Frequently Asked Questions
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FAQs prepared by AJL, November 2009
A: General Questions
B: Physical Characteristics
Appearance (differences between the sexes; eye colour; feathers, beaks and
Senses (smell, taste, hearing, vision)
Grooming (bathing, preening, beak feaking)
Hunting and foraging
Function of the crop
Eggs (production, clutch size, laying interval, hatching
Stages (hatchling, nestling, fledgling, juvenile)
Parental care and feeding
Behaviours and learning (play, sibling competition, mantling, self-feeding)
Fledging process (perching, branching, nest departure, parental care)
Human impact on nest success
Threats to survival
A. General Questions
Q. What does the bald eagle's name mean?
A. Its scientific name is Haliaeetus leucocephalus (Latin: Haliaeetus or "sea eagle"; leucocephalus or "white head").
Its common name, bald eagle, may be from the old English
word balde (white), or may be a derivation of piebald,
which describes the eagle's white head and tail
feathers and dark body feathers.
Q. How many bald eagles are there?
A. Scientists estimate that there may be more than
70,000 bald eagles in the wild.
Q. Where are bald eagles found?
A. Canada, the continental United States (including
Alaska), and northern Mexico (small population). More
than 50% of the population occurs in Alaska and British
B. Physical Characteristics
Q. How big are bald eagles?
A. Sizes and weights vary greatly:
- Southern birds are
smaller and lighter than northern birds; an Alaskan male can weigh about the same as a southern female.
- Average lengths range from 71 to 96 centimetres (2.3 to
- Average weights range from just under 3 kilograms to 6.3
kilograms (6.6 pounds to 14 pounds) although weights as
high as 7.7 kilograms (17 pounds) have been recorded for
- Averaged across their entire range, male weights range
from 3.6 to 4.1 kilograms (8 to 9 pounds); female
weights range from 4.5 to 6.4 kilograms (10 to 14
- Average wingspans range from 168 to 244 centimetres (5.5
to 8 feet).
Q. How can I tell the adult female and male bald eagles
A. The female is about 25% to 30% larger than the male.
Her beak looks somewhat deeper than his, and has a more
pronounced hook. Plumage is the same in both sexes.
Mom Hornby is larger than Dad. Her head feathers appear
longer and less 'groomed' than his; at the back of
her head, the feathers have a unique growth pattern,
making it look like she has a dark part.
Q. What colour are an eagle's eyes?
A. The eaglet's and juvenile's eyes are dark brown.
They begin to fade to a buffy brown and gradually to a
creamy colour; when the bird reaches sexual maturity,
its eyes are yellow.
Q. How does the eagle's vision compare with human
A. The eagle's vision is about 3 to 4 times sharper
than ours. Flying at 305 metres (1000 feet), it can see
a 4.8 kilometre (three-mile) radius; it can spot prey
that is about 1.6 kilometres (1 mile) away.
Q. Can eagles see at night and do they fly at night?
A. They can see at night, but not nearly as well as they
can see during the day. We have, however, seen Mom
Hornby and several other eagles fly to their nests after
Q. How well do eagles hear?
A. It is thought that their hearing is similar to ours.
Q. Do eagles have a sense of smell and taste?
A. Eagles are thought not to have a strongly developed
sense of smell but this is under review for all birds.
Q. Do eagles sweat?
A. No; birds cool themselves by panting.
Q. What are an eagle's feathers, beaks, and talons
A. They (as well as the scales that cover the foot) are
made of keratin, a fibrous protein. Our hair and nails
are also made of keratin.
Q. How many feathers does a bald eagle have?
A. The bald eagle has about 7200 feathers.
Q. When do bald eagles attain adult plumage?
A. The transition from first year to adult plumage (as
well as beak and eye colour) is gradual; the distinctive
adult colouration is achieved at around 5 years of age.
You can see photographs of the phases here: http://www.swbemc.org/plummage.html
Q. When do bald eagles moult?
A. They moult gradually from spring through autumn. They
do not moult all their feathers each year; some of the
feathers moult over two (or possibly more) years.
