Golden Eagle

Tony Hisgett
 

Scientific Name
Aquila chrysaetos

Introduction
The golden eagle is one of the largest, fastest, and nimblest raptors in North America. Lustrous gold feathers gleam on the back of its head and neck;a powerful beak and talons advertise its hunting prowess. Although they had never bred historically on the Channel Islands, golden eagles were able to colonize the northern Channel Islands in the mid 1990s due to the presence of an alien prey base (feral pigs and mule deer fawns) and the absence of the native bald eagle, extirpated from the islands by chemical contaminants and by direct persecution. Golden eagles also preyed on the vulnerable island fox, nearly driving foxes to extinction. Subsequent conservation efforts successfully relocated golden eagles to the mainland, and restored bald eagles to the Channel Islands, helping to bring back the island fox from the brink of extinction.

Quick and Cool Facts

  • The golden eagle is the most common official national animal in the world, being the emblem of Albania, Germany, Austria, Mexico, and Kazakhstan.
  • Golden eagles are important to many Native American cultures, which include the bird and its feathers in ceremonies.
  • Golden eagles are not typically found in the densely populated eastern portion of the United States, but are found instead in the rugged solitude of the sparsely populated western U.S.
  • Although capable of killing large prey such as cranes, wild ungulates, and domestic livestock, the golden eagle subsists primarily on rabbits, hares, ground squirrels, and prairie dogs.
  • Golden eagles possess astonishing speed and maneuverability for their size. Diving from great heights, they have been clocked at close to 200 miles per hour.
  • Nests are huge, averaging some 5-6 feet wide, and 2 feet high, enclosing a bowl about 3 feet by 2 feet deep. The largest golden eagle nest on record was 20 feet tall, 8.5 feet wide.

Appearance
The golden eagle is a large, dark brown raptor with broad wings. Its size is variable: it ranges 28-33 inches in length, has a wingspan of 6-7 feet , and weighs 7 to 13 pounds.Sexes are similar in plumage but display the typical reversed sexual dimorphism of raptors, in which the female is much larger than the male.Adults are primarily brown, with gold on the back of the crown and nape, and some grey on the wings and tail. Tarsal feathers range from white to dark brown. In addition, some birds have white epaulettes on the upper part of shoulder feathers on each wing.The bill is dark at the tip, fading to a lighter horn color, with the waxy top of the beak, called a cere, colored yellow.

Range
Golden eagles can be found throughout much of the northern hemisphere, typically in sparsely populated areas

Habitat
The golden eagle seeks open areas with large, rocky cliffs or large trees, such as pines, cypress or sycamores. They are often found in alpine parkland, open forests and mid-elevation clear-cuts, as well as in chaparral or plains areas.

Feeding
The golden eagle's predominant prey in North America are medium-sized mammals such as rabbits and ground squirrels. Other species, such as foxes, martens, young deer are also taken. Ranchers have historically battled the eagle because of its ability to prey upon small livestock such as lambs and small goats. In Channel Islands National Park, predation by the golden eagle on the endemic island fox brought the latter close to extinction, with golden eagle breeding on the islands supported by feral pigs on Santa Cruz Island and deer on Santa Rosa Island Other important prey include birds; indeed,virtually any bird, from jays to swans, are potential prey. Golden eagles also r steal prey from other raptors. While not as large as some vultures, golden eagles are capable of driving vultures and other raptors from carrion. Golden eagles are avian apex predators, meaning they make their living at the top of the food chain (nothing preys on a golden eagle).

Reproduction
Golden eagles usually mate for life. They build several eyries within their territory and use them alternately for several years. These nests consist of heavy tree branches, upholstered with grass when in use. Old eyries may be quite large as the eagles repair their nests whenever necessary and enlarge them during each use. If the eyrie is situated on a tree, supporting tree branches may break because of the weight of the nest. The female usually lays two eggs between January and September, depending on the locality. The eggs vary from all white to white with cinnamon or brown spots and blotches. They start incubation immediately after the first egg is laid, and after 40 to 45 days the young hatch. They are covered in fluffy white down and are fed for fifty days before they are able to make their first flight attempts and eat on their own. In most cases only the older chick survives, while the younger one dies without leaving the eyrie. This is due to the older chick having a few days' advantage in growth and consequently winning most squabbles for food. This strategy, called asynchronous nesting, is useful because it makes the parents' workload manageable even when food is scarce, while providing a reserve chick in case the first-born dies soon after hatching. Golden eagles invest much time and effort in bringing up their young; once able to hunt on their own, most golden eagles survive many years, but mortality even among first-born nestlings is much higher, in particular in the first weeks after hatching.

Migration
Some golden eagles live in their nesting territory all year. Others may migrate due to lack of food during the winter. As a rule, they do not have to migrate large distances because of their excellent hunting abilities.

Golden Eagle Status in the Park
From 1999 through 2006, golden eagles were live-trapped and removed from the park, because golden eagle predation was the primary source of mortality for island foxes and was responsible for the massive island fox decline from 1994–2000.

Until the 1990s, golden eagles never bred on the Channel Islands. Golden eagles nested on both Santa Cruz and Santa Rosa Islands from the mid-1990s to as recently as 2006. They were able to colonize the islands because of several factors. First, bald eagles were absent from the Channel Islands, having disappeared by the mid-20th century due to both human persecution and the presence of DDT in the environment. Territorial bald eagles may have deterred goldens from establishing. Second, golden eagles arriving on the islands found food sources that were not available prior to the ranching era: feral pigs on Santa Cruz Island, and mule deer on Santa Rosa.

In order to mitigate golden eagle predation on island foxes, The Santa Cruz Predatory Bird Research Group, with the support of the Park Service and The Nature Conservancy, relocated golden eagles to distant sites on the California mainland. A total of 44 golden eagles, including 10 eaglets born on the islands, were trapped and relocated, and monitoring indicates that none have returned.

Other ecosystem-wide actions, such as the removal of feral pigs from Santa Cruz Island and the restoration of bald eagles, have tipped the balance in favor of island foxes and away from continued golden eagle use of the islands. As of 2009 the occasional golden eagle visits the islands, but the level of predation on island foxes is negligible;all three island fox subspecies in the park are recovering rapidly.

Conservation Status
In North America the situation is not as dramatic as it has been in in temperate Europe, North Asia, North Africa, and Japan, but there has still been a noticeable population decline. The main threat is habitat destruction which by the late 19th century already had driven golden eagles from some regions they used to inhabit.In the 20th century, organochloride and heavy metal poisonings were also commonplace, but these have declined thanks to tighter regulations on pollution. Within the United States, the golden eagle is legally protected by the Bald and Golden Eagle Protection Act. Available habitat and food are the main limiting factor nowadays. Collisions with power lines have become an increasingly significant cause of mortality since the early 20th century. On a global scale, the golden eagle is considered by the IUCN as of least concern,thanks mainly to the large Asian and American populations.

Additional Information

Last updated: June 28, 2016

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