have been taken as well.

To hunt fish, easily their most important live prey, the eagle swoops down over the water and snatches the fish out of the water with its talons. They eat by holding the fish in one claw and tearing the flesh with the other. Eagles have structures on their toes called spiricules that allow them to grasp fish. Osprey also have this adaptation. Bald Eagles have powerful talons. In one case, an eagle was able to fly off with the 6.8 kg (15 lb) carcass of a Mule Deer fawn.

Sometimes, if the fish is too heavy to lift, the eagle will be dragged into the water. It may swim to safety, but some eagles drown or succumb to hypothermia. Occasionally, Bald Eagles will pirate fish away from Ospreys and usually the smaller raptors will have to give up their prey, a practice known as kleptoparasitism.

National bird of the U.S.

The Bald Eagle is the national bird of the United States of America. It is probably one of the country's most recognizable symbols, and appears on most of its official seals, including the Seal of the President of the United States.

Its national significance dates back to June 20, 1782, when the Continental Congress officially adopted the current design for the Great Seal of the United States including a Bald Eagle grasping arrows and an olive branch with its talons. Some states had earlier done so in 1778.

In 1784, after the end of the Revolutionary War, Benjamin Franklin wrote a famous letter to his daughter from Paris criticizing the choice and suggesting the Wild Turkey's character as a desirable trait:

For my own part I wish the Bald Eagle had not been chosen the Representative of our Country. He is a Bird of bad moral character. He does not get his Living honestly. You may have seen him perched on some dead Tree near the River, where, too lazy to fish for himself, he watches the Labour of the Fishing Hawk; and when that diligent Bird has at length taken a Fish, and is bearing it to his Nest for the Support of his Mate and young Ones, the Bald Eagle pursues him and takes it from him.

With all this Injustice, he is never in good Case but like those among Men who live by Sharping & Robbing he is generally poor and often very lousy. Besides he is a rank Coward: The little King Bird not bigger than a Sparrow attacks him boldly and drives him out of the District. He is therefore by no means a proper Emblem for the brave and honest country of America who have driven all the King birds from our Country...

I am on this account not displeased that the Figure is not known as a Bald Eagle, but looks more like a Turkey. For the Truth the Turkey is in Comparison a much more respectable Bird, and withal a true original Native of America . . . He is besides, though a little vain & silly, a Bird of Courage, and would not hesitate to attack a Grenadier of the British Guards who should presume to invade his Farm Yard with a red Coat on.

Despite Franklin's objections, the Bald Eagle remained the emblem of the United States. It can be found on both national seals and on the back of several coins (including the quarter dollar coin until 1999), with its head oriented towards the olive branch. Between 1916 and 1945, the Presidential Flag showed an eagle facing to its left (the viewer's right), which gave rise to the urban legend that the seal is changed to have the eagle face towards the olive branch in peace, and towards the arrows in wartime.

Bald Eagles as religious objects

The Bald Eagle is a sacred bird in some North American cultures and its feathers, like those of the Golden Eagle, are central to many religious and spiritual customs amongst Native Americans. Some Native Americans revere eagles as sacred religious objects, including the feathers and other parts and are often compared to the Bible and crucifix (AP 2004).

Eagle feathers are often used in traditional ceremonies and are used to honor noteworthy achievements and qualities such as exceptional leadership and bravery.

Despite modern and historic Native American practices of giving eagle feathers to non-Native Americans and Native American members of other tribes who have been deemed worthy, current eagle feather law stipulates that only individuals of certifiable Native American ancestry enrolled in a federally recognized tribe are legally authorized to obtain Bald or Golden Eagle feathers for religious or spiritual use (AP 2002) Attempts to extend this permitted use have met with resistance from members of federally recognized Native American tribes, who even under the permissive legislation sometimes have to wait for years before a good specimen can be procured for their use (AP 2004).