Q. How do bald eagles groom themselves?
A. Most eagles fish and wade (and often swim), so they
have opportunity to bathe. They preen their feathers
(using the tips of their beaks) to remove food or
debris, to distribute oils and to 'zip' the feathers
for waterproofing. They remove food from their beaks by
'feaking' (rubbing them back and forth) along hard
branches. Feaking also helps keep the beak trimmed.
Q. How does the bald eagle get its food?
A. The eagle soars over water and the ground looking for
prey, and also looks for prey while it is perched. It
tries to catch its prey while flying but isn't always
that successful, so it relies heavily upon dead and
dying fish, birds, and mammals. The bald eagle will also
steal (pirate) food from other birds and mammals.
Q. How much force do eagle's feet or talons have for
A. It is said to be about 2600 pounds per square inch.
Q. What are bald eagles' favourite foods?
A. Their favourite food is fish but they are
opportunistic feeders and the menu can include mammals,
birds, reptiles and amphibians.
The Hornby eagles primarily eat fish; they can be
fresh-caught, stolen from other birds, or scavenged.
During the 2009 nesting season, in addition to fish they
also delivered the remains of several opossums, a mink,
a partial waterfowl, a crow, and possibly a gull to the
Q. How much food do bald eagles need to eat in a day?
A. It depends on the bird's size, weight, level of
activity, general health, weather, and other stressors.
An adult might need about 5 to 10 percent of its body
weight, depending on circumstances.
Q. Where do bald eagles usually eat?
A. If they find a larger carcass they will eat some at the site; manageable chunks can be flown off to a tree, rock, or other spots where the eagles can eat in privacy. They will sometimes eat in the nest, especially while breeding or incubating eggs; they also eat the parts that are tough and less digestible or nutritious for the eaglets.
Q. Do bald eagles bring carrion to the nest?
A. Much of their food is scavenged (dead) and they do
indeed bring carrion to the nest.
Q. What size of prey will a bald eagle be able to take
A. A strong bird might be able to fly off an item that
is about 1.8 kilograms (four pounds). A smaller bird
would be able to carry less weight than would a larger
Q. Do bald eagles and eaglets need to drink water?
No; they derive water from their food. Fledged birds and
adults will sometimes drink while bathing, if fresh
water is available.
Q. Do bald eagles eat bones?
A. Yes, eagles of all ages eat (and require) bones for
Q. How do bald eagles deal with bacteria that would be
in the road kill that they eat?
A. Their stomachs are highly acidic, and most organisms
are killed in that environment.
Q. What is a crop? What is its purpose?
A. The eagle's crop is a sac-like out-pouching of the
oesophagus and it functions as a storage area, allowing
the bird to eat large quantities of food when it is
available (a.k.a. gorging).
Q. Why does an eagle throw its head back and open its
beak several times and stretch and twist around?
A. Eagles of all ages stretch and twist in this way in
order to move pieces of food from the crop to the
Q. I saw an eaglet that seemed to be choking; then it
threw up something. What was that?
A. Eaglets and eagles of all ages egest (cast) pellets,
and when they are doing so they can appear to be
vomiting or choking. The pellets are prey parts that
could not be digested (bits of feathers, fur, fish
scales, etc.); such items are squeezed into a pellet in
the bird's gizzard and then expelled.
Q. Do eagles mate for life?
A. Bald eagles are monogamous; a pair will mate for life
if all is well. A partnership may be broken if one of
the birds is infertile, and a widow or widower will take
a new partner.
Q. Do bald eagles stay together every day throughout the
year or only during nesting season?
A. This is not yet clear, but banded or tagged bald
eagles that migrate (spend part of their year in
breeding grounds and part in wintering grounds) have
been seen together in the wintering area. Eagles that
are year-round residents (eagles that breed and winter
in their territories, leaving only for the salmon runs)
appear to stay together throughout the year, although
one may leave for the salmon run and return from it
before the other.
