Eagles & Osprey

Large, striking and charismatic birds of prey,

the bald eagle, golden eagle and osprey seem

to embody power and majesty. All regularly

occur in Pennsylvania, but only the bald eagle

and osprey nest here. The golden eagle migrates

through the state on a pathway connecting its

breeding and wintering territories.

In the not so distant past, direct persecution and

environmental contaminants drove eagle and osprey

populations to catastrophically low levels. Protection at

both state and federal levels, tremendous conservation

efforts and improved waterway quality enabled them to

rebound in Pennsylvania and elsewhere.

While persecution and environmental contaminants con

tinue to impact these large raptors, today’s primary threats

include loss of habitat due to land-use changes and declin-

ing habitat quality.

Taxonomists place bald and golden eagles in the same fam

ily as hawks, kites, harriers and Old World vultures – the

family Accipitridae. The osprey is the only species of the

family Pandionidae.

Bald Eagle

The bald eagle’s scientific name, Haliaeetus leucocephalus,

means “white-headed sea eagle.” The word “bald” is a mis

nomer. The mature eagle’s head is covered with gleaming

white feathers. Its body is dark brown, its tail white. Imma

tures are brown, mottled with white on their wings and

body. Full adult plumage is attained in the fifth year. Both

adults and immature bald eagles have yellow bills and feet,

and their legs are feathered halfway down.

Bald eagles were listed as a federally endangered species

until 1995, when their status was upgraded to “threat

ened.” In 2007, following a remarkable population recov-

ery, the bald eagle was removed from the federal List of

Endangered and Threatened Wildlife in the lower 48 states.

Although no longer listed at the federal level, the bald

eagle remains protected under the federal Bald and Golden

Eagle Protection Act, the Lacey Act and the Migratory Bird

Protection Treaty Act. In Pennsylvania, the bald eagle is

given additional protections under the state Game and

Wildlife Code.

Adult bald eagles are 30 to 40 inches in length and weigh

8 to 14 pounds. Their wingspans are 6 to 8 feet, and they

stand about 2 feet tall. As with other birds of prey, the

female is larger than the male.

Bald eagles fly with strong, deep strokes, or soar on flat

tened wings. Their eyesight is among the keenest in the ani-

mal world, five or six times sharper than a human’s. A bald

eagle’s call is a rapid, harsh cackle, kweek-kik-ik-ik-ik-ik, or a

lower kak-kokkak.

Fish, either caught live or scavenged as carrion, make up

60 to 90 percent of a bald eagle’s diet. Bald eagles also eat

birds, small mammals, reptiles, amphibians and inverte

brates. Eagles soar above the water or sit on a perch, and

when they spot a fish near the water’s surface, they swoop

down and snatch it in their talons. They use their talons for

killing, and their heavy bills for tearing prey apart for eat-

ing. Sometimes an eagle will go after an osprey or another

fish-eating bird, forcing it to drop a captured fish, which the

eagle grabs in midair. This behavior is known as “pirating”

prey.

Generally, bald eagles mate for life, although when one

partner dies, the other quickly finds a new mate if one is

available. Nesting is preceded by a spectacular aerial court

ship, with the birds locking talons, diving and somersaulting

in the sky.

Eagles & Osprey

Wildlife Note - 32

Revised 07/2014

More Wildlife Notes are available from the Pennsylvania Game Commission, Bureau of Informaon

and Educaon, Dept. MS, 2001 Elmerton Ave., Harrisburg, PA 17110-9797. www.pgc.state.pa.us.

An eagle’s nest is called an eyrie. The big raptors choose large,

sturdy trees with good views of their surroundings. Nest sites

are near lakes, rivers, reservoirs, and seashores.

A new nest is about 5 feet wide and 2 feet high, with an inside

depression 4 to 5 inches deep and 20 inches in diameter.

Often a pair returns to the same nest year after year, repairing

damage and adding a new layer of sticks, branches and corn

stalks, plus a lining of grass, moss, twigs and weeds. Enlarged

annually, some nests grow so big and heavy that they break

the branches or tree supporting them. Unlike ospreys, bald

eagles are not likely to build on artificial structures, although a

few have done so in Pennsylvania.

The female lays two eggs (sometimes only one and occasion

ally three) during the span from February through April. Eggs

are about 2¾ by 2½ inches, dull white and unmarked.

Both parents incubate, with the pair taking turns at

the nest.

