THE GOLDEN EAGLE

and its economic status

Marine Biological Laboratory

JAN 2 5 ..55
WOODS HOLE, MASS.

CIRCULAR 27

FISH AND WILDLIFE SERVICE

UNITED STATES DEPARTMENT OF THE INTERIOR

THE GOLDEN EAGLE

and its economic status

By LEE W. ARNOLD

Biologist

CIRCULAR 27

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

The investigational work on which this report is based was done
while the author was a member of the staff of the Denver Wild-
life Research Laboratory of the United States Fish and Wildlife
Service. The report was submitted after the author had left the
laboratory, and parts of it were condensed and revised by
E. R. Kalnibach, (lien director of the laboratory.

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1954

For sale by the Superintendent of Documents, II. S. Government Printing Office
Washington 25, D. C. - Price 2.5 cents

CONTENTS

Page

Range 1

Characteristics 2

Life history 4

Age_ 4

Courtship and nesting 4

Young 7

Territoriality 8

Migration 9

Food and economics 9

Food habits 10

Stomach analyses 11

Carrion as food 12

The golden eagle and its prey 13

Rabbits and rodents 13

Big game 15

Pronghorn antelope 15

Deer 18

Bighorn sheep 20

Game birds 22

Sharp-tailed grouse 22

Pheasant 22

Sage grouse 23

Wild turkey 23

Waterfowl.^ 24

Other birds 26

Livestock 26

Sheep 26

Cattle 30

Summary and conclusions 31

Literature cited 33

III

The golden eagle. From a Fish and Wildlife Service p.iintiiii; in ((ilur liy I.mii;'

Agassiz Fuertes.

THE GOLDEN EAGLE

and its economic status

Arthur Cleveland Bent aptly
summarized the present economic
status of the golden eagle when he
stated that it had "a powerful in-
fluence for either good or evil ac-
cording to the conditions of its habi-
tat."' The present study has aimed
at determining the nature of this
influence under the varied condi-
tions within the range of the species.

To approach this goal, significant
life-history information was first
assembled as a background for an
understanding of the species. Data
were then gathered to aid in an ap-
praisal of the influence of the golden
eagle on certain wild and domestic
animals. Lastly, techniques useful
in the bird's management were
appraised.

This study was first assigned to
Kalph H. imler, of the United
States Fish and Wildlife Service,
who conducted some of the earlier
field work and examined numerous
stomachs of these birds. Early in
1947 the writer conducted additional
field research and reviewed the lit-
erature. Among others who con-
tributed substantially to this pres-
entation were members of several
State game departments, including
Frank W. Groves of Nevada, Rob-
ert R. Elliott of Colorado, and Paul
V. Jones and O. F. Etheredge of
Texas. Charles C. Speri-y and nu-
merous field personnel of the United
States Fish and Wildlife Sei-vice
also contributed.

RANGE

The golden eagle, Aquila chri/.s-
aetos in its various subspecies, has
a circumpolar distribution in the
Northern Hemisphere (Peters
1931) . Despite barriers formed by
oceans, mountain ranges, and great
distances, only slight racial differ-
ences appear among golden eagles
living in widely separated regions.
The American race, Aqmla ehri/s-
aetos canadensis^ the only recog-
nized subspecies on this continent,
breeds from northern Alaska and
Labrador southward into Mexico

and sparingly in the Appalachian
Mountains to western North Caro-
lina and eastern Tennessee. Its
principal breeding range in the
United States is in the area west of
the 99th meridian. The writer has
found it nesting from near sea level
in southern California to near tim-
berline in Colorado. During win-
ter it ranges below sea level in some
California valleys (Sumner 1929),
and it wanders casually over the
region east of the Rocky Mountains
south to the Gulf Coast.

Fossil remains indicate that the
golden eagle has been present in the
Western Hemisphere for m a n y
thonsands of years (Howard 1930) .
Deposits in caves of southern New
Mexico (Howard and Miller 1933)
sliow that this eagle lived during
the Pleistocene period along with
the California condor and sage hen,
species that have long since disap-
peared from the area now knowm as
southern New" Mexico.

