Bald Eagle

Wildlife Populations:
Bald Eagle
Background
Trend
The large, majestic bald eagle was selected as the U.S. national emblem
The steps taken to protect the bald eagle and foster its survival are paying
in 1782 “as a symbol of strength, courage, beauty, and freedom.”1 During
off. Data assembled by the ENSP show a consistent increase in the bald
the nesting season, bald eagles are always found close to a water body
eagle population in New Jersey over the last 15 years. In 2006, there were
where a ready supply of fish or waterfowl is available. They typically nest in
55 active nesting pairs of eagles that produced 82 young. (See Figure.)
old, large trees with a clear flight path on one or more sides, and often, a
view of the water. 2 The bird’s population in the lower 48 states decreased
drastically in the 1940s, 1950s and 1960s, exemplifying the dangers of
environmental contamination, loss of habitat, and human persecution of
Nesting Bald Eagles and Young in New Jersey
wildlife, and warning scientists of a loss of biodiversity throughout the
world.
90
A major threat to the birds’ survival was increasing contamination of the
80
environment after World War II with persistent chemicals such as DDT and
70
PCBs. Accumulating in fish and other prey, these endocrine system-
disrupting pollutants concentrated in eagles’ eggs and impaired hatching
60
and the survival of nestlings, primarily by weakening eggshells. Population
50
numbers also were affected adversely by the loss of quality large-area
forests and aquatic habitats. Historic records estimate more than 20 bald
40
eagle nests in New Jersey throughout the 1940s. By the 1970s, however,
the numbers had declined to a yearly average of one nest, and throughout
30
that decade there is no record of the successful rearing of nestlings.
20
In 1972, DDT was banned in the United States, followed by bans of other
10
pesticides such as aldrin, dieldrin, chlordane, toxaphene and PCBs in the
0
late 1970s and early 1980s. Subsequently, concentrations of these pollut-
1982
1984
1986
1988
1990
1992
1994
1996
1998
2000
2002
2004
2006
ants in the environment began to decline. At the same time, federal and
state wildlife agencies instituted programs to protect and enhance bald
Active Nesting Pairs
Eaglets Fledged
Eaglets Released
eagle populations. The New Jersey Department of Environmental Protec-
tion Division of Fish and Wildlife, Endangered and Nongame Species
Program (ENSP) coordinated the state’s efforts to restore bald eagle
populations. From 1983 through 1990, ENSP monitored the release of 60
young eaglets obtained from Canada; it also coordinated intensive man-
agement of failing nests and protection of nesting sites by biologists and
landowners.
Wildlife Populations: Bald Eagle
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Outlook and Implications
More Information
While the number and distribution of nests continues to increase, and the
Extensive information on the bald eagle and its status is available
bald eagle has been upgraded from endangered to threatened status at the
from ENSP. See www.nj.gov/dep/fgw/ensphome.htm
federal level, it is still considered an endangered species in New Jersey. It is
important to note that the recent success in restoring the population of bald
eagles has been due in part to active human intervention and protection.
Continuation of such efforts by ENSP and others is planned, and will likely
be necessary for the foreseeable future.
References
Eagles and other birds of prey nesting in the Delaware Bay region still
exhibit some reproductive impairment, which may be due to lingering
1 Simons, T., S. Sherrod, M. Collopy, and M. Jenkins, 1988, Restoring the
pesticide contamination in the environment.3,4 Such contamination prob-
Bald Eagle, American Scientist 76: 253-260, as referenced in Brauning,
ably will continue to decline, but it is necessary to document anticipated
Daniel, (Ed.), 1992, Atlas of Breeding Birds in Pennsylvania, University of
improvements by monitoring levels of banned chemicals in fledgling birds,
Pittsburgh Press, Pittsburgh and London.
as well as levels of other chemicals that have endocrine-disrupting effects.
2 Brauning, Daniel, (Ed.), 1992, Atlas of Breeding Birds in Pennsylvania,
University of Pittsburgh Press, Pittsburgh and London.
Loss of habitat continues to be a problem, but disturbance by indiscreet
3 Clark, K. E., L. J. Niles, and W. Stansley, 1998, Environmental contaminants
observers may be the biggest problem currently faced by the bald eagle
associated with reproductive failure in Bald Eagle (Haliaeetus leucocephalus)
population in New Jersey.5 Some people, apparently unaware that their
eggs in New Jersey, Bull. Environ. Contam. Toxicol. 61: 247-254.
presence may disturb the birds, tend to encroach on nesting areas, at times
4 Clark, K.E., W. Stansley, and L. J. Niles, 2001, Changes in contaminant
upsetting and disrupting the birds’ behavior to the point where reproduction
levels in New Jersey osprey eggs and prey, 1989 to 1998, Archives of
is impaired.
Environ. Contam. Toxicol. 40: 277-284.
5 Niles, L., K. Clark, and D. Ely, 1991, Status of bald eagle nesting in New
Jersey, Records of NJ Birds 17: 2-5.
Wildlife Populations: Bald Eagle
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