Bald eagle

Taxonomy and Subspecies

The bald eagle belongs to the genus Haliaeetus, a group of sea eagles, and its scientific name, Haliaeetus leucocephalus, derives from Greek and Latin roots meaning 'sea eagle' and 'white-headed'. The common name 'bald' references the older English meaning of 'white-headed' rather than a lack of feathers. The species was first formally described by Carl Linnaeus in 1766 under the name Falco leucocephalus. It forms a species pair with the white-tailed eagle of Eurasia, sharing a similar ecological niche, with the two lineages diverging from other sea eagles at least 10 million years ago, but possibly as early as 28 million years ago if certain fossil records are correctly assigned. Historically, two subspecies have been recognized, primarily distinguished by size following Bergmann's rule, where animals tend to be larger in colder climates.

The bald eagle has two historically recognized subspecies. The northern subspecies, H. l. washingtoniensis, is larger than the southern nominate subspecies, H. l. leucocephalus. This size difference follows Bergmann's rule, where the species increases in size further from the equator. It is believed these may represent clinal size variation within a single species rather than distinct taxonomic groups. The northern subspecies is found in the Northern United States, Canada, and Alaska, while the southern subspecies is found in the southern United States and Baja California peninsula.

Physical Description and Size Variation

The adult bald eagle presents a striking and unmistakable appearance with its dark brown body plumage and bright white head and tail. The beak, feet, and irises are a vivid yellow, and the legs are feather-free with powerful, short toes equipped with large talons, the highly developed hind talon being used to pierce the vital areas of prey. Sexual dimorphism is pronounced, with females being approximately 25 percent larger than males, though both sexes share identical plumage. Immature eagles are mostly dark brown overlaid with messy white streaking and mottling, a pattern they retain until they reach sexual maturity at four to five years of age, rarely at three years. Their distinctive white head and tail feathers fully develop at this stage, and they can be distinguished from the similar-sized golden eagle by their larger head and beak, straighter-edged wings held flat in flight, and feathers which do not completely cover the legs.

Size varies significantly across the species' range, generally increasing with distance from the equator in accordance with Bergmann's rule. The largest individuals are found in Alaska, where large females may weigh more than 7 kg and have a wingspan up to 2.44 metres. A survey in Alaska showed adult females averaged 5.35 kg and males 4.23 kg. In contrast, eagles from South Carolina average only 3.27 kg with a 1.88 metre wingspan. Intermediate-sized populations include wintering eagles in Arizona, which average 4.74 kg, and migrants in Glacier National Park averaging 4.22 kg. Standard linear measurements include a wing chord of 51.5-69 cm, a tail length of 23-37 cm, and a tarsus length of 8 to 11 cm. The bill size is unusually variable, with Alaskan eagles having a mean culmen length of 6.83 cm, nearly double the 4.12 cm average for eagles from the southern United States.

Range and Habitat in Canada

The bald eagle's natural range covers most of North America, and it is the only sea eagle endemic to the continent. In Canada, the majority of bald eagles are found along the British Columbia coast while large populations are found in the forests of Alberta, Saskatchewan, Manitoba and Ontario. The species occupies a wide variety of wetland habitats, requiring large bodies of open water with an abundant food supply and old-growth or mature trees for nesting and perching. Studies show a preference for water bodies with a circumference greater than 11 km, and lakes with an area greater than 10 square kilometres are optimal for breeding. Ideal nesting sites are in coniferous or hardwood trees over 20 metres tall with good visibility, an open structure, and proximity to prey, often within 200 metres of open water, though a nest in Florida was recorded over 3 kilometres from water.

During the breeding season, eagles are sensitive to human disturbance, typically choosing sites more than 1.2 km from low-density human disturbance and more than 1.8 km from medium- to high-density disturbance. However, they have adapted to some urban environments, such as nesting on Hardtack Island on the Willamette River in Portland, Oregon, in the John Heinz National Wildlife Refuge in Philadelphia, and a family moved to the Harlem neighbourhood in New York City in 2010. In March 2024, bald eagles were documented nesting in Toronto for the first time, indicating a continued expansion. Winter behaviour differs, as eagles become less habitat and disturbance sensitive and often congregate in large numbers where food is plentiful. From November until February, one to two thousand birds winter in Squamish, British Columbia, attracted by salmon spawning in the Squamish and Cheakamus Rivers. In northern regions, wintering eagles may also utilize upland, terrestrial habitats like prairies, meadows, or tundra when unfrozen water is not accessible, relying on concentrations of medium-sized mammals or carrion.

