Two bald eagles perch on the port buoy at the channel entrance to Granville Island in Vancouver. The bald eagle is Canada's largest bird of prey. (Chuck Stoody/Canadian Press)

There are 59 species of eagle found in the world. Only two – bald eagles and golden eagles – call North America home. Bald eagles are not found outside of this continent. They are Canada's largest raptor or bird of prey, and are found in every province and territory.

About one-third of the total bald eagle population (roughly 100,000) can be found in Alaska and British Columbia, particularly along the Pacific coast, according to Environment Canada. There are also healthy breeding populations in the boreal (or northernmost) forest between Alberta and northwestern Ontario. There are smaller populations found on the East Coast.

Some bald eagles call one area home, while others migrate short distances, either to breed or to escape the winter weather. Bald eagles live on the British Columbia coast all year round, and the numbers of eagles increase during the colder months. But those breeding in central Canada head south during the fall and winter. They migrate to west-central and southwestern United States and return only in the spring.

Bald eagles, despite their name, aren't actually bald. The name stems from "balde," an old English word meaning "white." Young eagles are dark brown with speckles of white, with dark grey bills and dark brown eyes. But, after four or five years, the feathers on their heads become white.

Female bald eagles usually weigh about six kilograms, while males weigh about four kilograms. When perched, the bird is about 76 centimetres tall. Both male and female wingspans are about two metres wide. They can fly higher than 3,000 metres, at speeds of 105 kilometres per hour. When diving, they can hit a top speed of 320 km/h.

Bald eagles eat fish, waterfowl, small mammals and carrion (dead animals). They hunt with their large beaks, talons and oversized feet, which have small spikes called spicules. But, most of their diet consists of sickly animals or those wounded by hunters.

These eagles usually have life-long mates and will only seek another if their companion dies. Or, if they have problems breeding, they may split up and look for new partners. The bald eagle courtship ritual usually involves elaborate calls and acrobatic displays, such as cartwheels, roller-coaster swoops and chases.

An immature golden eagle flies from a deer carcass near McCammon, Idaho. (Associated Press/Idaho State Journal, Doug Lindley)

They build the biggest nest of any bird species in North America, measuring about one metre deep and 1.5 to two metres across. The nests are lined with feathers, soft mosses, grasses and twigs.

Nests are built at the tops of very tall and sturdy trees, which are near water. Eagles usually nest in older forests, but also nest on cliffs and the ground when trees aren't available.

Eagles come back to the same nest to breed each year, and add more to the nest each time. Some nests can grow to more than three metres in width, six metres tall, and can weigh several tonnes.

Females lay one to three eggs in April or May (in Canada) about two or four days apart. These hatch after 35 days of incubation, two or three days apart. Both parents share duties such as egg incubation, hunting, nest watching, feeding and brooding until the young eaglet can fly. But, the female is usually in the nest almost all the time. The eaglets are fully-grown and ready to fledge at about 12 weeks. Eaglet mortality within the first year is high, at 50 per cent.

Total numbers of bald eagles have dropped since Europeans came to North America but this eagle is still fairly common in western Canada and Alaska. According to the Canadian Peregrine Foundation, prior to 1800, there were between 250,000 and 500,000 bald eagles in North America.

The Committee on the Status of Endangered Wildlife in Canada currently designates the bald eagle as not at risk. But, in the United States, they are listed as threatened and are protected under the Endangered Species Act of 1973, The Bald Eagle Protection Act of 1940, the Migratory Bird Treaty Act of 1918 and the Lacey Act.

Bald eagles may live for 50 years in captivity, but are unlikely to live that long in the wild. This is due to natural hazards and the eagles' biggest threat: humans. Habitat loss due to deforestation is the main threat. Others include shooting, collisions with power lines and windmills, and mercury and lead poisoning (which can be contracted after eating waterfowl shot with lead shotgun pellets).

As well, DDT, a chemical pesticide used in the 1940s and 1950s, devastated the bald eagle populations. It interfered with the eagle's ability to absorb calcium, and when they laid eggs, the shells were too thin and were crushed during incubation. According to the American Eagle Foundation, the eagle population in the continental U.S. dropped to less than 10,000 nesting pairs by the 1950s, and to less than 500 pairs by the early 1960s.

According to Environment Canada, in the early 1900s, about 200 pairs nested in southern Ontario, from the Ottawa River to the lower Great Lakes. By the late 1970s, however, there were less than 10 bald eagle pairs recorded. However, the northern and western parts of the country were not as drastically affected by DDT.

Laws were then passed in Canada and the United States to prevent the unrestricted use of the pesticides. And, conservationists worked with landowners to protect the eagles' nesting habitat, to encourage breeding. But, the effects of DDT lingered. In 1980, there were only three active bald eagle nests along the north shore of Lake Erie, and no young were produced, according to Bird Studies Canada.

Today, the bald eagles of Southern Ontario are recovering slowly. Across southern Ontario in 2000, 28 eaglets were known to fledge, from 18 of 23 active nests. Recent estimates put the bald eagle population in southern Ontario at about 20 pairs. But, eagle populations are flourishing in other parts of Canada.