 |
|
Because it can soar almost forever, the American bald eagle is a symbol of freedom. That’s why it also became a symbol of the United States.
The bald eagle population decreased in the 1960s due to the use of DDT as a pesticide. When the mother bird ingested DDT, the pesticide produced a brittle shell on the egg. The eggs did not survive to hatching, resulting in the decline of the bald eagle population.
Bald eagles were recently reclassified from endangered to threatened, which means that their numbers are increasing in the wild.
Physical Characteristics
The bald eagle is the largest bird of prey in Massachusetts, with a wingspan of 7 feet. It’s unusual in that the female is the larger of the species, weighing 10 to 14 pounds, compared to 7-9 pounds for the male.The bird’s skeleton weighs only about half a pound, while the feathers weigh twice as much.
Adults have a blackish-brown body with the distinctive white head, neck, and tail. The curved bill and the feet are yellow. It takes four to five years for the bald eagle to develop its characteristic plumage of a white head and tail.
Food and Diet
Their diet consists of fish, waterfowl, and carrion.
The eagle’s eyesight is legendary. It can spot a rabbit nearly a mile away, from an altitude of 1,000 feet. It can also sight fish swimming below the surface of the water.
When hunting fish, the eagle usually approaches in a shallow glide and uses a quick strike with its sharp talons to snatch the prey from the water. Sometimes, the bald eagle will actually dive into the water to catch a fish, and it then swims with its wings to gather enough speed for takeoff.
Life Cycle
Eagles mate for life. They pair off when they’re 4 or 5 years old to build a nest in a large tree or on a cliff. The same nest may be used year after year. One eagle’s nest, that had been used for 34 years, was 9 feet in diameter and weighed about 2 tons.
The mating season varies a great deal from region to region. A female eagle lays one to three eggs, spaced several days part. The incubation period is about 35 days.
The female spends most of her time in the nest, but the male will take over when she has to feed. Eaglets hatch with partially closed eyes and a covering of a soft, grayish-white down.
The parent birds feed the young with shredded pieces of meat. Eaglets grow very rapidly. At the age of 6 weeks, they’re nearly as large as their parents. When they’re about 8 weeks old, the secondary coat of gray down is replaced by juvenile feathers.
For the next four or five weeks, the young eagles remain around the nest, still being fed by their parents, while gradually learning to fly and then to hunt.
Juvenile eagles leave the nesting area 6 to 9 weeks after their feathers have grown in, when they’re about 20 weeks old. They often wander in a rather wide range for several years before reaching maturity. Some young eagles find an entirely new place to live, but others return to nest near the spot where they hatched.
Bald eagles live for 20 – 30 years.
Migration
Not all bald eagles migrate. Most of them live the year around in Florida. Those who live in the north, though, head south in the fall and return to their home nests in the spring. Bald eagles make their homes by constructing massive nests in trees near coastlines or major waterways.
The fall migration tends to be rather leisurely. The birds may stop in area for as much as a week before continuing. But in the spring they move much more quickly.
Speeds during migration average 30 miles an hour. Much of the time is spent soaring, during which the eagles use currents of warm air (thermals) and updrafts to carry them along with little wing movement.
Newly-fledged eagles usually begin migrating before their parents. It’s not known how they know where to travel.