Diet and Hunting Behaviour

The bald eagle is an opportunistic and carnivorous feeder with a highly varied diet, though fish consistently form the majority of its food intake. Studies across its range show that fish comprise about 56 percent of the diet for nesting eagles, birds 28 percent, mammals 14 percent, and other prey 2 percent. The species is known to prey upon more than 400 different species, a number that may be second only to the red-tailed hawk among North American accipitrids. To hunt fish, the eagle typically swoops down over the water and snatches its prey from the surface with its powerful talons. Specialized structures on their toes called spicules help them grasp slippery fish securely, a trait shared with ospreys. Eagles will also hunt bird prey in flight, attacking and killing birds as large as Canada geese in mid-air by swooping underneath them and thrusting their talons into the breast.

They are powerful fliers, capable of reaching speeds of 56-70 km/h when gliding and flapping, and dive speeds between 120 and 160 kilometres per hour, though they seldom dive vertically. When carrying fish, they can fly at about 48 kilometres per hour. Their grip strength is estimated to be ten times stronger than that of a human. Bald eagles often pirate food from other birds, including ospreys, a behaviour known as kleptoparasitism. They eat by holding the fish down with one foot and tearing flesh with the other, and they will also readily scavenge carrion, especially during winter months. This dietary flexibility is key to their survival across diverse habitats, from the bayous of Louisiana to the Sonoran Desert and the eastern deciduous forests of Quebec.

Life Cycle, Nesting, and Flight

Bald eagles reach sexual maturity at four to five years of age. They are monogamous and often mate for life, returning to and enlarging the same nest year after year. These nests, called aeries, are the largest built by any North American bird and are among the largest tree nests recorded for any animal species. Nests are constructed from sticks and lined with softer materials like grass, moss, or cornstalks, and are typically built in the forks of large trees near water, but can be as low as 6 metres above ground in mangroves or as high as 38 metres in trees on dry ground. The largest recorded nest, found in Florida in 1963, measured 2.9 metres wide and 6.1 metres deep. Nests can weigh up to one metric ton.

The female typically lays one to three eggs per clutch, which are incubated for about 35 days. Both parents share incubation duties and feeding of the young eaglets. The young fledge at around 10 to 12 weeks of age but may remain near the nest and depend on their parents for several more weeks. Key nesting tree species vary by region. The bald eagle is a powerful flier that soars on thermal convection currents, and it selects migration routes to take advantage of thermals, updrafts, and food resources. Migration is diurnal, usually occurring between 8:00 a.m. and 6:00 p.m. when thermals are produced by the sun. Populations with access to open water year-round are resident, while northern birds migrate south or to the coast when water freezes.

• Florida: Slash pines (Pinus elliottii), longleaf pines (P. palustris), loblolly pines (P. taeda), cypress trees, and mangroves in coastal areas.
• Wyoming: Groves of mature cottonwoods or tall pines along streams and rivers, and old-growth stands of ponderosa pine (Pinus ponderosa).
• Southeast Alaska: Sitka spruce (Picea sitchensis), comprising 78% of nesting trees, followed by hemlocks (Tsuga) at 20%.
• Chesapeake Bay: Nesting trees averaged 82 cm in diameter and 28 m in height.

Population Decline and Recovery

By the mid-20th century, bald eagle populations in the contiguous United States and parts of southern Canada had plummeted to the brink of extirpation. The primary causes were widespread shooting, habitat loss, and, most critically, poisoning from the pesticide DDT, which caused eggshell thinning and reproductive failure. At its minimum population in the 1950s, the species was largely restricted to Alaska, the Aleutian Islands, northern and eastern Canada, and Florida. The species' status in the U.S. was upgraded from 'endangered' to 'threatened' in 1995. Due to sustained population growth, it was officially removed from the U.S. Endangered Species List in 2007.

From 1966 to 2015, bald eagle numbers increased substantially throughout their winter and breeding ranges. As of 2018, the species nests in every continental U.S. state and Canadian province. This recovery is considered one of the most successful conservation stories in North America. Major conservation actions that facilitated the bald eagle's recovery include:

1. Legal protection under the U.S. Endangered Species Act (1978) and the Migratory Birds Convention Act in Canada.
2. Strict enforcement of laws against shooting and nest disturbance.
3. Active reintroduction and hacking programs in areas where populations had been wiped out.
4. Protection of nesting habitats and key wintering areas.
5. Public education campaigns to reduce human disturbance and promote stewardship.

The bald eagle population has recovered substantially since its low point in the mid-20th century. This recovery followed measures such as banning hunting and the harmful pesticide DDT. Its status was upgraded from endangered to threatened in 1995 and it was removed from the U.S. Endangered Species list in 2007. While threats like lead poisoning, electrocution, and habitat degradation persist, ongoing monitoring and habitat protection continue. The overall population is now considered stable and secure, with the species nesting in every continental U.S. state and Canadian province.

