Bald Eagle Biology
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© American Eagle Foundation.
59 species worldwide.Birdlife.orglists all species with links to more information.
[/av_toggle] [av_toggle title='How big is a bald eagle?' tags=” av_uid='av-8ktys2o'] Northern eagles are larger than southern eagles. Male bald eagles can weigh anywhere from 6 to 9 pounds, with females usually weighing 20 to 30 percent more. Alaskan females reach up to 15 pounds. Florida males may only weigh 6 pounds. The average female bald eagle is 35 to 38 inches tall.
The wingspan varies between 6 and 8 feet.
[/av_toggle] [av_toggle title='What are the differences between bald and golden eagles?' tags=” av_uid='av-7xuvehs'] The main difference is that bald eagles belong to a group of “sea eagles” that live on or near bodies of water and are piscivorous (fish eaters).
Golden eagles belong to an entirely different group of eagles known as true or "booted" (legs with feathers versus scales) eagles, and are highland eagles, meaning they don't go near water. They mainly hunt upland mammals versus fish. These are only 2 out of 59 species of eagles worldwide, but the only two we have here in North America (with the exception of another species that occasionally shows up in far southwest Alaska).
The "bald eagle" takes its name from the Old English word "balde", meaning white-headed (not hairless!). "Golden eagles" likely get their name from the top and back of their heads and necks, which are a beautiful golden color. - PN
[/av_toggle] [av_toggle title='How do bald eagles control their body temperature?' tags=” av_uid='av-7g2ff28′] Eagles are very efficient at adapting to changes in temperature. They have an underlayer of fluffy down feathers under their outer feathers to insulate them from the cold. They "thermoregulate" (control their temperature) by panting with their mouths open or by losing heat through their featherless legs and feet. Babies can “thermoregulate” between the ages of 10 and 14 days. Until then, the adult parents (usually the mother) hold the babies close to keep them from getting too cold.
[/av_toggle] [av_toggle title='What are the differences between male and female bald eagles?' tags=” av_uid='av-79oyyio'] Females are about 1/3 larger than males on average.
Two measurements of size, beak depth and hallux (toe claw) length, show the greatest segregation of the sexes. These measurements can be used in the following equation: Sex = (Beak Depth x 0.392) + (Hallux Length x 0.340) -27.694 (measurements are in millimeters). If the answer is affirmative, the eagle is a female. If the answer is negative, the eagle is a male.
The fluting calls of the males are almost a scream; Female is tuned much lower. - PN
[/av_toggle] [av_toggle title='What is the lifespan of a bald eagle and how long can it breed?' . The longest life span of a bald eagle in the wild is 39 years. In captivity, they can live to over 50 years due to less danger and veterinary care.
About 50 percent died in the first year due to their inexperience with the dangers of life in the wild. After their first year, about 90 percent survive each year.
It is believed that eagles can reproduce throughout their lifespan, but little documentation is available. An eagle has been documented successfully rearing young in its 26th year of life.
[/av_toggle] [av_toggle title='What are some facts about bald eagle feathers?' tags=” av_uid='av-60wc9ds'] Bald eagles have 7,200 feathers. To see examples of the feathers,Click here.
A bird's feathers are superbly crafted to shape its aerodynamic shape and protect it from the challenges of water and weather. In this sequence from FLIGHT: THE GENIUS OF THE BIRDS, slow-motion photography and computer animation demonstrate a remarkable level of engineering and design.
Feathers, like the scales on the feet, or the claws or horny sheath of the beak are keratin-like outgrowths of the skin, similar to our nails. Feathers grow from skin follicles, just like human hair. The skin holds the feather cone to the follicle, and tiny bundles of "feather" muscles in the skin at that location and between the follicles hold the feathers and cause them to move. The skin surrounds and grows over the shaft.
A needle feather, sometimes called a "blood feather," is a feather that develops on a bird. It is supplied by blood, and if damaged, a bird can bleed profusely. As it gets longer, blood supply is concentrated only at the base of the shaft. At this point, it is no longer referred to as "Blood Feather". The feather comes out wrapped in a thin tissue shaft, which eventually splits, allowing it to unfold and grow to its full size.
Eagles make a moulting experience with their feathers. The molting process is still not well understood. Before reaching sexual maturity at about 5 years of age, we need to think of moulting in terms of different plumages: Young eagles go through four different plumages until they reach their sexually mature, adult plumage, which would be the fifth plumage type. These are (as described by Clark and Wheeler in Hawks of North America): Juvenile, White-belly I, White-belly II, and Adult transitional plumage.
