THE BALD EAGLE

and its economic status

Marine Biological Laboratory!

X.IBRARY

OCTlu 1956
WOODS HOLE» MASS.

CIRCULAR 30

FISH AND WILDLIFE SERVICE

UNITED STATES DEPARTMENT OF THE INTERIOR

THE BALD EAGLE

and its economic status

By RALPH H. IMLER and E. R. KALMBACH

Biologists

CIRCULAR 30

UNITED STATES DEPARTMENT OF THE INTERIOR, Douglas McKay, Secretary
FISH AND WILDLIFE SERVICE, John L. Farley, Director

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1955

For sale by the Superintendent of Documents, U. S. Government Printing Office
Washington 25. D. C. - Price 30 cents

CONTENTS

Page

Range and abundance- 3

Characteristics 9

Plumage 9

Age 9

Sex ratio 9

Size and weight 10

Nests and young 13

Enemies 18

Legislation 18

United States ' 18

Alaska 19

Canada 21

Food 22

Sources of information 22

Alaska 22

United States 24

Analysis of food 26

Fish 26

Alaska 26

United States 31

Canada 32

Wildbh-ds "_ 32

Alaska 32

United States 34

Canada 35

Mammals 36

Big game 36

Small mammals 37

Domestic animals 38

Blue fox 38

Other domestic animals 40

Poultry 41

Invertebrates 41

Carrion 41

Vegetable matter 44

Attacking HUMANS 44

Summary 46

Literature cited 49

111

The bald eagle; juvenile above and adult below. (From a Fish and Wildlife Service
painting in color by Louis Agassiz Fuertes.)

THE BALD EAGLE

and its economic status

Attaclied to the bald eagle is a
degree of popular interest far be-
yond that normally associated with
our birds of prey. Early in the
Nation's history the bald eagle, of
all the varied forms of wildlife in
North America, was selected as our
national emblem. By act of the
Congress, June 20, 1782, a design
for the national coat-of-arms dis-
playing the bald eagle was adopted.
As narrated by Dr. Francis H. Her-
rick (1924a, p. 90) :

The principal figure in the obverse was
thus described in the report of William
Barton and Charles Thomson, Secretary
of Congress. "The Escutcheon placed on
the Breast of an American (the bald-
headed) Eagle, displayed proper, holding
in his Beak a Scroll, inscribed with the
Motto, viz., 'E pluribus Unum' — and in
his dexter Talon a Palm or an Olive
Branch — in the other a Bundle of 13
Arrows ; all proper."

Despite the esteem in which
many have held the bald eagle
through the years, some have seen
it in a less complimentary light.
This impression goes back, in at
least one notable instance, to one of
the founders of the Republic, Ben-
jamin Franklin. Gaillard Hunt
(1909, p. 65) in his History of the
Seal of the United States, quoted
Franklin as having written :

For my part, I wish the bald eagle had
not been chosen as the representative of
our country ; he is a bird of bad moral
character ; he does not get his living hon-
estly ; you may have seen him perched
on some dead tree, where, too lazy to fish
for himself, he watches the labor of the
fishing-hawk ; and, when that diligent
bird has at length taken a fish, and is
bearing it to his nest for the support of
his mate and young ones, the bald eagle
pursues him, and takes it from him.
With all this injustice he is never in
good case ; but, like those among men
who live by sharping and robbing, he is
generally poor, and often very lousy. Be-
sides, he is a rank coward ; the little king-
bird, not bigger than a sparrow, attacks
him boldly, and drives him out of the
district.

No attempt is made here to judge
the merits of the selection of the
bald eagle as the emblem of this
country, nor to appraise the ethics
or the bravery of the bird. Instead,
information has been assembled
from reliable sources and from the
examination of a series of bald
eagle stomachs and crops, and food
remains at nests, to permit a cur-
rent appraisal of the economics of
the bird both within the borders of
the United States and in the Terri-
tory of Alaska. A brief summary
is made of data on its distribution,
abundance, migration, and general
life history.

Study of the economics of the
bahl eagle was prompted hirgely by
the need for information to ap-
praise the merits of bounty and
other legislation afTectino; the eagle
in the Territory of Alaska, where
it long has been the subject of con-
troversy. There also was need for
information regarding the influence
of the bald eagle in the United
States, where its economic status
was little undei'stood.

These demands led to the assign-
ment of the senior author to a sinn-
mer's field work (May to September
1941) in Southeastern Alaska. As-
sisted by Game Management Agent
Hosea R. Sarber, he collected eagle
stomachs and recorded pertinent in-
formation. Previous to this, Sarber
collected stomachs of bald eagles in
1940 and continued to do so during
1942 and 1943. The senior author
was again in Alaska in 1945 and
1946 to study the food habits of
hair seals and sea lions and, in the
course of that work, he collected
additional information and stom-
achs of eagles in Southeastern
Alaska and at points westward
along the coast. The stomachs were
later examined by him mainly at
the Denver Wildlife Research
Laboratory, and by personnel of the
Patuxent (Md.) Wildlife Research
Refuge, particularly Francis M.
Uhler, who assisted in identifying
individual food items. At a later
date, the junior author tabulated
and analyzed the data from stom-
ach examinations, reviewed the
publislied literature, and prepared
the numuscript.

Two earlier expeditions to the
Aleutian Islands (in 1936 and 1937)

led by Olaus J. Murie, assisted by
C. S. Williams, Victor li. Scheffer,
and others, collected valuable food-
habits data at 28 nests of the bald
eagle on a number of the islands in
this chain west of the Alaskan Pen-
insula. This work, reported on by
Murie (1940), has supplied infor-
mation concerning the bald eagle in
the western part of its range in
Alaska.

To complete the historical record,
mention should be made of three
earlier publications issued by the
U. S. Department of Agriculture.
The first of these appeared in 1893
as Bulletin 3 of the Division of
Ornithology and Mammalogy, The
Hawks and Owls of the United
States in Their Relation to Agri-
culture, b}^ A. K. Fisher, and con-
tained a section devoted to the bald
eagle. The second appeared in 1906
as Bulletin 27 of the Biological
Survey, The North American
Eagles and Their Economic Rela-
tions, by H. C. Oberholser. Its text
was devoted to a discussion of both
the bald and the golden eagle. The
third was Circular 370, Food Habits
of (\)mmon Hawks, by W. I^. ^Ic-
Atee. Published in 1935, it con-
tained brief suuunaries of the food
habits of both tlie golden and the
bald eagle.

Literature on the bald eagle
wliich has appeared through other
channels is voluminous, and in the
assembling of this pa])er judicious
use has been made of it. Manuals
dealing with the ornithology of sev-
eral States have been fruitful
sources of information. I'lie most
extensive contribution on the habits
and ecology of tlie bald eagle pub-

lished in this country is the series
of documents by Dr. Francis H.
Herrick based on his studies of this
bird at nesting sites in northern
Ohio, made over a period of many
years. Outstanding also is the
study of the bald eagle in Florida
carried on for many years by
Charles L. Broley, who, to a greater
extent than any other individual,
has banded juvenile bald eagles and
leported on their movements.
Shorter articles and notes that have
appeared in ornithological journals

are legion, and only a significant
few could be drawn upon in the
preparation of this text. Appre-
ciation for employment of numer-
ous published notes is expressed
collectively at this point.

Acknowledgment also is made of
assistance given by the managers
of national wildlife refuges
throughout the country who have
submitted information on the
abundance and economic status of
the bald eagle on areas under their
jurisdiction.

RANGE AND ABUNDANCE

The bald eagle in its two subspe-
cific forms, Haliaeetus leucocefha-
lus leucocephalus (Linnaeus) and
H. I. washingtonii Audubon, is es-
sentially a North American bird.
The northern form {washingtonii)
is found from northeastern Siberia
(formerly), northwestern Alaska,
Mackenzie, Manitoba, northeastern
Quebec, and Newfoundland, south-
wardly across the continent where
it intergrades with the southern
form in a broad belt across the mid-
section of the United States (Fried-
mann 1950). South of the area of
integration, the southern form
ranges eastward from Baja
(Lower) California, Arizona, New
Mexico, and Texas to Florida, and
southwardly to the Gulf of Mexico.

Throughout this continent-wide
range, the bald eagle is most com-
mon in the vicinity of the seacoast
or bodies of fresh water where it is
assured an ample supply of its sta-
ple food, fish. For that reason,
concentrations are found in South-
eastern Alaska, around the Great

Lakes, and at points along the At-
lantic coast, especially in the vicin-
ity of Chesapeake Bay, and in
Florida. Migration also concen-
trates numbers of bald eagles in
winter along the Mississippi and
other large rivers in Illinois, Iowa,
and Missouri, and even westward in
Oklahoma.

In recent years, there has been an
appreciable reduction in bald eagle
numbers in many areas in the
United States where these birds
formerly were abundant. J. C.
Howell (1937, 1941) has pointed
out that in a section of northeastern
Florida where Dr. William L.
Ralph found more than 100 occu-
pied nests in 1886, only 24 were lo-
cated in 1935. In his more recent
appraisal of that population, How-
ell (1949) stated that during the
period 1935-46 the nesting popula-
tion had decreased almost 30 per-
cent. This was corroborated by
Broley (1950, 1951, 1952) who has
noted a pronounced reduction in the
number of nesting eagles in Florida

where he banded more than 800
young- during the period, 1939-46.
Since that time he has encountered
a steady reduction in their numbers.
Whereas, formerly he banded 100 or
more young birds in a season, in
1950 he was able to band only 25
young; in 1951, 24; in 1952, but 15;
and in 1953, 18. Not all of this de-
crease can be charged against kill-
ing of the birds since, in many in-
stances, there has been a marked
change in the environment through
cutting of timber and exposure of
nesting sites to the elements. Bro-
ley (1951) is inclined to believe that
the severe storm that swept the
Atlantic coast in 1950 played an im-
portant part in the destruction of
nests and the abandonment of
others.

An idea of the density of nesting
bald eagles in an optimum nesting
area may be gained from Howell's
reference to nests found in Volusia
County, Fla., in 1935. In the 18
miles between the towns of Shiloh
and New Smyrna there was an eagle
nest to each 2 square miles and one
nest in use to each 3 square miles.
In 1940, the manager of the St.
Marks National Wildlife Eefuge
reported nine known nests and pos-
sibly three to five others on that
65,000-acre area along the gulf
coast in northwestern Florida.

In contrast with its abundance as
a breeder in some of our coastal
areas, the bald eagle is relatively
scarce in the interior. If the birds
encountered during migration were
excluded and only resident birds
considered, the bald eagle certainly
would be termed an uncommon bird
throughout most of our eastern

mountains, the central valleys (ex-
clusive of the Great Lakes area),
the plains, and the western moun-
tains. This appraisal has been sub-
Ktantiated by the testimony of
informed individuals in numerous
States. Speaking with respect to
the whole of Canada, Taverner
(1934, p. 137) stated that "except
on the seacoasts the Bald Eagle is
nothing more than a rare, interest-
ing, and picturesque feature of the
landscape." Even in Michigan witli
its abundance of suitable habitat
for bald eagles, the Department of
Conservation reported in 1940 and
1941 that, conservatively estimated,
there were 50 breeding pairs of
these birds in the State (Wood
1951). In other widely separated
States including New Jersey, Mas-
sachusetts, Minnesota, Louisiana,
and California, reliable published
information indicates that the bald
eagle is much reduced in numbers
or absent as a breeding bird from
areas where it once nested regularly.
That food supply affects eagle
movement and local abundance
during winter is evident in the Mid-
west where these birds congi^egate
in open-water areas of the large
rivers. Musselman (1949) has re-
corded fluctuations in their num-
bers along the Mississippi River in
western Illinois. He states:

Bald eagles (Haliaeettis leucocephaJus)
have been seen at Keokuk [Iowa] in
small numbers for more than half a
century. Originally they were attracted
by ofifal thrown into the river from the
pork packing houses to the south. The
water of the river was almost always
open during the winter due to the Des
Moines rapids ; an occasional dead fish
along with the offal supplied an abun-
dance of food.

4

The packing houses are gone, yet
recently the number of these great birds
has increased due to the fact that the
water below the Keokuk dam is always
open, and an abundance of fish are killed
as they pass through the turbines which
are creating electricity.

In the winter of 1947 and 1948, there
was the largest accumulation of eagles
in the history of this location. Mr. Cyrus
Phillips makes almost daily trips through
the territory in which these birds roost
and reports that he counted 83 eagles at
one time. * * * The birds start to gather
about December 1.5, and fly north about
February 15 when the upper river begins
to open.

An appraisal of the abundance of
bald eagles on national wildlife
refuges in 1940 revealed that of 37
refuges reporting, 16 were not fre-
quented by bald eagles, 10 had them
in moderate numbers, mainly dur-
ing migration, and 11 reported them
as common with greatest numbers
during migration or in winter.
Whereas the terms "moderate num-
bers" and "common" are subject to
a wide range of interpretation and
the sizes of the various refuges also
add a variable to the picture, it was
evident that refuges in the North-
west, on the South Atlantic coast,
and along the Mississippi Eiver
were visited by the greater number
of eagles. At only one, the St.
Marks Refuge in Florida, was an
increase reported in the years previ-
ous to the 1940 census.

Similar appraisals were made of
bald-eagle abundance on national
wildlife refuges in subsequent years,
the last survey being conducted in
the fall, winter, and spring of 1953-
54. At that time, comparisons were
made with the numbers recorded in
former years. The map (fig. 1)
presents the result of this appraisal,

and the legend explains the code
used in recording the data. Of 89
refuges reporting, 21 showed an in-
crease, 41 no change, and 27 a de-
crease in eagle numbers. Yet, of
the 23 refuges reporting the larger
numbers (10 or more), 16 showed
an increase, 3 no change, and 4 a
decrease. The aggregation of bald
eagles along the Mississippi River
in the Central States may have been
a reflection of the mild winter of
1953-54, with open water prev-
alent. In addition to 300 bald
eagles recorded in 1953-54 on the
extensive Upper Mississippi Na-
tional Wildlife Refuge, the Louisa
Refuge in Iowa recorded 40, Reel-
foot in Tennessee 100, Swan Lake
in Missouri 40, and Salt Plains to
the west in Oklahoma reported 108
eagles, probably more than three-
fourths of which were bald eagles
(Van den Akker 1954).

An analysis of bald eagle records
that appeared in the Christmas
bird counts sponsored by the Na-
tional Association of Audubon So-
cieties was made by Chandler Rob-
bins. This appraisal, covering the
period 1930 to 1953, clearly indi-
cated the concentration of these
birds in the Chesapeake Bay area,
the South Atlantic coast, Florida,
and the central Mississippi River
drainage. Fluctuating numbers
characterized the returns with in-
creases noted in the Mississippi
Valley and in Oklahoma in recent
years. These data have, in the
main, been substantiated by records
of U. S. game-management agents
who report on the abundance of the
bald eagle in their respective areas.

