Bald Eagle

Bald Eagle
Haliaeetus leucocephalus
State Status: Endangered
Federal Status: None
DESCRIPTION: The Bald Eagle is one of the most
impressive and majestic birds in North America. It is
one of eight species in the genus Haliaeetus, the "fish"
or "sea" eagles, and is the only member of the genus that
occurs regularly in North America. This species is one
member of the family of Accipiters, all of which are in
the order Falconiformes. It is also the largest raptor (bird
of prey) in Massachusetts, attaining a wingspan of 2.0 to
2.2 meters (6.5 to 7.0 feet) with a body length of 0.9
meters (3.0 feet), and a weight ranging from 3.6 to 6.6
kilograms (8 to 15 lbs.) at maturity. The sexes are
similar in appearance but, as with most raptor species,
the females are notably larger than the males.
Photo by Bill Byrne, MassWildlife
Adult Bald Eagles are distinctively colored with a white
head and tail, brown body, pale yellow eyes, and bright
yellow beak and feet. The adult plumage is attained at 4
SIMILAR SPECIES IN MASSACHUSETTS: The
to 5 years of age. The plumage of immature Bald Eagles
large size and distinctive plumage of the Bald Eagle
may vary considerably. Immatures go through a
make it very easy to distinguish from all other birds in
sequence of plumage types before reaching maturity.
Massachusetts, with the exception of the Golden Eagle
These plumages include a uniformly dark phase in the
(Aquila chrysaetos). Both grow to approximately the
first year, followed by phases with various amounts of
same size, but the white head and tail of the adult Bald
white on the belly, back, underwings, tail, and head. The
Eagle differentiates it from the Golden Eagle. Immature
eye and beak color also change with age, from dark
Bald Eagles may be confused with both immature and
brown and blackish-gray at hatching to bright yellow in
adult Golden Eagles. The adult Golden Eagle is nearly
adults. In all feathered stages, the tail is rounded and the
uniformly dark without any of the mottling found on the
lower half of the tarsus is unfeathered.
immature Bald Eagle. Golden Eagles at any age may
have relatively sharply defined, bright, clean white
Bald Eagles fly with heavy, deep strokes and soar on
patches of varying size at the base of the inner primaries
flattened wings. In silhouette, the beak, head, and neck
and outer secondaries on the wings and a clean white
are almost as long as the tail.
area at the base of the tail. All immature Bald Eagles
have whitish axillaries and, depending on age, can have
extensive, “dirty” white mottling virtually anywhere on
the head, body, wing linings, and tail. The Golden
Eagle’s legs are feathered to its toes; the legs of the Bald
Eagle are unfeathered.
The Turkey Vulture is similar to an immature Bald
Eagle in size and general coloration. At a distance, a
distinction can be made by looking at the birds as they
soar. Turkey Vultures hold their wings somewhat
upright, forming a shallow "V" when soaring and rock
from side to side as they ride thermal air currents. Bald
Cumulative Nesting Distribution in
Eagles hold their wings straight out from their body
Massachusetts
while soaring, with only the tips of the primary feathers
1987-2008
Based on records in Natural Heritage Database
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‘endangered wildlife conservation’ on your state income tax form, as these donations comprise a significant portion of our operating budget.

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curved slightly upward. Eagles do not rock from side to
age, but the birds may be considerably older before they
side as they soar, but rather make broad, sweeping
breed for the first time.
circles as updrafts lift them skyward. At close range, the
Turkey Vulture's small, featherless head (which is red in
The breeding season for Bald Eagles in Massachusetts
adults and gray in juveniles) makes identification quite
begins with courtship during late fall or early winter.
simple.