Consequently, it may be assumed
that the golden eagle is a tolerant
and resourceful species and is capa-
ble of adjusting itself to a variety
of environmental and habitat con-
ditions when not subject to uudue
interference by man. Yet, it is
signiticaut that within the memory
of man this bird has been almost
eliminated as a breeding species in
the mountainous regions of Eastern
North America.

CHARACTERISTICS

The golden eagle is a bird of
many aliases. Conunon names for
this species ^ include the American
war bird, bird of Jupiter, brown
eagle, calumet bird, calumet eagle,
Canadian eagle, gray eagle, king of
birds, ringtail, ring-tailed eagle,
ringtail falcon, royal eagle, war
bird, and white-tailed eagle. The
same authority records the follow-
ing folk names: American eagle,
black eagle, black Mexican eagle,
black Spanish eagle, dark eagle,
grepe, Mexican eagle, mountain
eagle, and war eagle. The names
jackrabbit eagle and German eagle
have also found usage.

Partly responsible for this va-
riety of names is the fact that in its
juvenile })lumage the basal half of
the tail of the golden eagle is white
and white blotches are conspicuous
on the under surfaces of the wings.
With each molt during the first
lew years, these white markings be-
come less extensive. When 4 or 5
y( ars old, the adult has the appear-
ance of a uniformly colored, dark-

^ W. L. McAtee, Dictionary of vernacular
names of North American birds. MS.

brown or blackish bird (Jollie
1947). At close range, however,
the ocherous cast to the feathers
of the hind neck and the tarsus,
feathered to the base of the toes,
make identification of the adult
simple.

The golden eagle is a large bird.
The average weight of 13 Colorado
individuals was 9.1 pounds, the
largest bird weighing 12.25 pounds.
The average w^ingspread of six
eagles taken near Las Cruces, N.
Mex., and measured by Cecil Ken-
nedy, manager of the San Andres
National Wildlife Refuge, was 6
feet 81/2 inches. Other published
accounts have indicated a wing-
spread of 7 feet and more. That
the golden eagle is superbly adapted
to soaring-gliding flight is empha-
sized by the fact that although it
weighs approximately the same as
the whistling swan it has almost
double that bird's wing surface
(Poole 1938).

The golden eagle's stomach ca-
pacity also is substantial. Although
C. C. Sperry (laboratory notes) de-
termined that the maximum weight

of the crop and stomach contents
of nine birds killed in the wild was
1.24: pounds, it is reasonable to as-
sume that when the golden eagle is
gorged, its crop and stomach ca-
pacity exceeds this amount. In
captivity, a golden eagle will con-
sume as much as 2 pounds of meat
daily (Oberholser 1906).

The size of the burden carried in
(light varies with the characteristics
of the individual, its incentive, the
altitude, wind conditions, speed at
the moment, and possibly other fac-
tors. Once the momentum of its
first thrust from the ground is lost,
the golden eagle is dependent either
on its own laboring flight or on the
irregularities of air movements in-
cluding thermals.

During the spring of 1937, C. C.
Sperry (field notes) tested the
weight-lifting ability of a wild bird
caught in the vicinity of Fort
Davis, Tex. He did this by fasten-
ing weights to its feet and then re-
leasing it. The 11-pound bird with
which he experimented could not
raise itself from the ground with a
51/4-pound weight attached to its
feet.

Walker and Walker (1910) con-
ducted experiments with a captive
bird in good condition near sea level
in southern California. When re-
leased from a platform about 15 feet
above the ground, the eagle, with a
weight of 8 pounds attached, beat
the air wildly and was able to fly
only 10 to 14 yards before coming-
down to earth.