At the Hawk Mountain Sanctu-

332664—55-

FiGTjRE 1. — Bald-eagle abuudauce on 89 national wildlife refuges in the fall, winter,
and spring of 1953-54 compared with that of former years. The solid black dots
indicate an increase from estimates made in the 1940's ; the half -black dots, no
change; and the circles, a decrease. An outer circle indicates 10 or more eagles
reported. The greatest number was on the Upper Mississippi River "Wild Life and
Fish Eefuge, an extensive area reaching into the States of Minnesota, Wisconsin,
Illinois, and Iowa, where 300 bald eagles were reported in the winter of 1953-54.

ary located on a principal flyway
for birds of prey in east-central
Pennsylvania, Dr. Maurice Broun
has recorded an appreciable in-
crease in the number of bald eagles
passing through in recent years.
Although the number noted has in-
creased appreciably at this point
during the past 20 years, part of
this may be the result of more ex-
tensive field observations. He states
(in correspondence) that the high
count of 142 eagles in 1950 was due
in large part to ideal flight condi-
tions— strong winds from the north-
west over a period of time. In 195?),
poor flight weather obtained and
only GO individuals were counted.
Of significance may be Dr. Broun's
observation that in the early 1980"s,
about 50 percent of the bald eagles

passing through were immature
birds, while in recent years the fig-
ure remained consistently around
20 percent. This variation in the
proportion of yearling birds may be
indicative of a decrease in the east-
ern population of the liald eagle.

Even in areas where the bald
eagle is only moderately abundant
there is a tendency for the birds to
gather at nightly roosts, and an ex-
aggerated idea of their numbers
often results locally. The senior
author (19o4) observed such a roost
near Stockton, Kans., in the early
thirties that was said to have been
occupied since the settlement of the
country. The first birds appeared
at this roost in November and the
last left in March. At one time.

Imler saw 23 eagles concentrated
]iere.

Althoug-h adnlt bald eagles, once
established in a nesting area, may
spend much of the year in that
vicinity, they usually migrate south-
ward Mhen confronted with severe
cold weather. Not only do northern
birds move southward with the
arrival of cold w^eather but the
young of southern nesters wander
northward in summer after they
have acquired their powers of
flight. The latter fact has been
conclusively demonstrated by
Charles L. Broley, who, during the
period 1939-46, banded and released
814 young bald eagles along the
gulf coast of Florida (Broley 1947) .
Most of these birds were released
in January and February and 48
returns were obtained from them.
Whereas no recoveries were re-
corded north of Florida during
January, February, or March, none
was made in Florida during the
]^eriod June to October, indicating
that the young leave the State soon
after they can fly. Several had
travelled more than 1,000 miles to
the northeast and one had reached
Kings County, Prince Edward Is-
land, Canada, in the Gulf of St.
Lawrence, more than 1,600 miles
away.

Bruce Wright (1953, p. 56) has
picked up evidence of this north-
ward drift of bald eagles in late
summer on the estuary of the St.
John River in New Brunswick,
Canada. He states:

The peak population is reached by
August 1st. After this date there is a
steady decline until only a few are left
in luid-September. In 1949 the peak
population on the 40-square mile study

area was counted and estimated to be
f)4, and in 1950 it was 45. This is in
exces.s of one eagle per square mile,
which suggests a total population of at
least 100 eagles in the area. * * * They
are not a local population, altliough there
are a few breeding records. Banding
recoveries show that birds rai.sed in areas
as far apart as Ontario and Florida sum-
mer in the estuary.

Elsewhere in the United States
and Canada there is less informa-
tion on the seasonal movements of
bald eagles based on the returns
from banded birds. Broley (1947)
has called attention to the fact that
at "Hawk Mountain" in northern
New Jersey the peak of southward
eagle migration is in September, but
he attributes this to the return of
southern birds that had moved
northward after the nesting season.
Northern breeders, he pointed out,
leave for the South at a later date.

In Southeastern Alaska, before
the bounty had reduced their num-
bers, bald eagles were recognized as
the most abundant predatory bird,
other than possibly the raven.
George Willett, who was well ac-
quainted with conditions there, had
the following to say in 1923 (in cor-
respondence) :

I would hesitate even to make a guess
at the number of eagles that are within
50 miles of Craig, but they would un-
doubtedly number several tliousand.
Along a great part of our shoreline there
would probably be a nest every lialf mile
at least and there is plenty of shoreline.
In March, when the herring spawn here
in Klawak Inlet, I have seen over 40
eagles in one tree and have counted over
700 in 3 miles, and tliese were probably
only a small portion of those that were
present.

Writing at about that same time,
E. P. Walker, executive officer of

the Alaska Game Commission, com-
mented in a similar vein when he
stated that —

In Alaska they are still probably more
abundant than they ever were in the
States and the majority of the Alaslia
lands adjacent to the coastline frequented
by eagles are so rugged and uninhabited
that when the eagles get away from
salt water or away from the immediate
lower reaches of the streams they are
practically free from danger from moles-
tation by human beings.

Notwithstanding the fact that
during the period of bounty pay-
ments the bald eagle of the coastal
region of Alaska was reduced in
numbei^, the area still is one of
great eagle abundance, far exceed-
ing that existing any place in the
States. This is a fact seldom appre-
ciated by those who have never
witnessed the bald eagle in and
adjacent to tlie waterways of South-

eastern Alaska. This thought was
expressed by Dr. T. Gilbert Pear-
son (1928), former president of the
National Association of Audubon
Societies, who made a personal in-
spection of the area in 1927, when
tlie bounty law had been in efl'ect for
10 years and more than 40,000 bald
eagles luid been removed. Although
he stated that the "bald eagle had
been greatly reduced in num-
bers, * * * as a species, it cannot
be considered as being in any im-
mediate danger of extermination."
No doubt that statement has com-
l^lete application today in Alaska,
where the bald eagle is now relieved
of the pressure formerly exerted by
tlie bounty and may be killed only
when causing damage.

In the course of field studies con-
ducted in Southeastern Alaska

FiGUEE 2. — Typical bald-eagle habitat, iiiuuth of Koduian Creek, Baranof Island,
Alaska. Nineteen bald eagles were in sight at this point at one time on August 9,
1941. (Photograph by K. H. Iniler.)

8

during the summer of 1941, the
senior author recorded 677 bald
eagles along 837 miles of shoreline.
Other eagles, particularly the less-
conspicuous immature birds, no
doubt M'ere present but were not
seen. After making allowance for
them, it was believed that an esti-
mate of 12 to 15 eagles for each 10

miles of shoreline was a reasonable
one. Concentrations were observed
usually in areas of alnindant food,
as on Baranof Island, where for a
distance of 6 miles along the shore
and up a salmon stream, at least 45
eagles were seen. At one point
along the stream 19 birds were in
sight at one time (fig. 2).

CHARACTERISTICS

PLUMAGE

The newly hatched bald eagle is
clothed in a thick, light-gray down
whicli fades into white on the head
and underparts (fig. 3). In about
3 weeks, this first down is followed
by another coat of darker-hued
down that is retained until it is
pushed out by the young bird's Ju-
venal plumage. The juvenal plum-
age begins to appear when the eaglet
is 5 or 6 weeks old, and is rather
uniformly brown with flight
feathers of the wings nearly black.
It is the plumage of the young
birds when they leave the nest at
about 12 weeks of age and is re-
tained until the first annual molt,
which takes j^lace during their
second summer (figs. 4 and 5).
Through subsequent annual molts
the bird ultimately acquires the
whiteness of head and tail so char-
acteristic of the species. Complete
maturity of plumage is not attained
until the bird is 3 or more years old
(frontispiece). Etta S. Wilson
(1922) described a captive bald
eagle which retained its juvenal
plumage through its third year, but
the feathers of both head and tail
were pure white a year later. On

the other hand, Lee S. Crandall
(1941) has reported the develop-
ment of the plumage of a captive
bird which did not acquire a white
head and nearly white tail until its
sixth year and did not possess a
completely white tail until its
eleventh year. Once attained, the
immaculate whiteness of the head
and tail are retained throughout
the rest of the bird's life.

AGE

Little is known of the length of
life of bald eagles living in the
wild, but the longevity of captive
birds may be construed as an indi-
cation of what happens when the
hazards of outdoor life are re-
moved. Stott (1948), summarizing
longevity records of birds in the
San Diego, Calif., zoo, reports two
eagles that lived 15 years.

SEX RATIO

That the sex ratio of the bald
eagle is about 1 : 1 was revealed by
the dissection of 187 specimens by
the senior author in the course of
his Alaskan fieldwork in 1941. Of
these, 54 were immature birds, half
of which were males and half

Figure 3. — Downy young of the northern bald eagle on Ananiuliak Islniid in the
Alontian Islands, Alaska. (Photograph by V. B. Scheffc^r.)

females. Of loo adults, 64 were
males and (il) females.

SIZE AND WEIGHT .

In size and wei<;ht, the bald eagle
is not greatly diU'erent from the
golden eagle, and with the excep-

tion of the California condor these
eagles are the largest birds of prey
in North America. Only in the tail,
which is somewhat k)nger in the
golden eagle, is there a noticeable
difference in the dimensions of the
two species.

10

Figure 4.— A nearly fledged young liald f;ii;U'. St-ney National Wildlife Refuge, Mich.
Flexing its wings, it is almost ready to take its first short flight. The character-
istic flat-topped nest of sticks is lined with finer material and is located 65 feet
from the ground in a red pine. ( Photograph by 0. J. Henry. )

As in most birds of prey, the
female bald eagle is larger and
heavier than the male. Friedmann
(1950) stated that the average wing
length of 16 adult male bald eagles
from Southern United States was
529.2 millimeters (20.83 inches) and
that of 29 adult male northern bald
eagles, 588.6 mm. (23.18 in.) . Com-
parable measurements for the wings

of adult females were 526.5 mm.
(22.70 in.) in 11 southern birds and
640.2 mm. (25.21 in.) in 42 Alaskan
birds. Similar differences were dis-
closed in the measurements of the
tail, bill, and other features of the
two groups of birds.

In the course of Alaskan field-
w^ork, the senior author recorded
the dimensions and weights of 108

11

FiGiTEE 5. — A nearly lk'dj,^ed yuuu;; l)ald eagle, Atka Island, Aleutian Islands, Alaska.
The dark plumage of the head, the dark bill, and the dark iris of the eye are in
marked contrast with the coloration of the adult bird with its white head and lijiht-
yellow bill and iris. ( Photograph by V. B. Scheff er. )

bald eagles including adults and
juveniles of both sexes. These data
appear in table 1.

The adult females averaged 2.26
pounds lieavier than the adult males
and the immature females averaged
2.31 pounds heavier than the im-
mature males. In fact, tlie differ-
ence in weight between the sexes
(both adult and immature birds)
was so pronounced that little over-
lapping occurred even between
weights of the heaviest males and
tlie lightest females.

The immature birds (1 year or
older) revealed average measure-
ments (except that of the bill)

greater than those of the mature
birds of the same sex. On the other
hand, the average weight of the
immature birds was less than that
of adults of the same sex, indicating
that the greater dimensions of the
young birds are attributable to
greater length of wing and tail
feathers, and not to greater body
size.

The greater size of the Alaskan
birds is reflected even in the eggs.
Bent (1937) has assembled data
showing that the average size of the
eggs of the bald eagle increases
gradually northward through the
bird's ranjre.

12

Table 1. — Weights and measurements of 108 bald eagles collected in Alaska

Weight (pounds)

Measurements (inches) of—

Maturity and sex '

Gross

Net

Wing

Tail

Spread s

Length *

BOls

Adult males (35):

10.70
8.10
9.30

10.61
8.01
9.09

24.1

21.87

23.06

11.9
10.8
11.41

85.50
80.75
82.83

34.75
31.25
33.19

2.69

2.44

2.57

Adult females (37):

14.10
10.20
11.78

14.09
10.11
11.56

25.80
23.25
24.61

12.80
11.10
11.97

91.87
85.00
88.36

37.80
34.20
35.88

2.94

2.69

2.81

Immature males (18):

10.10
7.80
8.91

10.07

7.77
8.85

24.70
22.62
23. 85

13 50
11.50
12.48

88.50
81.62
84.34

35.70
33.40
34.33

2.65

2.50

2.57

Immature females (18) :

13.20
10.15
11.48

12.69
9.61
11.22

27.25
24.50
25.68

14.75
12.20
13.43

95.50
87.87
91.63

39.87
35.25
37.37

2.95

2.69

2.79

1 Number of specimens in parentheses.

2 Obtained by subtracting weight of the food in the stomach and crop from bird's gross weight.

3 The laterarmeasurement from wingtip to wingtip when the wings are extended to their limit on a flat

< The measurement from the tip of the bill to the tip of the longest taO feather when the bird is fully extended.
5 The measurement from tip of bill to the feathers at base of the cere.

NESTS AND YOUNG

We owe much of our knowledge
of the nesting habits of the bald
eagle to the initiative and persever-
ance of Dr. Francis H. Herrick,
head of the department of biology
at Western Keserve University,
who, during the years 1922 to 1930,
conducted intimate studies of this
bird in northern Ohio. From tow-
ers constructed at the nesting sites,
he observed and photographed the
courtship, nest building, egg laying,
incubation, and raising of the
young eagles to flying age. In the
course of his studies, an original
wooden structure was extended to
a greater height, and this in turn
was replaced by a steel tower 80
feet high. When this tower was
uprooted in a severe storm in 1929,
a second, 96 feet high, was con-
structed and used to the end of the
studies. The steel tower, equipped
with a platform and blind at the

top, was moved from one nest to
another as required by changing
conditions.

Bald eagles are inclined to use
the same nest year after year unless
disturbed (fig. 4). Herrick (1924a,
p. 94) traced the history of six
successive nests in the vicinity of
Vermilion, Ohio, over a period of
nearly a century. One of these
nests, the oldest and the largest, was
destroyed during a storm in the
36th year of its occupancy. Having
been added to throughout the years,
it had acquired enormous propor-
tions, and near the end of its exist-
ence was 12 feet high and 8i/^ feet
across the top. The upper surface
had an area of nearly 50 square
feet and its total weight was com-
puted to be about a ton (Herrick
1924b).

Broley (1947) records a still
larger nest near St. Petersburg,

332664—55-

13

Fla., wlijcli lie coiu'ludes may liave
been the large.st in America. This
nest, typical of many found in that
State, Avas higher than it was
wide — 20 feet deep and 91^ feet
across at tlie top.

Another nest of substantial size
formerly located on the Eastern
Shore of Maryland has been de-
scribed by Frank IJ. Smith (1936).
This nest had been occupied for
more than 30 years when a hurri-
cane blew it down in 1933. "The
remains of the nest were carefully
sifted by hand and placed in bas-
kets for weighing. * * * The forty-
three bushels of material in the
nest weighed 1274 pounds."' Had
sticks which remained attached to
the nest tree been included, the total
weight would have been more than
1,300 pounds.

The main structure of the bald
eagle's nest is composed of sticks
and small limbs, and clods of earth
and masses of A^egetation are added
in the central portion. There may
be a lining of pliable vegetation, but
the nest surface is nearly flat sur-
rounded by a rim of sticks (fig. 4).
As the nest is reconditioned in sub-
sequent years more material is
added, thus gradually increasing
the weight of the nest in height and
in width until it finally may crash
because of the extreme weight.

In Ohio, Dr. Herrick found that
eagles chose hickory, elm, or syca-
more trees for nesting sites. Origi-
nally, many of these trees were in
the borders of wood lots, but as time
went on some of them became iso-
lated by the cutting of surrounding
timber, and the nesting trees were

preserved only through the solici-
tude of landowners. In the Pacific
N(n-thwest and in Southeastern
Alaska, tall conifers are used as
nesting sites. Altitude, as a rule, is
sought (fig. 6), and nests in Ohio
often are 70-80 feet above the
ground, while those in the spruces
and hendocks of the Xorthwest may
be more than 100 feet from the
ground.