Mom and Dad Hornby winter together as well as breed on
Q. Do bald eagles build nests only in trees?
A. Most eagles build their nests in trees, but those
that nest in treeless areas will build ground nests on
cliffs and ridges. Eagles will also use man-made nest
Q. What are bald eagles' nests made of, and how big
A. They are made of interwoven branches, with fillers
like grass and moss. The birds repair and add to the
structures every year.
The largest nest recorded so far was 2.7 metres (8.9
feet) in diameter and 3.6 metres (11.8 feet) high; its
estimated weight was almost 2 metric tons. Most nests
are about 1.5 to 1.8 metres (4.9 to 5.9 feet) in
diameter and 0.7 to 1.2 metres (2.3 to 3.9 feet) tall.
The Hornby's nest is 36.6 metres (120 feet) from the
ground, in an old Douglas Fir tree that is about 5.5
metres (18 feet) in diameter.
Q. What affects the reproduction of bald eagles?
A. Food supply, weather, chemical-induced infertility,
general health, and age (too young or old) can affect
Q. Do bald eagles mate only to make eggs?
A. They mate to reproduce, but some of the mating
efforts in breeding season strengthen the pair bond; not
all efforts result in eggs.
Q. Why do some eggs fail to hatch?
A. Some eggs are not fertilized. Some fertilized eggs
fail to develop normally due to extreme cold, soft
shells, and microorganisms that can cause embryonic
Q. Will bald eagles produce more eggs if the first ones
A. Birds that breed at southern latitudes lay earlier
than those that breed at higher latitudes; this gives
them a larger window of opportunity, thus southern
females attempt second clutches if the first eggs are
lost in the early stage of incubation. Females that
breed further north have a smaller window of opportunity
and appear to attempt second clutches rarely.
Q. How long is it from copulation to egg laying?
A. Reported intervals for bald eagles range from 5 to 10
Q. How many eggs are average for one bald eagle nest?
A. Two-egg clutches are most common (79 %). One-egg
clutches are less common (17 %). Three-egg clutches
occur sometimes (4 %), but 4-egg clutches are rare.
Mom Hornby usually lays two eggs.
Q. How big are bald eagle eggs?
A. On average, the eggs are 7.0 to 7.6 centimetres (2.8
to 3 inches) long and 5.3 to 5.6 centimetres (2.1 to 2.2
inches) wide. Reported weights range from 110 grams to
as much as 130 grams (3.9 to 4.6 ounces), with Alaskan
birds producing the largest and heaviest eggs.
Q. How long are the laying and hatching intervals for
A. The interval between eggs is usually two to four
days, depending upon how many eggs are laid. In 2009,
Mom Hornby laid her second egg three days after the
The hatching interval usually corresponds with the
laying interval. Mom Hornby's eggs hatched three days
apart in 2009.
Q. When does incubation of bald eagle eggs begin?
A. Incubation begins as soon as the egg is laid; the
first chick will have the size and developmental
advantage because it is older than its sibling or
Q. What is the incubation period for bald eagle eggs?
A. The average period is 35 days, give or take a few
In 2009, the Hornbys incubated the first egg for 35
days; the chick began to vocalize in the shell late that
day. The pip (hole) was evident on the morning of the
36th day and the chick was fully hatched in the early
morning of the 37th day. The second egg followed suit.
Q. Do male and female bald eagles spend the same amount
of time incubating the eggs? How does one partner know
when the other wants a break?
A. The female does most of the incubating, but the male
takes his turn so that the female can feed, groom,
stretch, and fly. When a partner wants a break, he or
she will call for the other but a partner often also
just flies in to check on the spouse.
Q. Are bald eagle eggs and young in danger from
A: They can be; larger birds (crows, ravens, birds of
prey) and some mammals (e.g., raccoons, bears) will take
eggs and some can take young nestlings. The parents are
always on guard.