Cameron (1908) observed an
eagle carrying a T-pound jackrabbit.
Under exceptionally favorable con-
ditions greater weights might be

carried. Conversely, personal ob-
servations of the writer and various
i-eferences in the literature show
that under unfavorable conditions
golden eagles with no more than a
gorged crop are unable to "take off"
in the absence of air movements.
Dixon (1937) also observed that
with a burden the size of a ground
squirrel the eagle will often take a
circuitous route to its nest to utilize
the lifting power of air currents and
thermals. It is fundamental to
recognize, however, that the golden
eagle will kill animals that it cannot
carry away under any conditions.
In view of the apparent inability
of the eagle to carry heavy objects,
reports of eagles attempting to
carry off children are worthy of
comment. The writer has investi-
gated the facts associated with three
such alleged attacks. Two reported
attacks occurred during August
1950 near Albuquerque, N. Mex.
The first of these appeared to be
based on the fact that a Buteo hawk
did nothing more than circle 50 to a
100 feet over a suburban home. In
the second case, a "huge bald eagle"
was described by eye witnesses as
being a pure-black bird with about
a 3-foot wing-spread which alighted
in the yard of a suburban home only
to be frightened away by a dog.
The third alleged attack occurred
in the vicinity of Carlsbad, N. Mex.,
during February 1948 (Arnold
1948) and was the only incident of
the three in which a golden eagle
even was involved. In this case the
bird had been in captivity for some
time and could not fly. The "at-
tack" actually was occasioned by a

boy tossinjr the weakened bird on n
smaller boy's head.

Despite the unlikelihood of a
<j^olden eao'le carrying olf even small
children, instances of these birds
attackino; achdt human beings are

on I'ecord. The noted ornithologist,
Kobert Kidgway once reported an
attack by two golden eagles upon a
friend who had flushed the birds
from a nearby carcass on wliich they
were feeding (Ridgway 1889).

LIFE HISTORY

The following synopsis of the life
history of the golden eagle sets
forth only those aspects considered
essential for a|)]:)raising its economic
status.

AGE

The maximum age of the golden
eagle in the wild state is unknown,
although Dixon ( 1*.>:)7) jiresents
fairly conclusive evidence that one
bird lie studied lived at least 30
years under natural conditions.
Cameron (1908) records an eagle
that lived at least 23 years, while
other writers indicate an even
greater life span in captive birds.

COURTSHIP AND
NESTING

The time of courtship varies both
with altitude and latitude. In the
Mount McKinley, Alaska, area,
Sheldon (1908) stated the birds ar-
rived in April and inuuediately
started nesting activities. In moi-e
southerly aicas. where the bii-ds
may i-emain in the viciuity of the
nesting teri'i(oi-y tlii-oughout the
year, courtshij) may begin considei'-
ably earliei' with efi<r laying taking
place in Januaiy and February.

Courtshii), including d-isj)lays of
aerial gymnastics, is i)articipated in
by both sexes and may be continued
thi'ou<rhout tlic uestinir season

( Bent 1938) . During this period
as well as the nesting season, the
selected territory is defended
against other golden eagles.

There may be great variation in
nest sites. One actiAe nest observed
by the writer near Hereford, Colo.,
was constructed in a crevice on a
cliif above a sheer drop of some 100
feet. Another nest, in the vicinity
of Middletown, Tex., was placed
about 15 feet from the ground on a
horizontal limb of a lone cotton-
wood. Several nests on cliffs were
so located that a rock overhang gave
protection from the elements ; other
successful nests were afforded little
or no protection. In some localities
favorable to nest building, a pair
may construct several "dumm}^"
nests; in other areas, where appar-
ently there is oidy one satisfactory
nesting site, nest building may be
confined to it .

During this study, no consistency
has been found with regard to the
direction of exposure of the nests.
Dixon ( lO;')") noted a t«Mideiicy foi'
the bii'ds to j)lace their nests so that
they could kee|) a watchful eye on
golden eagles in adjoining terri-
tories.

Nests actually used by the golden
eagle may vaiy in size from struc-
tures some 3 feet across^ and of
equal or greater depth, to platforms

,#*^^

Figure 1. — Nest of a golden eagle. (Photograph by Lee W. Anidld.

502440—54 2

5 feet across and little more than a
foot thick. Basic nest materials
consist of sticks variable in size.
The lining may include the ends of
pine branches, soapAveed, shredded
bark, oak moss, burlap bags, news-
paper, matted cattle hair, or, as ob-
served in one nest in Utah, a silk
stocking. This latter article is of
interest in view of a somewhat
legendary case in which the discov-
ery of a part of the clothing of a
small boy in an eagle's nest led to
the deduction that the eagle had
killed the boy.