If all goes well, the eggs begin hatching after

about 35 days. Young birds (eaglets) are fed by

their parents. Because eggs hatch over several

days, age and size differences among

hatchlings often gives the first

hatchling a head start and a com

petitive advantage at feeding

time. A large, healthy eaglet might

kill a smaller, weaker one or out-

compete it for food.

Eaglets develop most of their feath

ers by 3 to 4 weeks, walk in the

nest at 6 to 7 weeks, and begin

to fly at about 3 months. Young

separate from their parents in

autumn.

Factors affecting nest success

are many. Bald eagle nests and

young eagles are easily disturbed

and nest failure can occur when

people get too close to an active

nesting area. Adults might aban

don a nest site altogether or leave

eggs or hatchlings exposed to sun,

cold temperatures, severe weather

and predators. Also, when growing

eaglets are disturbed before their first

flight, they may fledge prematurely which makes them

vulnerable to terrestrial predators and inclement weather. To

protect eagles, people should keep their distance from active

nests, roost sites or feeding areas, and avoid approaching a

nest directly. Federal regulations prohibit any intrusion within

660 feet of the nest.

Eagles do not breed until 4 or 5 years of age. Their natural

reproduction rate is slow. High water quality, riparian for

est and wetland habitat are vital for Pennsylvania’s breeding

eagles. Breeding habitat – tall, sturdy trees near bodies of

water in protected areas—continues to dwindle. Toxic chemi-

cals introduced into the environment cause repeated nest

failures.

Bald eagles are now fairly widespread in Pennsylvania, and

may show up here in all seasons, and particularly along major

river systems. Nesting pairs might remain in their territories

year-round. Many eagles migrate through the state, some

from the north and others from southern parts of the United

States. In fall, bald eagles are among the earliest raptors to

pass through, soaring on thermals over mountain ridges and

along large streams. Many of the early migrants are southern

bald eagles that have wandered north into Pennsylvania and

other northeastern states following nesting and are return

ing south again. During winter, bald eagles are seen around

water bodies across the state. During colder winters, when

open water is rare, eagles congregate in areas where

water remains unfrozen and they can forage.

Bald eagles congregate at several locations

in winter, including sites along the lower

Susquehanna River, upper Delaware River,

Raystown Lake, and the reservoirs and wet-

lands of northwestern Pennsylvania. In order

to record wintering eagle populations and to

get a preview of nesting behavior, the Game

Commission each year coordinates

a mid-winter bald eagle survey in

cooperation with volunteer eagle-

watchers and the U. S. Army Corps

of Engineers.

While bald eagles today appear in

Pennsylvania in good numbers, not

so very long ago, the future for

the state’s eagles looked bleak. In

1983, when the Game Commission

launched what would be a seven-

year restoration program, only three

pairs of nesting eagles remained in the

state—all of them located in Crawford

County, in northwestern Pennsylvania

along the Ohio border.

As part of a federal restoration

initiative, the Game Commis

sion sent employees to the

Canadian province of Saskatch-

ewan to obtain eaglets from

wild nests. From 1983 to 1989,

88 eaglets were brought to Pennsylvania, where they were

raised in specially constructed towers and released into the

wild through a process known as “hacking.” Hacking is a fal-

coner’s term for maintaining a young bird in a semi-wild con-

dition, providing food until it can fend for itself. Pennsylvania’s

reintroduction effort jump-started a remarkable recovery.

By 1998, Pennsylvania was home to 25 pairs of nesting bald

eagles. Within the next three years, the number of nesting

pairs doubled. By 2006, more than 100 nests were confirmed

statewide. And the number of nests topped 250 in 2013, with

bald eagles nesting in all but a handful of the state’s counties.

A bald eagle’s head

feathers change as

it matures.

Pennsylvania Game Commission: Managing wild birds, wild mammals and

their habitats for current and future generaons. www.pgc.state.pa.us.

The nesting population continues to grow in size and expand

in geographical range, and a lot of good habitat remains.

Bald eagles can live 32 years or longer in the wild. They have

few natural enemies and mortality is often directly or indi

rectly related to humans. They are sometimes killed by motor

vehicles, occasionally shot and some get lead poisoning from

ingesting contaminated prey. Eagles are sometimes electrocut-

ed when they land on powerlines, and are at risk of colliding

with wind turbines on ridgetops during migration.

The bald eagle was chosen the United States’ national symbol

in 1782. At that time, an estimated 100,000 lived in what is

now the lower 48 states. In 2007, the U.S. Fish and Wildlife

Service estimated that at least 9,789 nesting pairs populated

the contiguous United States.

