Bald Eagle Facts
More Bald Eagle Facts
Characteristics
Q. Is there any significant reason why bald eagles have yellow eyes?
A. Great question. I really don't know if there is any reason that the adult iris is light, except that it is a morphological difference with the immature birds which have darker, brown iris' till sexual maturity. Could the yellow eyes look more threatening?
Q. Does a female bald eagle have a white head like a male?
A. Yes, they look identical. The female is larger than the male though, and measurements taken of certain body parts such as the bill and rear claw (hallux talon) can distinguish the two sexes; otherwise you can't tell.
Q. How does an eagle see an animals on the ground while soaring high above?
A. They have extremely keen vision. Their eyes are specially designed for long distance focus and clarity. The eye is large with a large retinal surface area with a high concentration of cones (all of our eyes have rods and cones which allow us to see) which aid in visual acuity and color perception, among other features. It has been estimated that eagles can see 3-4 times farther than humans and that they can see another eagle soaring nearly 50 miles away.
Q. What is the bald eagle's diving speed?
A. Pretty fast when they do it, i'd bet 75+mph, although they seldom really "dive".. They catch prey by flying low and "snatching with their feet mostly, not like ospreys or peregrine falcons that actually dive at their prey.
A. Great question. Absolutely. They are very good swimmers, and i've even seen older nestlings who can't fly yet swim. It's not uncommon for an eagle to "misjudge" and latch into a fish too heavy/large for it to fly with, so they then may swim quite a distance to shore (wouldn't want to let go of lunch now would we), drag the fish up on shore and then eat it.
Q. How fast and how far can a bald eagle fly when flying for 30 minutes?
A. That depends on what the eagle is doing. If it is just flying from one feeding area to another or from its nest to the end of the lake say, it probaly flies about 20-30 miles per hour. When migrating, eagles seldom flap their wings; rather, they use thermal updrafts to gain great altitude and the saor in a long, descending glide within which they can hit 50-75 mph easily.
A. No. They "thermoregulate" (control their temperature) by panting with their mouth open or through heat loss through the unfeathered legs and feet.
Life Cycle
Q. How long does the bald eagle live?
A. Typically in the wild probably between 20-30 years. Some eagles in captivity havelived up to 50 years, but in the wild they would not live as long.
Q. How do you determine a bald eagle's age?
A. By plumage until they are 5 years old, then after that you cannot age them.
Q. Does the bald eagle mate with different kinds of eagles?
A. No.
Q. Do bald eagles have only one mate for life?
A. Typically, yes, although occasionally an intruding adult (not one of the pair) comes in (usually a female) and battles the resident bird for the territory, sometimes then taking over. If one of the pair dies, the other will find a new mate and usually keep going in the same territory.
Q. Do bald eagles build their nests in low trees?
A. No, nor do they prefer to. Given the option, eagles will choose a "super-canopy" (one rising above the rest) tree with sturdy limbs and a commanding view of the surrounding terrain, which is also always very near to water. Typical nest heights are 50-125 feet high.
Q. How tall do trees half to be for a Bald Eagle to nest in?
A. The higher the better!
Q. Why do bald eagles have such big nests if they only have two eggs?
A. They are large birds and their young become quite large, demanding of lots of space to fit all the birds and their 6 foot plus wings.
Q. How do eagles find their old nest?
A. Since the nests are so large, it's probably pretty easy, especially if they haven't gone too far! I suspect though, that you are asking about birds that migrate long distances to and from their nests. In that case, since eagles are diurnal (daytime) fliers, we believe they use familiar landmarks to guide them to the general area, and once there, use more familiar and specific cues to find their particular lake and then the nest tree. Such cues as extensive mountain ranges or large water bodies or the coastline might first be used. These birds obviously "store" great amounts of information or "memory" of the landscapes in their lives, as they easily move 50 - 100 miles in a winter day in search of food.
Q. About how long does it take for the bald eagle's eggs to hatch and how long until it can fly?
A. It takes 35 days to hatch, then young in nest 10-12 weeks more unti lthey fledge (fly from nest).
Q. How old are they before young eagles can fly?
A. At 10-12 weeks, when they leave their nest.
Q. When do eagles learn to fly and how?
A. At between 10-12 weeks as they first leave the nest (fledge), and then with more and more practice to and from the nest and surrounding trees over the next month or two.
Q. How old does a baby have to be to leave its mother?
A. 10-12 weeks to leave the nest, although fledglings then often stay around "learning from their parents and honing their flying and feeding skills for another 1-2 months.
