SPECIES

Bald Eagle Haliaeetus leucocephalus Scientific name definitions

David A. Buehler
Version: 2.0 — Published October 7, 2022

Habitat

Habitat in Breeding Range

Typically breeds in forested areas adjacent to large bodies of water or large rivers. At the macro scale, the breeding habitat is typically mature forest patches with openings/edges, relatively close (usually < 2 km) to water with suitable foraging opportunities. The size of forest tract holding the nest tree may be unimportant if tract is isolated from human development and disturbance. Forested tracts with nests have relatively open canopies, some form of cover discontinuity or edge, or high levels of diversity in foliage-height so that there is access to nest trees (110, 111, 112, 113). Summer habitat for foraging is characterized by the presence of tall, easily accessible, often super-canopy trees adjacent to shorelines, usually away from human disturbance (114, 115, 116). A wide range of trees are used for feeding perches, including both coniferous and deciduous species; most are live trees, although standing dead trees are preferred if available (18, 114).

Habitat in Nonbreeding Range

Habitat in Migration

The Bald Eagle is capable of migrating over otherwise unsuitable, human-developed habitat, such as the extensive urban-suburban corridor along the East Coast . The suitability of stopover areas is likely more related to food availability rather than vegetative composition or structural characteristics. This conclusion is supported by the collapse in salmon at Glacier National Park, Montana, followed by the abandonment of this historic stopover site by Bald Eagles (117). Locations with abundant food resources along traditional migration pathways are often used by adults and immatures in fall and at least by immatures in spring. These sites include locations with consistent fish-kills (e.g., below dams on the Missouri River and Mississippi River [118, 119] and at salmon spawning runs along the Chilkat River, Alaska [120], and at Hauser Reservoir, Montana 121), reliable waterfowl concentrations (e.g., Chesapeake Bay 122), or the reliable presence of dead large mammals (123). Most stopover sites have traditional roost sites, which are often clumps of mature deciduous trees in riparian areas that are protected from human disturbance and proximate to foraging opportunities.

Habitat in Overwintering Range

Winters primarily in the temperate zone (124), generally below 500 m elevation, except in some western states where they winter as high 2,500 meters above sea level (e.g., San Luis Valley, Colorado 125). Most spend the winter near aquatic habitats that have some open water for foraging, although some birds may be found in arid regions of the desert southwest. Wintering locations must have sufficient food as well as roost sites that provide protection from inclement weather. Most wintering areas lack substantial human disturbance, although greater human activity is tolerated in areas of high prey availability, such as below the hydroelectric facilities on Missouri and Mississippi Rivers (119). Wintering individuals require suitable perches for resting and roosting (such as tall trees) within 50 meters of foraging sites (119, 126, 127, 128, 114, 116).

Roosting Habitat

The presence of suitable roosting habitat significantly impacts where Bald Eagles choose to winter, and to a lesser extent, stop during migration. The use of roosts and their and characteristics has been extensively studied in the central and western United States (e.g., 118, 129, 130, 131, 127, 132), but there has been relatively little study on roost use and site characteristics for eastern populations except in New York (133), North Carolina (128), and Chesapeake Bay (134, 135).

Throughout its range, selects large, super-canopy trees that are open and accessible to roost in (129, 130, 136, 131, 128, 134, 137). Roost trees in eastern North America are deciduous or coniferous (118, 130, 128, 134), while most western roost trees are conifers (129, 136, 131, 137), except in some riparian zones (138, 139). Roost trees range in diameter from 30–110 cm and 15–60 m in height (18). The age of roost trees varies widely from old-growth trees in the Pacific Northwest that are 200–300 years old to trees in eastern United States that are 50–100 years old (136, 131, DAB).

Macro-scale roost-site characteristics differ in several significant ways from nest-site characteristics. The location of both roosts and nests are generally associated with aquatic foraging areas, but roosts need not be located as close to water as nests, especially in some western states. A roost site in Utah was 29 km from the major foraging area (140), and roost sites in the western United States were located > 10 km from foraging areas (129, 125, 141), except in northwestern Washington, where roosts are typically located proximate to salmon-bearing rivers (132). Roosts in North Carolina and the Chesapeake, in contrast, were < 1 km from aquatic foraging areas, in relatively large forested blocks but adjacent to large, open flight corridors for easy access (128, 134). Throughout the range, roost sites are located away from houses and roads (129, 125, 134).

The ultimate factors driving roost-site selection may be energetics, information exchange, as well as other social functions. Most roosts are located in areas that are somewhat protected from prevailing winter winds (129, 142, 141, 143). However, roost-site selection might also be affected by characteristics that facilitate social interaction such as information exchange (144). In Washington, Bald Eagles saved energy by selecting more protected coniferous sites < 4.0 km from foraging areas rather than roosting in less protected deciduous stands that were even closer (142). In the Klamath Basin of Oregon, Bald Eagle selected distant protected conifer roosts, but the energy savings did not offset cost of flying there, suggesting other benefits (141). In the northern Chesapeake Bay, Bald Eagles also did not save energy by flying back to the protected communal roosts at night, even though distances and flight costs involved were rather small (143).

Recommended Citation

Buehler, D. A. (2022). Bald Eagle (Haliaeetus leucocephalus), version 2.0. In Birds of the World (P. G. Rodewald and S. G. Mlodinow, Editors). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bow.baleag.02