In the course of his Alaskan field-
work, the senior author computed
bald-eagle nests to average about
51/^ feet high and 6% feet across.
On the basis of 11 nests measured or
estimated, the height from the
ground to the top of the nest varied
from 45 to 137 feet, with an aver-
age of 77 feet. In this region, Sitka
s])ruce was the favorite nesting tree.

In contrast with the nesting sites
described, bald eagles may be
forced by lack of tall arboreal
growth to nest in low vegetation,
or even on the ground. Such a con-
dition prevails in the Aleutian Is-
lands in Alaska, where their nests
are placed on rocky cliffs or pin-
nacles (fig. 7) : and in Florida,
I^i'oley (1947) recorded a nest only
15 feet above water in a mangrove.
Bendire (1892), quoting Capt. \^. V.
Grove, reported the finding of two
eagle nests placed on the ground of
small islands in the Gulf of Mexico
off the Texas coast. One, estab-
lished by a pair of birds still in
their innnature plumage, consisted
of a few sticks on the otherwise
bare ground. The other nest had
been built up through successive
years of use to a height of 6 feet.
Also on record is the nesting of a

U

Figure 6. — A typical lU'st of the bald eagle, Seney National Wildlife Refuge, Mich.
Lo(5ated in a dead red piue, 40 feet from the ground, it was used for seA'eral years
in ,the late 1940's. A Canada goose used its platform as a nest site in 1950.
(Photograph by C. J. Henry.)

15

Figure 7. — Young bald eagles in their nest on offshore pinnacle, Rat Island, Aleutian
Islands, Alaska. (Photograph by V. B. Scheffer.)

pair of eagles on the ground in
Crawford County, Mich. Here the
birds had constructed their nest on
a knoll in the burned-over plain of
a pine forest (Sharritt 1939).

Although the laying of eggs by
one species of bird in the nest of
another occurs frequently, nesting
in the occupied nest of another spe-
cies is less common. Yet, such an
instance \vas reported by J. Warren
Jacobs (1908), when he found a
great horned owl incubating two of
its eggs in a cavit}' in the side of
the large nest of a bald eagle. The
eagle was also incubating a set of
its own eggs at the top of the great
nest pile. The diurnal fish-eating
habit of the eagles apparently did

not conflict unduly with the noc-
turnal rodent feeding of the owls.
Dr. Herrick (1933) observed a pair
of English sparrows that had built
their nest in the side of a bald
eagle's domicile and availed them-
selves of the down shed by the
eaglets to line their nest.

That bald eagles mate for life is
a common and apparently a well-
substantiated belief. If one of a
pair is killed, the other usually ac-
quires a new mate and may continue
to nest at tlie former site. Since
bald eagles apparently become sex-
ually mature even before they have
acquired adult plumage, it is pos-
sible to find a bird in juvenal plum-
ajre mated with one in full adult

16

dress. Hoxie (1910) reports a case
of both birds of a mated pair being
in Juvenal plumage.

Dr. Herrick (1932, p. 311) re-
corded a female which had four
different mates, namely, in 1924,
1925, 1928, and 1931. In the latter
year, her mate apparently was
killed, and after an absence of 1-1
weeks she returned with another.
They successfully raised a brood the
following year.

The clutch of the bald eagle may
vary from 1 to 3 eggs with 2 being
the normal number. Frequently
only 1 of the young is raised to ma-
turity. According to Herrick
(1932, p. 318), the normal incuba-
tion period in northern Ohio is 34 to
35 days. In Florida, Nicholson
(1952) established the incubation
period as 35 days. The period of
egg laying varies greatly from the
southern to the northern portion of
the bald eagle's extensive range.
Bent (1937) has shown that from
Georgia and Florida to Texas eggs
may be found from the end of Octo-
ber to the end of Februarj', with
half of the records falling between
the dates of December 8 and Janu-
ary 27. From New Jersey to Vir-
ginia, he found that the spread was
from February 2 to May 27, with
half of the records falling between
February 27 and March 9. Six rec-
ords from the area, Maine to Michi-
gan, revealed that egg laying took
place between April 1 and April 21.
In Alaska and Arctic America,
eggs were laid from March 24 to
June 24, with half of the records
falling between May 7 and May 14.

On the basis of these figures, the
median dates of egg laying for
Florida, New Jersey, Michigan, and
Alaska are roughly, January 2,
March 3, April 10, and May 10,
respectively.

In the southern part of the bald
eagle's range, should the eggs be
removed from a nest or a nest de-
stroyed during the egg laying or
early part of the incubation period,
a second clutch often is laid. The
same nest may be used, but usually
there is a shift to a new location.
Farther north, except j)ossibly in
the mild climate of Southeastern
Alaska, the shortness of the season
and the necessity of finding food for
the young over an extended period
prevent the laying and hatching of
second clutches.

The nestling life of the bald
eagle, as determined by Dr. Her-
rick in northern Ohio, lasts from
10 to 13 weeks during which the
3"oung undergo one change of
downy plumage and gradually ac-
quire their juvenal plumage with
which they leave the nest (fig. 4).
Even after the young leave the nest
they often remain in the vicinity
and at times are fed at the nest
site by their parents throughout
their first summer. In this respect,
the young of the bald eagle are
quite different from the offspring
of most passerine birds, which, once
they have left the nest, seldom re-
turn to it. On the other hand, the
young bald eagles are not permitted
to use their home territory for
breeding purposes unless in later
years one of them should be mated
with a parent.

17

ENEMIES

The bald oaglo 1ms few if any
vertebrate enemies other than man.
Many of the smaller birds are })rone
to jiester bald eagles, partieidarly
dnrino- the nesting season, bnt noth-
ing more serions than temporai'V
discomfort can be charged to these
attacks. The crow and the eastern
kingbird frequently harass the bahl
eagle, which on rare occasions will
turn on its tormentors. Herri ck
relates an incident in which a pair
of diminutive gnatcatchers, only
slightly larger than hummingbirds,
irritated an adult eagle to the point
that it moved to another perch far-
ther from the home tei'ritory of the
small birds.

Man. however, has had a marked
effect on the abundance of the bald
eagle. This Avas amply demon-
strated in tlie coastal region of
Alaska where, over a period of ol
years, possibly as many as 100,000
bald eagles were killed as the result
of the bounty law. It is the con-
sensus of many comi)etent observers
that bald eagle numbers were mate-
rially reduced along the principal

waterways in the southeastern part
of the Territory.

Tlii-oughout the United States
tlie status of the Iwild eagle has been
one of steadily di'creasiiig numbers
largely because of the activities of
man either against the birds them-
selves or through modilication of
their habitat and destruction of
nesting sites. Of significance in
this connection is the fact that the
nestling bald eagles banded by
Charles T.. Broley (1047) during
the i)eri()d lO.'iO—tC) and recovered
later (48 of tliem ) weiv. with two
e.\ce])tions, killed within 1 year
after tlieii- I'elease. And this degree
of shooting })ressure was exerted in
our Eastei-n States largely through
a ])eriod of years when the bald
eagle had been given com])lete i)ro-
tection under Federal law (see
p. ID).

Periodically, storms of hurricane
intensity have dealt havoc to nest-
ing eagles not only by destroying
their nests but also the young,
which require 12 or more weeks
before they are equipped to live
awav from their home.

LEGISLATION

UNITED STATES

Although (he Continental Con-
gress ado])ted the bald eagle as a
national symbol to be used on the
Great Seal of the Cniled States, on
coins, and in other ways, 4a ws pro-
tecting the bird were not considered
until many years later. Early in
l'.>.")(». ;i serious and iicarlv success-

ful etlort was made to enact Federal
legislation to jirotect it. On Janu-
ary (), bills entitled "Bald Eagle
Protection Act" were introduced in
both the Senate and the Tfouse of
IJepi'esentatives. 4'liis would have
;i ll'oi'dcd ])rotection to t he hald eagle
with lln' |)i-ovis() that "it shall not be
unlawful to kill any such eagle * * *
A\lieii ill the act of dest roviiiir wild

18

or tiune lambs or fawns oi- foxes on
fox farms.-- Favorably acted on
by tlie Senate after certain amend-
ments, the bill later failed of pas-
sage in the Honse of Represent-
atives.

Companion bills to protect the
bald eagle again were introdnced in
the Senate and the Honse of Repre-
sentatives in the spring of 19J:0.
Their provisions followed closely
those of the earlier bills with the
exception that the Territory of
Alaska was exclnded, a sitnation
brought about by strenuous objec-
tion to the protection of the bald
eagle in an area where it was abund-
ant and had potentialities for harm
to fishing and fur-farming indus-
tries. This act was passed, signed
by the President and became a law
(Title 54, Stat. 250) on June 8,
1940.

The salient features of this legis-
lation provide that, except in the
Territory of Alaska, it shall be un-
lawful to "take, possess, sell, pur-
chase, barter, offer to sell, purchase
or barter, transport, export or im-
port, at any time or in any manner,
any bald eagle, commonly known as
the American eagle, alive or dead, or
any part, nest or egg thereof.'' The
act also provides for the granting
of permits to collect eagles for
scientific purposes and for the pro-
tection of wildlife or agricultural
or other interests locally. Author-
ity and moneys provided inider the
Migratory Bird Treaty Act of July
3, 1918, were made available for the
administration and enforcement of
the Bald Eagle Act.

With the bald eagle now afforded
protection under Federal law, pro-

visions in State laws contrary
thereto lose their import. A review
of State statutes made several years
prior to the protection of the eagle
disclosed that in 5 States the bird
was specihcally protected, in 39 it
was protected by implication, and
in 1 it was unprotected. Conse-
quently, in the United States enact-
ment of a Federal law for the pro-
tection of the bald eagle conformed
to prevalent thought and strength-
ened enforcement procedures.

ALASKA

Legislation enacted by the Terri-
torial Legislature of Alaska regard-
ing the bald eagle has been that con-
nected with enactment or repeal of
bounties for the birds' destruction.
In appraising such legislative ac-
tion, one must take into considera-
tion the circumstances prevailing in
the areas affected by such action.
Although there have been marked
changes in human populations and
activities in recent years in this ex-
])ansive region, throughout much of
the bounty-payment period, Alaska
was largely a primitive, sparsely
])opulated area. The abundance of
bald eagles in the coastal region of
Alaska, to which they are partial,
was and still is many times that
prevailing in those areas in the
States where the bird is most plenti-
ful. If we consider also that, in its
fisheries and fox farming, Alaska
has industries that could be vulner-
able to eagle depredations, and that
a bounty system often is looked
upon as a source of income, the
reason for the popularity of such a
law in the Territory becomes
obvious.

19

The initial bounty law, enacted
by the Territorial Legislature in
1917, provided a payment of 50
cents for each pair of eagle feet.
In that year and in subsequent
years, payments were made on the
following numbers of eagles : 1917,
2,048 ; 1918, 3,181 ; 1919, 2,641 ; 1920,
2,377; 1921, 2,121; 1922, 3,318; or a
total of 15,745 in the 5-year period.
In 1923, the bounty was increased
to $1 and from then until 1940 avail-
able records show that an additional
79,746 eagles were killed. In this
computation, however, there appear
to be some discrepancies, and, no
doubt, many eagles were killed and
not retrieved or were crippled only
to die later.

Although the bounty remained in
force in subsequent years, no money
was appropriated by the Terri-
torial Legislature for biennial peri-
ods either in 1941 or 1943. In 1945,
the law was repealed only to be re-
enacted in 1949 with the bounty in-
creased to $2 for each pair of eagles'
feet. To February 11, 1951, pay-
ments were made on 7,455 eagles
under the revised statute.

On July 1, 1952, a regulation
adopted under the provisions of the
Alaska Game Law, provided that- — •

these birds may be killed only when
committing damage to fishes, other wild-
life, domestic birds and animals. No
carcass or any part thereof including
feathers of birds so taken may be pos-
sessed or transported for any purpose.

Eight months later, March 2, 1953,
the territorial eagle bounty law was
repealed. Consequently, ,the bald
eagle no longer has a bounty on its
head in Alaska and may be killed
only when causing damage.

That the bounty law reduced the
number of eagles in the coastal re-
gion of Alaska is attested by a num-
ber of reliable observers. George
Willett, able ornithologist and field
observer of many years of experi-
ence in Southeastern Alaska, had
the following to say regarding the
number of eagles in Alaska at about
the time the bounty law was en-
acted (Pearson 1928) :

Bird lovers in the States, to whom the
sight of an eagle is an event, can hardly
conceive of the great numbers of the birds
to be seen along the Alaskan Coast. In
this region the eagle probably outnum-
bers all other raptorial birds a thousand
to one.

After several years' absence from
Alaska, Willett again spent a sum-
mer along the southeastern coast.
The following comment (in corre-
spondence) made at a time when
the bounty had been in effect for
19 years, gives his impression of
the reduction in eagle numbers :

I spent the summer of 1936 in south-
eastern Alaska and found that the eagles
had decreased to such an extent that
destruction by them must be small. This
was admitted by many Alaskans with
whom I talked. * * * Unfortunately, the
question has stopped being one of con-
servation and has become economic, in
that many Indians and some whites * * *
have come to consider the eagle bounty
as part of their income.

Even after the bounty had been in
effect for only a short period, those
who were in close touch with the
problem became aware of the reduc-
tion in eagle numbers. C. D. Gar-
field, Secretary of tlie Alaska Fish
and Game Club, wrote apprehen-
sively in 1920 :

Since December 6, 1918, bounty has
been paid on 3,256 eagles or a total of

20

8,356 since the passage of tbe Act. * * *
A vast difference is noted in the numbers
of this bird showing in southeastern
Alaska and it is a safe prediction that,
if the slaughter continues for a few years
longer, the species will become practi-
cally extinct.

Ernest P. Walker, formerly ex-
ecutive officer of the Alaska Game
Commission, stated in 1927:

The Eagle buunty system has consid-
erably reduced the Eagles in southeast-
ern Alaska in the ten years that it has
been in effect, and to a lesser degree it
has reduced Eagles along the southern
coastline westward as far as the Kadiak
region. It is doubtful, however, if the
birds have been materially reduced far-
ther westward, and evidence that they
have been materially affected through
the interior and northern country is
lacking.

Hosea Sarber, an observant and
reliable game-management agent of
the U. S. Fish and Wildlife Service,
stationed for many years at Peters-
burg, Alaska, commented (in corre-
spondence) on the possible effect of
the failure of the Legislature to
provide the necessary bounty funds
in 1941 and 1943, as follows :

There is no question but that the eagle
will increase now to its former numbers.
They are still plentiful throughout the
country and they will now increase un-
molested as no one will be shooting
them * * *.

There is little question but that
with the removal of possibly 100,000
birds during the years the bounty
laws were in operation the number
of eagles was noticeably reduced, at
least along the Southeastern Alaska
coast, where the population is con-
centrated. Farther to the west
where the birds are less abundant

and certainly inland, where rela-
tively few exist, the effect on their
total number was never appreciable.
As with the operation of most
bounty systems, where the birds
were not abundant or where the
hunting pressure was limited, a
surviving nucleus remained. This
was true even in Southeastern
Alaska in the area of greatest hunt-
ing pressure. With the termination
of bounty hunting, the residual
eagle population can be expected to
recoup normal numbers within a
few years. That something of that
nature has taken place might be in-
ferred from the observations of
enforcement agent Clarence Mat-
son, who reported an estimated 750
eagles in the Haines area at the
northern end of the Lynn Canal
early in 1954.