Q. How long does it take the eaglet's feathers to turn brown?
A. The feathers are brown as soon as they start to appear, which happens starting at 5 weeks of age; they are pretty well fully feathered by 9 weeks.
Q. Out of twenty eaglets, how many will live to be adults?
A. This varies with the population in question. From our work releasing eagles in New York, about 2.5 adults would survive for every 20 (1 in 8). Mortality is highest for eagles in their first year of life, especially their first six months. The first winter is crucial. Some biologists (two studies) have estimated mortality as high as 72 % within one year of fledging (leaving the nest). Another study estimated that only 11 % of eagles were alive after 3 years of life. In general, we believe that only about 1 in 10 eagles survive to adulthood ( 5 yrs of age).
Ecology
Q. How many pounds of food does a Bald Eagle eat in a day?
A. Approximately .5 - 1.5 per day.
Q. Would an eagle eat other birds? I know that the eagle's favorite food is fish. I know that sometimes little birds tease big birds because eagles cannot manuver as well as the other birds, so could they eat them?
A. Very good and accurate observation dale. Yes they do and will eat other things, although fish are preferred when they can get them. They also like waterfowl. We check all of our nests each year when we climb up to band the eaglets, especially looking for prey (food) remains. We have found rabbits, muskrats, gulls, ducks, turtles, and lots of kinds of fish, just to name a few!
Q. What are the eagle's enemies?
A. An occasional racoon in the nest, or rarely a great horned owl in the nest (threat to nestlings only), but otherwise only human beings.
Q. What is the largest prey animal that they have been known to kill?
A. Good question. The key word here is "kill". Bald eagles are much more opportunists than killers, meaning that if they can get an easy meal without expending much energy (i.e. by killing something) they will do that. So, reports of bald eagles feeding on deer, whales, or other large animals, are usually because they found it/them already dead. Eagles are capable of killing geese, turkeys, swans (especially if they are already somewhat debilitated), and large salmon. I would not be surprised if they took any prey that was under about 3-4 pounds, which would be their max. No type of food item (meat) would surprise me either, except that obviously their favored prey is fish.
Q. In what kind of habitats do bald eagles live?
A. Almost exclusively aquatic based habitats, with forested, generally undisturbed uplands.
Q. How old are Bald Eagles when they migrate?
A. Soon after they leave the nest they begin (sometimes long distance) wandering--at about 6 months of age.
Q. How do scientists test Bald Eagle's navigational patterns?
A. We really haven't "tested" their navigational skills, but have deduced some of their pathways and patterns from banding and marking numerous birds and then receiving sightings or recovering dead birds. Also by affixing both conventional and new satellite radio telemetry devices to the birds then following their movements and analyzing where and when they go, deducing clues from their movements. For example from the satellite data, it's easy to see if an eagle is following a water course, where they stop for the night, etc. See above for more about migration behavior.
Q. Out of all the eagles that migrate, how many make it to their destinations?
A. Once they become adults, they have a high survival rate year to year, likely 90% or more.
Q. Do the same eagles come back each year to the same place?
A. Generally, yes they do, which is why it is so important to protect those areas eagles are known to use. You are lucky in maine, as you have a good population of eagles and some very dedicated biologists trying to save them. Your department of inland fisheries and wildlife can give you lots of additional info on eagles in Maine.
Q. If bald eagles do migrate, do they go to the same spot every year?
A. Generally (especially with adult birds) the answer is yes. That is one of the things our research is trying to answer using satellite tracking
Q. How exactly are satellite transmitters attached to an eagle?
A. As a "backpack", exactly like the one you might wear to school. Straps in front of and behind both wings are stitched together in the front.
Q. Do bald eagles fly in flocks or are they a solitary bird?
A. They usually fly alone, although some may follow others to feeding grounds, like from the morning roost, or when going back to the roost in the late afternoon.
Q. If eagles migrate south for the winter, why do they bother to go back north? Why don't they just stay in the south?
A. Great question. They have an inborn tradition to their general area of fledging, called "fidelity", which draws them back there. This instinct has probably evolved over thousands of years because if they were successfully born in a certain area, the chances of their success at nesting in the same general area are probably pretty high. It also helps keep the birds distributed. If they all decided to stay where they wintered, things would get pretty crowded in a hurry!
Q. Do bald eagles migrate from summer to winter?
A. Sometimes, especially when they nest in areas far to the north where these areas freeze over in fall/winter, so they must leave to find open water and survive. That is what this study. We think our eagle #32 summers in Canada and winters in southern New York state. We will find out as she migrates back to her nesting ground this spring.