After courtship, the mated pair builds a large nest during
December–February. The nest is constructed with large
RANGE: Bald Eagles occur from Alaska and Canada
sticks and lined with sprigs of pine, grasses, and other
south throughout the United States to Florida and Baja
soft materials. The male eagle collects the nest material
California. In the lower 48 states, they occur
and delivers it to his mate, who is responsible for most
sporadically over a wide area with notable seasonal
of the actual nest construction. Once the nesting site is
concentrations in Florida, the Chesapeake Bay area, the
chosen, the mated pair will usually return every year to
Mississippi Valley and Pacific Northwest. In
the same site and add to the existing structure. The nests
Massachusetts, occurrences are possible statewide,
are located in hardwoods or conifers from 9 to 37 meters
especially during migration in March-April and
(30 to 120 feet) above the ground and may measure up
September-October; however, wanderers can appear
to 3.6 meters (12 feet) high and 2.6 meters (8.5 feet)
virtually anywhere at anytime. In Massachusetts, Bald
wide, with a weight of hundreds of pounds. Trees
Eagles use the Quabbin Reservoir, the Connecticut
selected for nesting (and sometimes for roosting and
River, the Merrimack River, and the Assawompsett
perching) tend to be relatively large and, preferably,
Pond complex throughout the year as both nesting and
taller than their surroundings. Ideally, the nest lies below
wintering habitat. Bald Eagles also overwinter along the
the top of the crown in a live tree, where the young are
coast of Cape Cod, Buzzard's Bay and the islands of
sheltered from the elements but the parent birds are still
Martha's Vineyard and Nantucket. Historically, the Bald
afforded adequate aerial access (generally, from the
Eagle bred throughout most of North America prior to
direction of the nearest water).
its widespread, well-publicized population decline
during the early to mid-1900s. However, during the past
The female Bald Eagle lays one to three (two average)
several decades, the Bald Eagle has recolonized much of
dull white eggs several days apart, usually during a
its historic range and continues to repopulate areas
period between early March and early April. The eggs
where suitable habitat still exists.
are incubated (mostly by the female) for approximately
35 days until hatching. The eggs do not hatch at the
HABITAT IN MASSACHUSETTS: Bald Eagles
same time, giving the first hatchling a significant
usually inhabit coastal areas, estuaries, and larger inland
advantage over its siblings. Competition for food is
waters. This species requires a great amount of shoreline
intense, and if the adult eagles are not able to provide
habitat containing stands of forest for nesting and trees
enough for all of their young, the older chick will take
projecting above the forest canopy for perching, an
advantage of its greater strength and size to seize most
adequate supply of moderate-sized to large fish, an
of the food provided by the parents, causing its younger
unimpeded view, and reasonable freedom from human
siblings to starve. This behavior increases the
disturbance. Wintering eagles require suitable roost trees
probability that at least one chick will survive. Young
for night roosting. Some such roosts may be 20 km or
eaglets grow rapidly and may eat up to two pounds of
more from feeding areas, occurring in favorable thermal
fish per day. Ten weeks after hatching, they begin to
environments where roost trees are protected from the
make short flights from the nest, spending much time
wind by topography or other trees. The use of these
with the parent birds observing the adults as they catch
protected sites helps minimize the energy stress
and find food. By late fall the adults will no longer care
encountered by wintering birds. The absence of a
for their young, and the fledgling eaglets begin life on
suitable night roost could limit the use of otherwise
their own. The entire breeding cycle, from nest
suitable habitat.
construction to fledging of young, lasts 6–8 months.
Most Bald Eagles appear to nest within 200 miles of
LIFE CYCLE/BEHAVIOR: Courtship occurs in mid-
where they hatched.
to late winter and is a spectacular sight consisting of
aerial loops, cartwheels, dives, and ending with the
When available, fish (both marine and freshwater) is the
prospective mating pair locking their talons together and
Bald Eagle's preferred food. Fish may be captured by
diving straight downward for hundreds of feet while
swooping from a perch or by coursing low over the
spinning head over heels. Bald Eagles may live up to 30
water and dropping straight down when a fish is spotted.
years, but mortality is relatively high in the immature
An eagle may plunge into the water to capture fish and
age classes. They mate for life, but if one member of a
may also steal fish from an osprey by harassing it until it
pair dies or is killed, the other will actively court another
drops its catch. Prey too large to carry may be dragged
mate. Sexual maturity is reached at four to six years of
Please allow the Natural Heritage & Endangered Species Program to continue to conserve the biodiversity of Massachusetts with a contribution for
‘endangered wildlife conservation’ on your state income tax form, as these donations comprise a significant portion of our operating budget.

