An adult bald eagle's plumage is uniformly dark brown with a white head and tail. The tail is medium in length and fashioned like a wedge.
Males and females have the same plumage colouring, however, there is sexual dimorphism in the species, with females being 25% larger than males.
The beak, feet, and irises are all vibrant yellow. The toes are small and powerful, with big talons, and the legs are featherless.
The hind toe's highly developed talon is utilised to puncture the critical parts of prey while the front toes keep it motionless.
With a yellow cere, the beak is big and hooked.
Until the fifth year, when it reaches sexual maturity, the immature plumage is a dark brown with untidy white striping.
The bald eagle is distinguished from the golden eagle, North America's only other large, non-vulturine raptorial bird, by its larger, more projecting head with a larger beak, straighter edged wings that are held flat and with a sharper wing beat, and feathers that do not entirely cover the legs.
The golden eagle has a more solid warm brown colour than an immature bald eagle, with a reddish-golden patch on its nape and a very contrasted pair of white squares on its wing when seen up close.
A black, yellow-tipped beak distinguishes the immature bald eagle from the mature bird, whereas the mature eagle has a totally yellow beak.
The bald headed eagle is commonly referred to as North America's largest real raptor. The California condor, a New World vulture that is no longer regarded as a taxonomically of real accipitrids, is the only larger raptor-like bird.
Furthermore, the bald eagle's close cousins, the slightly longer-winged but shorter-tailed white-tailed eagle and the overall larger Steller's sea eagle may occasionally migrate from Asia to coastal Alaska.
The bald eagle's body length ranges from 70 to 102 cm or 2.5 to 3 feet.
The average bald eagle wingspan is between 1.8 and 2.3 metres.
The average bald eagle weighs between 3 and 6.3 kg. Females are around 25% larger than males, averaging 5.6 kg vs 4.1 kg for males.
The bald eagle size varies by location and generally follows Bergmann's rule, as the species grows larger as it moves away from the Equator and the tropics.
South Carolina bald eagles are smaller than their northern counterparts, weighing 3.27 kg and having a wingspan of 1.88 m.
The bald eagles from Florida have an average weight of 4.13 kg which is more than the bald eagles from South Carolina.
The average weight of migrant bald eagles in Glacier National Park was found to be 4.22 kg.
The bald eagles which spend their winters in Arizona are found to average 4.74 kg which is because the winter weights of bald eagles are typically the highest throughout the year, as many raptors spend the majority of their time foraging in the winter.
The largest eagles are found in Alaska, where huge females can weigh up to 7 kg and have a wingspan of 2.44 m. A survey of adult American bald eagles in Alaska found that females weighed 5.35 kg on average and males weighed 4.23 kg, compared to immatures who weighed 5.09 kg and 4.05 kg, respectively. An outsized Alaskan adult female eagle weighed around 7.4 kg.
The bald eagle wing chord is 51.5–69 cm.
The tarsus measures 8 to 11 cm in length and the tail measures 23–37 cm.
The culmen is 3–7.5 cm long, and the bill is 7–9 cm long from gape to tip.
Alaskan eagle bills can be up to twice as long as those of southern birds, with mean culmen lengths of 6.83 cm and 4.12 cm from these two areas, respectively.
A strong flier, the bald eagle soars on thermal convection currents. When gliding and flapping, it can achieve speeds of 56–70 km/h, and about 48 km/h when hauling fish. It dives at a speed of 120–160 km/h and rarely dives vertically. Despite being morphologically less well adapted to quicker flight than golden eagles, especially during dives, the bald eagle is thought to be extremely agile in flight.
The call of bald eagles includes weak staccato, chirping whistles, kleek kik ik ik ik, in the range of the call to the gull. Young birds tend to call deeper and more shrill than adults.
The existence of the bald eagle covers the greater part of North America, including most of Canada, the rest of the continental US and northern Mexico.