CANADA

In British Columbia, bounties
were paid on golden eagles taken
during the period 1910 to 1924, but
in the course of this program pay-
ment no doubt had been made on
numbers of juvenile bald eagles.
Whereas $3 was paid in 1910, in
later years it was reduced to $1.
Even with the lessened payment,
7,095 eagles were reported to have
been killed in 1922. Subsequent to
1924 no bounties were paid on
eagles in British Columbia but
numbers of them were removed by
game wardens. Again, there may
have been bald eagles among the
total of 902 eagles killed in that
Province during the '5-year period,
1948-52.

332664—55-

21

FOOD

Information on the food of the
bald eagle as revealed by stomach
examinations and data assembled
from Held sources has been pre-
sented separately for Alaska, the
United States, and Canada. There
are several reasons for this. The
bald eagle is much more abiuidant
in Alaska than in other parts of its
range in North America with a re-
sultant increase in its economic in-
fluence in that area. In Alaska, it
is also thrown into direct contact
with commercial fisheries and fox-
farming — activities that are less ex-
tensive or even nonexistent else-
where in its range. In addition, in
Alaska the bald eagle has had a
background of bount}' history sup-
ported to a large extent by popular
opinion, which is markedly at vari-
ance with the public attitude
throughout the United States,
where it has had legislative protec-
tion since 1940. Such varied condi-
tions and attitudes have compelled
the writers frequently to discuss the
status of the eagle against the en-
vironmental background where it
arose, and have led to the inevitable
overall conclusion that, in several
respects, the economic role of the
bald eagle in Alaska may be quite
different from that in the States.

SOURCES OF
INFORMATION

ALASKA

Southeastern Alaska. — The col-
lectinsf of bald eaole stomachs in

Alaska for this study began early
in 1940 when Hosea R. Sarber gath-
ered material on Prince of Wales
Island, the Stikine Kiver Flats, and
elsewhere in the southeastern part
of the Territory. In the following
year Sarber continued his collecting
and was joined, early in May, by the
senior author and together they col-
lected on the islands and mainland
of Southeastern Alaska until late in
August. For the remainder of 1941
and during the following 2 years
Sarber gathered additional stomach
nniterial. In 1945, the senioi' author
collected eagle stomachs not only in
Southeastern Alaska but also at
points to the northwest. In 1946,
he collected additional eagle stom-
achs on the Copper River Flats and
also in Southeastern Alaska. As a
result of tliis intensified effort, ap-
proxinuitely 500 stomachs were col-
lected during the period 1940-40,
of wliicli Sarber, working alone,
took about 130 during the fall and
winter months.

Xot withstanding the fact that
Alaska is much better represented
than the States, the eagle stomachs
collected in the Territory were ob-
tained largely in the coastal area
south and southeast of Juneau (fig.
2). Only 20 were obtained else-
where, mainly near the mouth of the
Copper River, the shores of Cook
Inlet, and on Kodiak Island to the
west. Consequently, analysis of
bald eagle stomachs fi'oni Alaska
nnist be construed as an appraisal
of the bii-d ]n-iniarily in the area of

22

its ^Terttest abundance, the coastal
area south of Juneau. The number
of Ahiskan eaole stomachs that con-
tained suiiicient food for the esti-
ination of percentages is set forth,
by months, in table 2.

Aleutian Islands. — Because of the
peculiarities of the prey fauna of
the bald eagle on the Aleutian
Ishmds, the available information
on its food habits on those far-
Hung islands has been segregated
liere. Much of our knowledge on
tlie subject rests on the observations
made and specimens collected by
Glaus J. Murie and his associates in
11)36 and 1937 (Murie 1940). Al-
tliough the eagle studies were inci-
dental to a more comprehensive bio-
logical survey of the area, food
remnants and ejected pellets of the
bald eagle were gathered from 10
nests in 1936 and 18 nests in 1937,

and a total of 399 food items identi-
fied therefrom. Collections were
nnide at various points from the end
of the Alaskan Peninsula to islands
near the end of the chain, 700-800
miles to the west. Material from
the 1936 expedition was examined
l)y Cecil S. Williams in "Washing-
ton, 1), C, while the remainder was
examiiied by Murie, aided (in a few
determinations) by the senior au-
thor of this paper.

Table 3, condensed from two ta-
bles in the earlier article (Murie
1910), and including a few addi-
tions from later identifications, re-
veals the bald eagle's dominant
foods on the Aleutian Islands. Be-
cause of the nature of the material,
the percentages listed for the differ-
ent items have been based on the
proportion that the number of in-
dividuals of each species bears to

Table 2. — Food of 435 Alaskan hald eagles, expressed as volumetric percenfatjcs of
the several groups of items and arranged under the months of the year

[Based on stomach analyses]

Food item

Jan.

Feb.

Mar.

Apr.

May-

June

JvOy

Aug.

Sept.

Oct.

Nov.

Dec.

Aver-
age

Nimiber of stomachs

Fishes:

10

10.0
28.8
20.0
22.0

28

30

25

OS

2.0
22.0

6.1
11.4

9.0
19.5

70

11.8
16.7

8.0
14.4

1.4
18.5

59

24.1
10.5
11.0
17.4
2.3
8.0

64

35.8
5.2
6.5
5.6
4.7

13.0

23
85.0

11
25.4

11

9.1
9.1

6
"33.3"

16.9

44.2
13.7
15.9

23.3
14.4

'io'b~

10.0

5.7
30.2
21.6

"i2."2"

16.6

Trace
1.8
.2

3.8
1.8

9.4

9.3

2.3

other fish

27.3

9.1

16.7

11.2

Total

80.8

19.2
Trace

73.8

3.6
9.6

57.7

8.7
25.4

69.7

22.3
4.0

70.0

2.2
2.9

70.8

2.1
4.3

73.3

70.8

87.0

58.3

5.3
9.1

27.3

52.7
9.1

50.0
'33."3'

65.7

Birds:

9.7

Other birds'

6.4

2.5

2.6

9.1

Total-

19.2

13.2

34.1

26.3

5.1

6.1
8.2
10.6

6.4

4 2
2.2
16.4

6.4

2.5

2.6

4.3
1.8
4.3

14.4

61.8

33.3

18.8

1.2

4.8
8.2

1.5
6.7

"I'o

3.9
16.4

.6
26.1

2.0

27.3

10.9

16.7

12.3

1 Salmon, trout.

2 Pollack, cod.

3 Sculpins, scorpion fishes, rockflshes.

* Flounders halibut.

5 Herrings, anchovies.

* Ducks, geese.

' Mainly auklets, murres, and other sea birds.
» Crustaceans and miscellaneous invertebrates.

23

Tables. — Food remains collected at nests
of iald eagles on the Aleutian Islands,
1936 and 1937

Food item

fishes:
Dolly Varden trout {Salvelinus
malma)

Handsavvflsh (Alepisaurus sp.)-
YoWack (.TheTagrachalcograjnma).
Pacific cod {Gadiis macTocephalus)

Rockfish {Sebastodes sp.) -.

Greenling {Hexagrammos sp.)....
Atka mackerel {Pleurogrammus

monopterygius)

Sculpins (Cottidae)

Unidentified fish..

Occurrence

Number Percent

Total -

birds:

Shearwater (Puffinus sp.)

Fulmar (Fulmarus glacialis)

Forked-tailed petrel (Oceano-

dro ma furcata) —

Cormorant (Phalacrocorax sp.)--
Emperor goose (Philaclecanagka).

PintaU {.Anas acuta) --

Teal (probably Anas crecca)

Old-squaw (Clangula hyemalis)..
Harlequin duck {Hisfrionicus

hisfrionicus)

Unidentified duck

Common eider {Somateria mol-

lisima)

Red-breasted merganser (Mergus

senator)

Bald eagle nestling (Haliaeetus

leucocephalus)

Rock ptarmigan {Lagopus miUus).
Glaucous gull {Larus hyper-

boreus)

Glaucous-winged gull {Larus

glaucescens)

Kittiwake (Rissa Iridactyla)

Murres {Uria aalge, U. lonivia)..
Pigeon guilleniot {Cepphus

columba) __-

Ancient murrelet {Synthliboram-

phus antiquum) -

Paroquet auklet {Cyclorrhynchus

psittacula) --

Crested auklet (.'iethia crista-

fella) -- --

Least auklet (Aethia pusilla)

Horned puffin (Fratercula cor-

ntculata)

Tufted puffin (Lunda cirrhata)..

Unidentified alcid

Raven (Corvus corax)

Unidentified bird

Total.

mammals:

Domestic sheep

Blue fox (Alopex sp.)

Aleutian grotmd squirrel {Citel-
lus p. albusus), --

Field mouse (Microttis amakensis)
House rat (Patlus norvegicus) —
Sea lion (Eumetopias jubata)

Total.

invertebrates:

Squid (Chondrophora).

Snail (Gastropoda)

Crab (OxjThyncha)

Clam worm (Nereidae).

Total

Grand total.

360

0.2
.9

2.0
2
.2
.9

3.1
1.6
.7

9.8

4.7
18.3

.2

5.4

.4

2.2

.7

.7

1.6

.2

. 2
_ 2

.4

6.9

7^6

1.3

2.2

2.2

9.2
3.6

2.9

6.1

1.1

.4

.9

80.7

1
1

.2
.2

30

6.8

1

, 6

4

1

.2
1.4
.9
.2

12

2.7

446

100.0

the total number of food items
collected.

In appraising this type of mate-
rial, which contains food pellets as
well as nest debris, attention should
be called to the fact that, when
eagles are feeding exclusively on
fish, compact pellets are seldom
formed. On the other hand, when
mammals are eaten and, to a less
extent, birds, pellets usually are
formed. It is possible, therefore,
that the, recorded amount of fish
eaten by these Aleutian eagles may
have been minimized somewhat in
the tabulation.

UNITED STATES

In marked contrast with the
stomach material from Alaska,
gathered in recent years and in con-
siderable volume, that available
from the United States was col-
lected largely in earlier years
(more than half of it in the past
century), and the 31 stomachs so
assembled were from 18 different
States. Furthermore, earlier ex-
aminations, while adequate with re-
spect to the identity of the items,
were not conducted in conformity
with modem volumetric methods,
and thus prevented their combining
with more-nearly current examina-
tions. For these reasons, a tabular
presentation of the data from bald-
eagle stomachs taken in the United
States is impractical. Further in-
sight into the food preferences of
bald eagles in the mid-Atlantic
States is obtainable, however, from
the analyses of pellets and food
debris found at nests and roosts.
In table 4, food items found at the
nests of bald eagles in coastal areas

24

of Maryland and Virginia by W. B. alone tends to minimize the record-

Tyrell during the spring months of ing of fish which the eagles may

1936 and 1937 are listed. These have eaten to the exclusion of ani-

food-habit examinations were made mals clothed in fur or feathers,

by C. F. Smith and Clarence A. ^^^y of the smaller fish bones are

Sooter completely digested in the eagle's

stomach and, without a binding ma-

Table 4. — Food remains collected at nests terial, the bones of fishes eaten are

of bald eagles in coastal regions of y^^^i ^^ i^^ scattered when regurgi-

Maryland and Virginia, 1936 and 1937 i i i • fe fe

tated and no definite pellet foraied.

Accordingly, it is safe to assume
that the amount of fish eaten by the
Chesapeake Bay eagles was some-
what greater than that indicated.
These pellets were examined and
the material identified by A. L. Nel-
son and C. S. Williams. The num-
ber of occurrences of a food item
indicates the frequency with which
it was recorded in the material ex-
amined and the percent indicates
the proportion comprised by each
major group.

Examination of 630 bald-eagle
pellets collected by the senior au-
thor near Stockton, Kans., during
the winters of 1935-41, revealed that
the birds were subsisting almost
entirely on rabbits. Their remains
were found in 619 (98.3 percent) of
the pellets and 607 of these con-
tained nothing else. Jackrabbits,
very largely if not entirely the
black- tailed form {Lepus calif orni-
Additional data on the food cws), comprised the bulk of the rab-
preferences of the bald eagle in the bits eaten. The remains of cotton-
Chesapeake Bay region are obtain- tails {Sylvilagus floridanm) were
able from pellets collected by F. R. found in 12 of the pellets. Rodents,
Smith on the Blackwater National constituting 1.6 percent of the re-
Wildlife Refuge in Maryland dur- mains, included prairie dogs {C^/-
ing the period March 1933 to March noinys ludovicianus) in 3 pellets,
1934. Table 5 presents this infor- fox squirrels {Sciurus niger) in 3,
mation in detail, but it is important a wood rat {Neotoma floridana) in
to point out that pellet material 1, and unidentified cricetids in 3.

Food item

Occurrence

Number

Percent

fishes:
Herring (Clupeidae)

1
1
3
6
19
1
2

Cyprinidae (other than carp) —

Channel cat (Jctalurus punctatus)

Unidentified fish

Total ---

33

52.4

Horned grebe ( Colymbus auritus)

2

1

2
4

1

2

2
1

2

1
1

1

1

Great blue heron {Ardea herodias) .
Common mallard (Anas platy-

Black duck (Anas rubripes)

Ring-necked duck {Aythya col-

Lesser scaup duck {Aythya

Bald eagle (^Haliaeetus leuco-

Oalllnaceous bird - -

Domestic pigeon {Columba livia)

Long-eared owl (Asio wilsonia-

Total ---

21

33.3

mammals: Muskrat {Ondatra zi-
bethicus)

3

3
1

4.7

reptiles:
Mud turtle {Kinosternon sub-

Painted turtle {Chrysemys picta)

Total .-

4
2

6.3

VEOETABLE MATTER: Seeds of per-
simmon {Diospyros virginiana) . -

3.3

25

Remains of moles (Scalopm aqua-
ticus) were present in ;> pellets.
Birds were found in 7 ( about 1 per-
cent) of the })ellets and of these, ?>
were domestic chickens, 1 a mea-
(lowlark (Sfit/'/N'/la) . and '> were
niiidentified.

Tahlr T). — AiinhisiN of 59 ijcllrts of ha hi
eafjhff rollcctcfl on the Blarkivntcr
National Wildlife Refuye, Md., March
1933 to March 193/t

Occuirence

Number

Percent

fishes:

Gizzard shad (Uorosoma cepe-

1

2
1
2

Fresh-water eel (Anguilla ros-
tTota)

Toadflsh {Opsanustait)

Total

6

4.2

BIKDS:

Pied-billed grebe (Podilymbus

2

1

4
3

4
5
3

1
2
7

1

1
1
17
2
9
1
6
1

Atlantic brant '{Branta bernida)
Common mallard (Anas plafy-

Pintail (Anas acuta)

Green-winged teal (Atias caro-

Baldpate (Mareca americana)

Woodduck (Aix sponsa)

Canvasback (Ayfhya valisineria)

Ruddy duck (Oxyura jamaicen-

Hooded merganser (Lophodytes

Unidentified gallinaceous birds..

Total -

71

50.4

mammals:

1

29

1

5
6

Muskrat {Ondatra :ibethicus)

Meadow mouse (Microtus)

Cottontail rabbit {Sylvilagus

Total

42

29.8

reptiles:

1
2

Total .

