Bald Eagle Facts
By Mike Celentano
Scientific classification
Kingdom
Phylum
Class
Order
Family
Genus
Species
Animalia
Chordata
Aves
Falconiformes
Accipitridae
Haliaeetus
H. leucocephalus
The bald eagle's scientific name signifies a sea (halo) eagle (aeetos) with a white
(leukos) head. At one time, the word "bald" meant "white," not hairless. Bald eagles are
found over most of North America, from Alaska and Canada to northern Mexico. About
half of the world's 70,000 bald eagles live in Alaska. Combined with British Columbia's
population of about 20,000, the northwest coast of North America is by far their greatest
stronghold for bald eagles. They flourish here in part because of the salmon. Dead or
dying fish are an important food source for all bald eagles.
Eagles are a member of the Accipitridae family, which also includes hawks, kites,
and old-world vultures.
There are two subspecies of bald eagles. The "southern" bald eagle, Haliaeetus
leucocephalus leucocephalus, is found in the Gulf States from Texas and Baja
California across to South Carolina and Florida, south of 40 degrees north latitude. The
"northern" bald eagle, Haliaeetus leucocephalus alascanus, is found north of 40
degrees north latitude across the entire continent. The largest number of northern bald
eagles are in the Northwest, especially in Alaska. The "northern" bald eagle is slightly
larger than the "southern" bald eagle. Studies have shown that "northern" bald eagles
fly into the southern states and Mexico, and the "southern" bald eagles fly north into
Canada. Because of these finding, the subspecies of "northern" and "southern" bald
eagles has been discontinued in recent literature.
The golden eagle is larger than the bald eagle in average height and wingspan, but
there isn't much difference in their average weight.
Body Temperature - 102 degrees Fahrenheit (38.8 degrees Celsius)
Eagles do not sweat, so they need to use other cooling methods such as perching in
the shade, panting, and holding their wings away from their body.
Tolerance to cold temperatures - A bald eagle's skin is protected by feathers lined
with down. The feet are cold resistance because they are mostly tendon. The outside of
the bill is mostly nonliving material, with little blood supply.
Eagles sit at the top of the food chain, making them more vulnerable to toxic
chemicals in the environment, since each link in the food chain tends to concentrate
chemicals from the lower link.
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The wings and soaring - An eagle's wings are long and broad, making them effective
for soaring. To help reduce turbulence as air passes over the end of the wing, the tips of
the feathers at the end of the wings are tapered so that when the eagle fully extends its
wings, the tips are widely separated.
To help them soar, eagles use thermals, which are rising currents of warm air and
updrafts generated by terrain, such as valley edges or mountain slopes. Soaring is
accomplished with very little wing-flapping, enabling them to conserve energy. Longdistance migration flights are accomplished by climbing high in a thermal, then gliding
downward to catch the next thermal, where the process is repeated. Several eagles
soaring in a thermal together is described as a "kettle of eagles".
Bald eagles can fly to an altitude of 10,000 feet. During level flight, a bald eagle can
achieve speeds of about 30 to 35 mph.
Feathers - Bald eagles have 7,000 feathers. Eagle feathers are lightweight yet
extremely strong, hollow yet highly flexible. They protect the bird from the cold as well
as the heat of the sun, by trapping layers of air. To maintain its body temperature an
eagle simply changes the position of its feathers. While an eagle suns itself on a cold
morning, it ruffles and rotates its feathers so that the air pockets are either opened to
the air or drawn together to reduce the insulating effect. Feathers also provide
waterproofing and protection, and are crucial for flight.
Feather structure makes pliability possible. Overlapping feathers can form a dense
covering, which the birds can open or close at will. The bald eagle has several layers of
feathers, each serving a different function. Under the outer layer of feathers is an inner
layer of down or smaller feathers. The inter-locking of feathers is an astonishing design
of nature.
The feathers enable eagles to live in extremely cold environments. Eagles do not
have to migrate to warmer areas each year to fulfill temperature requirements; they
migrate to available food supplies.
Respiratory system - Eagles have external nares opening on both sides of the bill. A
bald eagle never reaches speeds that would interfere with normal breathing. The
eagle's lungs and air sac system is adequate for its size. Air moves in through the lungs
and on into the air sacs before moving back through the lungs and out again. Air passes
through the lungs twice with each breathing cycle - twice that of mammals.
The beak of a female eagle is deeper (distance from top to chin) than the beak of a
male.
The beak and talons grow continuously, because they are made of keratin, the same
substance as our hair and fingernails. The beak of a captive eagle is not warn down
naturally, so must be trimmed annually.
