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Haliaeetus leucocephalus, the bald eagles scientific name translates: a sea (halo) eagle (aeetos) with a white (leukos) head. Its name comes from the old English word, balde, which meant white-faced. In the past, the word bald meant white, not hairless. Adult bald eagles have a blackish-brown back and breast; white head, neck, and tail; and yellow feet and bill. Their feet are not feathered like golden eagles. There are no other large black birds in North America with white heads and tails. The sex of a bald eagle can be determined by its beak. Females have deeper ones.
Newly hatched Bald Eaglets are light grey. They turn dark brown about 12 weeks of age, before they leave the nest. At age 3 and 4, they have mottled brown and white feathers under their wings and on their head, tail, and breast, along with black bills, and are easily confused with the golden eagle. At 4 to 5 years of age, when they are sexually mature, their distinct plumagewhite head and tail feathersappear and their dark brown eyes turn yellow.
One of the largest birds in North American, they are about 29 to 42 long, weigh 7 to 15 pounds, and can have a wing span of 6 to 8 feet. Females and northern eagles are larger, with females ranging from 35 to 37 with a wingspan from 79 to 90. The golden eagle is larger than the bald eagle in height and wingspan. Although male eagles are smaller, they are quicker and more agile, which is ideal for catching prey. The females larger size is good for incubating eggs and brooding the young chicks. She can use her body to shelter them from cold, soaking rains or hot sun.
Long and broad wings are effective for soaring, which requires very little wing-flapping and allows them to conserve energy. Their feather tips at the end of their wings are tapered and this helps reduce turbulence as air passes over the end of the wing. While they can swoop down to seize prey in their talons, they can only lift about half their weight in flight. If a fish is too heavy, they can swim ashore using their wings as paddles. Their flight speed can range between 65 miles per hour to 200 miles per hour depending on whether or not it is a level flight or a dive. They can soar for hours using rising warm air wind currents and thermal updrafts generated by terrain like valley edges or mountain slopes. They can fly to altitudes of 10,000 feet or more. For long-distance migration flights, they climb high in a thermal, then glide downward to catch the next one. A kettle of eagles is when several soar in a thermal together.
Eagle tails are very important for flight and maneuvering by helping eagles soar or glide in flight, brake when landing, and stabilize during a controlled dive or swoop. Their skeletons weigh around a .5 pounds and are only 5 to 6 percent of their total body weight. Their feathers weigh twice that much. Their hollow bones are light and their beak, talons, and feathers are made of keratin, the same substance that human hair and fingernails are made of. Since their beak and talons grow continuously because of this fact, the beaks of captive eagles have to be trimmed annually without the benefit of natures wearing down of it. The hook at the tip of their beaks is used for tearing and the upper mandible behind it is sharp enough to slice tough skin. Their talons are important for hunting and defense.
Eagle body temperature rests at 102 degrees Fahrenheit. Their skin is protected by down-lined feathers that aid in their tolerance of cold weather, along with their cold resistant feet made of tendons, and cold resistant bills that are made of nonliving material with little blood flow. Eagles have 7,000 lighweight feathers that are very strong and flexible, but hollow. The feathers, which have an interlocking design, protect from cold and heat by trapping layers of air and provide waterproofing and protection in rain that are crucial for flight. The different layers of feathers each serve their own purpose. Eagles do not migrate to warmer areas because of extreme cold, they move for available food supplies.
Their respiratory system consists of external nares opening on both sides of their bills, an air sac system, and lungs that air pass through twice with each breathing cycle (twice that of mammals).
Eagles do not have vocal cords. Their shrill, high-pitched, and twittering sounds are made by their syrinx. Their bird calls reinforce male/female bonds and warn other eagles and predators that an area is under their defense.
Renowned for their superb vision, they have two centers of focus that allows them to see both forward and to the side simultaneously. They can sight fish from several hundred feet above while in flight, which is remarkable because fish tend to be counter-shaded (darker on top) and harder to see from above. Their eyelids close when they are sleeping and for blinking they have a translucent inner eyelid that slides across the eye from front to back every three to four seconds that wipes dirt and dust from the cornea, while still allowing the eagle to see. Eagles have color vision like all birds and although their eye is almost the size of humans, they are at least four times sharper.
Diurnal (active by day) birds of prey like hawks and eagles use their hearing to locate prey or other birds, but it is not as essential, therefore, not as sharp as that of an owl who can find prey in the dark by sound.
What Do Bald Eagles Look Like? Physical Descriptions
What Do Bald Eagles Eat? Food Sources and Hunting Habits
Breeding Cycles of Bald Eagles Mating and Nesting
Migration Patterns of Bald Eagles
Normal Lifespans and Causes of Death for Bald Eagles
Patriotic Poetry The Eagle as National Emblem
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