3

2.1

crustaceans: Edible crab (Colli-

1

8
10

0.7

VEOETABLE MATTER:

Total

18

12.8

ANALYSIS OF FOOD

Fish
ALASKA

That lish are the "staff of life" of
Alaskan bahl eagles has been em-
])hatically demonstrated by exam-
ination of the 485 stomachs of these
l)irds collected in the Territory.
Fisli in some form and quantity
a])peared in 1)25 of the 4;)5 stomachs
(74.7 percent by volume), either as
freshly caught i)rey or as carrion
(see table 2). Of the 227 stomachs
collected during the summer period,
.June to October, only 15 ((').(> ])er-
cent) of the eagles had failed to feed
on tish. Although the tish ^vas con-
strued by the examiner to have been
carrion in only .'37 instances, there is
reason to believe that much more of
the tish eaten had such an origin.
In fact, the senior author who
heljjed collect much of this material
considers that much more than half
of the fish eaten by Alaskan eagles
were dead when found by the birds.

When digestion of tish is far ad-
vanced there is little evidence left to
reveal to the examiner the nature of
the food eaten. The same ])rocess
when ])rolonged, also obliterates
many diagnostic bones and other
parts from which identitication of
the tish can be made. This has re-
sulted in unidentified Hsh being
recorded in a substantial number of
stomachs (50), and in numerous
others only the genus or the family
to which the fish belonged could be
determined.

An undetermined portion of the
fish eaten by eagles in Alaska must
be construed as carrion in origin.
Mui'ie (1'.>-I<») comments that this

26

must be true of tlie deep-water fishes
such as the cod, although "at times
fishes were seen at the surface of the
water under circumstances tliat
would permit capture by an eagle.
This was particularly true of the
Atka mackerel." The total amount
of fish taken by the bald eagle in the
Aleutians definitely is much less
than that eaten by this l)ird in
Southeastern Alaska. In fact, on
the basis of these data, our national
bird appears to have no significant
economic effect on the fishing indus-
try of the Aleutians, unless it be at
the extreme eastern end of the chain,
in the vicinity of False Pass.

It is impossible to say whether
the fluctuation in the amounts taken
from month to month indicates a
variation in acceptance, supply, or
simply an inadequate sample of
stomachs. All three factors may
have entered the picture, but it
would appear that seasonal changes
in the diet of the bald eagle in Alas-
ka are governed, not by the supply
of fish, which is ample at all times,
but by the bird's feeding on other
birds, a subject discussed later.

Sal/mon. — Salmon and a few
trout were present in one-third
(108) of the 325 stomachs in which
fish occurred and, in volume, they
comprised nearly IT percent of the
annual food. The bulk of this
food item was consumed in late
summer and early fall (table 2).
The humpback, or pink, salmon
{Oncorhynchus gorhimchci) was
most frequently identified (39
stomachs), while lesser numbers of
the sockeye {O. nerha)^ dog {0.
heta)^ and chinook salmon {O.
tshawytscha) ^ were found. In two

instances the remains of Dolly
Varden trout {Salvelinus malma),
a persistent feeder on salmon eggs,
were detected. In 9 stomachs the
eggs of salmon were present, but in
at least 2 of these the whole mass
was considered carrion.

It was the considered opinion of
the senior author and Hosea Sar-
ber, his companion in the collecting
of the Alaskan eagle stomachs, that
the salmon eaten by the bald eagle
was principally carrion, and that,
at least during the period when they
Avere collecting material in South-
eastern Alaska, probably much less
than 10 percent of the salmon eaten
were captured alive (fig. 8).

As recorded by Imler in notes
taken July 11, 1941, on Anan Creek :

Three eagles, each at a different place
were observed while feeding on salmon.
When later examined the fish were ob-
served to have been dead a day or two
since their gills were discolored and the
flesh was a milky gi'ay. An estimated
350,000 salmon were in the creek at the
time and, although spawning had not
started, many dead fish were observed
in the stream.

And again in .Inly 21: the comment
was made that —

on Pack Creek, on Admiralty Island,
eagles were observed feeding on two
salmon, both in a stale condition. One
was a dog salmon and the other probably
a humpback but the latter was so dis-
integrated that identification could not
be made with certainty. All the eagles
here seem to be feeding entirely on stale,
dead salmon. Two collected yesterday
gave off a disagreeable odor from the de-
cayed fish held in the gullet.

Speaking of conditions before
1927, Ernest P. Walker, formerly
executive officer of the Alaska Game
Commission, had the following to

27

Figure 8. — Pink salmon in Rodman Creelv, Baranof Island, Alaska, on August 10,
1941. Observations revealed that bald eagles were feeding on salmon which was
largely, if not entirely, carrion. (Photograph by R. H. Imler. )

say regarding the relation of the
bald eagle to salmon.

The fish [salmon] taken are mainly
those that have exhausted themselves in
spawning, but unspawued fish are often
taken when they are in shallow water on
riffles or rising at the surface of quiet
shallow pools. Eagles also make use of
fish which are left on the banks by bears
and wolves. * * * i have counted 150
Eagles from one point, and there were
others nearby, though out of sight.

Allan Brooks (1922, p. 556) made
a somewhat different appraisal in
neighboring British Colnmbia when
he commented :

My first acquaintance with the species
was in the lower Eraser Valley where,
although it was a very scarce breeder,
large numbers were resident throughout
the year, but increasing in the fall when
the run of the various salmon was at its
height. Here they confined themselves
mainly to a fish diet as this was avail-
able throughout the year. Salmon were

largely taken before they had spawned
and there were always large numbers of
eagles watching the wide shallow estuary
of the Chilliwack or Veddar River where
it empties into Sumas Lake. Here the
salmon, except such species as ascended
in June and July when the water was
deep, had a very hard time, very large
fish were eaten alive as they attempted
to cross the shallow bars, a strong fish
would often flounder clear of the Eagle's
claws a dozen times before it succumbed.

With such diverse conclusions be-
ing reached regarding the relation
of tlie bald eagle to salmon, one must
assume that local conditions play an
important part in deciding the
eagle's role. Certainly the relative
abundance of eagles from ])liice to
place is important, and a broader,
more comprehensive perspective of
the problem is called for. In this
connection, the words of John H.
Cobb (1931) formerly Dean of the

28

College of Fisheries at the Univer-
sity of Washington may be restated.

Much is said by certain people of the
ravages amongst the salmon of certain
animals as the seal, sea lion, bear, eagle,
kingfisher, crane, cluck, loon, and hawk.
While in the aggregate the ravages of
these animals are considerable, they are
not a drop in the bucket as compared with
the direct or indirect ravages of man and
his agencies.

Pollack and cod. — Nearly equal-
ing the salmon as a favorite food
of Alaskan bald eagles are the pol-
lack and cod (Gadidae). These
fish were present in 101 of the 325
stomachs examined that contained
fish and comprised nearly 17 per-
cent of the volmne. The Alaska
pollack, or whiting {Theragra
chalcogramTna) , was dominant in 57
stomachs and the Pacific cod
{Gadus macrocephalus) , in 27
stomachs, was next.

The seasonal pattern of the bald
eagle's feeding on these fish was ir-
regular but greater quantities were
taken during the colder months
(table 2). In marked contrast with
the abundant references to the bald
eagle's relation to salmon is the al-
most complete absence of recorded
information on its relation to the
pollack and the cod. This is true
despite the fact that these two fishes
comprise approximately the same
proportion of the bald eagle's food
as the salmon, on the basis of stom-
ach examinations. Two possible
explanations present themselves,
one being that predation by the
eagle on living codfish seldom comes
to the immediate attention of com-
mercial fishermen and the other
(which appears plausible) is that
much of the codfish was picked up

as carrion on the beaches. Never-
theless, the Alaska pollack often
feeds near the water surface and at
such times may be captured alive
by the bald eagle.

Rockfishes and scovpionfjshes. —
The varied group of fishes (Cata-
phracti) under which are classified
the rockfishes, scorpionfishes, scul-
pins, sea ravens, and others, ap-
peared in 83 stomachs, and com-
prised 9.4 percent of the food of the
eagles examined — the bulk of these
fish being taken during the first half
of the year (table 2) . No less than
eight different genera (mainly scul-
pins) were identified. Conspicuous
among these were the widely dis-
tributed red sculpin, or Irish lord
{H emilepidotus) , in 19 stomachs,
rockfishes of the genus Sebastodes^
in 11, and the smooth sculpin {Lep-
tocottus a,rniatus)^ in 13. These
fishes, like the cod, were taken
largely during the first half of the
calendar year.

Although it appears logical that
deep-water fishes such as rockfishes
and sculpins would fall prey to the
bald eagle only after they had
floated to the surface or drifted to
the beach as carrion, the senior
author witnessed numerous in-
stances in which these fishes, as well
as flounders, were taken alive by
bald eagles. Sculpins often were
isolated in exposed shallow pools by
the receding tide whereupon they
became easy prey not only for the
eagles but for the innumerable gulls
as well.

Flounders and other -flat-fishes. —
The flounders and flatfishes (Heter-
osomata) in 57 stomachs, comprise
a group equal to the Cataphracti in

29

the food (9.3 percent) of the Ahiska
bald eagles (table -2). Of these,
the starry flounder {riatlchthi/H
stellatus), identified in 28 of the
stomachs, was most frequently
found. Halibuts of the genera
Atheresthes, Hipj^oglossus^ and
Hippoglossoides, and flounders
{Leindopsetta hilijieata) were dis-
closed in a total of 14 stomachs, al-
though the same species doubtless
occurred in others when identifica-
tion could not accurately be made.

The starry flounders were com-
mon in the shallow waters of the
tidal flats and stream mouths of
Southeastern Alaska and were easy
prey for the eagles. At Keku
Strait on June 29, 1941, a female
eagle visited its nest twice during
the evening hours, each time bring-
ing in a flounder of about II/2 to 2
pounds. This eagle and another,
carrying a fresh flounder, were
collected for their stomachs ; in each
case the feathers of the underparts
were wet indicating tliat the birds
probably removed the living fish
from the water. In this area,
eagles were seen bringing in not
only freslily killed flounders but
living ones as well.

Herring. — Herring were identi-
fied in 20 of the 435 Alaskan bald
eagle stomachs (table 2). This
does not indicate a significant con-
sumption of herring in these north-
ern waters, but the finding of 18 in
1 stomach shows that when the
birds encounter a convenient sup-
ply they satiate themselves on it.
Ernest P. Walker (1927) has de-
scribed eagle activity in the pres-
ence of a herring run in the
following!: words:

When the herring congregate in certain
favorable regions for a considerable
period prior to spawning, many kinds of
birds, including the Eagle, also congre-
gate there. Eagles then feed largely on
herring found dead on the beaches and
occasionally live herring are picked up
from the water when at the surface.
* * * The damage under such circum-
stances to the herring * * * is wholly
uegligilile.

On May 30, 1941, the senior
author observed bald eagles diving
for and capturing live herring near
Kootznahoo Inlet on Admiralty
Island; of 14 attempts, 5 were
successful.

How the bald eagle may take ad-
vantage of the activities of other
fish-eaters is well illustrated by an
incident recorded by Joseph S.
Dixon (1909, p. 190)^. One after-
noon this observer noticed a com-
motion in an Alaskan bay where a
flock of loons was fishing, possibly
on herring. An eagle was seen to
leave a nearby perch, swoop down,
and strike a fish in the water and
then return to its perch, where it
gave a shrill scream. According
to Dixon :

At the sound, eagles began to c()nK' from
all directions to the spot where he had
secured his fish, and within five minutes
there were inoic than twenty eagles
assembled. Only the first ones secured
fish, as the fish which had evidently
been driven to the surface of the water
by the loons, went down again : * * *

Otlwr fi-'<hes. — Other lishes. insig-
nificant in the total food of the
Alaskan bald eagle, included smelts

( Thaleich thy.s pacifious ) , sand
lances (Ammodyfes fob/'anih'^),
blennies (Pholis), Alaska blackfish

{l)(///Ja perforah's), and wolftish

( .1 nnirhichfhj/s).

30

UNITED STATES

Elsewhere, as in Alaska, fishes of
V'arious kinds are important in the
diet of the bald eagle. This fact
was brought out even by the limited
series of 31 stomachs collected in tlie
United States (p. 24). Fish were
present in 18 of these stomachs, of
which an indeterminate portion was
carrion in origin. Among the kinds
identified were perch, goldfish, cat-
fish, and eels.

Indication of tlie preference of
the bald eagle for fish in the ^Middle
Atlantic States may be gained from
the data set forth in table 4. Of the
fishes, the catfishes Ameiurms and
Ictalurws were most frequently en-
countered, while the birds were best
represented by waterfowl, particu-
larly ducks. Feathers of the bald
eagle in the stomachs may have been
indicative of cannibalism or exces-
sive preening of its own feathers by
the eagle involved. The seeds of
persimmon probably were in the
stomach contents of some prey on
which the eagle had fed.

The importance of fish in the diet
of the bald eagle was clearly sliown
in the observations by Dr. Ilerrick
(1924 b, pp. 404 and 400) at nests
in northern Ohio. Here, as is their
frequent custom, the eagles had con-
structed their nest about a mile from
the shore of Lake Erie, thus increas-
ing the availability of their favorite
food and at the same time reducing
the hours of search needed to supply
the dietary needs of themselves and
their growing young. In 1922, Dr.
Herrick found that 70 percent of the
food brought to the nest was fish. In
the following year fish constituted

96 percent of the young eagles' food.
In explanation, Herrick comments:

Among the fish, which were of various
sizes up to a possible weight of 3 or 4
pounds, and * * * often lacked the head,
we recognized the lake and common cat-
fish, sheepshead, sand and blue pike, carp
and perch— all common forms which can
be found almost any day, and in great
numbers after northerly storms have cast
them up on the beach. * * * We have
seen the eagles at Vermilion feeding regu-
larly on the dead fish which are swept on
the shores of the lake ; their preference
is undoubtedly for living prey, but like all
raptors they take readily to carrion when
nothing better is at hand and in this re-
spect perform a useful service.

At another time Herrick ( 1938,
13. 51) stated that the fish "might
be taken off the beach, or cap-
tured by immersing at the surface
of the lake; in many instances these
fish were alive when they reached
the nest, although they may have
travelled from three to four miles
in the eagle's clutches."

Mention has been made of the
bald eagle taking advantage of the
activities of other fish-eaters
(loons) to locate and attack schools
of fish in the water. The classical
incident of the opportunism of the
eagle is that associated with the
osprey, ^particularly along the At-
lantic coast in areas where both the
bald eagle and osprey are reason-
ably common. At such times the
eagle, usually at a height, will
watch and Avait for the osprey to
make a strike and rise from the
water with its prey. Then by per-
sistent and threatening swoops the
eagle either compels the osprey to
release its prey or, by striking from
beneath, will actually take the fish
from the talons of the osprey. If

31

it has induced the osprey to release
the fish, a swift dive often retrieves
the fish before it reaches the water.

CANADA

Althougli only two of the six bald
eagle stomachs collected in Canada
contained the remains of fish, a carp
and a salmonid, meager data from
the North give further evidence of
the importance of fish in the bald
eagle's fare. Taverner (1934) re-
ported on the examination of 15
stomachs of which 9 contained fish.

Wild Birds

The literature frequently records
incidents of predation of the bald
eagle on other birds and, although
identification may not have been
determined with unfailing accuracy
in all cases, the general character of
the birds eaten is apparent. Among
those so reported have been loons,
four species of grebes, young peli-
cans, cormorants, six species of her-
ons including the great blue, Can-
ada geese and black brant, seven
species of puddle ducks and six of
divers, wild turkeys and pheasants,
coots, sora and clapper rails, kill-
deer, three species of gulls and two
of terns and, lastly, the crow which
delights in pestering the bald eagle
at every opportunity.