Cultural Significance and Status

The bald eagle holds significant cultural status as the national bird and symbol of the United States, appearing on its seal, currency, and many government insignia. Its image represents freedom, strength, and longevity. While not an official national symbol of Canada, the bald eagle is a notable part of the Canadian wilderness, featured in Indigenous art and storytelling and valued as a key indicator of healthy aquatic ecosystems. Its dramatic recovery from near-extinction is a landmark achievement in environmental conservation on both sides of the border. The bird's imposing presence, majestic flight, and role as an apex predator make it a subject of public fascination and a flagship species for wetland conservation efforts across North America. The bald eagle's range has expanded from a few strongholds to reoccupy much of its historical territory, including recent nesting activity in major Canadian cities like Toronto, demonstrating its resilience and adaptability.

• National Symbol: Designated as the national bird of the United States, appearing on the Great Seal.
• Indigenous Significance: Featured in the art and oral traditions of many First Nations across North America.
• Conservation Symbol Its recovery is a flagship example of successful environmental legislation and species protection.
• Range Recovery: Nests in every continental U.S. state and Canadian province as of 2018.
• Urban Adaptation: Documented nesting in New York City (2010) and Toronto (2024).
• Vagrant Records: Rare appearances outside North America include individuals in Ireland (1973, 1987) and Anglesey, United Kingdom (1978).

Questions about Bald eagle

Are bald eagles actually bald?

No, bald eagles are not bald in the sense of having no feathers. The name derives from an older meaning of the word 'bald', which meant 'white-headed'. The adult eagle's head is covered in bright white feathers, which create a striking contrast with its dark brown body plumage. This distinctive white head and tail are the source of its common name and its scientific species name, leucocephalus, which translates to 'white head'.

What is the wingspan of a bald eagle?

The wingspan of a bald eagle typically ranges from 1.8 to 2.3 metres, which is approximately 5 feet 11 inches to 7 feet 7 inches. Size varies by location and sex, with females being larger than males. The largest eagles are found in Alaska, where some females can have a wingspan of up to 2.44 metres, or 8 feet. In contrast, eagles from South Carolina average a smaller wingspan of about 1.88 metres.

What do bald eagles eat?

Bald eagles are opportunistic carnivores with a highly varied diet, but fish form the majority of their food intake. Studies show fish comprise about 56 percent of the diet for nesting eagles. They also prey on birds (28 percent), mammals (14 percent), and other animals. They are skilled hunters, snatching fish from the water with their talons, but they will also scavenge carrion and steal food from other birds like ospreys. Their prey spectrum includes more than 400 species.

Why were bald eagles endangered?

Bald eagle populations crashed in the mid-20th century due to several factors. The widespread use of the pesticide DDT caused eggshell thinning, leading to reproductive failure. They were also extensively shot and persecuted, and suffered from habitat loss. By the 1950s, they were largely gone from the contiguous United States, restricted mainly to Alaska, Canada, and Florida.

Where can I see bald eagles in Canada?

In Canada, significant bald eagle populations are found along the coast of British Columbia and in the boreal forests of Alberta, Saskatchewan, Manitoba, and Ontario. A famous winter congregation occurs in Squamish, British Columbia, where one to two thousand eagles gather from November to February to feed on spawning salmon in the Squamish and Cheakamus Rivers. Eagles have also been documented nesting in urban areas, with the first recorded nest in Toronto observed in March 2024. The species' range includes most of Canada, and populations have recovered substantially since the mid 20th century. They are found near large bodies of open water with an abundant food supply and require old growth trees for nesting.

How big is a bald eagle's nest?

Bald eagles build the largest nest of any North American bird and the largest tree nests ever recorded for any animal species. These nests can be up to 4 metres deep, 2.5 metres wide, and weigh one metric ton. The largest recorded nest was found in Florida in 1963 and measured 2.9 metres wide and 6.1 metres deep. Nests are constructed from sticks and are often used and enlarged over many years. They are typically built in tall, mature coniferous or hardwood trees near water, with heights ranging from 6 metres in mangroves to 38 metres in trees on dry ground.

Sources and further reading

• Bald eagle (Wikipedia)
• Bald Eagle (kids.nationalgeographic.com)
• Bald eagle (Haliaeetus leucocephalus) - Parks Canada (parks.canada.ca)
• Bald eagle (nationalzoo.si.edu)
• Bald Eagle, San Diego Zoo Animals & Plants (animals.sandiegozoo.org)

Checked by the Your Space Hamilton desk. Last updated 2026-10-18.