Golden Eagle

The golden eagle, Aquila chrysaetos is a

magnificent predator of remote, moun-

tainous areas. The species occurs in

Europe, Asia, northern Africa and North

America, where it’s most common in the

western United States, Canada and Alaska.

The golden eagle is rare in the Northeast.

A small population exists in eastern North

America. This geographically isolated population

breeds in northeastern Canada in

the northern forests of Quebec,

Labrador and northern Ontario.

The eastern golden eagle is closely

linked to the Appalachian Moun

tains where it travels the moun-

tain ridgelines during southbound

and northbound migrations and

spends the winter on the steep

forested ridges of the central and

southern Appalachians, primar-

ily in Virginia and West Virginia.

Pennsylvania hosts its share of

migrating and wintering golden

eagles, mainly in the Ridge and Val-

ley Province between the Allegheny

Front and the Kittatinny Ridge.

Pennsylvania’s Wildlife Action Plan designates the golden

eagle as a vulnerable species, and as a top predator, it is an

indicator of habitat quality.

Like the bald eagle, the golden eagle is federally protected

under the Bald and Golden Eagle Protection Act, the Migratory

Bird Treaty Act and the Lacey Act. The golden eagle generally

prefers open country on its breeding range, but on migration

and during winter it favors the Appalachian’s forest ridges and

small openings along those ridges.

Adults and immatures have rich, dark-brown body plumage,

with gold-tipped feathers on the back of the head and neck.

The golden eagle is in a subfamily of “booted” eagles and its

legs are feathered to the toes. Adults resemble immature bald

eagles, but goldens are darker with fewer splotches of white.

Immatures have white wing patches and, for their first several

years, a broad, white band at the base of the tail. In flight the

eagle’s tail protrudes noticeably more than its small-looking

head protrudes. It also holds its wings in a slight “V” as

compared to the bald eagle’s flat plane, the so-called “flying

plank” of hawk watches.

Golden eagles are shaped like buteo hawks, with long, round

ed wings. They flap less and soar more than bald eagles. Body

length is 28 to 40 inches; wingspan is 6 to more than 7 feet,

and standing height is about 2 feet. Their calls are a series

of rapid, sharp chirps or yelps, although they are most often

silent. Neither eagle calls as much as the more common red-

tailed hawk.

A golden eagle’s prey includes small rodents,

hares, rabbits, birds, reptiles and fish.

They also eat carrion and are capable

of killing large animals. Golden eagles

crush prey in their sharp talons, and use

their large, hooked beaks to rip it apart

for eating. In Pennsylvania, golden

eagles are regular migrants in

mid-October through early

December. Northbound migra

tions occur in late winter and

spring with most sightings at

hawk-watch sites in March and

April.

Golden eagles do not breed in

Pennsylvania. Some occasionally

winter here in rugged, remote for

est terrain, remaining out of site

most of the time. Most golden

eagles breed across central Cana-

da, in the western United States,

Alaska and mountainous parts of

Mexico.

Breeding habits are similar to those

of bald eagles, except golden eagles

often locate their nests on cliffs. After

fledging, young remain in the nest area during summer, then

wander away from the site with their parents. They do not

breed until 5 years of age.

A recent four-year survey (2006 to 2009) conducted by the

U.S. Fish and Wildlife Service suggests there may be 30,000

golden eagles across the United States. The eastern golden

eagle population is believed to be fewer than 2,000. The gold

en eagle is not on the federal threatened or endangered list,

but has disappeared from most of the northeastern states.

Osprey

The osprey, Pandion haliaetus, is a large, eagle-like hawk

found throughout North America and in the Eastern Hemi-

sphere. It inhabits seacoasts and the areas near large rivers

and lakes. In Pennsylvania, it shows up along the major rivers

Golden Eagle

Wildlife Note - 32

Revised 07/2014

More Wildlife Notes are available from the Pennsylvania Game Commission, Bureau of Informaon

and Educaon, Dept. MS, 2001 Elmerton Ave., Harrisburg, PA 17110-9797. www.pgc.state.pa.us.

and their tributaries and around lakes, ponds, reservoirs and

wetlands. The osprey prefers shallow water and requires an

abundant supply of fish within a reasonable distance from its

nest. Nests are usually nearby food sources, but occasionally

up to about 12 miles away. Ospreys are not as likely as bald

eagles to nest near flowing fresh water. Ospreys also are more

likely to nest in clusters at a lake or reservoir, and usually on

an artificial structure.