It is North America's only sea eagle endemic. The birds of North are migratory and of Southern Birds, residing on their breeding land all year long. Occupying varied habitats from the Louisianan bayouses to the Sonoran Desert and the eastern deciduous forests of Quebec and New England.
In the 1950s, the bald eagles were primarily restricted to Alaska, the Aleutian Islands, northern and eastern Canada, and Florida, at least in terms of population. The bald eagle population rose dramatically between 1966 and 2015 across its winter and breeding areas, and the species now nests in every continental state and province in the United States and Canada.
The majority of bald eagles in Canada can be found near the coast of British Columbia, with considerable concentrations in Alberta, Saskatchewan, Manitoba, and Ontario forests.
In the winter, bald eagles concentrate in specific areas. Thousands of birds winter in Squamish, British Columbia, between November and February, nearly midway between Vancouver and Whistler.
The salmon spawning in the area attracts the birds to congregate near the Squamish and Cheakamus Rivers. In the northern United States, similar gatherings of wintering bald eagles have been reported near open lakes and rivers where fish are easily accessible for hunting or scavenging.
During the nesting season, the bald eagle can be found in practically any type of American wetland habitat, including seacoasts, rivers, big lakes or marshes, or other big bodies of open water with plenty of fish. According to studies, bald eagles prefer bodies of water with a circumference greater than 11 km and lakes with an area greater than 10 km2 for breeding.
For perching, roosting, and nesting, the bald eagle prefers old-growth and mature stands of coniferous or hardwood trees. The height, composition, and location of the tree are said to be more essential to the eagle pair than the tree's species.
A profusion of comparatively large trees surrounding the body of water may be of critical importance for this species. Trees chosen for this project must have high visibility, be over 20 metres tall, have an open structure, and be close to prey. If the nesting trees are in a marsh with standing water, such as a mangrove swamp, the nest can be as low as 6 metres above the ground.
Nests can range in height from 16 to 38 metres in a more typical tree resting on dry ground. Nesting trees in the Chesapeake Bay averaged 82 cm in diameter and 28 m in height, whereas, in Florida, the typical nesting tree is 23 m tall and 23 cm in diameter.
In the Greater Yellowstone area, nesting trees are on average 27 metres tall. Trees or forests utilised for nesting should have a canopy cover of no more than 60% and no less than 20%, and be within walking distance of water.
The majority of nests have been discovered within 200 metres of open water. In Florida, the highest distance from open water for a bald eagle nest was almost 3 kilometres.
Mangrove swamps, lake and river shorelines, pinelands, seasonally flooded Flatwoods, hardwood swamps, and broad prairies and pastureland with scattered tall trees are all common nesting locations in Florida.
Bald eagle nesting grounds in Wyoming include forests of old cottonwoods or tall pines along streams and rivers. Wyoming eagles can be found in a variety of habitats, from huge, old-growth ponderosa pine stands to tiny riparian forest strips flanked by rangeland.
Sitka spruce provided 78 percent of the nesting trees used by eagles in Southeast Alaska, followed by hemlocks at 20 percent. Eagles are increasingly laying their eggs in man-made lakes stocked with fish.
While nesting, the bald eagle is usually extremely sensitive to human activity, and it is most typically found in places with little human disturbance. It selects areas that are at least 1.2 kilometres away from low-density human disturbance and at least 1.8 kilometres away from medium- to high-density human disturbance.
Bald eagles are less habitat and disturbance sensitive throughout the winter. They'll concentrate in areas with plenty of perches, as well as waters with plenty of prey and partially frozen waters. Non-breeding or wintering bald eagles, on the other hand, spend their time in diverse upland, terrestrial environments, often quite far away from waterways, especially in locations where human interference is minimal.
Bald eagles are migratory to some extent, depending on their habitat. If its region has access to open water, it will stay there all year, but if the body of water freezes over during the winter, it will migrate to the south or to the coast in search of food.
The bald eagle chooses migration paths based on thermals, updrafts, and food availability. It may fly up in a thermal and then glide down, or it may fly up in updrafts formed by the wind against a cliff or other terrain during migration.
