Threatened and Endangered Species - Status Reports
Date Published: October 2001
Number of Pages: 102
Author(s): Derek W. Stinson, James W. Watson and Kelly R. McAllister
The early summer population of bald eagles when white settlers first arrived in Washington may have been around 6,500. Persecution, the cutting of forests, commercial exploitation of salmon runs, and finally the use of DDT reduced the state’s population to only 105 known breeding pairs by 1980. Loss of wetlands, contamination of estuaries, and declines in water quality also probably have reduced the carrying capacity for eagles. The erection of >1,000 dams and the introduction of warm water fishes, however, has likely added nesting and wintering sites and produced changes in local distribution and abundance of eagles. The population has recovered dramatically with the ban on DDT use after 1972 and increased protection for eagles and eagle habitat. In the past 20 years, the population of nesting bald eagles grew about 10% per year as eagles reoccupied habitat. Based on a model, the population is predicted to reach carrying capacity at about 733 nesting pairs. In 1998, there were 664 occupied nests, and there are some indications that the population has reached carrying capacity in parts of western Washington. The population may still be increasing in northeastern Washington and along some western Washington rivers. Though the nesting habitat may be saturated around Puget Sound and other marine coasts, the total late spring/early summer population may continue to grow with an increase in the pool of non-breeding adults until all available food resources are exploited. If there is no decline in the number of nest sites, productivity, or survival, the population may stabilize around 4,400.
Comprehensive, statewide surveys of wintering eagles in Washington from 1982-89 counted 1,000-3,000 eagles in the state. The increasing trends in those surveys and in resident breeding birds predict a population of 3,200 winter visitors and a total winter population of about 4,500 bald eagles in Washington in the year 2000; this assumes that winter carrying capacity limits have not been reached. Statewide winter counts have not been conducted in recent years, and the carrying capacity is unknown. The number of resident breeders, and trends in localized winter counts suggest that Washington hosts perhaps 3,500 – 4,000 bald eagles each winter. Up to 80% of the eagles seen in mid-winter in Washington consists of migrants, largely from the Canadian provinces and Alaska. Wintering eagles will most benefit from protection of salmon runs and communal roosts, and managing human disturbance at eagle concentration areas.
Almost no late seral forest remains in the lowlands around Puget Sound, and eagles nest in small patches of residual large trees and second growth. The large trees along shorelines used by eagles are a diminishing resource, as more and more shoreline is dedicated to residential development. Only 1% of the Puget Sound Douglas-fir Zone is found on lands dedicated to the conservation of biodiversity. Conservation of bald eagle nesting habitat is difficult because 80% of the land within ½ mile of shores is privately owned, and contains desirable view property. Two thirds of the aggregate land within eagle territories and two thirds of eagle nests are on private lands. The state bald eagle protection rule (WAC 232-12-292) requires a management plan for development, forest practices, or potentially disturbing activities on state and private lands near eagle nests and roosts. Over 1,200 management plans have been signed by Washington landowners since 1986. There are indications that some eagles in Washington, and other states, have become fairly tolerant of human activity near nests. Most eagles, particularly those in rural areas, remain rather sensitive to disturbance during nesting.
The U.S. Fish and Wildlife Service is expected to remove the bald eagle from the federal list of threatened and endangered species in 2001. Bald eagles will still be protected by the Bald and Golden Eagle Protection Act and the Migratory Bird Treaty Act. The Bald and Golden Eagle Protection Act also prohibits disturbance or molesting of eagles. Despite state and federal protection, a large percentage of fatalities of adult bald eagles have human related causes, including shooting, poisoning, vehicle collisions, and electrocution, and a black market trade in eagle feathers and parts still exists.
Although the breeding population of bald eagles in Washington has increased dramatically in the past 20 years, two thirds of nests are on private lands. Only about 10% of eagle nests are on lands where their habitat values could be considered secure in the absence of habitat protection rules. Land near shores is highly desirable for residential development and the human population of Washington is expected to increase by 2 million to 7.7 million in the next 20 years, and double to 11 million by 2050. Forest near shores is rapidly being cleared, and the needs of eagles and desires of humans are increasingly in conflict. Without protections of nesting and roosting habitat, the bald eagle could again decline dramatically and require re-listing as threatened or endangered in the state. For these reasons we recommend that the bald eagle be down-listed to sensitive, but not de-listed, in the State of Washington, and that the bald eagle protection rule be amended to apply to a Sensitive species.
Stinson, D. W., J. W. Watson, and K. R. McAllister. 2001. Washington state status report for the bald eagle. Washington Dept. Fish and Wildlife, Olympia. 92 pp.
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