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Bald Eagle (Haliaeetus leucocephalus)
Bald Eagle. USFWS photo.
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The bald eagle is easily recognized by its white head,
brown body and white tail. The scientific name, Haliaeetus leucocephalus,
means "white-headed sea eagle." Immature birds are dark brown, mottled
with white. The white head and tail begin to appear at 3-4 years of age
and is complete by 4-5 years. Adults measure about 3 feet from head to
tail, weigh 10-12 pounds and have a wingspan of 6-7 feet. In flight, the
bald eagle has a distinctive, flat-winged profile.
Bald eagles usually nest in mature loblolly pines, tulip
poplars and oaks along the shores of the Chesapeake Bay and rivers. Eagle
nests tower 80-110 feet above the ground. The massive nests are often
used year after year, growing to 6-8 feet in width and averaging 4 feet
deep.
In late winter, bald eagles usually lay one to three
eggs which hatch after 35 days. The young are covered with soft down.
Within three months, however the young have grown feathers and are flying.
By the fourth month, they are on their own. Bald eagles feed primarily
on fish, but also eat ducks, geese, small mammals, rodents, snakes and
turtles.
Historical records show that in the early 1900s more than 1,000 pairs
of birds nested around the Chesapeake Bay each year. However, just prior
to the 1940s, bald eagles began to decline due to the direct killing of
birds, loss of habitat and decline of prey. In 1940, the Bald Eagle Protection
Act made it illegal to kill, harm, harass or possess bald eagles. Possession
of dead eagles, their eggs or feathers also became illegal. They began
to recover but another culprit entered the picture.
Just before WWII the use of the pesticide DDT to control
mosquitoes was widespread in coastal areas. Bald eagles fed on prey contaminated
with the pesticide. By the late 1960s and early 70s, researchers found
that DDE, a breakdown product of DDT, caused bald eagles and other birds
to produce eggs with very thin shells. Chesapeake Bay area surveys of
revealed a drop in eagle nests and eaglets produced. In the 1930s, an
average of 1 to 2 eaglets were produced per nest, but by the 1960s that
average dropped to 1 for every 5 active nests.
Use of DDT was banned in then United States in 1972,
but our Nation's symbol was still in trouble. By that time, there were
fewer than 90 breeding pairs of eagles in the Chesapeake area. In 1973,
bald eagles were listed as endangered throughout most of the lower 48
states, including the Chesapeake Bay watershed.
Since the DDT ban, more young eagles have hatched. Nesting
success has steadily increased each year. By 1996, 378 active bald eagle
nests in the Maryland, Virginia and Pennsylvania portions of the Chesapeake
Bay watershed produced 517 young!
During the past 25 years of recovery, eagles have made
a rebound in part due to the replacement of healthy adult nesting pairs.
Bald eagles have responded to the DDT ban and the protection afforded
by the Endangered Species Act , which includes preventing shootings and
protecting habitat through landowner agreements.
The Chesapeake Bay now has one of the highest concentrations
of bald eagles in the lower 48 states. In addition to the breeding population,
the Bay supports winter migrants from as far north as Canada and summer
migrants from Florida.
In order for bald eagles populations to improve, they
need suitable nesting trees near open water, isolation from human activity
and a stable food supply that includes mostly fish, other birds, mammals
and reptiles and amphibians. Through habitat protection, identification
of important nesting, roosting and feeding sites, and monitoring potential
contaminants, the bald eagle will continue its journey of recovery.
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