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Talons - Talons are important tools for hunting and defense. Eagles kill their prey by
penetrating its flesh with their talons.
Eagles can open and close their talons at will. If an eagle is dragged into the water
by a fish too large for the eagle to lift, it is because the eagle refuses to release it. In
some cases this is due to hunger. An eagle might drown during the encounter with the
fish or if it's unable to swim far enough to reach shore. The eagle can not fly again until
it's out of the water, so it uses its large wings to swim. The eagle is a strong swimmer,
but if the water is very cold, it may be overcome by hypothermia.
Eyesight
All eagles are renowned for their excellent eyesight, and the bald eagle is no
exception. They have two foveae, or centers of focus, that allow the birds to see both
forward and to the side at the same time. Bald eagles are capable of seeing fish in the
water from several hundred feet above, while soaring, gliding, or in flapping flight. This
is quite an extraordinary feat, since most fish are counter-shaded, meaning they are
darker on top and thus harder to see from above. Fishermen can confirm how difficult it
is to see a fish just beneath the surface of the water from only a short distance away.
Young bald eagles have been known to make mistakes, such as attacking objects
like plastic bottles floating on or just below the surface of the water. Bald eagles will
locate and catch dead fish much more rapidly and efficiently than live fish, because
dead fish float with their light underside up, making them easier to see.
Eagles have eyelids that close during sleep. For blinking, they also have an inner
eyelid called a nictitating membrane. Every three or four seconds, the nictitating
membrane slides across the eye from front to back, wiping dirt and dust from the
cornea. Because the membrane is translucent, the eagle can see even while it is over
the eye.
Eagles, like all birds, have color vision. An eagle's eye is almost as large as a
human's, but its sharpness is at least four times that of a person with perfect vision. The
eagle can probably identify a rabbit moving almost a mile away. That means that an
eagle flying at an altitude of 1000 feet over open country could spot prey over an area of
almost 3 square miles from a fixed position.
Hearing
Eagles are not distinguished for their hearing, but this does not mean that they have
poor hearing. Diurnal (active by day) birds of prey like hawks and eagles use their
hearing to locate prey or other birds, but the sharpness is not as essential as in some
owls, which can locate prey in the dark only by their sound. The eagle’s ears are located
just behind its eyes.
Because of the energy expended during hunting, an eagle has to spend a lot of
time resting quietly. It's estimated that only one out of eighteen attacks are successful.
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Bald Eagle Facts
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Though not as fast as falcons, bald eagles are fast fliers. When diving, where lift is
less important than reaching drag, the eagle pulls in its wings to minimize their surface
area.
Bald eagles have been seen hunting in pairs.
An eagle protects its food by partially opening its wings, or tenting.
An eagle can consume one pound of fish in about four minutes. The eagle holds its
prey with one talon, holds onto its perch with the other, then tears off each bite with its
beak.
Eagles have an out pouching of the esophagus, called a crop, where they can store
food when the stomach is full. The crop also separates indigestible substances, such as
feathers, fur, and scales from the meat. The indigestible substance is mixed with mucus
and formed into a mass. After the meal, the eagle eventually regurgitates the mass as a
casting.
Eggs - In the Vancouver area eggs are laid in late March and early April, while in
northern Canada and Alaska eggs are laid in May. In Florida, eggs are laid from
November through January. Eagles lay from one to three eggs. Five to ten days after a
successful copulation, the female lays a speckled off-white or buff colored egg about the
size of a goose's. The second egg is laid a few days later, followed by a possible third.
The 35 days of incubation duties are shared by both male and female, but it is the
female who spends most of her time on the nest. Trading places on the nest can be a
tense time. The brooding parent may have to call for relief, or may be reluctant to leave
and have to be pushed off the eggs or young. During incubation, the male bald eagle
regularly brings green sprigs of conifer branches to the nest. Why he does this, no one
knows, but it could be for deodorizing the nest or possibly providing shade for the
eaglets.
During incubation, one parent is always on the nest, not only to keep the eggs warm
but to protect them from squirrels, ravens, and gulls which will break open and eat the
eggs.
Eaglet Growth - The young birds grow rapidly, they add one pound to their body
weight every four or five days. At about two weeks, it is possible for them to hold their
head up for feeding.
By three weeks they are 1 foot high and their feet and beaks are very nearly adult
size.
Between four and five weeks, the birds are able to stand, at which time they can
began tearing up their own food.
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At six weeks, the eaglets are very nearly as large as their parents.
