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Physiology
and Physical Adaptations of Bald Eagles
 Vision
Vision is
definitely the most important sense of the bald eagle.
A bald Eagles
eyes are very powerful - they have vision up to 4 times that of
humans and can spot another eagle soaring at a distance of 2
miles.
A bald eagles
eyes are so large that they take up most of the space in its head.
They are not very capable of moving their eyes in their sockets,
but can rotate their heads to almost three-quarters of a circle.
The eyes are
adapted to their harsh environment and are equipped with a
translucent membrane called a nictitating membrane, much like a
second eyelid. It travels side-to-side across the eye to cleanse
and protect it. A parent eagle will often draw this membrane
across the eye when feeding its young so that the eaglet doesn’t
accidentally hit the parent’s eye while grabbing food out of
their beak. Often when flying to a perch in a heavily forested
area the eagle will make use of this protective eyelid.
The bald eagle has a ring of bones that surrounds the eye for
protection and the brow juts out slightly from the top of the eye.
This extended brow is useful for protection, reducing glare and
also gives these birds a very “serious” appearance.
Hearing
The eagle’s
outer ear opening is just behind its eye and is covered by a light
layer of feathers which do not interfere with sound waves, and has
hearing comparable to that of humans. The eagle has an inner ear
similar to ours and also has canals in the inner ear that assist
with equilibrium.
Taste
Eagles have a
poorly developed sense of taste. It is developed enough to allow
it to distinguish foul tasting prey, however they do not seem to
mind the taste of food that may be repulsive to humans.
Smell
A bald
eagle’s sense of smell is also poorly developed. If, for
example, rotten carrion were covered in snow, the eagle would not
be able to find it.
Touch
An eagle’s
sense of touch is well developed throughout its skin and body,
especially on the beak and the feet. This allows a bald eagle to
capture prey more effectively.
Beak
The eagle has a
sharp, hooked beak that it uses to tear open even the toughest
prey to be consumed. While this appendage can do some damage to
anything in its path it is not as effective as an eagle’s
talons.
Bald Eagles
also have saw-tooth serrations on the roof of its mouth to prevent
fish from slipping out.
Talons
An eagle’s
talons are equipped with two-inch long razor sharp claws. Three
point forward and one back. Talons are the primary weapons used to
grasp and kill prey. It is said that an eagle has enough power in
it’s talons to break a person’s forearm with one determined
squeeze.
Since much of
what the eagle catches are slippery fish, the bottoms of their
feet are covered in “spicules,” rough, scaly knobs that allow
eagles to hang on to fish and allow them a better grip on their
perches.
Wings and
Feathers
Bald eagles
cruise at about 40 mph but their powerful wings allow them to
reach speeds of up to 60 mph. in level flight. If real speed is
needed (catching prey in flight or driving off intruders) bald
eagles can dive up to 100 mph.
Bald eagles have powerful, finely toned muscles that control the
position of each wing and tail feather. They learn to use air
efficiently, only flapping when absolutely necessary. They also
take advantage of air currents, wind direction and thermals to
soar with little effort - soaring for eagles, for example, is
comparable to standing for humans - it is effortless.
Eagles use their feathers as flight sensors. They transmit signals
through the feather shaft to sensory cells at the base. This
signal is then sent to the flight muscles that adjust wing
position.
Feathers not
only control flight maneuvers, but regulate body temperature,
repel water and act as camouflage. Eagles use their beaks to preen
their feathers, and use oil from a gland at the base of their
tails to keep their feathers flexible and water repellent.
A good Raptor
Identification Guide is provided by the University of
Minnesota's College of Veterinary Medicine's Raptor Center. |
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