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to shore. Birds, especially waterfowl, are sometimes
slowly but steadily since that time. During 2008, an all-
taken by bursting into a large flock and pursuing a
time high of at least 26 pairs of Bald Eagles maintained
straggler until it tires and can be captured. Bald Eagles
breeding territories in Massachusetts: Quabbin
also take crippled waterfowl and seabirds, small
Reservoir (8), Connecticut River (7), Merrimack River
mammals and carrion, particularly dead fish. In winter,
(2), Pocksha Pond (1), Great Quittacas Pond (1), North
eagles of all ages may gather in large numbers at areas
Watuppa Pond (1), Wachusett Reservoir (1), Quaboag
with open water where fish or waterfowl are abundant.
Pond (1), Swift River (1), Westfield River (1),
This "social grouping" is believed to facilitate locating
Housatonic River (1), and Onota Lake (1). During the
and acquiring food and may possibly aid in establishing
2008 Midwinter Bald Eagle survey, 72 Bald Eagles
or maintaining pair bonds.
were counted in Massachusetts: Quabbin Reservoir (36),
Merrimack River (8), Connecticut River (9), Wachusett
HISTORICAL THREATS: The history of the Bald
Reservoir (5), Lake Assawompsett (4), and other sites
Eagle is one of human contradictions. On one hand, the
(10). Population abundance in Massachusetts is limited
Bald Eagle’s noble image has been portrayed on public
mainly by amount of potential breeding habitat (i.e.,
documents, coin, currency, etc. as our nation's symbol
number of large water bodies surrounded by mature
since 1782, making it one of the most well-known
forest and having shallow waters and abundant fish).
creatures on earth. On the other hand, its environment
Population viability is limited mainly by the species’
has been reduced and degraded, and the bird itself was
rarity and the possibility of catastrophic events (e.g.,
treated as vermin throughout North America for the
storms, disease).
better part of a century. As a result of deliberate killing
by people (who incorrectly believed that eagles kill
MANAGEMENT RECOMMENDATIONS:
livestock or significantly threaten salmon fisheries),
Protection and enhancement of potentially suitable
combined with substantial habitat loss (conversion of
wetland and forest habitats, and maintenance of known
forest to development and agriculture), the Bald Eagle
breeding, roosting, and wintering areas will be critical to
decreased in numbers in much of its range for many
long-term conservation of Bald Eagles in Massachusetts.
years. From 1917 to 1952, at least 128,000 Bald Eagles
To achieve these objectives, landowners should first
were believed to have been killed in Alaska where there
work to limit development near shorelines of large water
was a bounty on the species. In the 20th century, the
bodies, as loss of nesting habitat is a primary threat to
introduction of man-made chemicals and pollutants to
Bald Eagles in the state. Prevention, identification, and
the environment was implicated in death, increased
remediation of environmental contamination (e.g., lead,
susceptibility to death, and diminished reproductive
mercury, PCBs, and other toxic depositions) are also key
success of Bald Eagles. DDT and its metabolites, as well
to maintaining adequate foraging habitat and
as other organochlorines, are well-documented causes of
maximizing long-term reproductive success and survival
eggshell thinning, breakage, and toxicity. The Bald
of Bald Eagles. Landowners who wish to harvest timber
Eagle was listed federally as an Endangered Species in
near potential eagle habitat should consult the
1967.
Massachusetts Forestry Conservation Management
Practices (CMPs) for Bald Eagle; these practices, which
A decline in human persecution and reductions in use of
are published by the Natural Heritage and Endangered
DDT and other toxins are credited with recent recoveries
Species Program, provide guidance for protecting (or
of Bald Eagle populations during the past quarter-
even enhancing) nesting and foraging habitat during
century. The federal status of the species was upgraded
forestry projects. Increased public education about the
to Threatened in 1995, and the species was removed
potentially detrimental effects of human disturbance on
from the federal list of threatened and endangered
reproductive success of Bald Eagles is another measure
species in August 2007. However, Bald Eagle
that can be taken.
populations remain imperiled in a number of states, as
prior habitat loss, prior and current habitat degradation,
Direct mortality does not appear to be a leading threat to
and ongoing disturbance from growing human
long-term conservation of Bald Eagles in Massachusetts.
populations continue to limit population viability.