Q. How much food does an eaglet require daily?
A. That would depend upon the eaglet's age, weight,
growth stage, level of activity, and other physiological
factors; requirement thus varies or changes from day to
Q. How much of an impact do humans have on the feeding
and care of the eaglets?
A. Human activity has significant impact. Studies show
that parents spend much more time on the nest protecting
their young than foraging and feeding on weekends and
other times of heavy recreational use near the nest and
hunting areas. Bald eagles prefer to nest away from
built-up areas and human activity for this reason.
Q. Please explain sibling aggression in bald eagles.
A. The older bird is larger, heavier, and more developed
than the younger bird, so it requires more food and is
avid for its share. Siblings will thus compete for food
and parental attention, with one bird attempting to
out-compete or dominate the other. The younger bird soon
learns to keep a low profile until the older has been
satisfied and quickly learns to use its wits, making
grabs for food or doing 'end runs' around the larger
bird. This behaviour occurs more within the first two
weeks of life, declining as the siblings learn.
Siblicide (one eaglet killing or causing the starvation
of another) appears to be rare in bald eagles.
Q. Is the smaller eaglet able to get enough to eat?
A. The smaller eaglet normally gets enough to eat over
the course of the day.
Q. How does the eaglet learn to feed itself?
A. The eaglet learns by watching the parents prepare and
pull off pieces of food; when the eaglet's ability to
move about improves, it will begin to pick up small
pieces of food that have been dropped and gradually will
try to pull off pieces of food.
Q. Is it normal for bald eagle parents to be gone for a
long time between feedings?
A. In the first weeks, there is almost always a parent
on the nest. As the eaglet's ability to regulate its
body temperature improves and as it grows and requires
more room, the 'parent on duty' will begin to perch
outside the nest, either somewhere on the nest tree or
beside it. It may appear that the parents are gone a
long time, but a parent is actually there, if out of
The Hornbys watch over the nest from atop the cam boxes,
from the top of the tree stump, from the 'babysitting
tree', and from another tree right beside the nest
Q. What is mantling and why does the eagle/eaglet do
A. Mantling describes a display; the eagle or eaglet
will hunker over the food with its wings outspread,
often vocalizing to warn off competitors (i.e., "This
is mine, go away").
Q. Why do eaglets lie down on the nest?
A. Eaglets, like all growing babies, sleep a lot and
conserve energy by resting and lying down. The
development of leg and foot muscles takes time; like
human infants, young eaglets don't yet have the muscle
strength to sit up or move about at first.
Q. Are eagles or eaglets adversely affected by prolonged
and heavy rain?
A. Adults are less affected by weather, as they are
protected by their (waterproof) feathers and can go
without a meal for some time. Nestlings, especially
those under two weeks of age who can't regulate body
temperature and whose first down doesn't offer
protection, can succumb to hypothermia in extreme
Q. Why do some eaglets seem to rub their behinds on the
A. Sometimes a bird is just itchy or irritated by a bit
of grass or a food particle around the vent, but this
can also be a sign that the bird (young or adult) has
Q. Do young eagles play?
A. Yes; scientists believe that picking up and moving
sticks and other objects (and passing them back and
forth) are a form of play. Eagles of all ages have been
seen passing sticks while flying and 'playing' with
objects; it is thought that they learn skills in this
Q. How old are the eaglets when they fledge?
A. Nest departure as early as 8 weeks of age has been
reported, but 11 to 13 weeks appear to be the most
The Hornby eaglets have usually fledged at 12 weeks of
age. In 2009, the chick fledged at 85 days of age (the
exact age reported in Doug Carrick's book).
Q. Do bald eagle siblings fledge at the same time?
A. They fledge a few (or more) days apart, depending on
hatching interval and sex.
Q. When they fledge, are the eaglets just pushed out of
A. No. While some eaglets fledge 'prematurely' (have
a mishap when over- or underestimating distance to a
branch), the majority take their first flights by choice
and under their own control.
