Front Range Colorado Naturalist: Bald Eagles

American Bald Eagle

Haliaeetus leucocephalus

January is National Bald Eagle viewing month, and so to celebrate I think it’s a good time to write a blog about these beautiful birds!

Remember when viewing Eagles to try to avoid disrupting them! It is best to give them space so that they do not waste precious energy avoiding you, when they could be hunting prey.

IDENTIFICATION:

The bald Eagle in its adult form is a highly recognizable bird. The only eagle unique to North America, its large brown body and white head and tail make it easy to identify. From a distance, you may see it soaring, rarely flapping its wings, and holding its wings flat. It has yellow feet, legs and a yellow hooked bill.

It takes about five years for a juvenile eagle to get its adult plumage. Until then, they have mostly dark heads and tails, with mottled white in varying amounts.

HOW TO TELL THE DIFFERENCE BETWEEN A IMMATURE BALD AND GOLDEN EAGLE:

This is often difficult to distinguish. Golden eagles have smaller heads and are more streamlined, and will have a blonde or golden nape.

The immature Golden Eagles also have a mottled white color, and they have large white patches under the wings and a solid broad white band at the base of their tails that immature Bald Eagles do not have.

While Bald Eagles soar with their wings flat, Golden Eagles soar with their wings slightly raised.

Golden Eagles tend to live in more mountainous regions, and are not common in the Eastern part of North America.

FUN FACTS:

The Bald Eagle has been the national emblem of the United States since 1782
Because Bald Eagles often steal their prey from other birds, Ben Franklin disagreed with using the Bald Eagle as the National bird, suggesting the ‘noble’ turkey instead.
Bald Eagles are believed to mate for life.
Bald Eagles in the Northern parts of North America get to be much larger than Bald Eagles in Southern North America.
Bald Eagle nests are some of the world’s largest nests, the largest on record was 9.5ft wide and 20ft high. It weighed more than two tons!
Bald Eagles sometimes play, and one spectator has even seen these eagles passing sticks to each other in flight!
Bald Eagles can fly hundreds of miles a day searching for a place to call their own.
While typically solitary, Bald Eagles can congregate by the hundreds at communal roosts and feeding sites, especially during the winter when prey is scarce.
The female is larger than the male

MIGRATION:

In some places the Bald Eagles are residents and stay year round. In Colorado there are only a few places where there are year-round residents, and many migrate here during the winter to breed and then away again when spring arrives.

DIET:

Bald Eagles are mostly fish eaters, but they also eat mammals, waterfowl, and even carrion or garbage. They often will harass other birds and take their prey.

LIFE HISTORY:

Bald Eagles are thought to mate for life, and can live as long as 28 years in the wild and 36 years in captivity.

Mating season may be anywhere from late September to early April, depending on the region. They lay about 1-3 eggs, and the eggs incubate for 35 days.

Bald Eagles build some of the largest nests, and both male and female will bring materials to build the nest. The female, however, does most of the placement. Weaving together sticks and filling in the cracks with soft materials like grass, these nests are usually five to six feet in diameter and two to four feet tall.

The shape of the nest can also vary. Depending on the supporting tree, the nests can be round, flat or even conical.

The inside of the nest is lined with woody material like lichen, and then covered with soft material like downy feathers.

These nests can take up to three months to build, and are often reused and added to year after year.

Bald Eagles typically nest in trees, but in some areas they will make due when only cliff faces and ground sites are available. They tend to prefer tall sturdy pines that rise above the canopy, giving them easier flight access and visibility. It is unknown whether the male or the female choose the nest site.

Bald Eagles have some of the most amazing courtship dances, where they fly high into the sky and lock talons, where they then cartwheel downward together, breaking off at the last minute before crashing into the earth below.

BALD EAGLES AND DDT:

While Bald Eagles are now up to 5,000 nesting pairs in the lower 48 states, with roughly 70,000 estimated to be in North America, this number was as low as 500 nesting pairs in the lower 48 states.

DDT was a harmful pesticide that was being used on crops. The chemicals were washed off of crops, usually by rain, and made it into rivers and lakes where the chemicals built up in fish. When the eagles ate the fish, their main diet, and the chemicals weakened the eggshells and the young often did not hatch.

DDT was not restricted until 1972, and in 1978 Bald Eagles were protected under the Endangered Species Act. Since DDT’s restriction, Bald Eagles, along with many other birds of prey who were affected by DDT have made a tremendous comeback. By the late 1990s, breeding pairs of Bald Eagles can be found throughout most of North America again.

While Bald Eagle numbers have made a significant comeback, they are still most abundant in Alaska and Canada, where people compare them to nuisance birds like gulls because they are so common.

In June of 2007, Bald Eagles were removed from the Endangered Species list, and are now listed as least concern. This is a huge improvement for the Bald Eagles and a fantastic success story for a National Symbol that was almost driven extinct.

Bald Eagles are still facing human threats, such as car collisions, habitat loss, lead poisoning from hunter shot prey, and are still vulnerable to environmental pollution.