When the Europeans first arrived here the bald eagle had a breeding
range that extended from Baja California across to south Texas and the
peninsula of Florida all the way up into Alaska and Canada. Their numbers
were larger in the 1800s than they are today.(Gerrard 1988)
The nesting populations began to decrease in the late 1900s due to
reduction of habitat suitable for both breeding and wintering grounds, to
develop land for farming and housing. Eagles were also trapped and shot for
either the sale of their parts or because they were thought to be
destroying livestock.
There are no known natural enemies of the bald eagle, however man has
played that role all too well.. From the 1920s until the 1970s mans
nearly wiped the bald eagle out. One of the main problems was getting the
protection for this majestic creature came very slowly. It wasn't until
1940 that any legislation was passed to start to protect the bald
eagle.This started with the Bald Eagle Act which outlawed the killing of
bald eagles in the lower 48 states. However in Alaska, the killing was
allowed until 1953. There bounties on eagles in Alaska fro 1917 to 1945 and
again from 1949 to 1953. Finally in 1953, the Territorial Bald Eagle
Bounty Law was repealed in Alaska, but not before more than 100,000 eagles
had been killed merely for the sale of their feet. The illegal shooting of
eagles greatly affected bald eagle populations. Even though it has been
illegal since 1953, and there are large fines and time in prison for
committing this act there are still numerous eagles shot and killed every
year. (Wusk 1999).
Another major factor brought on by man was the use of the pesticide DDT.
In the 1940s to 1970s the bald eagle populations were nearly wiped out by
this pesticides and other chemicals that contaminate the environment. The
decline ranged from 50 percent in some areas to as high as 100 percent in
others, thiscoming from reports in the late 1960s. An amateur
ornithologist reported in 1950 in one area that there was only a 25
percent rate of reproduction. This was the case all across the country.
The contaminant residues were found in adult birds, eggs and nestlings as
well as in their food sources. The DDT contaminants found in adult birds
resulted in abnormal breeding behavior , thin eggshells, and dead embryos
within the eggs. Some other pesticides that were implicated in causing
acute poisonings , which quite frequently resulted in immediate death of
individual birds, are Dieldrin and Endrin (Beans 1996). A major step was
taken in the 1970s on stopping the decimation of the bald eagles and other
raptors by banning the use of several organochlorine pesticides, including
DDT. The inception of the Endangered Species Act of 1973 was another major
step in protecting the bald eagle and its habitat in the future. The bald
eagle was added to the list of endangered species in 1978 along with this
came the inception of fines of $10,000 to $ 20,000 and/or imprisonment of
one to two years for either killing or selling a bald eagle(Wusk 1999).
For more information on the effects of pesticides on bald eagles visit
http://www.Cws-scf.ec.ca/nwrc/bldeagle.htm
Lead poisoning can also affect bald eagle populations. Eagles can and
have died from lead poisoning after eating water fowl that have ingested
lead pellets embedded in the waterfowl's flesh and gizzards. There have
also been cases of eagles having toxic levels of lead from directly
contaminated flesh. Another limiting factor affecting the bald eagle
mortality is electrocution from power lines(Gerrard 1988).
The use of recreational vehicles on areas where bald eagles winter has an
effect on their staying in one place. Once disturbed from an area eagles
may not return to that area. This has also had an adverse effect on the
eagles returning to an area. In some cases it has even been seen on their
nesting grounds as well as their breeding grounds (Stalmaster 1998).
It is thought that there is an estimated 2600 nesting pairs of bald
eagles in the lower 48 states and as many as 13,500 birds wintering in this
same area. There have estimates of as many as 50,000 bald eagles living in
Alaska and British Columbia with another 12,000 living in Saskatchewan.
These two populations are the ones that have recovered the most from the
decimation that occurred during the 1940s thru 1970s(Gerrard 1988).
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