Q. Is it true that 40% of bald eaglets do not survive
their first flight?
A. While this is widely reported on some websites and in
some books, more recent studies (and nest cam studies)
indicate that this is not the case. (See "survival",
Q. Do bald eagle parents starve out the eaglets to force
them to fledge?
A. No; they continue to bring food to the nest.
In 2009, Mom and Dad Hornby delivered 19 fish to the
nest the day before their chick fledged.
Q. Do the eaglets try to follow the adult when they
leave the nest?
A. Yes; once the eaglet has flown from the nest and
landed, the parents will coax it to follow (luring it
with food). The eaglets will follow the adults back to
the nest and feed there until such time as they begin to
feed alongside the parents; at that point, their
foraging abilities improve quickly and they become less
and less dependent upon their parents.
Q How long will bald eagle parents continue to feed the
chicks after they fledge?
A. Studies indicate that this period varies; the average
across the entire range is about six weeks.
Q. How does an eaglet learn what food items to hunt? Do
eaglets learn to hunt from their parent or is this
A. The eaglet first learns to recognize foods in the
nest; when it fledges and follows the parents, it learns
by watching them and other eagles. It continues to learn
by observation and through trial and error. The
predator's instinct to pursue prey is innate and is
fine-tuned through learning and experience.
Q. How do you sex eaglets?
A. Biologists measure beaks and feet to determine sex
but this method, while good, is not always accurate.
Eaglets in studies are weighed and measured prior to
banding and many biologists now also take blood samples
to confirm sex.
Q. How long can bald eagles live?
A. Their potential lifespan appears to be 40+ years of
age. A pair in the Winnipeg Zoo was still reproducing
and fledging young at 41 years of age.
Free-ranging eagles face more challenges; 30 years is
considered to be a long lifespan in the wild. Studies
suggest that resident populations may live longer than
those that migrate.
In 2009, the Hornby eagles were thought to be around 26 years of age.
Q. Do bald eagles have any predators?
A. The adult bald eagle's only predator is the human.
Small eaglets are vulnerable to larger birds of prey,
ravens, and larger climbing mammals such as bears and
raccoons. Grounded non-flying young are vulnerable to
other mammalian predators (e.g., wolves, coyotes) as
Q. Is it true that 50% of bald eagle fledglings will not
survive their first year?
A. This may not be the case; some scientists say that
earlier estimates were speculative. As radio telemetry
study data increase, it appears that first-year survival
is better in some areas than in others, with urban
eaglets not faring quite as well as those from rural
Findings from some of these studies (all of which had
good sample size):
- Chesapeake Bay: 100% survived from 8 weeks of age to
nest departure at 10–12 weeks of age; 100% survived
their first year
- Texas: 97% survived to nest departure
Florida: 93% survived to nest departure; a minimum of
63% survived their first year
- California: 77% survived
the first year
- Montana: 91% survived their first year
- Yellowstone National Park: 87% survived their first
- Maine: minimum of 73% survived their first year
Survival chances improve with each succeeding year.
Q. What are the main causes of death in bald eagles?
A. The most common causes of death are human-related and
include collisions (e.g., vehicles, power lines),
electrocution (from power lines), toxins (pesticides and
other chemicals), lead poisoning (from ingested lead
pellets, bullets, and fishing sinkers) and rodenticides
(eating poisoned rodents and other poisoned animals).
Eagles are still illegally shot and trapped by people
who see them as nuisances, or for their feathers, beaks,
or talons. Natural causes include diseases like West
Q. What are the threats that bald eagles are now facing?
A. Habitat loss (due to forestry and human habitation)
and degradation are serious threats. Nest trees and
roosting habitat are lost to developers and logging, and
increased recreational use and human activity in these
areas as well as in hunting and fishing areas, have
negative impact. According to studies, human activity
can lead to permanent displacement from suitable habitat
and can reduce survival, notably in winter when food and
good hunting areas are no longer available to the birds.