At eight weeks, the appetites of the young birds are at their greatest. While parents
hunt almost continuous to feed them, back at the nest the eaglets are beginning to
stretch their wings in response to gusts of wind and may even be lifted off their feet for
short periods.
At three or four weeks, this eaglet is covered in its secondary coat of gray down. In
another two weeks or so, black juvenile feathers will begin to grow in. While downy
feathers are excellent insulators, they are useless as air foils, and must be replaced with
juvenile feathers before an eaglet can take its first flight, some 10 to 13 weeks after
hatching.
Approximately 40% of young eagles do not survive their first flight.
Six to nine weeks after fledging, juvenile eagles leave the nesting area.
Today, there are an estimated 7,066 nesting pairs of bald eagles. Newly fledged eagles
migrate before their parents. No one knows how the young birds know when and where
to travel.
Some fledgling eagles wander in a wide range their first few years. Some return to
their origin, while others do not. Only the young eagle knows if this is a conscious
decision, or if it simply loses its way.
Causes of death to the bald eagle are:
Fatal gun shot wounds by careless and ignorant recreational hunters, malevolent
people, and those hunting them for their feathers and talons to sell on the black market.
Electrocution from taking off and landing on power poles when their large wings
bridge two wires, resulting in fatal burns or heart failure.
Lead poisoning from eating wounded deer, ducks, and other game which eluded the
hunter and later died. Three pellets can kill an eagle.
Less adept at hunting, young eagles are more likely to eat carrion, and possibly
ingest poisoned meat used to bait wolves and coyotes.
Collisions with vehicles.
Starvation where the food is scarce. Up to half of them starve to death their first
winter, due to lack of hunting skills.
If an eagle ends up in the water due to misjudgment of altitude or snagging a large
fish, there's a danger they may die of exposure
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As the total numbers decline, the death of an individual eagle assumes an
increasing seriousness in relation to the remaining population. Today's eagles survive in
a chamber of horrors. The hunting parent lifts a sick fish from the water and with it
carries along to the nest a new portion of chemical insecticides. And fish may be
attached to a tangle of tough mono-filament fishing line, in which the young become
entangled and die. Another eagle, a young inexperienced bird, meanwhile falls victim to
an automobile. Others drop before thoughtless gunners, are caught in traps, or are
methodically executed by sheepmen using poisons, shotguns, traps, and airplanes.
More insidious than these recognizable hazards are the invisible pressures exerted
on the remaining eagles: stresses from crowding, noise, and environmental pollution,
some of them only speculative, inconclusive, and not measurable. There are other
factors that can only he revealed by sophisticated chemical analysis of the tissues,
among them DDT (Dichloro Diphenyl Trichloro Ethane), DDE (Dichloro Diphenyl
Dichloro Ethylene), PCBs (Polychlorinated Biphenyls), and heavy metals. Whether one
such agent alone brings Death to the individual eagle or they combine in some
unfathomed mixture scarcely matters. Total pressures upon the eagles are
overwhelming.
There are flickers of light in all this darkness. We have been acting to set aside land
for eagles and the other species that share their world. We are working to save those
eagles that have been pushed to the edge of extinction ---captive breeding programs,
brood manipulation of Cain and Abel species, and, in extreme cases, armed guards at
nests are fighting to keep us from losing birds like the Philippine Eagle forever.
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SUMMARY OF BALD EAGLE FACTS
o Once removed from threatened list, eagles will still be protected by law under
Migratory Bird Act,the Bald/Golden Eagle Protection Act and the Lacey Act.
o Largest member of the Hawk family.
o About 90% of eagles do not survive their first year.
o About 40% do not survive their first flight.
o Eagles are capable of breeding from age 4
o Some eagles do not breed every year. (Reason unknown).
o Eggs are generally laid in late March or early May, depending on the area of the
country.
o Incubation period is 35 days.
o At 10 to 12 weeks of age, eagles are fully grown and capable of flight.
o Nesting territory roughly 1 to 2 square miles.
o ½ of world eagle population lives in Alaska.
o Bald eagle’s skeleton weighs approximately ½ pound. (200-300 gram range)
o There are some 7,200 feathers on an eagle’s body.
o Feathers weigh twice as much in total weight than the skeleton.
o Beak, talons and feathers are all made of keratin; therefore they are in a constant
state of growth.
o Eagles can shift and fluff their feathers in order to protect themselves from harsh
weather, wind and temperatures.
o Eagles have color vision
o Body temperature is 102º Fahrenheit (38.8º C)
o Eagles do not have vocal cords; sound is produced in the Syrinx, a bony
chamber located where the trachea divides to go to the lungs.
o Bald eagles have two centers of focus or Foveae, which gives them the ability to
see forward and to the sides simultaneously.
o Eagles do have hearing, it is used to help locate and “lock in” on prey when
necessary. It is not as strong or remarkable as their eyesight or an owls hearing.
o Eagle’s ears are located just behind the eyes.
o Bald eagle’s feet are resistant to cold, due to being made up mostly of tendon.