ALASKA

Remains of birds were found in
71 of tlie 435 stomaclis of eagles col-
lected in Alaska, and, in volume,
comprised nearly 19 percent of the
annual food. Reference to table 2
shows that, on a volumetric basis,
birds are taken largely during the

colder months, October through
April. Circumstances associated
with the collecting of the stomachs
indicate that much of this food is
taken as live prey, not carrion.
Nevertheless, it is conceivable that
decreased availability of fish in the
form of carrion during the winter
months had a bearing on the greater
consumption of birds at that time.

Water birds, particularly ducks,
were dominant among the avian
food of eagles collected in South-
eastern Alaska. Twenty-nine rec-
ords were of waterfowl, including
7 species of ducks and the Canada
goose. The mallard (Alias platy-
rhynchos) with 7 records and the
surf scoter {Melanitta 'perspicil-
Jata) with 6 were the most frequent
items. The white-winged scoter
{M. fusca)^ a scaup {Aythya),
goldeneye [BucephaJa) ^ bufflehead
{B. alheola), and a green-winged
teal {Anas caroUnen^is) , also were
included.

Remains of four horned grebes
( Colytnhus auritus), one red-necked
grebe {Colyiiibiis grisegena)^ and
two loons, one of which was a red-
throated loon {Gavia stellata),) in
the stomachs examined testify to
the ability of the bald eagle to cap-
ture these persistent and capable
divers. In fact, the eagle which
had fed on the red-throated loon
was shot as it was feeding on the
freshly killed bird. Some of the
same marine species of waterfowl,
connnonly fed on by bald eagles in
the Aleutians (see p. 24) also were
taken b}' eagles in Southeastern
Alaska. The most vulnerable to
attack was the murre ( Uria adlge) ,
of which 10 specimens were de-

32

tected; a few specimens of the
crested auklet {Aethia crlstatella) ^
the horned puffin {Fratercula cor-
niculata) , and the pigeon guillemot
(Cepphus columha) also were iden-
tified. Two gulls, the glaucous-
winged {Larus glaucescens) and
the mew {L. caniis) , with which the
eagle often feeds, likewise were vic-
tims, and, on the basis of somewhat
doubtful identification, the remains
of a heron, a tern, crow or raven,
and sandpiper havei been added to
the list. Finding the reuuiins of a
young eaglet in one stomach indi-
cated that cannibalism may at times
occur in the eagle household.
Feathers and other fragments of
a domestic fowl found in the stom-
ach of an eagle collected at a fox
farm may have been carrion in
origin.

Many of the birds captured were
taken under conditions of adversity
for either the eagle or the victim.
Severe weather with frozen lakes or
deep snow always adds to the likeli-
hood of unusual prey being cap-
tured. Also in areas of abundance,
as in the case of dense flocks of coots
or of herons and ducks in Florida
waters, ease of capture determines
the issue.

The senior author observed a bald
eagle feeding on a freshly killed
loon in Pybus Bay, Southeastern
Alaska, on May 10, 1941, and later
in the same year the remains of a
bird apparently a mew, were found
in an eagle's nest nearby. At an-
other time the feathers of a recently
killed scoter were picked up at a
point where a bald eagle had been
seen feeding.

The alertness of the bald eagle
in detecting the disability of avian
prey is exemplified by the experi-
ence of Alfred M. Bailey (1927),
who shot at and crippled a duck at
the mouth of the Stikine River in
Southeastern Alaska. The bird
glided down to the offshore ice,
where it was promptly picked up by
a passing bald eagle which flew
shoreward. The collector again
fired, this time at the eagle, and
missed completely, but the shot so
startled the big bird that it dropped
its prey on the beach where the duck
was retrieved.

Probably nowhere in its range
does the bald eagle subsist on birds
to the extent it does in the Aleutian
Islands. Much of the information
on which this conclusion is based
comes from the field studies and
material collected by Olaus J.
Murie and his associates in 1936 and
1937. Since its food includes items
other than birds, the reader is re-
ferred to table 3, where he will find
a list of the avian victims of eagle
predation.

Murie (1940) separated the data
for the 2 years of collecting in the
Aleutians and found that an appre-
ciably higher percentage of bird re-
mains was recorded in 1937 than in

1936. For this he gives a logical ex-
planation that —

It is likely that the material obtained in

1937, consisting of 325 items [as against
121 for 1936], is somewhat more repre-
sentative of the Bald Eagle's diet in the
Aleutian Islands as a whole.

To simplify matters and to include
all available information, the data
for the 2 years have been combined
in table 3.

33

Our conclusions relative to the
feedino; of the bald ea^rle on other
birds are essentially the same as
those advanced by ]\Iurie. who
stated that—

birds are the chief food, and this won hi
be exi)ected in view of their supremacy
in the fauna of tlie Ah'Utiiin Islands. It
is signilicaiit also that tlic eaules prey
extensively on so-called sea birds, which
are the most plentiful there * * *.

On a percentage basis, those birds
most freciuently captured, as re-
vealed by a combintition of the '■I
years' data, were fulmars, crested
auklets. nuirres, o-Uiucous-wino-ed
oulls, tufted puffins, cormorants,
and shearwaters. In the aggregate,
birds of all kinds comprised more
than four-fifths of the food of the
bald eagle in the Aleutian Islands.

UNITED STATES

Bird remains, all waterfowl, were
found in 6 of the ol stomachs of
bald eagles collected in the United
States in earlier days. All were
taken during winter and early
spring and in one case a lead shot
surrounded by a mass of duck
feathers indicated that that indi-
vidual probably was a cripple or
dead bird when picked up by the
eagle.

The attack of bald eagles on
waterfowl usually is a dramatic
episode most frequently observed
during winter when the waterfowl
are congregated and the eagles are
pressed for food. Although not
usually considered to j)Ossess great
speed in ilight, when in pursuit of
waterfowl the bald eagle can ma-
neuver with the speed and dexterity

of a falcon. William Brewster
(Bent 19;3T) in earlier days wit-
nessed attacks on geese and brant
along the Virginia coast :

When close npon its (piari'y the Eagle
sudderdy sweeps lieneath it. and. turning
hack downward, thrusts its powerful
talons into its breast. A Brant or Duck
is carried off bodily to the nearest marsh
or sand-bar. but a Canada Goose is too
heavy to be thus easily disposed of. The
two great birds fall together to the water
beneath, where the Eagle literally tows
his prize along the surface until the
shore is reached. In this way one has
been known to drag a large Goose for
nearly half a mile.

An incident that occurred on the
Tule Lake National Wildlife Ref-
uge in northern California reveals
that, on occasion, the bald eagle
may attack and kill pheasants. In
April r.):jl), two ring-necked pheas-
ants attempted to cross an opening
between clumps of tules. Sud-
deidy a btild eagle swooped out of
the skies and struck one of the birds
with such force that, although the
eagle was driven ott", the pheasant
died after a bi ief struggle.

In earlier days, when both eagles
;ind wild turkeys were more abun-
dant, predation on the latter was
occasionally observed. Examina-
tion of food debris associated with
a bald eagle's nest at (Jadsen Point,
I lillsborotigh County. Fla., in lt)13,
revealed the bones and feathers of
a wild turkey.

Although robbing the osprey of
its legitimate lish has fre((ueiUly
been recorded, larceny by the bald
eagle of other birds' food is sel(h)ni
noted. Such an event, however,
was observed on tiie Cap(» Ivomain

34

National Wildlife Kefuge in 1;>;')J).
In the words of the refuge manager :

as we looked over the dead SixirtiiKi
marsh, we saw a mai'sh hawk drop to the
s;round several times after prey. A few
mlmites later it flew out over the ad-
jaeent ocean beach, fairly close to us.
At this point an adult bald eagle which
liad been circling above, dropped on the
marsh liawk and forced it to release its
lirey. 'Ilie eagle quickly landed on the
beach and. within a few steps, seized the
object and was off again. Arriving at
the spot we picked up a few scattered
feathers which proved to be those of a
sora i-ail (Porzana Carolina).

CANADA

In eastern Canada, Bruce S.
"Wright (1948) })resented an un-
usual as})ect of eagle-waterfowl re-
lations which might easily be over-
looked were all pertinent facts not
available :

This eagle is the most important
waterfowl predator on the area, but what
data we have show that, exclusive of
the hunting season where it takes many
cripples, the diet of the eagle is made
up of four-fifths fish and carrion and
one-fifth ducks. The most frequently
taken fish is tlie eastern chain pickerel
(Esox nif/cr), and the pickerel taken are
usually large enough to be duckling pred-
ators themselves. Therefore, it appears
to be good management to retain the
eagles as they do more damage to the
pickerel, an undesirable species in a duck
marsh, than they do to the ducks.

At another time Wright (1953)
presented the seasonal picture of
eagle predation.

As the winter progresses and shoi'e
ice forms in the shallows, they have
been known to concentrate around flocks
of wintering waterfowl and to become
predators of first importance. However
the total number of eagles remaining in

the north throughout the winter is not
large, and their depreilations are only
of local importance.

At the first signs of open water inland
they leave the coast once more for the
freshwater habitat and resmne tiieir fish
diet as soon as possible. The waterfowl
gradually lose the fear of the eagles they
have acquired during the winter months
and both pass the summer together in
harmony on the marshes. A few eagles
persist in taking ducks at intervals all
summer, but they are the exceptions.

As a defensive measure against
the attacks of the biild eagle, coots
have evolved a unique method of
defense that has been observed on a
number of occasions. In the words
of James A. Munro (1988) , who has
witnessed the performance in Brit-
ish Columbia :

When attacked the ( 'oots come together
in a close flock and move rapidly across
the water with necks outstretched ; they
do not dive. The pursuing eagle planes
down but checks its flight when a few
feet above the mass of birds, ascends,
circles over the flock, then again hurls
downward with tremendous force that
again is suddenly braked. This maneu-
ver may be repeated a dozen times with-
out a capture being made and each time,
terrified by the eagle's nearness, the
Coots surge across the water. Appar-
ently the eagle rarely takes a bird from
the midst of the flock, although it would
seem an easy thing to do, but pursues
directly any straggler, and almost invari-
ably captures it.

A very similar performance has
been observed in Florida (Bent
1937), where wintering flocks of
coots supply a frequent item of diet
of the eagle. While in massed con-
centrations the coots appear to be
reasonably secure, but the moment
an individual bird forsakes the flock
it is a doomed bird.

35

Mammals

BIG GAME

Veer. — Stomach examinations
supplied some corroborative evi-
dence of the eagle's reported preda-
tion on deer in Alaska, remains of
this animal being found in 12 of the
435 bald-eagle stomachs (table 2).
In four instances the material defi-
nitely was carrion when eaten; the
remains of a fawn was found in
another.

In the course of the senior au-
thor's field studies in Southeastern
Alaska in 19-10, deer were often seen
along the beach throughout the
summer in the presence of an abun-
dant eagle population, yet, at no
time, was evidence of eagles molest-
ing them encountered. During 17
days (June 15-July 2) spent in the
vicinity of Keku Strait, deer in-
cluding some fawns were seen al-
most daily. At times the}' would
swim the strait in direct view of
numerous eagles which disclosed no
predatory inclinations towards
them. No opportunity was afforded
to appraise deer-eagle relations in
areas inland from the coast.

George Willett (1027, p. 591) , an
ornithologist of wide experience in
Alaska, often contended that the
casual visitor to the Territory was
not in a position to judge the activi-
ties of the bald eagle with respect to
the killing of deer fawns. He wrote
that unless the observer is able to
appraise matters in the month of
Juh^ when the fawns are small and
helpless and the eaglets are large
and hungry, he would not encounter
eagle predation at its worst.

Bald eagles, in common with most
other predators, apparently avail
themselves of the helplessness of
other animals and may resort to
''gang attack" to gain their end.
Such a circumstance was reported
from the eastern shore of Lake
Huron late in the last century
( Thurston 1891-92) . The narrator
stated :

The winter of 1S90-1S01, I spent in
company with a friend trapping in that
section of country lying north-west of
Lake Joseph. Returning one day from
a visit to our traps, we were going round
an arm of the lake when five eagles rose
from the ice. * * * We went to where
they rose from, and found the remains
of a doe fawn of about seventy-five
pounds weight ; the animal had ventured
out on the ice, and being some distance
from cover had fallen an easy prey to
the flock of hungry birds. We went back
on the tracks some distance, and not see-
ing the tracks of any other animal were
quite sure that it was killed by the Eagles.

Mountain goat. — The finding of a
substantial quantity of hair of a
mountain goat {0 reaimios) in the
stomach of a bald eagle collected
May 17, 1946, on one of the Broth-
ers Islands near the southern end
of Admiralty Island, presents an
unusual situation since no mountain
goats have been reported on this
small island although these game
mammals are present on the main-
land to the east and were introduced
some years ago on Baranof Island,
to the west. Even at the nearest
point it would appear that the
gorged bird had travelled at least
15 miles after it had fed on the goat.

In a Montana area, where golden
eagles Mere dominant, the following
incident concerning a bald eagle
and mountain goats has been re-

36

corded by Brown and Couey (1950) .
The observer, Stewart Brandborg,
in the Sun River country witnessed
a bald eagle fly past cliffs on which
two nannies, two kids, and a year-
ling were feeding. As related :

One of the nannies, that was feeding
in a narrow ravine, was seen to crowd
close to the side of her kid as the bird
circled about 25 feet above her. The
eagle then swooped within a few feet
of these two goats and landed on a pin-
nacle of rock ten feet above where they
stood. The nanny started toward the
eagle and was within five feet of the
bird, when it jumped from where it had
been perched, glided low to pick up the
kid, and sail out over the face of the
cliff. The kid hung helplessly from the
talons of the bird as it sailed to a point
where it began to lose elevation, and
finally landed a third of a mile away
and just out of sight of the observers.
The mother goat was seen to spend sev-
eral minutes searching up and down the
slope near the point where she had left
the kid. * * * The kid * * * could not
have weighed more than six or seven
pounds and was probably not more than
a few days old. The eagle soared with-
out moving its wings during the entire
flight with the kid.

Antelope.— Although the golden
eagle is more common than the bald
eagle in antelope country, the latter
may at times attack the fleet-footed
ruminant. R. L. Clennon of Buf-
falo, S. Dak., describes (in corre-
spondence) such an incident in the
following words :

On November 8, 1938, while running
some coyote traps * * * in Harding-
County south of the State Antelope Pre-
serve, I noticed an eagle wheel over the
edge of a small rocky butte as if pursuing
some animal. * * * Upon looking over
the butte I saw three American or bald
eagles. One was an old bird, the other
two were young. The birds were circling
over and diving at a young (three-fourths

grown) antelope. * * * The eagles kept
diving and striking with breast and tal-
ons until the antelope went down and
then they started to tear away the flesh.
* * * When I walked to the antelope it
was dead.

SMALL MAMMALS

Rabbits and rodents. — Both stom-
ach examinations and field observa-
tion disclose the fact that the bald
eagle, normally, is not as persistent
an enemy of rabbits and rodents as
is the golden eagle. Yet, it would
appear that when these animals are
available the bald eagle adapts it-
self to such a diet.

