The bald eagle is one of the largest birds of prey found in North America. It is the national bird and symbol of the United States of America. This sea eagle has two known sub-species and forms a species pair with the white-tailed eagle. Its range includes most of Canada and Alaska, all of the contiguous United States, and northern Mexico. Bald eagles typically can be found near large bodies of open water with an abundant food supply and old-growth trees for nesting. In Channel Islands National Park, due to the persecution by humans and the effects of organochlorine chemicals such as DDT, breeding bald eagles were eliminated by the mid-1950's. In an innovative reintroduction program conducted 2002 and 2006, sixty-one young bald eagles were released on the northern Channel Islands.
Quick and Cool Facts
Historical records indicate that in the early 20th century bald eagles bred on all islands within the park, with at least two dozen nesting pairs over the 8 Channel Islands. Breeding bald eagles provided important ecosystem functions in the northern Channel Islands. For example, bald eagles were once the top marine aerial predator and probably fed upon a variety of seabirds and fish. Bald eagles are generally highly territorial, and in the past this behavior may have prevented golden eagles from colonizing the islands. Due to the persecution by humans and the effects of organochlorine chemicals such as DDT, breeding bald eagles were eliminated by the mid-1950's. In an innovative reintroduction program conducted 2002 and 2006, sixty-one young bald eagles were released on the northern Channel Islands. Bald eagles have also been reintroduced on Santa Catalina Island
Fishing is a learned behavior for the bald eagle, and so juvenile eagles spend their first year eating carrion (carcasses) until they become proficient at fishing (Dooley et al. 2005). Prey remains from bald eagle nests on Santa Catalina Island contained almost 90% fish (Newsome etal. 2010), but an historic bald eagle nest on San Miguel contained more bird remains than fish (Collins et al. 2005). The abundance of seabirds and pinnipeds on the northern Channel Islands means eagles likely take advantage of those resources more than in other areas. This could pose a problem for recovery of bald eagles on the northern Channel Islands (see below), because pinniped sand seabirds contain more DDE than do marine fish, due to bioaccumulation at higher trophic levels.
On the Channel Islands, where large trees are scarce, bald eagles have built nests on cliff faces, rock shelves and shallow cliffs, as well as in island pines and Torrey pines. One pair even attempted nesting in a grassland on Santa Cruz Island.
Bald eagles build some of the largest of all bird nests—typically5 to 6 feet in diameter and 2 to 4 feet tall and ranging in shape from cylindrical to conical to flat, depending on the supporting tree. Both sexes bring materials to the nest, but the female does most of the placement. They weave together sticks and fill in the cracks with softer material such as grass, moss, or cornstalks. The inside of the nest is lined first with lichen or other fine woody material, then with downy feathers and sometimes sprigs of greenery. Ground nests are built of whatever's available, such as kelp and driftwood near coastal shorelines. Nests can take up to three months to build, and may be reused (and added to) year after year. The female lays one to three eggs with a usual clutch size of two eggs. The eggs are incubated for approximately 35 days, and the young eagles fledge 10 - 12 weeks after hatching. Bald eagles become sexually mature at five to six years with maturity usually corresponding to when their head and tail feathers become white.
In 2002, with funding from the Montrose Trustees
Restoration Program, the park (in conjunction with partner, Institute for Wildlife Studies) began to
introduce juvenile bald eagles to the northern
Today, bald eagles are again an important part of the island ecosystem. 2006 marked the first successful bald eagle nest on the Channel Islands in over 50 years, and since that time, the recovering bald eagle population on the islands has grown. As of 2013 there were five breeding pairs on Santa Cruz Island, two on Santa Rosa, and one on Anacapa, and a total of over 40 bald eagles on the northern Channel Islands.
Recovery of bald eagles on the northern Channel Islands was seen as critical to recovery of the endangered island fox, since nesting bald eagles might dissuade dispersing golden eagles (Aquila chrysaetos) from establishing breeding territories on the islands (Coonan et al. 2010). Golden eagle predation was responsible for the massive decline of island foxes on the northern Channel Islands in the 1990s.
In June 2007, the bird's recovery prompted its removal from the Endangered Species list. Continuing threats to bald eagle populations include lead poisoning from ammunition in hunter-shot prey, collisions with motor vehicles and stationary structures, and development-related destruction of shoreline nesting, perching, roosting and foraging habitats.
Based upon information of population trends, the IUCN Red List of Threatened Species has listed the bald eagle a species of Least Concern and current data demonstrates that the population is presently increasing.
Did You Know?
The Channel Islands are home to the most well-preserved archeological sites on the Pacific coast, with more than 10,000 years of continuous human occupation recorded.