So you might think 5 years to maturity, 5 plumage, one molt per year. Not exactly. Moult can be influenced by a variety of biological and species-appropriate factors (such as food availability, densities of other eagles, and others), and not all moults are always complete moults.
Once they have reached their final "adult" plumage, bald eagles are likely to shed their flight feathers almost every year. However, some signs of molting can be seen at almost any time of the year.
This flight feather moult is not simultaneous; Rather, matching flight feathers are generally lost at different times, so the birds are never left flightless. - PN
[/av_toggle] [av_toggle title='What specific muscles help fly?' tags=” av_uid='av-5st55eo'] Flying requires a network of hundreds of muscles, ligaments, and tendons. In this sequence from FLIGHT: THE GENIUS OF VIRDS, the structure and design of a snow goose's primary flight muscles (the engines that lift it and propel it through the air) are demonstrated in stunning detail.
[/av_toggle] [av_toggle title=’Was ist ein Brutfleck?’ tags=” av_uid=’av-55cq24g’] ABrutfleckis an area on the parents' chest that has no feathers. This is the area that touches the eggs while the parents incubate them and allows for more efficient heat transfer to the eggs.
Not all birds develop a brood patch. In species like the bald eagle, both parents develop an incubation field because, as we see every day, they share incubation duties. The incubation patch begins to develop on the chest or abdomen just before the female lays her eggs through hormonal changes that cause the feathers covering that area to fall out on their own. This leaves a wrinkled patch of bare skin that fills the blood vessels with warm blood. If we see the female or male "wiggle" as they perch on the eggs, they spread this bare spot over the eggs to keep them warm. ….(Courtesy of CCB Nest Blog)
This image was captured in February 2017 near Reelfoot Lake in northwest Tennessee. It shows a brooding eagle with a clearly defined brood patch. Photo ©Mike Bohannon; used with permission.
[/av_toggle] [av_toggle title='What's happening inside these eggs?' tags=” av_uid='av-4zi9bs0′] In this sequence from Illustra Media's latest documentary FLIGHT: THE GENIUS OF VIRDS, you enter a fertilized egg to witness a bird's embryonic development. Spectacular animation and live-action footage document the extraordinary 21-day process of organizing and growing from a few cells into a chicken.
In a bald eagle, it takes approximately 35 days for the embryo to develop into a fully developed eagle once incubation has begun.
[/av_toggle] [av_toggle title='Why do eagles turn eggs while hatching them?' tags=” av_uid='av-477vdj4′] The eggs are turned over by both parents about every hour to 2 hours during the incubation period. The purpose of this role is to ensure that the lighter yolk does not rise to the surface of the egg and the delicate blood vessels covering the yolk touch and adhere to the shell surface, killing the developing chick. (Peter Nye)
Raptor Resource(Bob Hancock) adds: Turning or rolling aids in air exchange and helps maintain an even egg temperature.
[/av_toggle] [av_toggle title='Why do eagles sometimes leave their eggs uncovered during the breeding season?' lay their eggs for a certain period of time,Raptor resource explained: “A bird’s eggshell has thousands of tiny pores that allow water and gas to pass through. Mammals like us get oxygen through a navel, but developing birds get oxygen and remove carbon dioxide through the eggshell. Gases, including oxygen, enter and leave the egg by diffusing through pores in its shell, across the outer and inner shell membranes, and into the blood in the capillaries of a special tissue called the CAM, or chorioallantoic membrane. As the weather warmed up in Decorah, the snow began to melt and the humidity rose. Condensation can form on eggshells that are exposed to excessive moisture, clogging the shell pores and providing a vehicle for bacteria. The result? Fatal asphyxia and/or contamination. Only the eagles know for sure, but I think they've responded to the threat of rising humidity by leaving their eggs uncovered. Standing or abandoning it completely allows fresh air to circulate over the eggs, reducing humidity and providing fresh air to the developing embryos.”
This was an explanation for a specific situation - but the overriding reason seems to be the rising humidity, which clogs the pores of the shell and is therefore a vehicle for bacteria.
[/av_toggle] [av_toggle title='How does an eagle hatch?' tags=” av_uid='av-3d06kgw'] After about 35 days in the egg, the eagle is ready to hatch. An "egg tooth" was formed at the tip of its beak to aid in this process. In addition, a very strong neck muscle has developed to help pierce the membrane inside the egg.
Inside the egg there is an air pocket at the top, and the rupture of the membrane in the egg allows the eagle to breathe its first breath of air in the eggshell. This bit of air gives the eagle energy to continue detaching itself from the shell. During this time, the yolk is absorbed into the eagle's stomach and provides more energy.