Saving the Bald Eagle
"The bald eagle has been a major player in American conservation history. Chosen by Congress as the nation’s symbol in 1782, it was soon to become a casualty of the country’s social and technological transformation. Eagles were subject to widespread extermination efforts by settlers, and even fed to hogs in Maine. When the story of its poisoning by DDT was popularized in Rachel Carson's Silent Spring, a nascent environmental movement rallied around it: the great raptor was one of the first species listed under the 1967 precursor to today’s Endangered Species Act." ~ Learn about the Bald Eagle from the Center for Biological Diversity
The number of nesting bald eagle pairs has been monitored throughout the lower 48 states since 1967, when the species was listed as endangered. The Center for Biological Diversity published its 2007 Population Report online. It is the first-ever report on numbers of eagle pairs and long-term trends for every U.S. state. Read the report here: Bald Eagle Populations in the United States
The Eagle Nature Foundation provides results of the most recent Bald eagle counts as well as counts for the past 50 years and publishes an annual Status of the Bald Eagle report: Eagle Facts Report
Bald Eagle Trackers
Bald eagle telemetry, tracking, and movement reports
Ontario, Canada: follow the Great Lakes eaglets: Bird Studies Canada
New York State, USA: Journey North Bald Eagle Migration
Virginia, USA: Center for Conservation Biology Eagle Trak
Bald Eagle Information
For the young and young-at-heart, from some fine eagle biologists: Journey North
The Bald Eagle
by Mark V. Stalmaster
Published in 1987 and out-of-print, but may be available through used book
dealers on Amazon.com
The Bald Eagle: Haunts and Habits of a Wilderness Monarch
by Jon M. Gerrard and Gary R. Bortolotti
Published in 1988 and available new or used through Amazon.com
Field Guide to the Bald Eagle
by Audubon Society
Published in 2002 and available new or used through Amazon.com
Make a Difference for Bald Eagles
You too can participate in programs that monitor bald eagles!
USA: Eagle count volunteers: Eagle Nature Foundation Midwinter Count
Canada: Choose from several volunteer programs with Bird Studies Canada
USA: Nest monitoring volunteers: Eagle Nature Foundation Nest Monitoring Program
Make a Difference for All Wildlife
Know the issues- Read about breaking news at Environmental News Service
Take action - even your signature can save a wild life. Defenders of Wildlife.
See the big picture - Understanding and preserving biodiversity is the only way in which we can help nature regain balance. To learn more about biodiversity, ecosystems, and refuges that offer wildlife protected habitat, go to Wildlife International.
Act locally - Backyard habitats offer shelter, food, and water to many species that are trying to adjust to losses of native habitat due to human encroachment.
Advice for people in British Columbia is valid in other parts of Canada and the US: Identify and Protect Nests on Your land
Learn how to make your garden into a wildlife habitat at home from the National Wildlife Federation.
Human encroachment can also result in some conflicts with wild neighbours. Find solutions to conflicts, learn about wildlife safety, and read about ways you can create habitat and support for our dwindling wildlife from the International Wildlife Rehabilitation Council
the Humane Society of the United States (HSUS).
Project Feeder Watch
Help gather data on songbirds in your own back yard:
Canada: Bird Studies Canada
USA: Cornell Lab of Ornithology
Other bird monitoring projects:
Canada: Bird Studies Canada Volunteer Programs
USA: Audubon Society Christmas Bird Count
Report a Banded Bird
Have you spotted a bird with a silver (US Federal) or a colored (state) leg band?
Report your sighting to the USGS
Read the annual report on The State of the Birds:
"The state of our birds is a measurable indicator of how well we are doing as stewards of our environment. The signal is clear."
Now that you've been smitten with eagles, you may want to grab your binoculars and camera. For rare bird alerts, identification aids, birding organizations in your area and even information on gadgets and gear, go to Wildlife International Birding page
For fun kinds of eagle gear, visit our Cafe Press gift shop.