The date of egg laying varies
greatly in the southern and north-
ern parts of the golden eagle's
i-ange. Laying as recorded by Bent
(1938) is as follows: Arctic Amer-
ica (5 records) May 27 to June 29;
California to Texas (272 records)
February 9 to May 18. Thus, there
is about a 3 months' spread in the
dates on whicli the first eggs are
laid in the extremes of the golden
eagle's range. Tlie usual set is two
eggs. Sets of one egg are common
and of three rather rare; at least
one set of four has been taken, ac-
cording to Bent.

According to Dixon (1937), both
sexes share in tlie incubation of the
eggs. Although this point is de-
bated by some observers, all agree
that tlie male does lielp biood tlie
young. According to Bent, the pe-
riod of incubation is about 35 days.
Although a female may desert her
eggs if the nast is bothered by man,
she will rarely desert the young.
Dixon found that the eggs of vari-
ous females show great individual-
ity and, one might say, a family ic-
semblance as to sliape and coloi-.

This characteristic appearance of
the eggs can be used in determining
the tenure of a nesting female in a
given locality.

Adult eagles are usually ex-
tremely wary when a person comes
near the nest. Unless special pre-
cautions ai'e taken, an observer may
at best catch merely a glimpse of
one or both adults as they leave the
vicinity. His next view of the
birds may be when they reappear
in the distance on some vantage
])oint or as casually circling specks
high in the sky. Without adequate
observations it may even be diffi-
cult to determine which of several
nests in the vicinity is the one oc-
cupied at the time.

The exceptional wariness that
adult eagles display Avhen humans
are in the vicinity of their nests no
doubt plaj's an important part in
their ability to survive. It is the
basis for Dixon's (1937) comment
that in southern California the
golden eagle is better able to survive
than most })redatory birds, and for
Pierce's (1927) statement that the
golden eagle is holding its own in
southern California far better than
is perhaps to be expected.

Extreme wariness is such a uni-
versal trait in tlie golden eagle that
one may even sj)e('ulate as to the
etfect the unrelenting pressure ex-
erted on the '"war eagle'' by genera-
tions of North American Indians
may liaNc had in forming or
strengthen iny- this behavior. -

= Tail feathers of the immature birds, with
Ihoir broad, white bases were espeeiall.v
sought and, to assure uniformity, the two
central feathers were selected. Golden
entries wer(> even kejit in eaiitivity so that
Ihesc feallli'i-s nii-lil lie lilnrUeil wlieli tliey
xrew out.

YOUNG

Accounts of the groAvth and de-
velopment of the young of tlie
golden eagle have been recorded by
several observers (Cameron 1905,
Sumner 1929a, Bent 1938, and
Jollie •") . At about 9 or 10 weeks
of age the young are fully feathered
and ready for their first flight in
the vicinity of the nest (fig. 2).
Bent reports, and the writer's ob-
servations verify the conclusion,
t hat young eagles frequently renuiin
in the vicinity for some time after
they leave the nest. They aiv ap-
pi'oximately 3 months old before
they gain the full power oi flight.
On first leaving the nest they hunt

with their })arents, who normally
watch and guard them until they
learn to take care of themselves.
In northern Colorado, young and
old birds were ol)served together
until the last part of October.

An increase in the number of
eagles seen in early fall in certain
localities may be the result of the
appearance on the wing of the young
of the year and should not be con-
fused with winter aggregations of
migratory birds from other areas.
The young are, for the most part,
more fearless of man than the adults
and consequently more conspicuous.

2 Malcolm T. Jollie. The golden eagle — its
life history, behavior, and ecology. Unpub-
lished thesis, University of Colorado, 1943.

FiGURK 2. — Nestliui

golden eagles on Colorado State Antelope Refuge,
by Lee W. Arnold.)