This also aids in their incredible strength.
o The eagle can produce up to 1000 p.s.i. of torque on either of its feet.
o Hunting areas can cover from 1,700 to 10,000 acres.
o Eagles can rotate their heads about the same distance as owls, 270º
o Eagles have a second transparent eyelid (Nictitating Membrane) to protect its
eye while eating, hunting, feeding young, etc. It also cleans & moisturizes the
eye.
o Spicules are the small, rough projections sticking out from the undersides of the
eagle’s fleshy toes which help the eagle grasp slippery prey.
o Eagles have a Crop that stores food while the stomach is full, it also separates
indigestible foods that become coated in mucus, which is then expelled or
regurgitated much like an owl pellet.
o At a height of 1000 feet, the bald eagle has a range of view for small prey (rabbit
size) of about 3 square miles.
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o Average flight speed is 30-40mph. Dive speed can reach 100mph!
o Bald Eagles can swim! They use their wings much like a butterfly’s motion when
in this situation.
o Haliaeetus leucocephalus means “white-headed sea eagle” in Latin.
o Juvenile eagle feathers a larger than an adults; these are nature’s “training
wheels” to aid in stabilizing flight in their early flying days.
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Bald Eagle Facts
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Endangered Species Fact Sheet
Bald Eagle - Other Protections if Delisted
November 5, 2004 draft
The Bald and Golden Eagle Protection Act
The bald eagle will continue to be protected by the Bald and Golden Eagle
Protection Act if it is delisted under the Endangered Species Act. This law, originally
passed in 1940, provides for the protection of the bald eagle and the golden eagle (as
amended in 1962) by prohibiting the take, possession, sale, purchase, barter, offer to
sell, purchase or barter, transport, export or import, of any bald or golden eagle, alive or
dead, including any part, nest, or egg, unless allowed by permit (16U.S.C 668(a); 50
CFR 22). “Take” includes pursue, shoot, shoot at, poison, wound, kill, capture, trap,
collect, molest or disturb (16U.S.C. 688(c); 50 CFR 22.3). A violation of the Act can
result in a fine of $100,000 ($200,000 for organization), imprisonment for one year, or
both for a first offense. Penalties increase greatly for additional offenses. A second
violation of this Act is a felony, and can result in fines of up to $250,000 for individuals
($500,000 for organization). Rewards are provided for information leading to arrest and
conviction for violation of the Act.
The Lacey Act
Protections provided by The Lacey Act will continue if the bald eagle is delisted. This
law, passed in 1900, protects bald eagles by making it a Federal offense to take,
possess, transport, sell, import, or export their nests, eggs and parts that are taken in
violation of any state, tribal or U.S. law. It also prohibits false records, labels, or
identification of wildlife shipped, prohibits importation of injurious species and prohibits
shipment of fish or wildlife in an inhumane manner. Penalties include a maximum of five
years and $250,000 fine for felony convictions and a maximum $10,000 fine for civil
violations and $250 for marking violations. The maximum criminal fine for an
organization is $500,000. Rewards are provided for information leading to arrest and
conviction for violation of the Act.
The Migratory Bird Treaty Act
The Migratory Bird Treaty Act is a federal law that carries out the United States’
commitment to four international conventions with Canada, Japan, Mexico and Russia.
Those conventions cover birds that migrate across international borders.
The take of all migratory birds, including bald eagles, is governed by the Migratory
Bird Treaty Act’s regulations. The Migratory Bird Treaty Act (MBTA) prohibits the taking,
killing, possession, transportation, and importation of migratory birds, their eggs, parts,
and nests except as authorized under a valid permit (50 CFR 21.11).
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Additionally, the MBTA authorizes and directs the Secretary of the Interior to
determine if, and by what means, the take of migratory birds should be allowed and to
adopt suitable regulations permitting and governing take (for example hunting seasons
for ducks and geese).
Penalties under the MBTA include maximums of two years imprisonment and
$250,000 fine for a felony conviction and six months imprisonment or $15,000 fine for a
misdemeanor conviction. Maximum fines are doubled for organizations that are
convicted of a felony violation. The MBTA and its implementing regulations provide
authority for the conservation of bald eagles and protect against take if the Endangered
Species Act protections are removed.
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