American Bald Eagle
The source of the article below about the American Bald Eagle
(author unknown) is from the
U.S. Fish and Wildlife Service. Some additional
information, paraphrased from other sources, is included here.
The bald eagle is truly an all-American bird -- it is the
only eagle unique to North America. It ranges over most of the
continent, from the northern reaches of Alaska and Canada down to
northern Mexico. The bald eagle, our national symbol, is listed
as endangered under the Endangered Species Act in 43 of the lower
48 states and listed as threatened in Michigan, Minnesota,
Oregon, Washington, and Wisconsin. (There are about 40,000 bald
eagles in Alaska and none in Hawaii.) However, bald eagles have
improved greatly in numbers, productivity, and security in recent
Male bald eagles generally measure 3 feet from head to tail,
weigh 7 to 10 pounds, and have a wingspan of about 6 1/2 feet.
Females are larger, some reaching 14 pounds and having a wingspan
of up to 8 feet. This striking raptor has large, pale eyes; a
powerful yellow beak; and great, black talons. The distinctive
white head and tail feathers appear only after the bird is 4 to 5
Bald eagles are believed to live 30 years or longer in the
wild, and even longer in captivity. They mate for life and build
huge nests in the tops of large trees near rivers, lakes,
marshes, or other wetland areas. Nests are often reused year
after year. With additions to the nests made annually, some may
reach 10 feet across and weigh as much as 2,000 pounds. Although
bald eagles may range over great distances, they usually return
to nest within 100 miles of where they were raised.
Bald eagles normally lay two to three eggs once a year and
the eggs hatch after about 35 days. The young eagles are flying
within 3 months and are on their own about a month later.
However, disease, lack of food, bad weather, or human
interference can kill many eaglets; sometimes only about half
will survive their first year.
The staple of most bald eagle diets is fish, but they will
feed on almost anything they can catch, including ducks, rodents,
snakes, and carrion. In winter, northern birds migrate south and
gather in large numbers near open water areas where fish or other
prey are plentiful.
Wildlife experts believe there may have been 25,000 to as
many as 75,000 nesting bald eagles in the lower 48 states when
the bird was adopted as our national symbol in 1782. Since that
time, the bald eagle has suffered from habitat destruction and
degradation, illegal shooting, and contamination of its food
source, most notably due to the pesticide DDT. By the early
1960s there were fewer than 450 bald eagle nesting pairs in the
lower 48 states.
Bald eagles have few natural enemies. But in general they
need an environment of quiet isolation; tall, mature trees; and
clean waters. Those conditions have changed over much of the
bald eagle's former habitat.
History notes many wilderness areas were cleared for farms
and towns, and virgin forests were cut for timber and fuel. And,
today, an increasing number of people flock to the nation's
waterways for recreation, with growing impacts on bald eagle
Meanwhile, these birds of prey became prey themselves.
Although primarily fish and carrion eaters, bald eagles and other
raptors were seen as marauders that killed chickens, lambs, and
other domestic livestock. As a consequence, large numbers were
shot by farmers, ranchers, and others.
In 1940, noting that the national bird was "threatened with
extinction," Congress passed the Bald Eagle Protection Act which
made it illegal to kill, harass, possess (without a permit), or
sell bald eagles. In 1967, bald eagles were officially declared
an endangered species (under a law that preceded the Endangered
Species Act of 1973) in all areas of the United States south of
the 40th parallel. Federal and state government agencies, along
with private organizations, successfully sought to alert the
public about the bald eagle's plight and to protect its habitat
from further destruction.
The greatest threat to the bald eagle's existence arose from
the widespread use of DDT and other pesticides after World War
II. DDT was sprayed on croplands throughout the country and its
residues washed into lakes and streams. There, they were
absorbed by aquatic plants and small animals that were eaten by
fish. The contaminated fish, in turn, were consumed by bald
The chemical interfered with the bald eagle's ability to
develop strong shells for its eggs. As a result, bald eagles and
many other bird species began laying eggs with shells so thin
they often broke during incubation or otherwise failed to hatch.
Their reproduction disrupted, bald eagle populations plummeted.
As the dangers of DDT became known, in large part due to Rachel
Carson's famous book Silent Spring, this chemical was banned for
most uses in the United States in 1972.
In addition to the adverse effects of DDT, bald eagles also
died from lead poisoning as a result of feeding on hunter-killed
or crippled waterfowl containing lead shot and from lead shot
that was inadvertently ingested by the waterfowl. (In 1991, a 5-
year program to phase out the use of lead shot for waterfowl
hunting was completed by the U.S. Fish and Wildlife Service.)
Gradually, the U.S. Fish and Wildlife Service assembled the
largest colony of breeding bald eagles in captivity at its
Patuxent Wildlife Research Center near Laurel, Maryland, in a
major effort to return healthy eagles to the wild (the center is
now run by the National Biological Survey).
Patuxent's scientists enhanced the species' breeding
potential by removing the bald eagle's first clutch of eggs and
incubating them artificially. The bald eagles would usually then
lay a second clutch, which the birds were allowed to incubate
themselves. In all, 124 bald eagles were hatched at Patuxent.
These captive-hatched bald eagles were an important source
for restocking wild populations in certain areas of the country
and helped to reestablish a broader distribution. Patuxent's
program came to an end in 1988, as bald eagles began to reproduce
more successfully in the wild, and the center turned its efforts
toward other more critically endangered species.
Some states continue reintroduction efforts, and two methods
are generally used. Eaglets used for reintroduction may be
captive-hatched or, since usually only two young per nest
survive, they may be transferred from a bald eagle nest with a
clutch of more than two.
These "extra" eaglets are placed in the nest of an adult
pair whose own eggs are infertile or fail to hatch. The "foster
parents" readily adopt the chicks and raise them as their own.
Another method, called hacking, is a procedure adapted from
the sport of falconry. At 8 weeks of age, nestling eaglets are
placed on manmade towers located in remote areas where bald eagle
populations are low or non-existent. The eaglets are kept in an
enclosure and fed by humans who stay out of sight. When the
birds are capable of flight, at about 12 weeks old, the enclosure
around the artificial nest is opened and the birds are free to
leave. Food is still provided at the release site until the
birds learn to fend for themselves in the wild.
With these and other recovery methods, as well as habitat
improvement and the banning of DDT, the bald eagle has made a
remarkable comeback. From fewer than 450 nesting pairs in the
early 1960s, there are now more than 4,000 adult bald eagles
nesting pairs and an unknown number of young and subadults in the
conterminous United States. This represents a substantial
breeding population. In the last few years, several states have
had breeding bald eagles for the first time in years. While
habitat loss still remains a threat to the bald eagle's full
recovery, most experts agree that it is making encouraging
progress. Soon our national symbol soaring the skies may become
a common sight for Americans to once again behold.
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