|American Bald Eagle Information
Bald Eagle - Nesting & Young
|There are an estimated 7,066 nesting pairs of bald eagles, due to the efforts of federal agencies, tribes, state and local governments, conservation groups, universities, corporations, and thousands of individuals.
US map of estimated breeding pairs in each state.
Nests - The shape of the eagle nest or aerie is determined mainly by the branch point where it's built. Sticks placed in tree forks result in cylindrical or conical shaped nests. Disk shaped nests are built on the ground or a tree branch which is nearly level. Bowl shaped nests occur where the tree trunk branches off into smaller upright branches. Inverted cone shaped nest.
Bald eagles build their nests in large trees near rivers or coasts. A typical nest is around 5 feet in diameter. Eagles often use the same nest year after year. Over the years, some nests become enormous, as much as 9 feet in diameter, weighing two tons.
If the nest tree falls or a strong wind blows a nest down, the established pair usually rebuilds at or near the site within a few weeks if it is near the breeding season. A nesting pair will also build a new nest if they feel threatened. Essentially, it's not totally uncommon for eagles to build more than one nest within their nesting territory.
The nest is usually built in a tree, but may be built on a cliff or even on the ground if there are no other options available.
Eagles are territorial during nesting season. They will keep other eagles out of their own nesting territory, which is usually one to two square miles.
|Sexual maturity - An eagle reaches sexual maturity at around four or five years of age. At that time, the eagle's energies become concentrated on the effort of finding a mate and raising offspring. Bald eagles mate for life, but when one dies, the survivor will not hesitate to accept a new mate.
During breeding season, both birds protect the nest territory from other eagles and predators.
Mating season - varies greatly by region. In the South it may last from late September through November, while in the Great Plains and Mountain West, it may last from January through March. In Alaska it lasts from late March to early April.
One way to determine the sex of an eagle is to examine its beak. Females have deeper (distance from top to chin) beaks than males.
Pairs of bald eagles have been seen whirling through the air with talons locked together. This could be a form of courtship or a ritualized battle between an intruding eagle and one defending its territory. Whichever it is, eagles do not actually copulate in the air. Copulation usually takes place on a branch near the nest or on the ground.
On rare occasions, bald eagles have remained locked together by their talons long enough to fall to the ground. I received an email telling of two talon locked eagles falling into a bush beside a person's home. They remained locked for about eight hours, and then unlocked and flew away. Another case reported in a Georgia newspaper article, tells of a locked pair falling to the ground in a golf course. They were stunned by the fall and remained locked for several hours. Only after one eagle was touched by a bystander, did they unlock and fly away.
Some eagles do not breed every year. Bald eagles are capable of breeding annually from the age of four, but some of the adults, though paired, seem to choose not to breed. It might be an instinctive decision, based on the weather; availability of nesting sites, or food.
Because an eagle lives up to 30 years in the wild, it has many years in which to produce offspring.
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.
Bald eagle nesting seasons
| 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, 98% of the time one parent remains 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. If the adults leave the nest unattended too long, it can be consequential for the eggs. Diverse weather conditions could impact the temperature of the eggs; leaving the eggs nonviable.
| Human disturbance can have an impact on the bald eagle, as most of them need some privacy and quiet to breed. People wanting to observe or photograph the eagles can disturb them enough to cause them to abandon a nest. Use binoculars and spotting scopes for viewing, and keep at a reasonable distance.
Bald eagle disturbance sensitivity chart during the nesting cycle.
The eggs hatch in the order they were laid. Eaglets break through the shell by using their egg tooth, a pointed bump on the top of the beak. It can take from twelve to forty-eight hours to hatch after making the first break in the shell (pipping). Once the eggs begin to hatch, the female's vigilance becomes nearly constant. The male provides the majority of the food needed by his rapidly growing family. Eventually the female will take up her share of the hunting, but in the early days, all of her attention is given to the young eaglets in the nest.
Chicks - Sometimes two chicks will survive, but it is not uncommon for the older eaglet to kill the smaller one, especially if the older is a female, as females are consistently larger than males. Should one chick decide to kill its sibling, neither parent will make the slightest effort to stop the fratricide.
Newly hatched, eaglets are soft, grayish-white down covers their small bodies, their wobbly legs are too weak to hold their weight, and their eyes are partially closed eyes, limiting vision. Their only protection is their parents.
Eagles feed their young by shredding pieces of meat from their prey with their beaks. The female gently coaxes her tiny chick to take a morsel of meat from her beak. She will offer food again and again, eating rejected morsels herself, and then tearing off another piece for the eaglet.
While on the nest with very young eaglets, parents move about with their talons balled into fists to avoid accidentally skewering their offspring.
This photo as well as the preceding and proceeding photos were taken from the back deck of a home atop a ridge which surrounds a public park beside a university in the middle of a city. The nesting tree is located in the park at the bottom edge of the ridge. As a result, the height of the nest in the tree matches that of the deck, with 40 - 50 yards between. I asked permission from the homeowners to photograph the eagles. Having nested there for 10+ years, the eagles are very used to people on the deck; they go about their nesting duties and do not pay any attention. (400mm lens, with x2 extender...cropped photos)
|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.
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.
Quiet Please - Eaglets Growing by Carolyn Stearns / David Aiken (illustrator) describes the successful efforts of school children to save their eagle neighbors from developers near Chesapeake Bay.
