The word "bald" in bald eagle is shortened from the word "piebald" which means spotted or patched, especially in black and white. Piebald is a fitting description for the bald eagle because of its dark body and white head and tail (Cornell Lab of Ornithology 2003).
In 2007, there were approximately 122 occupied bald eagle nest sites of which 34 failed (did not fledge young). There are many sites on public land. During the non-breeding season, Bald Eagles are found throughout the state, but they tend to concentrate at wintering areas and roosts at about four open water sites in the state. While breeding and wintering populations are increasing in New York they are still faced with many threats including development, human disturbances, contaminated food base, collision with high speed trains, towers, wind generators, and electrical lines.
The number of breeding and wintering Bald Eagles has been increasing since the 1970s when the population was at one breeding pair. The pair often failed at nesting attempts apparently because of thin egg shells (Nye 1982). The population increase in recent years has been accomplished through protection and active management, as well as through enhanced reproduction after the DDT ban. The Department of Environmental Conservation started a reintroduction program that involved egg transplants, fostering, and hacking (hand rearing and releasing older nestlings in the absence of adult birds). Hacking proved to be the most successful in 1976 and 1988. A total of 198 nestlings were released at four sites in the state. Thirty-two of those birds did not survive; 16 were illegally shot (Levine 1998). In 1980 two hacked birds nested in Jefferson County. In 2007, there were 122 active breeding pairs and a total of 151 young fledged in the state (Nye 2007). In addition, there are many immatures and non-breeding adults that reside in New York during the spring and summer months. Between 2002 and 2007, 324-442 wintering birds were counted at the four main areas where the birds concentrate. The numbers likely vary based on the severity of winter weather. It is not certain how stable the Bald Eagle population is in New York at this time. The trends are mostly dependant on how much Bald Eagles will be affected by habitat loss and alterations due to development. Confirmed breeding was reported from two blocks during the first Breeding Bird Atlas. A dramatic increase is noted with the second Breeding Bird Atlas with 124 blocks with confirmed breeding (Andrle and Carroll 1988, McGowan and Corwin 2008). Breeding Bird Survey trend data is not available for Bald Eagles.
The earliest records of nesting Bald Eagles are from the late 1800s when breeding was documented in Essex, Erie, Jefferson, and Dutchess counties, although Bald Eagles were most likely present in New York before then. Between 1860 and 1960 there were 72 verified Bald Eagle nest sites in New York. Of the 72 nests, some were alternate nest sites and not all of the nests were occupied each year (Andrle and Carroll 1988). The population decline began before World War II for a number of reasons including habitat loss, increased human disturbances, and illegal shootings (Levine 1998). In 1946, DDT, an agricultural pesticide, was in widespread use. At the onset of DDT use the Bald Eagle breeding population was at approximately 20 pairs (Levine 1998). Runoff from areas sprayed with DDT made its way into the aquatic ecosystem. DDT accumulated in the tissues of fish and eventually poisoned Bald Eagles. DDT and its breakdown products caused egg shell thinning in Bald Eagles and many other raptor species. As a result, birds incubating eggs often broke the egg shells before the eggs hatched. By 1972, when DDT use was banned in the United States, only one breeding pair remained in New York and the pair rarely fledged young. Since then Bald Eagle populations have been recovering with 122 known active breeding pairs in New York in 2007. Breeding Bird Survey trend data is not available for Bald Eagles (Sauer et al. 2007). There is some uncertainty on what the future holds for this species in New York because of various anthropogenic factors (McGowan and Corwin 2008 and Nye 2005).
While Bald Eagle breeding and non-breeding populations are increasing in New York, there are still significant threats to the persistence of this species in the state. Habitat loss or alterations are probably the most significant threats. Many parts of New York are under high development pressure. This species prefers relatively undisturbed, wooded areas near wetlands or large bodies of water with abundant prey (fish). Areas with development or other human disturbances would likely be unsuitable for nesting and wintering Bald Eagles. Habitat destruction has been more extensive in the Bald Eagle wintering range (Nye 1994). Disturbance to wintering birds can be especially detrimental because it may deplete the birds' energy reserves. Bald Eagles spend most of the winter sedentary (approximately 99%); energy is reserved for foraging, feeding, thermoregulation, and other essential activities (Nye 1994). Depleted energy may result in a drop in an individual's reproductive rate for the year, or death (Nye 1994). In addition, if a feeding bald eagle is disturbed it may abandon its food and most likely will not return to the area for the rest of the day. Banning DDT has greatly increased the reproductive health of bald eagles, but there are many other contaminants that continue to affect the reproductive success of adult pairs such as lead, mercury, and PCBs. Other threats include vehicular collisions (such as high speed trains), and collisions with towers, wind generators, and electrical lines (McGowan and Corwin 2008 and Nye 2005).
