The bald eagle, Haliaeetus leucocephalus, is a raptor with a wingspan that can reach over seven feet. The species is instantly recognizable by its dark brown body, yellow beak, and the stark white feathers of its head and tail. This distinctive plumage appears when the bird reaches full maturity around five years of age. The eagle remains an enduring symbol across North America.
Current Geographic Range
The bald eagle’s modern distribution covers the majority of North America, extending from northern Mexico up through Canada and Alaska. The largest concentration of bald eagles is found in Alaska, which is home to an estimated over half of the global population.
In the lower 48 states, distribution is concentrated along major waterways, coastal regions, and the Great Lakes basin. The Pacific Northwest, including British Columbia, Washington, and Oregon, supports dense populations, with thousands congregating during winter. Minnesota and Florida typically report the highest numbers of nesting eagles among the contiguous states. The species is now recorded in every continental state and province in the U.S. and Canada.
Essential Habitat Requirements
Bald eagle distribution is tied to specific ecological requirements. The primary factor is proximity to large, reliable bodies of open water, such as seacoasts, rivers, and inland lakes, which provide an abundant supply of fish. As a sea eagle, the species relies heavily on finding prey near the water’s surface through hunting or scavenging.
For nesting and roosting, the birds require tall, sturdy trees with strong limbs to support their nests. They often select “super-canopy” trees that are taller than the surrounding forest, allowing for an unobstructed view of the foraging area and easy flight access. Eagles are sensitive to disturbance while nesting, so sites are typically chosen more than a mile away from high-density human activity.
Seasonal Movements and Migration Routes
Bald eagle populations include both permanent residents and migratory birds. Southern populations, such as those in Florida and California, are generally non-migratory and remain on their breeding territories year-round. Eagles that breed in the northern latitudes of Canada and Alaska are migratory, moving south as winter approaches.
Migration is triggered when freshwater feeding areas freeze, eliminating access to fish. These northern birds follow major flyways, such as the Mississippi River corridor, seeking open, unfrozen water. Major winter congregation sites occur along river systems where salmon spawn or where dams create open water. Illinois holds a significant wintering population, with thousands gathering along the Mississippi and Illinois Rivers.
Historical Range Shift and Recovery
The bald eagle’s current expansive range is a relatively recent development and a testament to successful conservation efforts. In the mid-20th century, the population in the contiguous United States faced a severe decline due to the widespread use of the pesticide DDT. The chemical caused eagles to produce eggshells that were too thin, leading to the collapse of eggs during incubation.
By 1963, the number of known nesting pairs in the lower 48 states had plummeted to a low of only 417. The ban on DDT in the U.S. in 1972, combined with protective legislation and active reintroduction programs, allowed the species to begin a recovery. This collective action resulted in a surge in population, with nesting pairs rebounding to over 71,400 by 2020.