With a white head and tail contrasting with a dark brown body and wings, the adult plumage of the Bald Eagle, attained at approximately 5 years of age, is unmistakable. In addition to the obvious white head and tail, other distinguishing features include the yellow bill, cere, iris, legs and feet. Second in size of North American birds of prey only to the California Condor (Gymnogyps californianus), the Bald Eagle ranges in total length from 71 to 96 cm, with an average wingspan of 168 to 244 cm and a body mass ranging from 3.0 to 6.3 kg (Buehler 2000). In general appearance the sexes are similar; with females approximately 25 percent larger than males. The plumage of the juvenile birds is much less distinct, being dark brown overall. The head, body, wings, and tail are dark brown with limited mottling on the underside of the wings and on the belly. While the legs and feet of the young bird are yellow, the bill and cere are dark gray and the iris is dark brown.

What does a Bald Eagle look like?

In adult plumage, the Bald Eagle is unlikely to be confused with any other species. Juvenile Bald Eagles may be confused with Golden Eagles (Aquila chrysaetos), especially with adult Goldens. A few characteristics differentiate these two species. The Bald Eagle has unfeathered legs, while those of the Golden Eagle are feathered. During flight, the head and neck of the Bald Eagle extend to about half the length of the tail, while the Golden Eagle is considerably less. This distinction is true for all age classes of both species. The terminal tail band on the Golden Eagle is dark and well defined, especially on the juveniles. In addition, the underwing and belly of the Bald Eagle show a greater amount of white compared to the Golden Eagle, whose white feathering is restricted to the base of the flight feathers (Buehler 2000).

Where does a Bald Eagle live?

In Montana, as elsewhere, the Bald Eagle is primarily a species of riparian and lacustrine habitats (forested areas along rivers and lakes), especially during the breeding season. Important year-round habitat includes wetlands, major water bodies, spring spawning streams, ungulate winter ranges and open water areas (Bureau of Land Management 1986). Wintering habitat may include upland sites. Nesting sites are generally located within larger forested areas near large lakes and rivers where nests are usually built in the tallest, oldest, large diameter trees. Nesting site selection is dependent upon maximum local food availability and minimum disturbance from human activity (Montana Bald Eagle Working Group 1994). See the Montana Bald Eagle Management Plan (1994) for further details including home range sizes and habitat requirements of fledgling birds.

The Bald Eagle is a resident species in the forested, mountainous areas of the state. Other individuals from more northerly latitudes either winter in Montana or migrate through the state to more southerly locations. Residents generally remain in the vicinity of their breeding areas throughout the year, while some, though remaining in the state, may move to the more temperate weather of lower elevations or to other areas with higher concentrations of food (Montana Bald Eagle Working Group 1994). This is especially true of individuals that nest at higher elevations.

Congregations of migrating Bald Eagles may be evident in autumn along the north-south mountain chains with an associated abundance of food sources; numerous eagles have been observed migrating over Rogers Pass and the Bridger Mountains (Hawk Watch International 2003). Large concentrations of eagles have formerly been reported feeding on spawning kokanee (Oncorhynchus nerka) in Glacier National Park and at Canyon Ferry Reservoir, north of Helena, when spawning fish were abundant (Montana Bald Eagle Working Group 1994). In the Bozeman area, birds arrive by November 20 and leave by April 25 (Skaar 1969).

What does a Bald Eagle eat?

The majority of their diet is comprised of fish. Important prey for Bald Eagles are waterfowl, especially in the winter, salmonids, suckers, whitefish, carrion and small mammals and birds (Bureau of Land Management 1986).

Information courtesy of Montana Fish, Wildlife, and Parks