Greatest Concentration of Breeding Bald Eagles in the Contiguous U.S.

| |

The San Juan Islands form an archipelago just east of Vancouver Island in the United States. The islands are part of the state of Washington in the Pacific Northwest. There are over  450 islands, rocks, and pinnacles that form San Juan Islands.

President Barack Obama designated the islands as a national monument in 2013 due to the archipelago’s ecological and cultural significance.

This image captured from the International Space Station shows the location of the San Juan Islands. The orientation of the photograph has north to the left.

The San Juan Islands are located in the Salish Sea, a marginal sea of the Pacific Ocean. The Haro Strait is between the San Juan Islands located in Washington, United States and Vancouver Islands located in British Columbia, Canada.

The Olympic Mountains are just south (to the right in this photograph) of the San Juan Islands. The mountains of part of Olympic National Park which was designated as a national park in 1938 by President Franklin D. Roosevelt.

A photograph taken from the International Space Station of the San Juan Islands archipelago.
The San Juan Islands archipelago can be seen in the middle of the photograph taken from the International Space Station. North is oriented to the right in this photograph. Image: NASA, public domain.

A North American Bird

The bald eagle is found only in North America. The largest populations of bald eagles are found in Alaska and Canada. Alaska is has the highest population overall of bald eagles in the United States with an estimated 1999 population of 50,000 birds and is home to about 75% of the country’s breeding pairs.

In the lower 48 states, a 2020 survey estimated that there are 316,700 individual bald eagles, including 71,400 nesting pairs.

A bald eagle sitting on a jagged tree stump next to the ocean.
Bald Eagle on a broken tree on Juneau Beach, Juneau, Alaska. Photo: Brian Uher-Koch, USGS, public domain.

This is a remarkable recovery of the bald eagle population in the contiguous United States. In 1963, only 417 nesting pairs of bald eagles were still in existence as a result of a decline in their prey and softening of bald eagle eggs from DDT, a pesticide. In 1967, the bald eagle was listed under the Endangered Species Preservation Act of 1966 and delisted in 2007.

Largest Breeding Population of Bald Eagles

San Juan Island in Washington is home to the densest population of breeding bald eagles (Haliaeetus leucocephalus) in the contiguous United States. The last inventory counted 154 breeding pairs of bald eagles.

While many of the bald eagles that breed on San Juan Island are migratory, the island is also home to resident bald eagles.

Many of the bald eagles live on the north and northwest side as the light is more favorable for hunting.

Bald eagle flies away from the surface of the water with spray flying behind it. It grasps a fish in its talons.
A bald eagle in flight over the open waters with a fish in its talon. Photo: K. Smith / NPS, public domain.

The island offers many sources of food that makes the island attractive to breeding bald eagles. Bald eagles feed on salmon and other fish, seabirds, and waterfowl in the sea to the west of the island. Inland, bald eagles hunt rabbits, voles, and snakes to feed upon.

Bald eagles are are known to steal other prey from other animals.

Bald eagles on San Juan Island rely on rabbit populations for much of their food. When a plague decimated the rabbit population in the 1970s and early 1980s, the bald eagle population also plummeted.

In the winter, the population of bald eagles drops as birds migrate.

Highest Concentration of Wintering Bald Eagles

During the winter, the highest concentration of wintering bald eagles outside of Alaska can be found at The Klamath Basin Refuges. Each year starting in November, bald eagles migrate to the Klamath Basin located in southern Oregon and Northern California.

Bald eagles arrive from as far away as Canada and Glacier National Park. The extensive marshes found in the Klamath Basin offer the bald eagle an abundant food source in the form of wintering waterfowl.  Despite being apex predators, bald eagles tend to prefer hunting for their meal the easy way. Injuries, weakness, and diseases leads to a significant number of dead ducks and geese, making it easy for the bald eagles to find food.

During January and February, bald eagle populations peak at over 500 birds in Klamath Basin.

References

Bald eagle. (2015, March 30). NPS.gov (U.S. National Park Service). https://www.nps.gov/sajh/learn/nature/bald-eagles.htm

Retfalvi, L. (1970). Food of nesting bald eagles on San Juan Island, Washington. The Condor72(3), 358-361. https://doi.org/10.2307/1366014

Wildlife. (n.d.). San Juan Island Chamber of Commerce – Friday Harbor, Washington. https://www.sanjuanisland.org/wildlife.html

Related

Share:


Enter your email to receive the Geography Realm newsletter: