Eagles Questions and Answers

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Eagles Questions and Answers

Post by jkr » Wed Feb 21, 2018 6:06 am

Frequently Asked Questions is intended as a guide to understanding the basic biology of the Bald Eagle. They do not apply to any one nest in particular, but the Bald Eagle in general.

If you have questions regarding eagles please post them here and someone will find the answers for you whenever possible.
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Re: Eagles Questions and Answers

Post by jkr » Wed Feb 21, 2018 6:09 am

Frequently Asked Questions about the Bald Eagle


What does a Bald Eagle look like?
Adult Bald Eagles have white heads and tails and dark brown bodies. They have large yellow feet with sharp talons and a large yellow beak and almond eyes. They can weigh up to 14 pounds (6.5 kg) and their wings can stretch to over 7 feet (2 meters) across.

Why are they called Bald Eagles?
Bald Eagles are not bald at all, but have a white head. Hundreds of years ago the English word for WHITE was BALDE and the word piebald meant mottled with white, so the eagles with white heads were called Balde Eagles.

Where do Bald Eagles live?
Bald Eagles live primarily along the waterways: the seashore, lakes, rivers and ponds. Bald Eagles live only in North America and all the way from Alaska to Florida.

How long do Bald Eagles live?
Bald Eagles kept in captivity can live 40 years or more. Although we don’t know for sure, we think that in the wild Bald Eagles may live to be 30 or a little older.

What do Bald Eagles eat?
Bald Eagles are primarily scavengers. Whenever possible they find and eat dead food like spawned-out salmon or road-killed animals. Their favorite food is fish, but they will eat small mammals like rabbits and water birds like ducks or gulls. Certainly bald eagles can hunt birds, particularly coots and wounded waterfowl, but they generally prefer to spend less energy on scavenged carcasses.

How well can a Bald Eagle see?
Bald Eagles see about 7 times better than people can. One thousand feet (300 meters) up in the air, a Bald Eagle can spot its prey over 3 square miles (8 square km). The binocular vision, where both eyes focus forward on the same object, enables them to have very accurate depth perception. Each eye can also see out the side. This is monocular vision and is very efficient at detecting motion.

What kind of sound does a Bald Eagle make?
Bald Eagles do not have very many kinds of calls. Their voice sounds something like a gull’s scream but in a series of notes. The female tends to have a lower sounding voice, while the male’s voice is higher and more like a scream.

How many feathers does a Bald Eagle have?
Bald Eagles have between 7000 and 7200 feathers.

How fast can a Bald Eagle fly?
A flying Bald Eagle can reach speeds of about 75 miles (120 km) per hour. When going long distances or just moving around their territory they tend to fly 20–30 miles (30–50 km) an hour. In a dive they can probably exceed 100 miles per hour.

Do Bald Eagles sweat when they get hot?
No, they have no sweat glands. To cool themselves, they open their mouths and pant. They also will hold their wings out from the body to let the cool breeze get closer to their hot 107 degree F (42 degrees C) body. This cooling posture is slightly different than when they holds their wings out from the body to dry off after a rain storm or a swim or bath. Getting wet with salt water causes their feathers to stick together and they usually follow a salt water dip with a fresh water bath.

How much food does a Bald Eagle eat in one day?
They eat approximately ½ to 1 ½ pounds (200 to 700 grams) daily. They are also adapted to going without any food for a week or more during storms or periods of low food availability.

Do the mother and father Bald Eagle stay together for life?
Yes, Bald Eagles mate for life. However, if one dies or is lost, the one remaining will take a new mate.

Where does a Bald Eagle build its nest and how big is it?
Bald Eagles build their nests near water and primarily in very tall trees, usually 50–150 feet (15–45 metres) tall. If they live where there are no tall trees, such as Alaska or Florida, they may build the nest on a cliff or a shorter tree. Their nests are usually about 4 to 8 feet (1.5 metres) across but have been known to be 12 feet (3.5 metres) across. The nest can weigh up to 1000 pounds (450 kilograms) and is so strong that a human would be able to stand in it without breaking the nest. Most coastal British Columbia nests in coniferous trees, which are ravaged by winter storms and subjected to a lot of decaying moisture, usually weigh about 100 to 500 pounds. In other words the annual nest additions equal the years wear.

How many eggs does a Bald Eagle lay?
The female Bald Eagle lays 1 to 3 eggs, but usually 2 eggs. The eggs are off-white in colour and about 3 inches (7.6 cm) long.

Why do Bald Eagles have such big, strong nests when they have only two small eggs?
Bald Eagles are about 3 feet (90 centimeters) from their head to their tail and before the nestlings leave the nest, they become larger than they will be as adults and need a lot of room for their 6 to 7 foot (1.8 metre) wingspan. The nests need to be very sturdy because the eaglets jump up and down, flapping their wings when they’re learning to fly.

When do the eggs hatch?
The parents take turns sitting on the eggs for about 35 to 36 days. The hatchlings weigh about 3 ounces (85 grams) and have white or light grey down feathers all over. By 10 days of age the chicks have their second plumage of darker grey down that offers much more warmth. The eaglet’s dark body feathers start to come in when they are four or five weeks old. The first egg laid will be the first egg to hatch and therefore the oldest eaglet may be a little larger and better able to fight for food than the younger ones.

How long do the nestlings stay in the nest? When do they learn to fly?
Eaglets stay in the nest and are fed by their parents for about 12 weeks. They practice flapping their wings and hopping in the nest, often jumping up to other branches, called branching, close to their nest. After days or weeks of jumping, flapping and branching, they fly off the nest. This first flight is called “fledging.”

How long is it before the chicks look like their parents?
It takes a juvenile (who is between 1 and 4 yrs old) eagle about 4–6 years before they get all their adult feathers and coloring. Until then, they have brown bodies including their head and tail, with some white feathers mixed in and they have brown eyes and beak.

Why do the chicks sometimes have a bulge on their chest?
That bulge is where the bird’s crop is. The crop is a little sack that is attached to their esophagus, the tube that goes from their mouth to their stomach. An eagle can swallow large chunks of food that are held in the crop until there is room in the stomach for the acids to digest it. You might see an eaglet or adult moving its neck in a funny way to help the food move from the crop to the stomach. Eagles need to eat fast before another eagles takes control of the carcass and this is a place to temporarily store their food.

How can you tell the difference between the mother and father eagle?
Male and female eagles have the same coloring but are different in size. Females are about 1/3 larger than males and the female’s call is generally lower pitched than the male’s call, which is almost a scream. Another way to tell them apart is to measure the height of their bill. The female’s bill is always deeper than the male’s and usually has a larger hook than the male’s.
Females weigh an average of 9 -12 pounds. Males weigh an average of 6 - 9 pounds.

Can Bald Eagles swim?
They are very good swimmers. Sometimes an eagle will catch a fish in its talons that is too heavy for them to carry and they will swim over a mile to shore dragging the fish so they can eat it.

What are a Bald Eagle’s enemies?
Sometimes a raccoon or other large bird, like an owl, may attack a nestling, but human beings are the eagle’s main enemy. Foxes has been seen to predate ground nesting eaglets and bears have been seen a couple of times climbing to nests. Humans cause most eagle deaths. The use of pesticide chemicals poisons the eagles food and they die scavenging the poisoned prey. Rodenticides often kill rats and mice and these poisoned rodents are then contaminated by eating the dead rodents. Automobiles sometimes strike eagles that are feeding on a road kill. By far the biggest killer of eagles is electrocution. Eagles land on power poles and if their wings or talons touch the two wires they cause a short and they get electrocuted. However, the biggest threat to eagles is the loss of suitable habitat, particularly the loss of suitable nest trees.

Are there very many Bald Eagles?
Bald Eagles were put on the official US Endangered Species list in 1976 and in 1995 they were upgraded to Threatened, because their numbers have been increasing. There are now an estimated 70,000 Bald Eagles in the world, with about 35,000 living in Alaska and 25,000 living in British Columbia. In 2011 the US removed the bald eagle from the Threatened and Endangered species list. About 50 -60 percent of the eagle population consists of breeding adults and the other 40 - 50 percent of juveniles.
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Re: Eagles Questions and Answers

Post by jkr » Sat Apr 07, 2018 6:40 am

NEST BUILDING FACTS

The bald eagle builds the largest nest of any North American bird, up to 13 feet deep, 8.2 feet wide, and 1.1 tons in weight.

A typical nesting landscape is usually forested and include areas of water. These landscapes provide for basic needs: water to drink, fish to eat, forest trees for shelter and a place to raise young, and perches for hunting and resting. With the increasing population of eagles many are becoming urbanized so it is not unusual to see eagles nesting within communities near water sources.

Together, the male and female bring new sticks to strengthen the structure, and also grass-like material to form a soft cup in the center of the nest where the eggs will rest.

Some pairs need to rebuild their nest almost from scratch if winds and bad weather have damaged it. This nesting activity starts one to three months before the female lays eggs.

Bald eagle's large nest is called an aerie. A typical nest will range from 1.8 to 3 meters (6-10 feet) in diameter and about 1.8 to 3 meters (6 to 10 feet) high. The nest cavity, where the eggs are laid, will be about 30 to 40 centimeters (12 to 16 inches) in diameter and about 10 centimeters (4 inches) deep.

First year nests are usually smaller, and the nest size will increase each year as eagles re-use the nest and add sticks to it.

Bald eagles are very territorial birds, and most breeding pairs return to the same nest site year after year. They may use the same nest annually for as many as 35 years, or they may build additional nests in their nesting territory, and alternate the use of them from year to year.

Bald eagles generally nest near coastlines, rivers, and large lakes where there is an adequate food supply.
In areas where trees are few and far between eagles will nest on the ground or on the tops of cliffs!

Ground nests are built of whatever's available, such as kelp and driftwood near coastal shorelines.

They nest in mature or old-growth trees, snags (dead trees), cliffs, and rock promontories. In forested areas, bald eagles often select the tallest trees with limbs strong enough to support a nest that can weigh more than 1,000 pounds.

Nest sites typically include at least one perch with a clear view of the water, where they forage.

Eagle nests are constructed with large sticks, and may be lined with moss, grass, plant stalks, lichens, seaweed, or sod.

Bald eagles pick up broken sticks from the ground, and sometimes break branches off trees. They naturally take as many sticks as they can find close to the nest, but may lug some branches as far as a mile, carrying them in their talons.

They usually start building in the top quarter of the tree, below the crown, near the trunk, where branches are thick and strong enough to support the heavy nest. They interweave the sticks, and fill in spaces with grasses, mosses, cornstalks, Spanish moss, and other fibers.

Throughout the season, and sometimes even during fall and winter, eagles keep adding sticks to the nest, and they reuse nests, continuing to build on to them, for many years. The average eagle nest is only 1.5-1.8 meters in diameter and 0.7-1.2 meters tall.

Both sexes bring materials to the nest, but the female does most of the placement. They weave together sticks and fill in the cracks with softer material such as grass, moss, or cornstalks.

Eagles tend to nest in tall, sturdy conifers that stick up above the forest canopy, providing easy flight access and good visibility.

Nesting behavior starts with some clearing out any unwanted debris, fixing any damaged areas of the nest, and adding on. The early season work is usually sporadic and not terribly serious.

Some non-migratory pairs may stay in the vicinity of their territory all winter and can be seen working on their nest sporadically all year long.

The renovation behavior makes the nest ready to house the next generation of eagle young and is part of the courtship process as it strengthens the bond between mates.

Eagles need some degree of insulation and isolation from human activity, though sensitivity to disturbance seems to vary widely.

The nest itself needs to be higher than the surrounding vegetation to provide both easy access and a clear view of possible threats to the nest.

The trees that are tall and strong enough to satisfy eagle nesting needs tend to be old and sometimes may be nearing the end of their life. Occasionally, the nest tree dies but stays strong for a time and the eagles will continue to use their nest, despite the death of the nest tree, often until the tree or nest falls down.

Pairs building a completely new nest often dedicate much of their springtime activities to carrying nesting material and working on the new nest.

The part of the nest where the eggs will be laid is often called the nest cup, and is lined with softer materials.

The nest is constantly being upgraded and rearranged according to available components. The nest grows larger and heavier during the nesting season and as the years pass.

Tree shape, size, and location are more important to an eagle looking to build a new nest than is the tree species, but some of the trees more likely to meet nesting needs are pines, spruces, firs, oaks, and cottonwoods.

Bald eagles usually like to have a clear view in all directions around their nests.

Nest trees tend to be the tallest in the surrounding area, called super-canopy trees. Nests tend to be very large and rather heavy, so the best nest trees are tall, strong healthy trees.

Pairs that are building a new nest usually choose a living tree as the base for their nest though there are often some dead trees, called snags, nearby that serve as lookout posts.

Some eagle pairs build an alternate nest (usually within a mile from first nest) within the eagle territory, and the pair may take turns nesting between these from year-to-year.

When an eagle nest blows down, the eagle pair will usually build another nest nearby.

Because some eagle nests are so large, it is not unusual to be able to spot these nests with a naked eye from a mile away.
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Re: Eagles Questions and Answers

Post by jkr » Sat Apr 07, 2018 6:51 am

Migrating in the Fall?

Fall migration is connected to food sources. Not all eagles migrate. If their breeding territory is a northern habitat where lakes and streams freeze or prey animals hibernate, eagles will leave to find open water and food. Depending on location, they usually migrate to the coast or to large rivers and gather at roosting areas where fish are abundant.

Eagles do not migrate in the way that many other birds do. Some biologists do not characterize bald eagles as true migrants, preferring to describe their movements away from and back toward their breeding territories as seasonal movements. This is because almost all bald eagles only move away from their nesting areas as far as they need to survive, meaning in order to find the food.

Bald eagles that migrate in the fall to areas with sufficient food return in the spring to nest.
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Re: Eagles Questions and Answers

Post by kboehner » Mon Apr 08, 2019 2:05 pm

1. The local nesting pair has had a failure this year, began setting in the nest a week early this year, then at 37 days, suddenly they stopped setting almost completely. For at least a week, both adults perched near the nest tree, both morning and evening, as if they didn't know what to do after 3 or more years of raising 2 eaglets. Then a week of re-arranging and fiddling in the nest, but nothing remarkable noticed. Then last week, the started building another nest, within a half mile of the original! Often perched between the two, but at roost time, most often seen at original nest. There has been a juvenile hanging around, too, sometimes making itself at home in the nest tree. Sometimes the adults protest, but don't do anything if the younger eagle chooses to stay. Is any/all of this reasonable behavior?
I'm disappointed at not having a nest to monitor, but still feel the need to stay watchful. Mostly to learn about them, which is what it was all about to begin with.

2. I've spotted an unexpected pair of eagles, in incubating/brooding posture, in a nest I believe was a hawk nest in the past. I did a double take when I noticed the increased size, and closer look at photo reveals an eagle! Do they ever just practice at nesting? I'm asking because of they seem like an unlikely pair, but they seem to be incubating, taking turns on the nest, settling, etc.
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Re: Eagles Questions and Answers

Post by JudyB » Fri Apr 19, 2019 3:04 pm

kboehner wrote:
Mon Apr 08, 2019 2:05 pm
1. The local nesting pair has had a failure this year, began setting in the nest a week early this year, then at 37 days, suddenly they stopped setting almost completely. For at least a week, both adults perched near the nest tree, both morning and evening, as if they didn't know what to do after 3 or more years of raising 2 eaglets. Then a week of re-arranging and fiddling in the nest, but nothing remarkable noticed. Then last week, the started building another nest, within a half mile of the original! Often perched between the two, but at roost time, most often seen at original nest. There has been a juvenile hanging around, too, sometimes making itself at home in the nest tree. Sometimes the adults protest, but don't do anything if the younger eagle chooses to stay. Is any/all of this reasonable behavior?
I'm disappointed at not having a nest to monitor, but still feel the need to stay watchful. Mostly to learn about them, which is what it was all about to begin with.

2. I've spotted an unexpected pair of eagles, in incubating/brooding posture, in a nest I believe was a hawk nest in the past. I did a double take when I noticed the increased size, and closer look at photo reveals an eagle! Do they ever just practice at nesting? I'm asking because of they seem like an unlikely pair, but they seem to be incubating, taking turns on the nest, settling, etc.
I'm sorry for the delay in getting back to you - and it does sound as if there are some interesting things happening in your area!

1. I'm not an expert, but my best guess about your local nesting pair is that something happened to the eggs during the nesting period, because sometimes when that happens, the eggs do collapse around the time they would normally hatch. If the weather was particularly bad just before they stopped incubating, they might have lost little chicks, but in my experience that only happens with really bad storms as the chicks are hatching, and you would have noticed that. I've seen eggs that have been left alone quite a bit when they are newly laid and still hatch just fine - but having warm incubated eggs exposed to cold rain for a prolonged period can cause the eggs to stop developing. I'm guessing that they have moved past nesting mode, so are more tolerant of the juvenile. It's great that you are continuing to watch - I have to admit I do wonder how we occasionally end up with nests with three adults like the Trio nest that's been in the news lately (our thread for that nest is here - viewtopic.php?f=44&t=340) - and while I don't think that will happen at your nest (just because it is rare) - it would be interesting to see how a trio forms.

Is the picture of the juvenile the one visiting the territory of your traditional nesting pair, or is he or she one of the pair in the new nest?

2. It's not uncommon for eagles to take over hawk nests and expand them. I've definitely seen eagles spending the night on the nest as if incubating before laying eggs - I'm thinking usually the female, but I really can't say for certain that we haven't seen the male do that too. Both adult definitely check out the nest as they prepare it, though usually not for more than a few minutes at a time. I don't think I've ever seen a pair taking turns settling into the nest unless there's an egg there - so my guess is that this is a new nesting pair.

If you would like to have a thread for reporting on your local nests and posting pictures about what's happening there, we'd be happy to help you set one up. We have forums for nests with local observers in BC and in the rest of North America here - viewforum.php?f=41

Thanks for posting!

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Re: Eagles Questions and Answers

Post by kboehner » Sat Apr 20, 2019 5:06 pm

I appreciate your response, Karen.
This post I'll include a photo of the original nest and pair. This nest is on a river bank, since discovering this nest 4 years ago. During this incubation period there was only 1 time the I observed the nest empty, and then only a couple minutes in well above freezing temperatures. One day we were expecting signs of hatching in the nest, the next, the pair wasn't incubating, brooding or feeding. They didn't seem alarmed, just perched nearby, visiting the nest, occasionally to and rearranging sticks. Every trip to the nest, I wondered if I'd seen the last of them, and they'd go elsewhere. They've been in the area consistently tho.
02.25.2019x IMG_3092.jpg
The photos included in the original post are of both eagles occupying the newly discovered nest. The younger as it perched in a spot more advantageous for photo. This nest is approx 5 miles from the other & it doesn't seem to be the same one that was loitering near the original nest. In the past 2 weeks, every time I've checked on this "south" nest, it has been occupied, & 2x "changing of the guard" was observed. This nest is not next to the river, but it's withing 3 miles or so, and several farm ponds and creeks are in the area. Waterfowl populations have declined in the past couple weeks, so am assuming the adults will go to the river for feeding. The tree this nest is in, doesn't seem nearly sturdy enough.

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