Few places in the contiguous United States offer a better opportunity to observe breeding bald eagles than Washington’s San Juan Islands. Surrounded by the productive waters of the Salish Sea, the archipelago supports one of the highest concentrations of nesting bald eagles in the lower 48 states, making it one of North America’s best locations for eagle watching.
The San Juan Islands are an archipelago of more than 450 islands, rocks, and pinnacles located off the northwestern coast of Washington, just east of Vancouver Island, British Columbia. In recognition of their ecological and cultural significance, President Barack Obama designated the islands as the San Juan Islands National Monument in 2013.
The photograph above, captured from the International Space Station, shows the San Juan Islands between Washington and Vancouver Island in the Salish Sea. The Haro Strait separates the islands from Canada, while the Olympic Mountains rise to the south. The islands’ productive marine waters, protected shorelines, and diverse habitats create ideal conditions for breeding bald eagles.
Bald eagle populations have rebounded
The bald eagle is found only in North America, with the largest populations occurring in Alaska and Canada. Alaska alone is home to an estimated 50,000 bald eagles and supports about 75% of the nation’s breeding pairs.
A 2020 survey by the US Fish and Wildlife Service estimated there are approximately 316,700 individual bald eagles in the lower 48 states, including 71,400 nesting pairs. The recovery of the bald eagle is considered one of the greatest wildlife conservation success stories in the United States.
Just a few decades ago, the outlook for bald eagles was far different. By 1963, only 417 nesting pairs remained in the United States. The widespread use of the pesticide DDT caused eggshells to become too thin to withstand incubation, leading to widespread nesting failures and a dramatic population decline.
The bald eagle was listed under the Endangered Species Preservation Act in 1967, followed by protections under the Endangered Species Act of 1973. After the ban on DDT and decades of habitat protection and conservation efforts, bald eagle populations steadily recovered. In 2007, the species was removed from the federal list of threatened and endangered species.
Why bald eagles thrive in the San Juan Islands
The San Juan Islands provide ideal breeding habitat for bald eagles (Haliaeetus leucocephalus). More than 125 nesting pairs have been documented across the archipelago, reflecting the islands’ abundant food resources and suitable nesting habitat.
The surrounding waters of the Salish Sea provide a rich and reliable food supply. Bald eagles feed on salmon and other fish, seabirds, and waterfowl along the coast. Inland, they hunt rabbits, voles, and snakes. They also readily scavenge carrion and steal prey from other birds when the opportunity arises.
Rabbit populations are especially important to the island’s breeding eagles. During the rabbit plague of the 1970s and early 1980s, rabbit numbers declined sharply, and the bald eagle population also fell. The close relationship between predator and prey illustrates how changes in one species can ripple through an ecosystem.
Although many bald eagles remain on the islands throughout the year, others migrate after the breeding season, causing the local population to decline during the winter months.
Where do bald eagles gather during winter?
Although the San Juan Islands are best known for their breeding population, one of the largest concentrations of wintering bald eagles outside Alaska occurs in the Klamath Basin along the California-Oregon border.
Each November, bald eagles migrate to the basin from across western North America, including Canada and Glacier National Park. The region’s extensive wetlands support large numbers of wintering ducks, geese, and other waterfowl, providing a dependable food supply.
Bald eagles are accomplished hunters, but they are also opportunistic scavengers. During winter, they frequently feed on ducks and geese that have died from disease, injury, or natural causes, allowing the birds to conserve energy while food is abundant.
Bald eagle numbers typically peak during January and February, when more than 500 eagles may gather in the Klamath Basin.
References
National Park Service. (n.d.). Bald eagles. San Juan Island National Historical Park. https://web.archive.org/web/20230128024133/https://www.nps.gov/sajh/learn/nature/bald-eagles.htm
Retfalvi, L. S. (1970). Food of nesting bald eagles on San Juan Island, Washington. The Condor, 72(3), 358-361. https://doi.org/10.2307/1366014
Siegel, R. B., Wilkerson, R. L., Pedersen, H. K., & Kuntz II, R. C. (2009). Landbird inventory of San Juan Island National Historical Park (2002). Natural Resource Technical Report NPS/NCCN/NRTR—2009/156. National Park Service. https://irma.nps.gov/DataStore/DownloadFile/444445
U.S. Fish and Wildlife Service. (2021). Bald eagle population size: 2020 update. Division of Migratory Bird Management. https://www.fws.gov/sites/default/files/documents/2020-bald-eagle-population-size-report.pdf
This article was original published in January 9, 2022 and has since been updated.
