Bald Eagle

“Some bald eagle’s nests can weigh as much as 2,000 pounds.”

The bald eagle is a large bird of prey native to North America. It is known for its distinctive white head and tail feathers and serves as the national bird of the United States. Once facing near extinction due to pesticide use, the species has remarkably recovered in recent decades.

3 Incredible Bald Eagle Facts!

• One of the most amazing facts about the bald eagle is its vision. This bird can see four to five times better than the typical human. It has superior color vision and the ability to see ultraviolet light. It also has a 340-degree field of view, which nearly wraps around behind its head. 
• The bald eagle will sometimes save energy by stealing the freshly killed prey of another bird. This behavior prompted Benjamin Franklin to say that the bald eagle was a bird of “bad moral character.”
• The bald eagle has been the national bird of the United States since 1782.

Scientific Name and Species

The scientific name of the bald eagle is Haliaeetus leucocephalus. Haliaeetus is the Greek term for the sea eagle, while leucocephalus combines two words: leukos, meaning white, and kephale, meaning head. This species is closely related to the African fish eagle, white-tailed eagle, and Steller’s sea eagle. This large bird of prey can be categorized into two sub-species: Northern bald eagle (Canada and Alaska) and Southern bald eagle (lower 48 states).

Evolution

Scientists believe birds evolved from reptiles called Theropods between 144 million and 65 million years ago during the Mesozoic Era. Feathers formed from reptilian scales and beaks eventually replaced teeth. Fossil records from this period indicate that the earliest birds had teeth. Bald eagles, part of the Haliaeetus genus, are descended from an ancient group of birds known as Kites. The first eagles descended from Kites 36 million years ago, known as sea eagles. They were like Kites in that they hunted fish and had featherless feet. The earliest fossil resembling the bald eagle dates back about one million years.

Where to Find the Bald Eagle

The bald eagle is the only member of the sea eagle genus to live exclusively in North America. Sightings have been reported as far south as Belize and Bermuda and as far north as the Arctic. The most common habitats are mature forests with a large water source nearby.

Size, Appearance, and Behavior

The identification of this American bird is a relatively simple matter. Measuring about 28 to 38 inches from head to tail, it easily ranks among the largest birds in North America. When its wings are outstretched, the bald eagle’s wingspan can sometimes reach more than 7 feet from one tip to another. It’s estimated that the female is about 25% larger than the male on average. Males typically weigh between 6.6 and 10 pounds, while females weigh between 10 to 14 pounds. Most of the body is covered in dark brown plumage, but the head and tail feathers are both covered in white feathers. Otherwise, both sexes look the same, making identification difficult unless standing side by side.

Bald eagles have developed many adaptations that help them hunt fish and waterfowl. Their feet each have four powerful toes with sharp talons and tiny projections called spicules that help them grasp their prey. They have serrations on the roof of their mouths to help hold slippery fish, and the black pigment in their wing feathers has evolved to provide strength to feathers when diving into the water. These majestic birds are made for hunting fish.

Bald eagles are extremely strong fliers that seem to glide effortlessly above the ground on thermal currents and strong updrafts for miles in all directions. While they mostly hunt and sleep alone in the non-breeding season, bald eagles do form strong pair bonds with each other to raise a new brood every year; they communicate through a series of high-pitched chirps, whistles, and chattering sounds. When nesting sites are particularly scarce, bald eagles may start dangerous or deadly fights with each other to challenge the territory.

Nests

The bald eagle pair prefers to construct its nest in the canopy of tall trees. It may choose a cliff face, an artificial structure, or the ground. Sticks are woven and lined with lichen or moss to construct the nest. Measuring some five to six feet in diameter, it is the largest nest of any American bird.

Migration

Northern populations from Canada and the upper United States tend to migrate south for the winter. Some eagles may only travel a few miles for better foraging opportunities, while others may travel hundreds of miles to escape the cold.

Diet

Bald eagles are opportunistic hunters, primarily feeding on fish such as salmon and trout but also preying on waterfowl, small mammals, and carrion. They use their sharp talons to grasp prey from the water or land.

Predators, Threats, and Conservation Status

An adult bald eagle does not have any natural predators in the wild. Bald eagle chicks and eggs are preyed upon by bobcats, wolverines, black bears, foxes, raccoons, owls, gulls, crows, and other large birds.

Bald eagles have been long threatened by hunting, trapping, accidents, and dangerous chemicals. Throughout the 20th century, they were nearly driven to extinction by pesticide use, which made adults infertile and thinned out their eggshells. Banning the pesticide DDT in 1972 and the hard work of conservationists have led to a revival in the fortunes of the bald eagle. It is currently listed as a species of least concern by the IUCN Red List.

Reproduction, Young, and Lifespan

Bald eagles are believed to form lifelong monogamous pairs until one partner dies. They reinforce their bond with extravagant courtship displays in which they lock their feet together while spinning toward the ground. They will also swoop down at each other in the air. The mating pair produces only a single brood of one to three eggs per year. The timing of reproductive season often occurs from the late winter to early spring. Both parents take turns incubating the egg while the other hunts for food.

It takes an average of 35 days for the chicks to emerge from their eggs sporting a brownish-gray head and tail mottled with white. In the 8 to 14 weeks it takes to gain their full-flight feathers, the juveniles spend a lot of time playing with each other, stretching their wings, and grasping objects with their talons for practice. They are among the fastest-growing birds in North America, but it still takes some five years for the juveniles to reach full maturity and gain their adult plumage. Since they look so radically different from the adults, it can make identifying the juvenile a little tricky. The average lifespan of a bald eagle in the wild is 15 to 20 years, though some individuals have been known to live much longer in captivity (up to 47 years).

Population

The bald eagle used to be among North America’s most persecuted and endangered birds. By the middle of the 20th century, its numbers had fallen to a low of only a few hundred breeding pairs. Today, however, they have rebounded to 250,000 breeding pairs, about 88% of which occur in the United States alone.