|Size:||Length: 30 to 37 inches (76 to 94 cm) Wingspan: 72 to 90 inches (183 to 228 cm)|
|Weight:||10 to 14 pounds (4.5 to 6.4 kg)|
|Diet:||Fish, waterfowl, small mammals and carrion|
|Young:||1 to 3|
|IUCN Status:||No special status|
|Terms:||Young: Eaglet Group: Aerie or convocation Soaring group: Kettle|
|Lifespan:||Up to 50 years in captivity and average 15 to 20 years in the wild|
· The bald eagle was chosen as the national emblem of the United States of America on June 20, 1782.
· It is the only eagle unique to North America.
· The scientific name is derived from Latin, meaning sea (halo) eagle (aeetos) with a white (leukos) head.
Adult bald eagles have a white neck, head and tail. Their wings, back and legs are dark brown and they have yellow feet and a yellow, hooked bill. Their feathers are lined with down, which enables them to survive in cold temperatures. They can trap warmth under their 7,000 feathers by ruffling and rotating them while sunning. The movement opens and closes air pockets that retain the warmth of the sun. Like most birds, bald eagles have hollow bones, in order to be light enough to be able to fly. Their beak, talons and feathers are made of keratin, which is the same substance found in human fingernails. Although bald eagles are capable of producing sounds such as shrill, high-pitched twitters, they do not have vocal chords. Instead, the sound comes from a chamber located where the respiratory passage divides on the way to the lungs. Eagles have an inner translucent eyelid that they can see through even when it is closed. The inner eyelid slides across the eye every three or four seconds to clean dirt or dust from the cornea. They have large eyes and are able to see in colour. Female bald eagles are typically larger than males.
There are approximately 70,000 bald eagles in North America and half of them live in Alaska. The bald eagle population of British Columbia is estimated at 20,000, and the reason for the high populations in these areas is because of the abundance of salmon and other fish, which are an important food source. The remaining bald eagles live in small populations ranging southward to northern Mexico.
Bald eagles have extremely sharp eyesight and are able not only to see prey at a distance of up to one mile (1.6 km), but they have two centres of focus that allow them to see both forward and to the side at the same time. Their favourite food is fish, and when they spot a fish swimming near the surface, they fly low over the water and then snatch the fish quickly with their strong talons. Once closed on prey, the talons are locked in that position and will not open until the eagles pushes them down on a solid surface. They are successful in one of 18 attempts to snatch prey, and expend a lot of energy, so when they have eaten, they rest quietly until they need to hunt again. Eagles can consume one pound of food in only four minutes. They hold the food in one talon while perching on the other, and tear off chunks with their bill. When they are unable to find fish, eagles will turn to other food sources such as small mammals, water fowl and carrion. They sometimes steal food from other eagles or birds of prey, chasing the bird until it drops its kill and even attacking if the bird does not let go. Bald eagles can store food in a pouch of the esophagus when their stomach is full, and therefore do not have to eat every day. The pouch, called a crop, also separates indigestible items such as feathers, fur, bones and scales from the food and forms it into a mass that is regurgitated.
At the age of four or five, bald eagles become fully mature and can begin to reproduce. Once they have found a mate, they stay together for life unless one of them dies, in which case the surviving partner will accept a new mate. Five to ten days after mating, the female lays one to three eggs within a nest that the couple have built in a large tree. The large, off-white eggs are laid several days apart. The nests are large, approximately five feet in diameter, and the eagles usually use the same nest each breeding season. The parents take turns incubating the eggs, while one of them goes to find food, although usually the female does most of the incubating. After approximately 35 days, the first egg hatches. The eaglets have a special egg tooth that they use to break through the shell. Eaglets are helpless when they emerge from the shell. Their legs are too weak to hold them up, they cannot hold up their heads, and their eyes are only partially open. They are covered in soft grey down and are fed shredded pieces of meat from the beaks of their parents. The parents are careful to keep their talons balled into fists while they are in the nest, to keep from accidentally hurting the eaglets. The eaglets grow at a rate of approximately one pound every four to five days. When they reach four to five weeks, they are strong enough to stand on their own, and can begin tearing up their own food. When they are six weeks, the eagles are just about the size of their parents, and because they need a large amount of food, their parents hunt for them almost continuously. Their black feathers have begun to grow in, and at 10 to 13 weeks the feathers they need to fly have grown in enough that they may make their first attempt at flight. Over the next few months, the eaglets are still fed by their parents, but observe them as they hunt, trying to learn the skills necessary so they can one day survive on their own. Gradually, the young eagles spend more time on their own, perfecting their hunting skills, and by winter, they are on their own. Juvenile bald eagles have brown and white feathers and a black bill. They do not get the colouring of adult bald eagles until they are four to five years of age.
Eagles are able to soar by making use of rising currents of warm air that are called thermals. When they extend their long wings as they pass over a thermal, the eagles barely need to flap their wings at all. They especially make use of the thermals during long distance flights, to conserve energy. In flight, bald eagles can reach flight speeds of up to 30 miles (48 km) per hour and when diving towards prey, they may reach speeds of 100 miles (161 km) per hour.
Although bald eagle numbers were high at one time, by the 1930s, the diminishing population became a concern, leading the Bald Eagle Act to be passed in 1940. Although this protected the eagles from being disturbed or harmed, their numbers kept diminishing due to a pesticide called DDT. The chemical was ingested by the eagle’s prey, entering the bloodstream of the eagle in a high concentration and harming not only their ability to reproduce, but creating thinner shells in their eggs, resulting in their loss. DDT was banned in the United States in 1972 and on July 4, 1976, the US Fish and Wildlife Service officially listed the bald eagle as a national endangered species. In July 1995, their status was upgraded to threatened. Today, the bald eagle has recovered to the point where discussions have begun to remove the bird from the USFWS list, but it will still be protected by the Migratory Bird Treaty Act and the Bald and Golden Eagle Protection Act. These acts make it illegal for anyone to own eagles, eagle parts, nests or eggs without a permit. Even having possession of a feather is a felony in the U.S., with a fine of up to $10,000 and/or imprisonment. Only federally recognized Native Americans are exempt, because of the traditional use of eagle feathers in their culture.
Raptors: North American Birds of Prey. Noel and Helen Snyder, Raincoast Books, 1991