During the twentieth century, bald eagle populations struggled for survival. Hawks and eagles were shot for sport because it was believed that they ate livestock. In 1940, the National Emblem Law was passed, which forbade the killing of bald eagles in the lower 48 states. Alaska continued to encourage the killing of eagles and until 1962 there was a bounty on them - $2 for each set of talons brought in.
This aggressive hunting had greatly reduced the population. The use of DDT brought the bald eagle to the edge of extinction. DDT and other pesticides weakened the shells and the eggs were not able to survive. The population did not recover until DDT was banned and scientist made an effort to manage populations
Eagles cannot reproduce until they reach they are 5 years old. This also had an impact on dwindling populations.
Bald eagles are large birds with a wing-span of 7 to 8 feet. One way to identify them in flight is that they hold their wings out straight, like a plank, while soaring.
The female is larger than the male. It is difficult to determine relative size when seeing birds from a distance. Usually the size difference can only be noted when the birds are sitting together.
It takes 4 or 5 years for eagles to gain the plumage that we associate with a bald eagle, the white head and tail.
During the first two years, the birds are mostly dark brown with a mottling of white on their tail and under their wings.
In the third year, the head becomes whiter but the tail remains mottled brown and white.
During the fourth year, the head and tail become a bright white and the body is all dark.
Bald eagles mate for life. If an eagle loses its mate, the mate is replaced. Mated pairs can be seen sitting close to each other near the nest site. One bird sometimes preens the other. Copulation usually occurs on or near the nest. Stages in the breeding cycle:
With fish as the primary source of food for New Jersey eagles, the habitat that they prefer are forests located near bodies of water. This is their favored foraging habitat. Eagles like to perch in tall trees when fishing. In the winter, open bodies of water are necessary. In New Jersey, the Delaware bay shore, with its tidal areas, usually has open water. Some parts of the Delaware River remains open as well as some deep reservoirs.
Eagles do not migrate in the way that many other birds do, but they will move from one area to another in search of food, particularly in winter. In New Jersey, most of the mature eagles that have established nests tend to stay in the area of their nests.
Stokes, D. & L. (1989). Stoke's Nature Guide to Bird Behavior, Vol. III. United States of America:Little, Brown & Company.