Down is gradually replaced by feathers, while the eaglets grow still stronger. Finally, an important moment arrives.
In An Eagle to the Sky (1970), Frances Hamerstrom, who spent many hours observing eagles, described the process for one young bird:
The.....EAGLET WAS now alone in the nest.
Each time a parent came flying in to toward the nest he called for food eagerly; but over and over again, it came with empty feet, and the eaglet grew thinner. He pulled meat scraps from the old dry-up carcasses lying around the nest. he watched a sluggish carrion beetle, picked it up gingerly, and ate it. His first kill.
Days passed, and as he lost body fat be became quicker in his movements and paddled ever more lightly when the wind blew, scarcely touching the nest edge; from time to time he was airborne for a moment or two.
Parents often flew past and sometimes fed him. Beating his wings and teetering on the edge of the nest, he screamed for food whenever one flew by. And a parent often flew past just out of reach, carrying delectable meals: a half-grown jack rabbit or a plump rat raided from a dump. Although he was hungry almost all the time, he was becoming more playful as he lost his baby fat; sometimes, when no parent bird was in sight, he pounced ferociously on a scrap of prairie dog skin or on old bits of dried bone.
The male eaglet stayed by himself for the most part. He was no longer brooded at night. Hunger and the cold mountain nights were having their effect, not only on his body but on his disposition. A late frost hit the valley, and a night wind ruffled his feathers and chilled his body. When the sunlight reached the eyrie's (the brood in a nest of a bird of prey) edge, he sought its warmth; and soon, again, he was bounding in the wind, now light and firm-muscled.
A parent flew by, downwind, dangling a young marmot in its feet. The eaglet almost lost his balance in his eagerness for food. Then the parent swung by again, closer, upwind, and riding the updraft by the eyrie, as though daring him to fly. Lifted light by the wind, he was airborne, flying--or more gliding--for the first time in his life. He sailed across the valley to make a scrambling, almost tumbling landing on a bare knoll. As he turned to get his bearings the parent dropped the young marmot nearby. Half running, half flying he pounced on it, mantled, and ate his fill.
Elf the Eagle, written by Ron Smith and Illustrated by Ruth Campbell is a delightful children's book about a baby eagle who worries about many things, including the distance from his nest, high up in a tree, to the ground, way, way down below.
Elf is an inspiring story, told with gentle humor. It will delight children, who will relate to Elf's fears and will realize, as he does, that they too will grow into their wings and fly, when the time is right.
The Unstoppable Eagles, written by Terri Lhuillier and Joanne Brady with illustrations by Sarah Brady is the inspiring true story about a pair of nesting bald eagles determined to remain at their existing nesting site, despite a cone being placed over their nest to deter them away from nearby bridge construction.
Bald eagle enthusiasts and animal lovers of all ages will enjoy this well written, beautifully illustrated inspiring book.
Approximately 40% of young eagles do not survive their first flight.
Once the young eagles have fledged (to acquire the feathers necessary for flight) they remain around the nest for four or five weeks, taking short flights while their primary feathers grow and strengthen. Their parents still provide all of their food.
The young birds, with the exception of their color, resemble their parents, but are nothing like them in behavior. They have to learn how to hunt, and they only have the remainder of the summer to learn. After that, they're on their own. The first winter is the most dangerous and difficult part of an eagle's life.
Higher predators are born with instincts that urge them to fly, to bite or to pounce, but precisely how to do these things is another matter. Through months of trial and error, eagles acquire basic skills such as lighting on perches or stooping on prey through practice. Eagles practice with almost fully developed bodies, and so sharpen their skills quickly.
An immature bald eagle is sometimes mistaken for a golden eagle. However, a young bald eagle has more white mottled into its coloration overall; a golden eagle is more solid in color, and its beak is more blue-black with a nearly black tip.
Eagles molt in patches, taking almost half a year to replace feathers, starting with the head and working downward. Not all feathers are replaced in a given molt. Until the bald eagle is mature, the replacement feathers are of different colors. As adults, the belly and back are dark, while the head is pure white. The distinct juvenile pattern, signaling that a bird is not ready to breed, may reduce aggression from territorial adults.
As juvenile bald eagles mature, their head and tail feathers gradually turn white; simultaneously the eyes and beak gradually turn yellow. Complete transformation to maturity is achieved sometime in the fifth year.
After fledging, young eagles stay near the nest for six to nine weeks practicing their ability to fly and hunt. The parents cannot tell juveniles how to hunt, they have to learn by watching the parents and practicing. During this time, they seem to spend more time looking at prey than they do actually attacking it.
Until the first winter after they fledge, young eagles near the nest are often still fed by their parents, but have little other contact with them. Although a young eagle has the instincts to hunt, it lacks the skills. Eventually, they learn to soar and spot prey. If food is scarce during the winter, it could die.
Nesting cycle - From the time the parents build the nest and the young are on their own, takes about 20 weeks. During the nesting cycle the parents remain within one to two miles of the nest.
Communal gatherings of bald eagles offer many advantages to younger inexperienced eagles. Not only is food abundant on the salmon spawning grounds, but here the juveniles can watch their elders to learn how food is caught. They also learn very quickly how to steal food.
The information and photos on this website may be used for student projects as long as neither are placed on other websites. The photographs are copyrighted by Hope Rutledge, the owner and author of the American Bald Eagle Information website, and are NOT available for other websites, photo galleries or commercial use of any kind.