Human disturbances should be minimized at breeding and wintering sites. Pedestrians can be more disturbing to Bald Eagles than some motorized vehicles (Nye 1994). A 500 meter buffer around the nest may be adequate (NatureServe 2005). A minimum buffer of 250-300 meters is recommended for perch and feeding sites; others have recommended a greater distance (Nye 1994). It may be beneficial to post signs and restrict access to areas when breeding or wintering Bald Eagles are present. Vegetative buffer zones may help minimize some disturbances associated with development (Nye 1994). Avoid the addition of new, tall structures such as wind-generators, towers, and electrical lines near breeding and wintering locations.
Determine the essential Bald Eagle breeding and wintering habitats through field observations and radio telemetry. Collect more data about site fidelity, familial relationships to habitat use, migratory patterns/pathways, and home ranges of breeding and wintering Bald Eagles in New York. Sample for contaminant loads periodically (Nye 2005).
Bald Eagles are typically found near large bodies of water, such as bays, rivers, and lakes, that support a healthy population of fish and waterfowl, their primary food source. Generally, Bald Eagles tend to avoid areas with human activities. They will perch in either deciduous or coniferous trees. Large, heavy nests are usually built near water in tall pine, spruce, fir, cottonwood, oak, poplar, or beech trees. Non-breeding adults and wintering birds are known to have communal roost sites. During the winter, the roost sites may be farther away from food sources. This may be due to the need for a more sheltered, warmer area. Feeding areas during the winter months usually have a high concentration of fish and waterfowl and open water (NatureServe 2005).
Bald Eagles breed throughout New York State, usually in areas with large bodies of water that support high fish populations. They are absent from Long Island, where they were known historically, at this time. Wintering areas are concentrated in four main areas: the Upper Delaware River, the Saint Lawrence River, the Lower Hudson River, and the Sacandaga River.
Breeding: Bald Eagles breed near water from Alaska throughout Canada and in scattered areas throughout the United States. Within the United States, they are very local breeders in the Great Basin and prairie and plains regions in interior North America, where the breeding range recently has expanded to include Nebraska and Kansas. Small numbers of breeding pairs have been found in Mexico. Non-breeding: Generally, non-breeding Bald Eagles are found throughout the breeding range except in the far north (AOU 1983 cited in NatureServe 2005, Sibley and Monroe 1990 cited in NatureServe 2005). Most commonly they are found from southern Alaska and southern Canada southward. The Chilkat Bald Eagle Preserve in Alaska supports the largest wintering population anywhere (Ehrlich et al. 1992 cited in NatureServe 2005). Winter concentrations occur in British Columbia-northwestern Washington, along the Missouri and Mississippi rivers, and in northern Arkansas. One of the largest fall (mid-October to mid-December) migrant concentrations (200-300 birds at any one time, close to a thousand individuals through the season) occurs at Hauser Lake near Helena, Montana.
Adult bald eagles can easily be identified by their white head, white tail, and large, bright yellow bill. The plumage is otherwise dark. Immature bald eagles are dark with variable amounts of light splotching on the body, underwing coverts, flight feathers, and tail base. They have a grey bill. Adult plumage and a yellow bill are attained at four to five years of age. The average size of an adult is 79-94 cm (31-37 inches) long with a wingspan of 178-229 cm (70-90 inches) (National Geographic Society 1987). Bald eagle nests are built near the top of sturdy, tall trees. The nest is a flat-topped mass of sticks that is lined with fine vegetation such as rushes, grasses, and mosses. Each year, the breeding pair adds to the nest resulting in a massive nest that can be seven to eight feet across and weigh up to several tons. Eggs are slightly smaller than a domestic goose egg and are dull white. Their call has been described as a harsh cackle, kleek-kik-ik-ik-ik or a lower kak-kak-kak.
At approximately 5 years of age, Bald Eagles reach sexual maturity. They typically mate for life, but exceptions are noted. Courtship displays can be observed late winter to early spring and involve elaborate aerial displays; the pair will dive with locked talons. Males and females build nests together and continue to add sticks each breeding season. In addition, the pair incubates and cares for young together. However, the female takes on most of this responsibility. After the breeding season, Bald Eagles are often found at communal roosts and feeding areas.
The Bald Eagle's primary food sources are fishes, injured waterfowl and seabirds, various mammals, and carrion. They are opportunistic feeders; they will hunt live prey, scavenge, and pirate food from other birds.
Concentrations of Bald Eagles can be found in New York during the winter months. In southeastern New York, Bald Eagles begin arriving on the wintering area in early November and are most abundant in February. During late February to early March, Bald Eagles are moving to their breeding territories.
The time of year you would expect to find Bald Eagle active and reproducing in New York.
Haliaeetus leucocephalus (Linnaeus, 1766)
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Information for this guide was last updated on: January 2, 2008
Please cite this page as:
New York Natural Heritage Program. 2019. Online Conservation Guide for Haliaeetus leucocephalus. Available from: https://guides.nynhp.org/bald-eagle/. Accessed January 18, 2019.