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Bald Eagle

Photo of American Bald Eagle (USFWS)

Scientific name: Haliaeetus Leucocephalus 

Status:  Delisted (USA, lower 48 states)

  •  Historical Status and Current Trends

    The bald eagle is the only eagle unique to North America. It ranges from central Alaska and Canada down to northern Mexico. The majority of nesting bald eagles in Oregon occur in the following areas: Columbia River below Portland, the Oregon coast and Coast Range, the High Cascades, Klamath Basin, and the upper Willamette River Basin. A nesting survey found 401 breeding pairs in Oregon and 40 on the Washington side of the Columbia River in 2002. Population goals in eight of 10 recovery zones in Oregon have been met or exceeded. Wintering bald eagles are found throughout the State but concentrations occur in areas with dependable food supplies such as Klamath and Harney Basins and along the Snake and Columbia Rivers.

    Habitat Associations

    Breeding. Bald eagle nest site selection varies widely from deciduous, coniferous, and mixed forest stands. Nest trees are usually large diameter trees characterized by open branching and stout limbs. Nests are in dominant or codominant trees often located near a break in the forest such as a burn, clearcut, field edge (including agricultural fields), or water. The majority of nest sites are within 1/2 mile of a body of water such as coastal shorelines, bays, rivers, lakes, farm ponds, dammed up rivers (i.e., beaver dams, log jams, etc.) and have an unobstructed view of the water. Bald eagle habitat occurs primarily in undeveloped areas with little human activity.

    Wintering. Winter foraging areas are usually located near open water on rivers, lakes, reservoirs, and bays where fish and waterfowl are abundant, or in areas with little or no water (i.e., rangelands, barren land, tundra, suburban areas, etc.) where other prey species (e.g., rabbit, rodents, deer, carrion) are abundant. Communal roost sites contain large trees (standing snags and utility poles have also been used) with stout lower horizontal branches for perching and may be used at night by three to greater than one hundred bald eagles, as well as during the day, especially during inclement weather. Perch trees used during the day possess the same characteristics as roost trees but are located closer to foraging areas.

    Life History. As our national symbol, the bald eagle is widely recognized. Its distinctive white head and tail do not appear until the bird is four to five years old. These large, powerful raptors can live for 30 or more years in the wild and even longer in captivity. Bald eagles may range over long distances, although adults may remain near their territories if adequate forage is available year round. They build huge nests near the tops of tall trees in January and February. While only one nest is used at a given time, a pair may build more than one nest within their territory. Nests are often reused year after year, and with additions made annually, the nests can become enormous. Bald eagles lay one to four eggs in late March or early April and both adults incubate the eggs for about 35 days until hatching. During the nest-building, egg laying and incubating periods, eagles are extremely sensitive and will abandon a nesting attempt if there are excessive disturbances in the area during this time. The eaglets are able to fly in about three months and then, after another month, they are on their own. The first year is particularly difficult for young eagles. Only half may survive the first year due to disease, lack of food, bad weather, or human interference.

    Food Habits

    The bald eagle is an opportunistic predator that feeds primarily on fish but also takes a variety of birds, mammals, and turtles (both live and as carrion) when fish are less abundant or these other species are readily available. Waterfowl are the most common avian prey, but shorebirds and landbirds are also eaten. A variety of mammals are also taken as prey, although mammals are less important than fish and birds. Mammals are taken as live prey or carrion in all seasons but become more important during the winter months.

    Reasons for Decline

    The major factor leading to the decline and subsequent listing of the bald eagle was disrupted reproduction resulting from contamination by organochlorine pesticides. Other causes of death in bald eagles have included shooting, electrocution, impact injuries, and lead poisoning. Loss of habitat and human disturbance are potential threats. Habitat loss results from the physical alteration of habitat as well as from human disturbance associated with development or recreation (i.e., hiking, camping, boating, and off-road-vehicle use). Activities that can and have negatively impacted bald eagles include logging, mining, recreation, overgrazing (particularly in riparian habitats), road construction, wetland filling, and industrial development. These activities, as well as suburban and vacation home developments, are particularly damaging when they occur in shoreline habitats. Activities that produce increased siltation and industrial pollution can cause dissolved oxygen reductions in aquatic habitats, and reductions in bald eagle fish prey populations followed by reductions in the number of eagles. Not all developments in floodplain habitats are detrimental to bald eagles, as some reservoirs and dams have created new habitat with dependable food supplies.

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