Life Cycle
Q&A about Bald Eagles with Peter Nye
New York Department of Environmental Conservation

Q. How long does the bald eagle live?
A. Typically in the wild probably between 20-30 years. Some eagles in captivity have lived 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 eagles push their young out of the nest to encourage them to fly?
A: No! The adults may withhold food as the eaglets get near fledging, and encourage them to fly to a nearby perch to get their meal, but that's about it. Usually, no coaxing is necessary and the eaglets are all too anxious to test their wings!

Q. If an eaglet falls, will a parent fly below the nest to catch it and carry it back to the nest?
A: No!

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 have 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. 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. The young remain in the nest for another 10-12 weeks until they fledge (fly from the 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. 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. 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).

Q. How many eggs does an average bald eagle lay in a lifetime?
A. The average bald eagle clutch size is just under 2 eggs/clutch (1.9). If we assume that a female eagle begins nesting at age 5, and lives until she is 25, she will have 20 years of egg-laying. There is no evidence that a healthy eagle reduces egg-laying as she gets older. So 2 eggs/year X 20 years = 40 eggs in her lifetime.

Q. Why are eagle nests so large for their body size?
A. Actually, eagles' nests are just about right for their body size. Most nests are about 6 feet across at the top, and with two adult eagles and one, two, or sometimes three young in the nest, it can get pretty crowded. Especially when you consider that as the nestlings approach fledging age, their wing span is six feet or more, taking up most of the nest. Nests can get very deep (one was recorded in Florida that was 22 feet deep!), because most pairs add sticks to the same nest each year, and use them for many years.

Q: Do eagles carry their young under any circumstances? There are legends about eagles like carrying their young on top of their wings, but I could not find an answer. One source states that eaglets are NOT carried, that they remain in the nest until they are 12-13 weeks old and ready for flight.
A: I have heard of this legend many times, and have been told there is some citation in this regard in the bible. However, I have never heard of this, and firmly doubt it. The reality of the biology is, eaglets indeed spend 10-12 weeks on their nest, do all of their own flight training, and fledge from the nest on their own, gradually gaining strength and honing their flight skills over the next month or two.

Q: What does the female eagle do when she gets older? I heard that she plucks all of her feathers out and she makes her beak fall off, then grows another and new feathers, and becomes more beautiful than she was before.
A: That is definitely not true. What is true, is that each year all eagles, regardless of their age or sex, molt (lose) and replace their feathers, so they do indeed get new, strong ones. It has nothing to do with age.

Q: Are eagles courting when they interlock talons and soar through the air?
A: With wildlife, it is often hard to determine reasons behind behaviors we may observe. Talon-grappling and tumbling are frequently observed behaviors; seen between all combinations of eagles. Meaning, between mated adults, un-paired adults, adult and immatures, immatures with immatures, etc. These are also likely "unions" of any-sex combination of birds. That variety of participants, tells me right away there is no one answer to what this behavior is for, but rather, that it happens for a variety of reasons. Three come to my mind immediately; pair-bonding, aggression, and play. So, yes, I believe paired adults do it as a "courting"/bonding activity. We also know from observations that these represent very aggressive encounters, where sometimes, one or both of the participants are killed (sometimes they cannot "un-lock" and crash to the ground together. The most often I see this, is with and between immatures, and I'm convinced it is both play and learning (flight capability). I do believe that eagles get enjoyment out of certain activities, which could be called play, such as when they chase each other in flight, tumble, roll, etc. As with humans, I think immature bald eagles are more prone to "play" than adult birds, who always seem to have something deliberate to do.

Q: How long can an eagle live? How long do they usually live?
A: That depends on what might happen to it! Unfortunately, many eagles don't live out the length of the life they are biologically capable of, due to a variety of factors. Contaminants, shooting, traps, cars, trains, wires (electrocution), collisions, and even other eagles, can cut an eagle's life short. Barring any of these events, an eagle is capable of living for 30 or more years. We captured an eagle in 2001 that we had banded in 1976, a female who was still breeding. Eagles held in captivity undoubtedly live longer than those in the wild, since they don't have the stresses that eagles in the wild face (such as finding food everyday and defending their territory. Two reports exist of captive eagles living 47 years.

Q: How long do the young stay with their parents after fledgling?
A: Depends on how "independent" they feel! Some youngsters "bust-out" quickly, thinking they are fully capable of being on their own. In many cases, they pay for this with their lives during their first fall and winter. On average, I'd say they spend 4-12 weeks in the nesting territory post-fledging, the time during which they learn to hunt and fly.

Q: Do young eagles learn to hunt from their parents or are their skills innate
A: An excellent question. Young eagles from wild nests develop their hunting skills on their own, but spend considerable time after they fledge watching their parents and undoubtedly learning by watching what the adults do. The actual skills involved are learned by trial and error, I'm sure. Much of the hunting skill (or at least the drive to hunt) is innate, as our hacked eagles were fledged into an environment without adults around to "teach" or "show" these young birds. Yet, these birds, again through trial and error, learned to hunt for themselves and survive. We felt it was important to continue to provide food at our hacking towers after the eaglets fledged, to give them a source of food for as long as they needed it. Eventually, each eagle at it's own pace, these young birds stopped using our offerings and began foraging on their own. Similarly in the wild, the adult parents will continue to provide food for some time after fledging, while the newly flighted birds hone not only their hunting skills, but there flying skills. On average, I would say it takes about 4-12 weeks for young eagles to start hunting successfully. True, fully refined, specialized hunting skills, probably take years to develop.

Q: In the wild, how long can Bald Eagles bare young?
A: The life span of eagles in the wild is generally around 30 years. Actually, little is known about the reproductive life of eagles as they age, due to the lack of known-age/banded birds and intensive observations of same. I can tell you that we captured one of our local breeders at her age 25 years, and she went on to breed and raise young successfully in her 26th year. It is my opinion that eagles are probably productive until they die. It would be mal-adaptive for adult eagles to remain in the population as non-contributing members. More often, I believe what happens is the aging/unproductive bird is actually killed and replaced by a younger, more productive and fit adult.

Q: We know that dog life spans are 7 years to 1 human's life span, so what is the eagle's life span to a human's span?
A: To answer that we have to explain how long eagles can live.
In captivity (a more coddled life...), bald eagles have lived well into their 40's. But in the wild, their life is undoubtedly much shorter, either cut short by human beings, by other eagles, or by the rigors of their life. In the wild, we believe eagles live around 30 years. Therefore, I guess you'd say an eagles life is about 2.5 to each human year, based on our current average life expectancy.

Q. What is the average lifetime of a bald eagle?
A. Most of what we know about how long eagles live is from birds kept in captivity. These birds may live 40 years or longer. Information from a few wild, banded eagles shows that they may live to be 30 or a little older in the wild. I suspect that a 25 year-old bald eagle in the wild is old, and a 30 year old eagle is very old.

Q: Do the golden eagle babies look different from the bald eagle babies?
A: Yet another great question from Ferrisburg!
Yes, golden eaglets look different than bald eaglets. When first hatched and as young nestlings (before feather growth starting at about 4 wks of age), golden eaglets are mostly white. Bald eaglets are much darker gray. Also, golden eaglets have a very noticeable yellow "cere" at the base of their bills, all through their nestling stage. Bald eagles do not; balds are uniformly dark. As golden eaglets age, they maintain a much lighter, whiter head than bald eagle nestlings. As they age they attain their very distinctive "golden" nape from which their name derives and which is the most obvious difference in older age eaglets. Check out some photos of both on the net and see for yourself!