Among the 435 Alaskan bald-
eagle stomachs examined, small
mammals were recorded only twice,
a meadow mouse in one and a shrew
in another. Rabbits or small ro-
dents also were detected in 5 of the
31 stomachs collected in the United
States, largely in earlier years.

Understanding of field condi-
tions is essential for the proper in-
terpretation of the amount and
nature of the mammal food eaten.
As Murie (1940) has pointed out:

Small rodents are not available on most
of the [Aleutian] islands. Ground squir-
rels have been introduced on Kavalga
Island for fox food, and the eagles ap-
parently take full advantage of that sup-
ply. These rodents are not available on
the other islands where nests were ex-
amined, except on Unimak Island.
House rats are common on Rat Island.
Probably on only three other islands
could these be found by eagles.

It is evident that of all the mam-
mals eaten, including the blue fox
and domesticated sheep of which
there was a herd on Unimak Island,
the Aleutian ground squirrel was
the most frequent victim. The sin-

37

gle record of a sea lion no doubt
represented feeding on carrion.

Xorman Criddle (IDlT), a keen
observer of wildlife generally in
Canada, believed that both golden
and bald eagles exerted a marked
suppressive ejffect on varying hares
in the North. At the other ex-
treme of the bald eagle's range,
Florida, Avhere the bird is essen-
tially a fish eater, O. E. Baynard
(correspondence) noted that, at
more tlian 1,000 nests examined,
rabbits comprised at least 20 per-
cent of the food remains.

Bald-eagle pellets collected ad-
jacent to tlie marshes of Chesapeake
Bay in Maryland are characterized
by an abundance of muskrat re-
mains. The muskrat also appears
in the diet of eagles living near the
marshes of the Sandusky River in
northern Ohio where Dr. Herrick
(1932) found at least 14 muskrat
traps in the ruins of an old eagle
nest that had been destroyed.

On western plains, the bald eagle,
like the golden, may feed exten-
sively on rabbits during winter.
This fact was brought out by studies
of the senior author in Kansas. ( See
page 25.)

Sea otter. — Some apprehension
has been felt regarding the possible
hazard of the bald eagle to sea
otters, particularly in the Aleu-
tians, where these marine furbear-
ers have increased in numbers.
Murie (1940) encountered reports
among the natives that eagles kill
young sea otters and lie was in-
clined to believe that sonje of these
accounts were coi-rect, but he was
unable to Icani the frequency of
such incidents. He was strongly of

tlie oi)inion that much of this food
was carrion, since carcasses of sea
otters not infrequently are washed
up on the beach where they would be
available to both foxes and eagles.

Domestic Animals

BLUE FOX

Of all the domesticated animals
on which the bald eagle has been
accused of preying in Alaska, the
blue fox has aroused the greatest
concern, at least in earlier days.
Predation on blue foxes is discussed
at this point, even though many of
the conditions under which these
fur animals were formerly raised
could hardly be considered do-
mestic.

During the summer of 1941, the
senior author had an opportunity
to interview numerous fox farmers
and to appraise the relation of bald
eagles to blue foxes in Southeastern
Alaska. Practically without excep-
tion tlu)se persons interviewed ac-
cused eagles of preying on their
stock and several of them related
acts of predation they had seen.
While the accuracy of some of these
accounts is unquestionable, it is be-
lieved that the owner, knowingly or
not, is likely to exaggerate the loss
involved. Under the limitations of
fieldwoi-k, it was impossible to in-
terview more than a small part of
the fox farmers of Alaska or to
visit more than a few of the islands
on wliich these furbearing animals
were i-aised. Consequently, the con-
clusions reached were based on the
assumption tliat the sample ap-
praised was representative of the
whole.

38

Tlie semidomesticated blue fox,
allowed to roam free on small
islands devoted to the industry, pre-
sented a unique problem with re-
spect to the bald ea^jle. Such ani-
mals received only food and, at
most, n o m i n a 1 care and were
trapped every 2 or 3 years. Because
of the concentrated population, vul-
nerability to eagle attack was prob-
ably greater than that which would
be experienced by a normal popula-
tion of completely wild foxes. Such
conditions were encountered by
O. J. Murie and his associates on
the Aleutians in IDoC) and 1937, yet
the remains of only a single fox pup
M^as found among the bald eagle
nest material collected there.
Murie's comments were, as follows:

On Amchitka Island, within 200 yards
of an eagle's nest containing no fox re-
mains, a family of young foxes was living
unmolested. There was another fox fam-
ily at a somewhat greater distance in the
opposite direction. Foxes were seen on
the beach within easy reach of eagles on
Kavalga Island. Many such instances
could be cited. * * * At any rate, the
evidence shows that eagles are not a
serious menace to the blue foxes in the
Aleutian Islands. An excellent fur crop
is generally harvested on islands with
suitable productive beaches.

INIurie also pointed out that on
islands where both foxes and eagles
originally subsisted largely on sea
birds that later were drastically re-
duced in numbers, the foxes may
have become a more important item
of eagle food.

Despite the adverse opinion of the
bald eagle encountered in the course
of field studies in Southeastern
Alaska in 1941, no first-hand evi-
dence of eagles feeding on foxes
was found. Eagles were collected

in localities where they had an op-
portunity to prey on blue foxes yet
in none of the 435 stomachs exam-
ined was the remains of a blue fox
found. Thus, the senior author was
convinced that under the conditions
then prevailing depredations on
blue foxes were not severe enough to
warrant a bounty or other concerted
effort to reduce the numbers of bald
eagles in fox-farming areas.

Since the time of that field ap-
praisal (in 1941) a marked change
has taken place in the blue-fox in-
dustr}^ which has had a bearing on
the relation of the bald eagle to the
industry. Prices paid for long-
haired furs had so decreased by the
early 1950's that most of the blue-
fox farmers of Southeastern Alaska
had gone out of business. Further-
more, James R. Leekley, biologist
in charge of the experimental fur
station of the U. S. Bureau of Ani-
mal Industry at Petersburg, Alaska,
is of the opinion that —

even though fox prices were to come
back, blue foxes would probably never be
raised on a free running island manage-
ment plan again. Research at the station
and actual practice by several of the more
progressive island ranchers has shown
conclusively that pen raising is much
more practical and profitable. It is
doubtful whether complaints against the
bald eagle will again be received from
blue fox farmers.

This statement is based on condi-
tions prevailing in Southeastern
Alaska and may not apply to pos-
sible future operations on larger
islands in the Aleutians.

Under prevailing regulations, ac-
tion may be taken against the bald
eagle wherever it threatens damage
to domestic or wild animals. Thus,

39

the fox farmer is in a position to
protect his property against eagle
depredations without fear of vio-
lating the law.

OTHER DOMESTIC ANIMALS

Reports, obviously gross misrep-
resentations but given wide public-
ity and credence, have long been
associated with the bald eagle's rela-
tion to the common domestic ani-
mals. For example, an eagle in
Maine was reported to have carried
off a 30-pound pig ; another in Cali-
fornia to have flown away with a 50-
pound lamb; and still others are
said to have carried calves in their
talons. Another aspect of the case,
frequently exaggerated, concerns
the digestive capacity of the bald
eagle. A news item in a southwest-
ern paper carried the statement of a
rancher that an eagle ate 40 pounds
of flesh at one meal. Even a tenth
of this amount would have exceeded
the facts.

Stomach examinations have
thrown little light on the relation
of the bald eagle to farm livestock,
including poultry. It is apparent
that the relation of the bald eagle
to such creatures will have to be
determined largely from published
records. The records, however, are
confused by the fact that observers
often fail to distinguish between
golden and bald eagles. Since
much livestock is raised in sections
where the golden eagle is prevalent,
it is apparent that many of the
stock-killing episodes reported are
chargeable to that bird. Neverthe-
less, tliere are some records of stock-
killing for which the bald eagle is
to blame.

One of the 31 bald eagle stomachs
collected in earlier years in the
United States contained the re-
mains of a himb, the origin of which
was not clear. Three of six bald
eagles collected in Canada disclosed
tlie fiesh and wool of domestic
sheep. These were obtained on a
coastal island of British Columbia
during the month of March.

Reports from the foothill coun-
try east of the Sacramento Valley
(Grinnell, Dixon, and Linsdale
1930) indicate that bald eagles for-
merly visited the area in substan-
tial numbers in late winter and
early spring and that in certain
3^ears they killed many lambs.

Near Blackfoot, Idaho, in Febru-
ary 1945, a Federal game manage-
ment agent was asked to investigate
the shooting of a bald eagle by a
ranclier. The circumstances, sup-
ported by the body of the dead eagle
and that of the lamb which it had
killed, verified the rancher's conten-
tion that the eagle had killed the
lamb.

The occasional tale of eagles
carrying oft' calves should hs rele-
gated to the category of fables.
But the molesting of cattle, at times
resulting in serious injury, is within
the capability of both bald and
golden eagles. The rarity of such
events, however, make them of no
significance in determining the
overall economic status of the bald
eagle. A single incident of this
type reported (in correspondence)
by a former supervisor of the Col-
ville National Forest in Washing-
ton reveals the tactics used by the
bird. The attack was made upon
a 2-year-old Hereford heifer and

40

lasted for nearly 2 hours. The
eagle alighted on the animal's head
or neck and, by beating its wings,
turned the heifer aside whenever
she tried to rejoin the herd from
which she had been separated by
the bird's attack. When finally
rescued the heifer Avas in a state of
exhaustion.

POULTRY

In areas where the bald eagle is
abundant, its tendencies, be they
for good or bad, are apt to be in-
tensified. Should that abundance
occur where poultry is available,
farmers are almost certain to voice
complaints. Such, apparently, was
the situation that prevailed on an
island in the Kennebec River in
Maine, where a farmer kept a flock
of turkeys in an open-top runway
fully a mile from his home. In
1933, the farmer lost TO turkeys and
was obliged to move the remainder
of the flock to a covered runway
nearer to farm buildings.

In writing of the food brought
into the great bald eagle nest at
Vermilion, Ohio, Herrick (1924 b,
p. 405) stated:

The chickens brought to the eyrie were
commonly white, to judge from the few
i-emaining feathers, and of broiler size ;
these were always plucked nearly clean,
and as with the fish they were often
lacking the head. The farmers natu-
rally resent the loss of their chickens, and
are commonly sworn enemies of the
Eagle in consequence ; but when we con-
sider the wide area over which these
birds range in the course of the season,
and the relatively small number of
domestic fowl destroyed, only one in
sixteen days in 1923, it is evident that
individual losses are bound to be small.

Despite the local seriousness of
such predation, the bald eagle has
been so drastically reduced in the
United States as to preclude its
being a significant menace to
poultry.

Remains of a single chicken,
which may have been carrion
picked up in the vicinity of a fox
farm, was the only evidence of this
kind disclosed in the 435 Alaskan
bald eagle stomachs examined dur-
ing this study.

Invertebrates

Crustacea and other aquatic in-
vertebrates comprised 2 percent of
Alaskan bald eagles' food as re-
vealed by the 435 stomachs exam-
ined (table 2) , and reflect the beach-
combing habits of the bird. Here
again it is problematical what por-
tion of this food was dead when
found by the birds but, whatever its
character, little of economic signifi-
cance can be attached to it. Crabs
of several species were found in 33
stomachs, the most frequently iden-
tified being the common edible crab
( Crmcer magister) . The remains of
a small octopus, a shrimp, and an
amphipod testify to the variety of
marine invertebrate food that the
bald eagle may pick up on the beach.
It would appear from the contents
of the stomachs that the eagle dis-
cards the heavily chitinized ter-
minal joints of the legs of crabs.
These seldom were found, whereas
the basal joints of the legs were com-
mon in the stomach contents.

Carrion

In the wildlife field, the term
"carrion" is applied to any dead

41

flesh. It may include flesh from an
animal that has just ceased to live to
that in the linal staf^es of bacterial
disintegration. In short, the word
has been used largely to distinguisli
the dead from the living. If that
connotation is applied, the bald
eagle may be considered a confirmed
carrion feeder, particularly in its
feeding on fish washed onto the
beach, killed and not entirely eaten
by bears on salmon streams, or fish
that may have been killed by, and
then stolen from, the osprey.

The carrion eaten by the bald
eagle comes from several sources,
but fishes and mammals supply the
bulk. The uncertainty of determin-
ing the nature of flesh eaten by a
predator is a perplexing problem to
the food analyst. Consequently, the
volume and frequency with which
carrion appears in any food ap-
praisal (table 2) are subject to wide
interpretation. Although the ap-
pellation of carrion was placed on
no less than 60 items in the 435
Alaskan eagle stomachs examined,
it is apparent that this represents
only an uncertain fraction of the
total carrion consumed. Among the
mammal remains considered to have
been carrion when eaten were deer
and two common marine mammals,
the harbor seal {Phoca) and the
northern sea lion {Eumetoinas ju-
hata) . Several eagles were shot in
the vicinity of carcasses of these
mammals that had been washed up
on the beach.

In volume, food classified as car-
rion com])rised 12.3 percent of the
annual food of the Alaskan eagles
(table 2), and, although there was
some irrejjularitv in the amount of

carrion eaten from month to month,
the great bulk of it was taken when
fish were plentiful, thus indicating
the carrion character of much of the
fish eaten.

Fortunately, the senior author
participated in the collecting of
much of the Alaskan material and
was closely associated with the late
Hosea R. Sarber, who collected most
of the remainder from the south-
eastern part of the Territory. Thus,
much pertinent information con-
cerning the environment and char-
acter of the foods taken by the
eagles was available to him. It is
against such a background that he
has drawn his conclusions regard-
ing the carrion nature of the food
in the stomachs of eagles taken in
Alaska.

Although the bald eagle has often
been reported feeding alongside the
turkey buzzard, a recognized car-
rion eater, as a rule the eagle's car-
rion food is not in as advanced a
stage of decay. Much of it, espe-
cially the fish on the beach and the
carcasses on the highway, may be
considered essentially fresh meat.
Dead flesh, however, requires no ef-
fort in ca[)ture and it often may be
found in substantial quantity.
Consequently, when the bald eagle
is feeding on a dead creature it is
merely following the natural in-
stinct of most predators: to make
a living in the easiest way possible.
For ihis reason, bald eagles are
abundant when salmon have
spawned and lived their life span,
and when dead or crip])led water-
fowl are to be found on areas being
hunted. Even along highways the
bald eagle is not averse to joining

42

the magpie and crow to feed on the
remains of the traffic's wildlife
victims.

On the Brevard National Wild-
life Refuge in Florida, bald eagles
have been observed feeding on the
waste and regurgitated fish in a
nesting colony of brown pelicans;
in Yellowstone National Park they
have been seen feeding on the car-
casses of elk in winter. With such
a diversity of items classified as car-
rion, it is no mean problem to inter
pret much of the partially digested
food found in the stomachs of bald
eagles, alternately aggressive pred-
ators or lowly carrion feeders. Sel-
dom when an eagle's stomach is
opened for examination can the re-
mains of a freshly killed creature
be distinguished from that of one
found dead by the eagle. Under
such conditions the evidence
brought from the field by the collec-
tor is indispensable — without it the
decision may be a surmise, at best.

The bald eagle in the role of a
carrion feeder has repeatedly been
observed on the Bear Eiver Migra-
tory Bird Refuge in Utah. As win-
ter visitors, the eagles may be seen
feeding on dead ducks and carp
frozen in the ice on the shallow,
flooded flats. An unusual concen-
tration of fully a hundred eagles,
both bald and golden, joined by
)iumbers of California gulls, oc-
curred in January 1954, when the
birds collected to feed on the many
carp killed by pollution in Bear
River the previous fall.