Osprey plumage is dark brown above and white below. Adults

and juveniles are colored similarly except juveniles show

buffy-white spots on their backs, a buffy shading on their

necks and chests and reddish-orange eyes. Adults have yellow

eyes. The osprey’s head is largely white, with a black patch

across each cheek. A conspicuous crook to the wings, creating

a characteristic “M” shape, and black “wrist” marks are good field

identifiers.

Except when migrating, ospreys flap more than

they sail. Wingbeats are slow and deep.

Ospreys hover 50 to 150 feet in the air

and then plunge to the water for their

fish prey, sometimes going all the

way under.

Ospreys are 21 to 24 inches from

bill to tail. Their wings span 4 ½ to

6 feet. They stand about 1 ½ feet

tall. Ospreys are quite vocal and use

several different calls to commu

nicate with one another. Their call

is a series of loud whistles, cheep,

cheep, etc.

Ospreys typically migrate south in win

ter and return to Pennsylvania in late

March and early April to nest. They

can be seen migrating south along the

mountain ridges in August, Septem-

ber and October, with peak migration

occurring around the middle of Septem-

ber. During fall, many migrating ospreys are

also observed along Pennsylvania’s rivers. Ospreys

migrate to southern wintering grounds along the Gulf Coast

and in southern Florida south through Central America and

South America.

Like eagles, ospreys build bulky nests of sticks and twigs, lined

with inner bark, sod or grasses. Sometimes they add debris

(rope, fishnet fragments, cans, seashells, etc.). Nests are in liv

ing or dead trees, on the ground, or on manmade structures

– cell towers, utility poles, fishing shacks, billboards, channel

buoys, light standards, chimneys and platform-topped poles or

towers erected specifically for osprey nesting. In Pennsylvania,

most known osprey nests are on manmade structures. Since

ospreys add to nests year after year, the nests can become

huge and conspicuous.

The nests usually include three eggs, sometimes two and

rarely four. Eggs are 2⅜ by 1¾ inches, and white or pinkish-

white with brown spots and blotches. The female incubates 36

to 42 days, and young leave the nest when they are 51 to 59

days old.

Dr. Larry Rymon of East Stroudsburg University in 1980 began

reintroducing ospreys to the state’s northeastern counties.

The first Pennsylvania-hacked osprey returned in 1983, and

two years later the state documented its first nesting pair

since 1910. An osprey has strong ties to the area where it

was hatched, and usually returns in the same area to breed.

Between 1980 and 1996, 265 young ospreys were released

into Pennsylvania at three different locations: the Poconos

in northeastern Pennsylvania, the Tioga County reservoirs in

northcentral Pennsylvania and Moraine State Park in western

Pennsylvania. These nestling birds were obtained from the

Chesapeake Bay, which has the largest nesting population of

ospreys in the world. A total of five reintroduction projects

between 1980 and 2007 helped fuel the

osprey’s recovery in Pennsylvania. The

recent Second Breeding Bird Atlas

(2004-08) documents the osprey’s

recovery with confirmed nests

reported in at least 90 atlas blocks,

a tenfold increase compared to the

nine blocks confirming nests during

the first atlas period (1984-89). Most

recently, osprey nest surveys in 2010

reported 115 osprey nests in 21 coun

ties with more found since that year.

The osprey is a state threatened species

and protected under the Game and Wild-

life Code. Although not listed at the federal

level, all migratory birds are protected

under the Migratory Bird Treaty Act.

Raptor Reproducon

Reproductive failure is a problem for

bald eagles and ospreys. Much of the

problem stems from man’s use of now-

banned toxic chemicals. DDT, dieldrin,

and other chlorinated hydrocarbons

sprayed to kill insects, which contaminates

water and prey species in the food chain.

Bald eagles eat a lot of fish, and accumulate

the chemicals in their bodies. Other pollutants such as PCBs

and heavy metals may also affect their reproduction.

The chemicals cause birds to lay infertile or thin-shelled eggs,

which break under the weight of an incubating bird. Although

environmental regulations have banned the use of “hard”

pesticides, some chemicals remain in our natural food chains

because they do not break down rapidly and some harmful

chemicals banned in the United States continue to be used in

other parts of the world. Many birds are still exposed to these

toxins during migration and on wintering territories. Moni

toring bald eagle nests helps the agency follow the recovery

process and determine their population status. It also allows

biologists to detect environmental problems that may be

occurring both locally and statewide.

Pennsylvania Game Commission: Managing wild birds, wild mammals and

their habitats for current and future generaons. www.pgc.state.pa.us.