Q: We had a pair of eagles with a nest in a large tree near the Missouri river near Nebraska City. This winter the tree went down and we're worried that the pair won't nest here again. We've seen an eagle on the ponds nearby standing on the ice eating something. Will "our" eagles still nest here or will they move on?
A: Sorry to hear "your" nest tree blew down; a not uncommon occurrence!
Not to worry. Eagles are very faithful to their nesting "territory", not necessarily to the actual "tree". I don't know how long the eagles have been nesting there, but I would fully expect them to build a new nest not too far away. This could be up to a mile, rarely further, but I'd suspect even closer, all other conditions (like food) being equal. Watch for them carrying sticks off in a certain direction.

Q. How long do eagles stay on nesting grounds after they migrate in spring?
A. It all depends on what latitude they breed at. Eagles migrating to and breeding at northern latitudes (i.e., Yukon Territory) probably stay a shorter period of time, and have a shorter nesting season than those at southern latitudes (i.e., California). That is because of the shorter season in the northern areas. The water stays frozen later into the spring, and fall comes earlier there.

If they are going to nest successfully, there a few things eagles have to do wherever they nest:

  • Build or refurbish their nest (may take only a day, but we'll say 1 week, 7 days)
  • Incubate eggs (35 days),
  • Raise young to independence (perhaps 120 days).

Adding these numbers up comes out to 162 days or a minimum of about 5 1/2 months on the breeding area. More typically, in temperate areas such as Washington state, the adults will remain on their territories at least 9 months of the year before fall migration.

Q: Could it be possible that a twig I saw an eagle break from a branch could be used for building a nest? After observing a bald eagle perched in a tree along a river for over 20 minutes, I observed it fly to a tree 10 yards away and break off a branch in its talons and fly off. This occurred in Iowa in early February. Two eagles have been seen in this area throughout the winter.
A: Absolutely it could! I assume the eagle you observed was an adult. Immatures may occasionally do this for play or practice, but it is typical behavior for adults prior to and during nesting. What you saw could be a local breeder getting its nest "ready" for the breeding season (here in NY we have some pairs who begin decorating their nests in early February, and I'd bet Iowa would too), or, it could have been a wintering bird just fooling around and "feeling its oats" in anticipation for migration and nesting back up north. Very rarely, some wintering birds will actually build a nest on their wintering grounds during the winter season, even though they have no intention of staying and using it (they just might be very stimulated breeders!); we have seen this in NY, and the pair return to their "winter" nest and decorate it and sit in it each winter, before leaving for their "real" nest somewhere up north in late March. The fascinating thing to me about what you describe, and which I've also seen, is how the heck the eagle "knows" that the stick they fly at and hit in mid-flight will give way! It's got to be a good decision between flying force at the stick to break it off versus not sort of flying yourself into a brick wall so-to-speak! How do they know ahead of time the stick they've "chosen" will break off ?? (that's a rhetorical question, not a challenge one!). Anyway, that is a neat thing to observe! I would look for a nest in the vicinity!

Q: Do they reach a point like humans where they cannot bear young?
For 3 years I have observed a nesting pair of Bald Eagles near my home. The pair has been nesting for 15 years in the same location. Last year the male crushed one egg in mid air. The other made it to a first flight only, never to be seen after a few days. It stayed in a tree near the nest, but then died. The pair is currently nesting. She laid the eggs on 2/28.
A: I'm curious to know where you live! Judging by the February 28th egg date, you must be in PA or south NJ? The mid-air egg-crushing you mention is quite strange and begs another question. Did this pair raise/fledge any young the same year? I think, you are saying one young was fledged. Often, one of the adults will remove egg-shells from the nest after hatching; could you simply have seen egg-shells being "cleaned" out of the nest and dropped? Adults will also sometimes remove whole eggs that don't hatch, fly from the nest with them and drop them (they will also simply eat them in the nest). I have never heard of anyone witnessing "crushing" of an egg in mid-air. Perhaps it was one of these normal behaviors you witnessed. I have no idea what could have happened to the fledgling. Again, after fledging, juveniles will often perch along the shore away from the nest for a long time, in hard to observe places. Were both adults present at the nest the whole season?


Peter E. Nye
New York State Dept. Environmental Conservation
Division of Fish, Wildlife and Marine Resources
Albany, NY