Q. In what areas would bald eagles live in Nebraska?
A. Any areas near large water bodies or rivers with good fish populations (or waterfowl in the winter), especially those with little or no human disturbance. I think that Nebraska has a good number of eagles wintering there each year, but i'm not sure where--is the platte river in nebraska?? Check with your state Fish and Wildlife agency.
Q. Why do Bald eagles only congregate on the West Coast?
A. They don't. They are distributed throughout north america (except hawaii). The greatest number of nesting eagles in the lower 48 states occurs in florida !!
Q. Can bald eagles be found in every state of the United States?
A. Yes, except Hawaii.
Q. Can you expain why so many eagles overwinter in Alaska ?
Q. Because of the available habitat up there. Open water, plentiful food, and undisturbed habitats abound.
Conservation
Q. Is it illegal to possess a bald eagles' feathers? If so, why?
A. Yes, eagles or any parts, unless you have a special federal and state permit to do so. The reason is that many eagles used to be killed for trophies and for their feet and feathers. Such unregulated killing can threaten populations of eagles and other species.
Q. If a bald eagle was released from captivity into the wild, could it survive?
A. That would depend upon how long the eagle had been in captivity and whether or not it was imprinted to eagles or to human beings. If one was recovered sick or injured and held in captivity so it could fully heal, even if that took up to 2 years, it would still likely be able to be released and survive.
Q. How did the eagle become the national symbol?
A. On 20 June, 1782, our Continental Congress adopted the bald eagle as our official national symbol, after much debate among the members. Thomas Jefferson jokingly suggested that the wild turkey should be chosen, but ultimately the symbolic power, strength and freedom associated with the bald eagle won out.
Q.
What might be the reasons for the increase in eagle numbers?
During the winter months in Southern Ontario, waterfowl and Christmas
Bird counts along the north shore of Lake Ontario are finding every increasing
numbers of bald eagles.
A. Bald eagle populations are increasing rangewide, and have been since about 1980. Reproduction and survival are both up, since ddt was banned in 1972, humans are more aware of their actions and what might harm eagles, and fewer are being shot.
Q. Is it wise or unwise to consider building nesting platforms for bald eagles? At Presqu'ile Provincial Park on the north shore of Lake Ontario, sightings of adult and immature bald eagles are increasing eash year. There are historical records of bald eagles nesting in the area many years ago.
A. It is not necessarily premature, and you may well have eagles attemp to nest in your region within the next 5-10 years. However, unless you think there is an absence of suitable nesting trees, you are looking at quite a bit of work with little chance birds might accept it. Eagles are prone to accept a platform when they are already on territory at a given site, especially when the platform is to bolster or replace a nest in the same tree or very nearby. But, platforms seldom simply attract eagles that are not already there; they prefer to start their own. If you have any super canopy white pines at all, you mught consider "dressing up" a crothch to make it hold sticks better, then just seeding it with a few sticks to look attractive.
Q. Why are Bald Eagles considered the most important bird in America? They seem to receive lots of attention. What about smaller species of birds and concern for their well-being?
A. I don't know if bald eagles are "the most important bird in America", but you are right that they attract and receive much attention, likely due to their size and strength and freedom (see also above on how they were selected as our symbol). Don't confuse their popularity with the idea that smaller birds don't get any attention. The federal government, state governments, and many private conservation groups spend much time and money on hundreds of other bird species and even on invertebrate animal life in need of attention. All of this is part of our mission to understand and perpetuate the entire "biodiversity" of our planet, which is essential if humans are to survive. Contact your state fish and wildlife agency to ask what other species are getting attention in your state--you'll be surprised!!!
Q. What's the definition of "game birds"? We have been having a class discussion about the difference between the terms - raptors, game birds, endangered birds, etc.
A. "Game birds" get that name from the fact that they are typically birds that are hunted for sport by humans; examples are pheasants, grouse, turkeys, woodcock, and most waterfowl (ducks and geese). Raptors (birds of prey) are not hunted (legally), except occasionally for falconry. You folks are not far from some great eagle watching at the montezuma national wildlife refuge--you should check it out!!
Other Questions
Q. When was the first Bald Eagle ever spotted?
A. I don't know, but they were around before human beings; fossil remains of ancient sea eagles date back some 25 million years, long before humans.
Q. Is the age of the bald eagle different than human years, like dogs?
A. No.
Q. Could you teach a bald eagle to talk and do tricks?
A. No.
Q. How many years have you been working with bald eagles?
A. 20 years (as of 1996).
Peter
E. Nye
New York State Dept. Environmental
Conservation
Division of Fish, Wildlife and Marine Resources
Delmar, NY
Spring, 1996
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