However, every effort should be made to prevent
avoidable deaths. Fishermen should be diligent in
POPULATION STATUS IN MASSACHUSETTS:
proper disposal of fishing line and equipment; eagles are
Breeding Bald Eagles were extirpated from
known to accidentally ingest hooks, and at least one
Massachusetts during the early 1900s. However, from
eaglet has been killed in Massachusetts after becoming
1982 to 1988, forty-one young Bald Eagles from
tangled in fishing line. Bald Eagles are still taken by
Michigan and Canada were relocated to Quabbin
shooting on occasion; hence, education and strict law
Reservoir in Massachusetts. Following this restoration
enforcement are additional measures that can be taken to
effort, Bald Eagles were confirmed to breed successfully
improve survival.
in the state by 1989. Eagle numbers have increased
Please allow the Natural Heritage & Endangered Species Program to continue to conserve the biodiversity of Massachusetts with a contribution for
‘endangered wildlife conservation’ on your state income tax form, as these donations comprise a significant portion of our operating budget.

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Population monitoring at both the state and regional
Palmer, R. S. 1962. Handbook of North American
level will be an important tool to help determine
Birds. vol. IV. Yale University Press, New
population status, growth potential, and possible
Haven.
conservation setbacks. With continued sound
management and increased public awareness, the future
Robards, F. C., and J. G. King. 1966. Nesting and
of the Bald Eagle should continue to be one of
productivity of Bald Eagles, southeast Alaska –
conservation's greatest success stories.
1966. U. S. Bureau of Sport Fisheries and Wildlife
Report, Juneau, Alaska, USA.
SELECTED REFERENCES:
Stalmaster, M. 1987. The Bald Eagle. Universe
Bonney, R. E., Jr., J.W. Kelley, D.J. Decker, and
Books, New York.
R.A. Howard, Jr. 1981. Understanding
Predation and Northeastern Birds of Prey.
Terres, J. K. 1991.The Audubon Society Encyclopedia
Ithaca, N.Y.: N.Y. State College of
of North American Birds. Wing Books, New York.
Agriculture/Cornell University.
Wiemeyer, S. N., C. M. Burick, and C. J. Stafford.
Buehler, D. A. 2000. Bald Eagle. No. 506 in A. Poole
1993. Environmental contaminants in Bald Eagle
and F. Gill, editors. The birds of North America.
eggs – 1980-1984 – and further interpretations of
Academy of Natural Sciences, Philadelphia,
relationships to productivity and shell thickness.
Pennsylvania, and American Ornithologists’ Union,
Archives of Environmental Contamination and
Washington, D.C., USA.
Toxicology 13:529–549.
Clark, W.S., and Wheeler, B. K. 1987. A Field
Guide to Hawks of North America. Houghton
Mifflin Company, Boston.
Fraser, J. D. 1985. The impact of human activities on
Bald Eagle populations – a review. Pages 68–84 in
J. M. Gerrard and T. M. Ingram, editors. The Bald
Eagle in Canada. White Horse Plains Publishing,
Headingley, Manitoba, Canada.
Fraser, J. D., L. D. Frenzel, and J. E. Mathisen. 1985.
The impact of human activities on breeding Bald
Eagles in north-central Minnesota. Journal of
Wildlife Management 49:585–592.
Johnsgard, P. A. 1990. Hawks, Eagles, and Falcons
of North America. Smithsonian Institution
Press, Washington, D.C.
Nisbet, I. C. T. 1989. Organochlorines, reproductive
impairment, and declines in Bald Eagle Haliaeetus
leucocephalus populations: mechanisms and dose
relationships. Pages 483–489 in B. U. Meyburg and
R. D. Chancellor, editors. Raptors in the modern
world. World Working Group for Birds of Prey,
Berlin, Germany.
Northern States Bald Eagle Recovery Team.1983.
Northern States Bald Eagle Recovery Plan.
U.S. Fish & Wildlife Service. Washington,
D.C.
Updated January 2009
Please allow the Natural Heritage & Endangered Species Program to continue to conserve the biodiversity of Massachusetts with a contribution for
‘endangered wildlife conservation’ on your state income tax form, as these donations comprise a significant portion of our operating budget.

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