The eagle scratches the inside of the shell with its egg tooth to weaken it. Eventually, a tiny hole or crack develops. This is called a "pip". Releasing itself from the egg is an extremely tiring process for the eagle and can take up to 2 days from the first core to actual hatching. During the process, the eagle sometimes rests for a while. During the hatching process, the eagle slowly rotates counterclockwise by waving its legs while all the while scratching the inside of the shell with its egg tooth.
A hatch is complete when the eagle is completely out of the shell.
The parent eagles don't help with this, but they seem to know when the eagle is ready to hatch. They can even hear the tiny peeps from inside the shell and occasionally move from the eggs they hatch and look down to see what's happening.
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In a 2018 post,"Elven Ruler"(www.elfruler.com) states: “The bird egg is a marvel of nature, a self-contained and fully effective living environment for the developing bird embryo. It is strong but flexible, hard but porous. It contains everything necessary for a small and frail organism to evolve into a chick with enough strength and dexterity to break through and emerge into the outside world.Click here for a report on the many factors involved in hatching a chick.”(Extremely detailed and better suited for older students and/or adults)
*Note:"Elven Ruler"is the pseudonym of the author of a well-known bald eagle blog(www.elfruler.com). "Elfruler" is a "retired university professor with a Ph.D. in a humanities discipline, has been a bird watcher for many years and has been an avid observer of internet bird cams (birds of prey and other wildlife) since 2009. During this time she also read extensively and deeply in ornithology, and has done so for 4 years. She has volunteered with raptor rehabilitation organizations and gained hands-on experience in trapping and rescuing, medical sighting and treatment, and rehabilitation of raptors and other birds .”
[/av_toggle] [av_toggle title='How do young eagles grow? ‘ tags=” av_uid=’av-2nx6f9c’] Baby eagles are born completely helpless. They can't hold their heads up; their vision is limited; Her legs are too weak to support her weight. are bald eaglesarticle, which means they have to rely 100 percent on their parents to protect and care for them.
It can take days to fully hatch from the first core to full release from the shell (at Romeo & Juliet's nest in Florida, the first hatched eagle (NE16) in 2016 took 40 hours to complete the process. Often it is much faster than that.
After hatching, the eagle dries and puffs out to a downy gray. Food is offered to the eagle by the parents, who mince meat from fish or whatever is available. Tiny bits are offered over and over as the eagle struggles to keep its wobbly head still long enough to eat. In a short time, the eagle gets stronger, and its eating and coordination skills develop quickly.
An eagle has a goiter - a storage area - under its chin. The food enters the crop and is then digested as needed. When the crop is "full" you can see it bulging. This harvest is actually part of the esophagus where food is stored and soaked. The crop regulates the flow of food through the digestive tract.
How fast do eagles grow?
- The eagles are growing rapidly, adding about half a pound to a pound of body weight each week until they are about 9-10 weeks old, depending on whether the eagle is male or female. Females are always larger.
- At about two weeks old, they are able to hold their heads up to eat. At this age, the eagles can toothermoregulieren.Thermoregulation means the eagles are now able to maintain a near-constant body temperature. They don't have this ability at birth, so the parent eagles must consistently hatch them until the juvenile eagles reach this important milestone.
- By about three weeks, they are 1 foot tall, and their feet and beak are almost the size of an adult.
- At about three to four weeks of age, the eagles are covered with a second layer of gray down.
- After about four to six weeks, the birds can stand, then they can start tearing up their own food.
- After about three to six weeks, young black feathers begin to grow in. While downy feathers are excellent insulators, they are useless and must be replaced with young feathers before an eagle can make its first flight, around 10 to 14 weeks after hatching.
- At about six weeks, the eagles are almost as big as their parents.
- The eagle's appetite is at its peak at around eight weeks. The parents hunt almost continuously to feed them, while at the nest the eagles begin to stretch their wings in response to gusts of wind, and they may even hover for brief periods. The eagles grow stronger.
- At about nine to ten weeks they begin to branch out, this is a preliminary stage to fledging.
- After about ten to fourteen weeks, the eagles will fledge or fly away from the nest.
- Once the eagles have fledged, they may stay near the nest for four or five weeks, making short flights while their primary feathers grow and strengthen. Her parents will still provide all her food. The juvenile chicks resemble their parents except for their color but are dissimilar in behavior. The fry now have to learn to hunt, and they're just learning what's left of summer. After that they are on their own. The first winter is the most dangerous and difficult part of an eagle's life.
[/av_toggle] [av_toggle title='Does an eagle have exceptional eyesight?' tags=” av_uid='av-1wwmulc'] All eagles are known for their excellent eyesight, and the bald eagle is no exception. They have two foveae, or centers of focus, which allow the birds to see forward and sideways at the same time.