That the bald eagle, even in areas
that are nearly metropolitan in
character, commonly resorts to car-
rion as food is a matter of record.

Along the lower reaches of the Hud-
son River immediately above New
York City, bald eagles may be
found floating downstream in win-
ter on cakes of ice and, in conjunc-
tion with gulls, feeding on dead fish
and other carrion. Not infre-
quently, they have been seen to take
advantage of a gathering of gulls
fighting for possession of a dead
fish. The tussle ends when the eagle
swoops in and removes the object of
the conflict.

Despite the large numbers of
waterfowl available to them, bald
eagles wintering on the Cape
Romain National AVildlife Refuge
in South Carolina are largely car-
rion feeders. The refuge manager
reported that —

on Bull's Island, eagles fed commonly
with vultures on carrion hogs. On a
liond that was turning from salt to brack-
ish, hundreds of impounded marine fish
died. Several hundred gulls, vultures,
crows, and a dozen eagles w-ere attracted
to the area by the sudden supply of food.
The eagles obtained the dead and dying
fish by wading in.to the shallow water and
pulling them ashore, or picking the
smaller ones off the water.

Munro (1938) has pointed out
that local conditions and the time
of year greatly modify the carrion-
feeding habits of bald eagles in
British Columbia. Along the tidal
flats on Graham Island the bald
eagle was found to be as "predatory
as a turkey vulture" and timed its
feeding with periods of low tide
when drifting carrion became avail-
able. Here, he stated :

Dogfish drifted ashore in considerable
numbers ; at one time I counted thirteen
on about a mile of beach and each of
these had been partially eaten by eagles
as could be told, in some instances, by the

43

tracks around them. Several times
eagles were seen feeding on dogfish and
as they tore at the carcass one or more
Glaucous-winged Gulls stood motionless
a few feet away awaiting their turn at
the carcass.

One morning it was noticed that since
the previous evening a doe deer had
washed up on the beach and been nearly
all consumed. Standing here and there
around the carcass on drift logs and on
the sand were eight eagles and three
ravens — their immobility indicating re-
pletion— while two Glaucous-winged
Gulls pulled at the shreds of meat still
adhering to the bones.

How an abundance of carrion in
the form of dogfish left stranded by
receding tides on an island off the
coast of British Columbia assured
the safety of living prey against the
attacks of bald eagles also has been
pointed out by Munro. His first
observations led him to believe that
the eagles were feeding on an abun-
dance of introduced rabbits and
pheasants, but he stated —

a diligent search revealed no "kills."
* * * This seemed the more remarkable
in view of the fact that rabbits nearly
always were in view hopping across the
open mossy glades. Pheasants were
more plentiful in this limited area than
in any other district of comparable size
in British Columbia according to my ob-
servations. It seems doubtful that this
species could have increasetl to such an
extent, from the small stock introduced
al)out fifteen years ago, if eagles had
preyed upon them consistently.

A flock of sheep accompanied by a num-
ber of young lambs pastured these woods
and frequently in their wanderings

loitered and sometimes lay down within
a few yards of trees in which eagles were
perched. The eagles paid no attention
to the lambs. For the past five years two
settlers have run flocks of sheep in this
area without suffering any losses through
eagles.

In New B r u n s w i c k, Bruce
Wright (1953) endeavored to dis-
cover the preference of the bald
eagle for several types of carrion
by placing various combinations of
bait beneath or near favorite roost-
ing trees. These were exposed
from the middle of June until near
the end of August, at which time
most of the eagles had left. The
remains of black ducks and snow-
shoe rabbits were offered along with
one or more species of fishes. In no
case did the eagles take a duck or a
rabbit in preference to the fish.
Among the latter were white suck-
ers, eastern chain pickerel, chub,
perch, and brown bullhead; of
these, the latter was accepted on
every occasion when it was exposed.

Vegetable Matter

The bald eagle ingests vegetable
food only by chance or by consum-
ing the stomach contents of some
vegetarian prey. Through some
such circumstances, needles of hem-
lock and other conifers, bits of ferns
and mosses, small fragments of eel-
grass {Zostera)^ and miscellaneous
vegetable debris Avere found in the
Alaskan eagfle stomachs.

ATTACKING HUMANS

Ileports of attacks by- the bald
eagle on people are less frequent
than those by the golden eagle, al-
though in either case the records

usually have been colored to provide
exciting news cop3\ As would be
expected, such attacks are most fre-
quently reported during periods

U

that the eagles have eggs or young
to defend. Herrick (1932) rehited
how a pair flew menacingly at a
group of persons examining the re-
mains of an eagle's nest that had
just been blown down by high
winds. And then there are those
occasions when the mere presence of
an eagle causes people to surmise
what might have happened had
someone not intervened. Such a
situation was the basis of a tale
emanating from Connecticut early
in this century. On that occasion,
a bald eagle perched on an arbor 8
feet above a 2-year-old child led to
the suspicion that an attack was im-
minent, yet nothing happened.
Alexander Wilson et al. (1832),
pioneer American ornithologist, re-
corded an incident in which a bald
eagle struck a small child and tore
its clothing. Thomas Nuttall
(1832), Wilson's contemporary,
tells an even more startling tale of
an infant carried to the eagle's eyrie
several miles distant. Realizing the
definite limitations on the weight
that can be carried by an eagle, one
is inclined to discount severely the
accuracy of such anecdotes. One
of the more fantastic of these stories
gained wide circulation in the late
1920's and concerned a bald eagle in
Kentucky that was alleged to have
attacked an 8-year-old boy, carried
him aloft 75 feet, and transported
him 200 feet.

It is not unreasonable to assume
that the lifting power of the bald
eagle is not greatly ditferent from
that of the golden eagle, since the
two birds are essentially the same
in body weight and wing spread.
Accordingly, the results obtained by

Walker and Walker (1940) in tests
with a captive golden eagle trained
in falconry are worth reciting.
AVlien a 1-pound weight w^as at-
tached to each foot, the bird aver-
aged 165 yards in normal, ell'ortless
flight before alighting. With the
weight doubled, it flew 64 and 58
yards in two trials during which
flight was labored. When the
weights were increased to 4 pounds
on each foot, the distances were cut
down to 10 and 14 yards in two
tests even though the bird was lib-
erated from the roof of a small
building. Arnold (1954, p. 3) has
presented additional information
on the weight-lifting ability of the
golden eagle.

The weight-lifting limitation of
the bald eagle was demonstrated by
N. R. Casillo (1937), who anchored
a 4-pound pickerel to a large rock
with the dead fish floating on the
surface of the water. A female
bald eagle grasped the fish but was
unable to lift it and the rock from
the water. Even though the sub-
merged rock weighed something
less than 10 pounds, the bird suc-
ceeded in dragging it only about 20
feet along the bottom.

In view of the bald eagle's limited
capacity to lift burdens, one need
not be seriously concerned over the
tales that have appeared in the
public press regarding the eagle's
aggressive predation on human be-
ings. This appears to be sound
reasoning regardless of the fact
that such factors as favorable air
currents, gliding flights, and wind
velocity may at times greatly in-
crease the ability of an eagle to lift
and carry a burden.

45

Coupled with the physical limi-
tations confronting an eagle at-
tempting to carry an excessive
weight, which would tend to dis-
count the likelihood of their trans-
porting human prey, is the mis-
taken interpretation that often is
placed on eagle flight activities.
Herrick (1924b, p. 407) has well
described the different approaches
employed by the bald eagle when
merely swooping, more or less as a
flight maneuver, and when seriously
intent on killing its prey.

When an Eagle stoops at an enemy or
at his prey, and is deterred at the strik-
ing point, he will immediately rise, and
might carry off a cap, as has been known
to occur when the attack was upon a
man who had invaded the nest, or "a

fragment of a frock" if a child were
assailed ; but whenever he strikes in
earnest and endeavours to master his
prey and rise with it in the air, as is said
to have been the case in the instances
given above, liis action is very different.
His aim then being to maim or kill, the
Eagle instantly drives his talons with all
his power into the body of his victim.
If danger is scented he will make every
etfort to lift his prey bodily from the
ground and bear it to a place of safety :
but if the place and time are propitious
he tries to finish the business on the spot
by repeated thrusts of beak and claw,
often "treading" his quarry, until its
vitals have been reached and resistance
is at an end. It is evident that an Eagle,
with claws nearly two inches long, or
more if measured on their curve, could
not strike a child of whatever age and
strive to bear it away, without the cer-
tainty of inflicting grievous injuries,
irrespective of the success of his efforts.

SUMMARY

1. Study of the economics of the
bald eagle was prompted largely by
the need for information to appraise
the merits of bounty and other leg-
islation affecting the eagle in the
Territory of Alaska, where it long
has been the subject of controversy.
To accomplish this, fieldwork by
the senior author was carried on
mainly in 1941 with additional ob-
servations being made in 1945 and
1946. Subsequently, he examined
the stomach material collected and
prepared initial tabulations of food
items. The junior author com-
pleted tabulation of the examined
stomachs, reviewed pertinent litera-
ture, and compiled the manuscript
in its present form.

2. As a background for better
understanding of the economics of
the bald eagle, this paper assembles

information concerning its char-
acteristics and life history. In-
cluded are data on range, abun-
dance, movements, plumages, age,
sex ratio, dimensions, weight, nest-
ing, eggs, young, and enemies.

3. Although the bald eagle was
noticeably reduced in Southeastern
Alaska during the years of bounty
payments subsequent to 1917, there
are indications that the bird is now
recouping its numbers and may
again assume its former abundance
in favored areas. In the United
States, even in its favorite habitats
in Florida and the mid-Atlantic
States, the nesting bald eagle has
decreased in numbers with a corre-
sponding lessening of its economic
influence. During fall, winter, and
s])ring, migrating eagles gather at
favorable feeding areas and in some

46

of these places increased numbers
liave been seen.

4. A brief resume has been pre-
sented of bounties and other legis-
hition alfecting the bald eagle in
Alaska, the United States, and
Canada.

5. As a basis for laboratory food
studies, 435 stomachs of Alaskan
bald eagles were collected and ex-
amined. In addition, there are
available data from 31 stomachs col-
lected in the United States, and 6
stomachs collected in Canada. An-
alysis of pellets and food debris
found at nests aided in judging the
food habits of the bald eagle at
points in the States and on the
Aleutian Islands in Alaska.

6. Nearly two-thirds (G5.7 per-
cent) of the food of Alaskan eagles
was c()ni[)()sed of hsh and of this
about one-fourth ( IG.O i^ercent) was
salmon. It is the considered opin-
ion of the senior author who partici-
pated in the collecting of much of
this material that most of the
salmon was carrion when found by
the birds. An appreciable, but mi-
certain, portion of the other fish
consumed also was dead when lo-
cated by the eagles. Although it is
not possible to determine statis-
tically from the data available the
significance of the eagle's feeding on
commercially valuable salmon, un-
der conditions prevalent at the time
of the field studies, we are convinced
that the bald eagle was not a serious
drain on that fishery resource. This
same appraisal applies to the other
commercially valuable fish in the
eagle's diet.

7. Less than one-fifth (18.8 per-
cent) of the Alaskan eagles' food

was derived from birds, about half
of which were ducks and geese, the
remainder being various marine
species so plentiful in the north
Pacific. Whereas there is no ques-
tion that during winter the bald
eagle takes a certain toll of migra-
tory waterfowl, many of them may
have been hunting casualties or
birds weakened by the elements.
Because of the eagle's decreased
numbers along the Atlantic coast,
predation on the waterfowl of that
area is not serious. Along the North
Pacific coast, including the Aleu-
tians, the bald eagle preys more
heavily on birds, particularly in
winter, but even then the pressure
is absorbed largely by scoters and
sea birds — fulmars, murres, auklets,
and puffins — which are exceedingly
abundant there.

8. Stomach examination has sub-
stantiated to a limited extent the re-
ported predation of the bald eagle
on deer, yet the senior author wit-
nessed nothing of this kind during
the period of his fieldwork in
Alaska which included three fawn-
ing seasons. The greater incidence
of mammal remains in eagle stom-
achs taken in May and June (table
'2) may be indicative that juve-
niles are more vulnerable to eagle
attack than are adults, as has
been emphasized by field observers.
Whether this pressure is significant
in the welfare of Alaskan deer was
not determined by this study; but
whatever its effect, it would be re-
stricted largely to the coastal areas
where the bald eagle maintains its
greatest numbers. There is no evi-
dence that the bald eagle exerts an
appreciable effect on the population

47

of small mammals unless it should
be cluriufr winter Avhen numbers of
these birds may congre^rate in areas
where jackrabbits are abundant.

9. Only in Alaska is the bald
eagle abundant enough to consti-
tute a significant hazard to domestic
livestock, and even there its most
important relation is with the semi-
domesticated blue fox. No remains
of foxes were found in any of the
435 stomachs collected in that Ter-
ritory, yet testimony of the eagle's
predation on these furbearers was
frequently encountered. In recent
years, this problem has been materi-
ally alleviated, not only by a great
reduction in the blue-fox industry
by reason of a lessened market, but
by the more progressive raisers con-
fining their animals under screens.
Within the United States, the bald
eagle has occasionally preyed on
domestic poultry, but here again the
small number it takes makes the
total effect insignificant.

10. The carrion- feeding habits of
the bald eagle may be construed as
neutral in their total economic ef-
fect. About one-eighth of the
bird's annual food (based on the
examination of 435 Alaskan bald
eagle stomachs) was interpreted to
be of that character. There is much
uncertainty connected with this in-
terpretation and, were all the facts
available, this portion of the bald
eagles' food might be appreciably
greater. By far the larger portion
of the carrion eaten stems from the
dead fish which the eagle finds on
the beach.

In summarizing briefly tlie eco-
nomic status of the bald eagle, it
will be well to recall the words of

an eminent ornithologist expressed
more than 40 years ago regarding
the bird's status in Michigan (Bar-
rows 1912, p. 288) :

AUhough it frequently captures worthy
prey, in open fight or by direct attack,
it often robs the Fish Hawlv, coniiielling
it to relinquish the fish which it has just
captured. When nothing better offers it
feeds freely upon decomposing fish
washed vip along the shore, or upon car-
rion, in company with the Crow and the
Raven. True, it kills many rabbits,
grouse, ducks and waterfowl of various
kinds, and even stoops to squirrels, mice
and snakes ; but on the whole it confers
no decided benefits on the agriculturist,
although on. the other hand, it is not
commonly injurious. On rare occasions
it picks up a hen, usually at a distance
from the house, and in early spring it has
been known to destroy young lambs, but
these are not common offenses.

This is still essentially true in the
United States, the principal difler-
ence being that, because of de-
creased numbers, the influence of
the bald eagle for either good or
harm is significantly less now than
formerly.

In Alaska, an area of much
greater eagle abundance, the influ-
ence of the bald eagle is correspond-
ingly greater. It is one of a great
number of factors that affect the
abundance and welfare of the salm-
on; it also exerts pressure (more so
formerly than now) on the domestic
blue-fox industry. With present
regulations permitting control of
individual birds causing damage to
domestic stock or Avildlife, reason-
able provision for pro])erty protec-
tion and rational management are
provided. Under prevailing condi-
tions, there is no need for any gen-
eral reductional program through
boinities, or otherwise.

48

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o

51

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