(Photograph

The juvenile pliimuj^e of tlic
golden eagle is retained for 1 year,
the only change being a wearing
away of tips of the feathers. From
tlie postjuvenile molt on, progres-
sive changes take place through
annual molts, each bringing the
bird a step closer to mature plum-
age. At times, one or the other of
a nesting ]5air may not have ac-
quired its full adult plumage. Tlie
fully adult ])lumage is acquired at
the age of ']^/2 years, or more ( Jollie
1947).

There is evidence that the golden
eagle, contrary to common belief,
does not mate for life but that, in
the jockeying of birds for better ter-
ritories or for more virile mates,
new matings are not uncommon
(Dixon 1937).

TERRITORIALITY

In northern Colorado, the writer
observed that each pair of golden
eagles occupied a specific territory.
Territory referable to the six nests
studied there embraced about six
townships. Feeding, roosting, and
soaring-playing areas w^ere all
found within each pair's territory.
and the size of these areas varied
with availability of food, nest sites,
and suitable terrain.

Dixon, in studying 27 pairs of
golden eagles, mapped their tei'ri-
tories and kept records ol" their ac-
tivities, lie found a dii-ect relation
between the amount of actual hunt-
ing area axailable to a i)air and
the overall size of the territory oc-
cupied. As a rule, a ])aii\of eagles
in a wihk'rness ai'ea with ample
food snp[)lies occtii)ied a smallei-
territoi'\' than one whose territor\

was planted to crops. Therefore.
it can be expected, if other things
are equal, that the geographical
area occupied by a pair of eagles in
hilly country will be smaller than in
flat, open country. The minimum
area studied encompassed 19 square
miles, the maxinmm 59 square miles,
and the average for the 27 pairs was
about 30 square miles, the equivalent
of a townshii).

Dixon (1937) noted that the
bonndaries of the territory claimed
by a pair of birds were definite and
the area was handeil down from
generation to generation. The
death of one bird of a pair soon led
to the choice of a new mate, and did
not affect the status of the area in-
volved. If both birds were de-
stroj'ed at the same time the area
became open territory but did not
seem to remain so for long. This
was substantiated by the observa-
tion that although the female of one
pair was kiUed in December, the
male had a new mate and a set of
eggs was laid In' February 20.

In describing nesting territories
of golden eagles, Baird, Brewer,
and Ridgway (1^74) rejxu'ted that
in sonthern Oregon each ]iair of
eagles seemed to confine itself to a
certain district, the nests being
about 2<) miles a pa it. AV. Steinbeck
of Hollistef. Calif., also observed
that each pair had its own I'ange
and wonld dri\'e any ontsider away
(liendire 1.S92). These fa nges were
nsnally from 2 to ('> miles wide, and
the hi rds became so att ached to them
that it seemed im|)ossil)le to drive
them away. In one case, wlu're he
took thice sets of eggs in successive
M'ais and killed the ft>male, the male

8

procured another mate and occupied
tlie same nest the next season.

A(l()li)h Murie (1944) stated lliat
in Mount McKinley National Park
individual pairs of goklen eagles
confined their activities to areas less
than 10 miles in diauietei-. l)nt he
suspected that at times tlicv cniistMl
considerably faither aticid, espe-
cially when carrion was available.

MIGRATION

There is evidence that the golden
eagle's movements in fall and winter
may be a somewhat more orderly
migration than was commonly sup-
posed (Broun 1930). That migra-
tion may not influence the entire
population is emphasized by the fact
that in some areas golden eagles
remain in their nesting territories

throughout the year and that in
other areas winter concentrations
may vary from year to year or even
from day to day. The available
food supply is probably a govern-
ing factor in this respect. Weather
conditions are evidently of second-
ary importance, as the birds are
(juite capable of surviving subzero
temperatures satisfactorily when
food is obtainable.

Concentrations and movements
during fall and winter have an im-
portant bearing on the economic
status of the golden eagle in a given
locality. Knowledge of these traits
and an understanding of the tend-
ency toward territoriality during
the breeding season is essential in
any contemplated ])r()gi"am of eagle
management.