The most common time for a migration is throughout the day, between the hours of 8:00 a.m. and 6:00 p.m., when the sun produces thermals.
The bald eagle is an opportunistic carnivore capable of eating a wide range of prey. Fish make up a large part of the eagle's food throughout its range.
Fish made up 56 percent of the diet of nesting eagles in 20 studies across the species range, followed by birds (28%), mammals (14%), and other prey (2%).
More than 400 species have been identified as part of the bald eagle's prey range, significantly more than its Old World ecological counterpart, the white-tailed eagle.
Waterbirds are the next most important prey base for bald eagles after fish. The amount of fish near the water's surface that such birds contribute to the eagle's diet varies depending on the number and availability of fish. In some areas, waterbirds can make up anything from 7% to 80% of an eagle's food selection depending on the season.
Rabbits, hares, ground squirrels, raccoons, muskrats, beavers, and deer fawns are species of mammalian prey. Mammals that are newborn, deceased, unwell, or already damaged are frequently targeted. More dangerous prey, such as adult raccoons and subadult beavers, are occasionally assaulted.
Bald eagles reach sexual maturity at the age of four or five years. They frequently return to the place where they were born when they are old enough to breed.
Bald eagles are supposed to mate for life. If one of the members of a pair dies or vanishes, the survivor will find a new mate.
A couple that has been unsuccessful in breeding endeavours may break up and look for new partners.
Male bald eagles perform elaborate, spectacular cries and aerial displays during courtship. Swoops, chases, and cartwheels are all part of the flight, in which they fly high, lock talons, and free-fall, separating moments before striking the earth.
Bald eagles are early breeders compared to most other raptors, who typically nest in April or May. Nest construction or reinforcing is normally completed by mid-February, egg-laying is usually completed by late February, occasionally during deep snow in the north, and incubation is completed between mid-March and early May.
The young fledge late June to early July after the eggs hatch in mid-April to early May. The nest of the bald eagle in North America is the largest of any bird. It has been utilised for many years, and additional material is added each year.
The bald eagle population was predicted to be 300,000–500,000 in the early 18th century, but by the 1950s, there were only 412 nesting pairs in the 48 contiguous states of the United States.
The bald eagle was badly harmed by a combination of reasons in the mid-twentieth century, including the weakening of eggshells caused by the pesticide DDT. Due to biomagnification, bald eagles, like many other birds of prey, were particularly harmed by DDT.
DDT did not kill adult birds, but it interfered with their calcium metabolism, rendering them sterile or incapable of laying viable eggs. Many of their eggs were flimsy enough to break under the weight of a brooding adult, making hatching practically difficult.
A broad loss of adequate habitat, as well as both legal and illegal killing, were other contributors to bald eagle population declines. In 1930, a New York City ornithologist estimated that 70,000 bald eagles had been shot in Alaska over the previous 12 years.
The 1918 Migratory Bird Treaty was the first to preserve the species in the United States and Canada, and it was eventually expanded to include all of North America.
The United States Congress passed the Bald and Golden Eagle Protection Act in 1940, which safeguarded the bald and golden eagles by preventing commercial capturing and killing of the birds.
In the United States, the bald eagle was listed as an endangered species in 1967, and between 1962 and 1972, modifications to the 1940 legislation further restricted commercial uses and increased penalties for violators.
DDT was banned from use in the United States in 1972 due to its ability to prevent many birds from reproducing. DDT was outright prohibited in Canada in 1989, after being heavily regulated since the late 1970s.
The eagle population recovered once controls were put in place and DDT was prohibited. The bald eagle is becoming increasingly common in the United States and Canada, especially near large bodies of water.
The projected overall population in the early 1980s was 100,000 bald eagles, increasing to 110,000–115,000 by 1992. Alaska, with a population of 40,000–50,000 bald eagles, is the most populous state in the United States, followed by British Columbia, with a population of 20,000–30,000 bald eagles in 1992.