Bald eagles are able to spot fish in the water from several hundred feet while soaring, gliding, or flapping. This is quite an exceptional achievement as most of the fish are counter shaded meaning they are darker on top and therefore harder to see from above.
Eagles have eyelids that close when they sleep. They also have an inner eyelid called the nictitating membrane for blinking. Every three to four seconds, the nictitating membrane slides back and forth across the eye, wiping dirt and dust off the cornea. Since the membrane is translucent, the eagle can see even when it is above the eye.
Like all birds, eagles have color vision. We believe they can see in color because of the numerous "cones" in their retinas. Cones are known to be necessary for visual acuity and color vision, as opposed to the "rods" which are designed for low-light vision, something eagles are not particularly adapted to.
An eagle's eye is almost as large as a human's, but its sharpness is at least four times that of a human with perfect vision. The eagle can probably identify a rabbit moving nearly a mile away. This means that an eagle flying at an altitude of 1000 feet over open country can spot prey over an area of almost 3 square miles from a fixed position.
A bald eagle's eye changes color as it matures. The nest eagle's eyes are almost black. Young eagles (first-year birds just out of the nest) have brown eyes (which can vary in lightness or darkness, but are usually quite dark). When they become immature eagles (around 2-3 years of age), their eye lightens to a light brown.
[/av_toggle] [av_toggle title='What are the special features of the bald eagle's feet and claws?' tags=” av_uid='av-1qe47eo'] The feet are featherless (scaly). They have 4 toes, each with a very heavy claw (talon). Three toes point forward; The 4th (the hallux) is longer and points backwards for easier prey grasping. These hallux claws are almost 2 inches long in large female eagles and only about 1.5 inches in small males. Claws are made of the same material as human fingernails and are very similar to a dog's nails. The true power of the claws comes from the muscles in the legs. When they contract, they pinch the tendons in the lower legs, locking all claws together in a vise-like grip. - PN
[/av_toggle] [av_toggle title='What are the characteristics of a bald eagle's digestive system?' tags=” av_uid='av-1860irk'] Birds generally have a higher metabolic rate than humans, requiring them to process their food quickly. That means getting them into a form from which they can extract the energy they need quickly and efficiently.
Birds, including eagles, have adaptations for this. Most importantly, part of their stomach has transformed into a gizzard, where food is ground down to a fine consistency to allow for quick digestion. In eagles, this is also where pellets are formed. These are masses of indigestible prey material such as fur, feathers, and occasionally bones, which then travel backwards from the gizzard to the mouth and are expelled (like vomit) from the mouth. Depending on the food intake, pellets are formed overnight after the meal, which are usually ejected the next morning.
Most fish are fully digested. Eagles have very strong stomach acids and are quite good at digesting bones, which helps them with their own bone formation and eggshell formation.
Another important feature of their digestive system is that eagles (and other birds) have something called a goiter in their upper digestive tract (esophagus), where food can be stored for days. This is extremely beneficial for eagles, which can store up to two pounds of food in their crop when prey is plentiful, allowing them to go several days without food if necessary. - PN
Click herefor more information and an illustration on the digestive system of eagles. (Source:Digestive systems in different tribes)
[/av_toggle] [av_toggle title='Visual description of the Bald Eagle's beak and eye.' tags=” av_uid='av-sx75c0′]
[/av_toggle] [av_toggle title=’Wie heißen junge Adler je nach Alter?’ tags=” av_uid=’av-ovmnxc’] Jungtier =
[/av_toggle] [av_toggle title='What is a Leucistic Bald Eagle?' tags="] Leucism is a genetic mutation that causes patches of white or altogether faded or pale feathers to appear on a bird - and bald eagles are included. When this happens, melanin or pigment is prevented from forming in parts of a bird's body animal to be produced. Birds lack pigment in some feathers, which can lead to weaker feathers and susceptibility to sunburn. Leucistic birds are rare, occurring in only about 1 in 1,800 individualsThe Audubon Society's Encyclopedia of North American Birds.Audubon continuesthat leucistic birds of prey, with weakened wings and susceptibility to sunburn, predators, and parasitic infestations, typically do not live long.
Links for images and more information are below:
National Geographic(Photo by Traci Walter)
The Cary Adventures(Photo by Peter West Carey, 2018, showing an overall faded appearance of the eagle.)
10,000 Birds: A leucistic bald eagle performs at the Winter Wings Festival in Klamath Falls, Oregon(several photos)
leucistic animals(Pinterest – lots of photos)