FOOD AND ECONOMICS

There is no easy way to deter-
mine the general economic influence
of the golden eagle, and, although
there are several methods of ap-
proach, each has advantages as well
as disadvantages. These methods
are discussed in the following para-
graphs in advance of the presenta-
tion of testimony used in arriving
at an appraisal. In the final anal-
ysis, conclusions must be drawn
from a summation of all evidence
and the weight to be given each will
rest largely on the analyst's famil-
iarity with local conditions.

Interviews with outdoorsmen
yielded evidence regarding the
golden eagle that ranged from high
praise to outright condenniation
and, whereas the author has en-

deavored to present all shades of
ralid testimony, including that in
published form, data unduly af-
fected by personal bias was dis-
carded or ai)propriately evaluated.
Careful analysis of crop and
stomach contents is probably the
most reliable source of information
concerning the food eaten, but even
this has its limitations. The in-
ability to differentiate carrion from
captured prey has long plagued the
food analyst. Also, after large
numbers of eagles are removed for
their stomachs, the relation between
the residual population and its prey
is different from that at the outset.
The examination of regurgitated
pellets of undigested food likewise
has advantages and disadvantages

9

(Errington 1930; Glading, Tillot-
son, and Selleck 1943). It has
merit in that it permits detection
of seasonal fluctuations in the food
of the same group of birds with no
individuals being removed from tlie
environmental complex. On the
other hand, the examination of pel-
lets, even more so than that of
stomachs, fails to reveal those items
that are readily obliterated in the
digestive process; and also, when
flesh, devoid of hair, fur, or bones,
is being ingested, pellets may not
be formed. This may happen when
the eagle is feeding on large car-
casses, yet Murie (1914) found in
Mount McKinley National Park,
that pellets ejected by golden eagles
frequently revealed evidence of the
birds having fed on the bodies of
caribou calves and Dall sheep —
construed to have been carrion.

Still another method of food ap-
praisal of the golden eagle involves
the inspection of food remnants
found in or under nests or in the
vicinity of perches frequently used
by the birds. Through frequent
collecting of freshly deposited ma-
terial, a picture of seasonal fluctua-
tion in food may be obtained by this
method. On the other hand, ac-
cumulations of food debris over a
period of years may have the picture
confused by the fact that other crea-
tures, particularly packrats {Neo-
totna) may add to or detract from
the accumulation.

The foregoing recital sets forth
some of the problems faced by the
student of the economy ~ of wild
creatures. The science is fraught
with many difficulties; it also has
many reassuring and coiiviuciiiir

characteristics, not the least of
which is an adequate and intimate
field acquaintance with the creature
being appraised. In his analysis,
the author has endeavored to make
use of all approaches available to
him.

FOOD HABITS

The American golden eagle is
both a predator and a carrion eater,
and at times it takes carrion even
though live food is available. Like
most widely ranging species its food
varies from place to place depend-
ing on availability.

Indicative of the golden eagle's
adaptability are the following items
which have been reported eaten by
this species. These lists were com-
piled from the literature and from
field records of the United States
Fish and Wildlife Service.

Among the birds taken are
herons, swans, geese, ducks, turkey
vultures, accipitrine hawks, Buteo
hawks, marsh hawks, falcon s,
grouse, ptarmigan, European par-
tridge, quail, pheasants, wild tur-
keys, coots, plovers, curlews, band-
tailed pigeons, owls, kingfishers,
magpies, ravens, crows, and various
smaller perching birds.

Mammals listed as taken by the
golden eagle include opossums,
moles, raccoons, ring-tailed cats,
martens, weasels, minks, skunks,
foxes, coyotes, bobcats, woodchucks,
ground squirrels, prairie dogs,
arboreal stpiirrels, pocket gophers,
native rats and mice, muskrats, por-
cupines, ])ikas, varying hares, jack-
I'abbits. cottontails, deer, elk, cari-
bou, i)rongli()ni antelope, mountain
sheep, and mounlain goats.

10

Anioiia- the reptiles reported
taken by the golden eagles are rat-
tlesnakes, vai'ious nonpoisonous
snakes, terrapins, chnck\A alias, and
other iguanas. There are also two
references in the literature and one
in the field notes of golden eas'les
eating frogs.

Domestic animals among the
eagle's prey include cattle, sheep,
goats, pigs, dogs, and cats, while
domestic fowl eaten include ducks,
geese, chickens, and turkeys.

STOMACH ANALYSES

The stomaclis and/or crops of
102 golden eagles have been ex-
amined in the laboratories of the
United States Fish and Wildlife
Service and the former Biological
Survey. This material was col-
lected under diverse conditions in
numerous States and in Alaska over
a series of years (table 1). In gen-
eral, it reflects relatively modern
conditions, 81 of the stomachs hav-
ing been collected since 1920. Al-
thouo-h a l)ird with such diversified

food habits as the golden eagle can-
not be judged adequately by a
mathematical presentation of data
from such a limited series, a digest
of findings is presented in the ajj-
pended tables. Table 1 sets forth
the areas in which the stomach ma-
terial was taken and table 2 gives
the results of tlie examinations.

Carrion, eaten largely during the
colder months, had its origin mainly
in the carcasses of larger mammals,
both wild and domestic. The inter-
pretation of carrion w^as made
largely on the basis of the circum-
stances observed at the time the
stomachs were collected. Observa-
tions made at that time often indi-
cated that the birds Avere shot while
feeding on a carcass, or were
trapped by carrion used as a lure.
The carrion nature of flesh cannot
as a rule be determined by labora-
tory examination and reliance must
therefore be placed on observations
made in the field.

There will be doubtful cases in
which the evidence is not clear and

Table 1. — Locations and months in which 102 stomachs and crops of golden eagles were

collected

state

Jan.

Feb.

Mar.

Apr.

May

June

July

Aug.

Sept.

Oct.

Nov.

Dec.

Total

Alaska

1
1
1

3

1

.-__-.

1

6

2

California - -

1

Canada

1

1

Colorado

1

1

......

1

2

Idaho -

1

Illinois

1

1

2

Iowa_ -.

1

1

Maryland

1

1

Minnesota.. . .

1

1

Montana

2
6

1

3

Nebraska

2

1
1
5

4

13

Nevada, . _-_

1

New Mexico

2

1

12
121

3

1

2

25

North Dakota

22

South Dakota

1
2

......

1

Texas

1

4

2

2

1

12

Virginia. _ _ . _ ...

1

Wyoming

2

1

1

1

1

6

Total

8

47

10

6

8

1

2

2

3

6

9

102

' Collected during the periods Jan. 1-Mar. 15 in 1940 and 1941 at a game farm in North Dakota.

11

Table 2. — Occurrence of food items in 102 stomachs and ciops of golden eagles

Month

Num-
ber of
speci-
mens
col-
lected

Rab-
bits!

Ro-
dents 2

Deer

Other
wild
mam-
mals'

Up-
land
game
birds <

Water-
fowl »

Other
wild

birds •

Sheep
and
goats

Poul-
try'

Car-
rion s

Tota
food
items

8
47
10
(>
8
1

0
2
2
3
6
9

4

21

4

1
4

1

1

1

1

10
1
3
4

February...

March -

April -

1
2

1

«19

1
1

2
3
1

54

1

1

12

May...

h

1

July

0

August-.-

September

--
6

1
1
2
2

1

2

i

1

3

1
2
3

3

1
1

-.

11

Total

102

43

8

2

4

20

1

3

8

1

25

115

1 Jackrahhits {Lfpus) ami fottontails (Sijlrihigus).

2 Gid'jiiil siiuincls iCitt/liix], iiianiiuts ( Mnnnota), and fox and grey squirrels (Sciurus).

3 Skunks {M(philix: and reindeer {Ranyiffr).

* Sagi' LTo'i.-;!' (('( niroctrcus) and game-farm pheasants (Phasiaiius).

5 Pintail duek (. l/('/.v).

« Turkey vulture (Cathartes).

7 Chicken.

8 Carcasses of domestic sheep, cow, horse, deer (Odocoileus), reindeer (Fangijer), and jarkrahhits il.epvs).
» 17 collected at a game farm in North Dakota.

those situiitions will have to be
charged to the inefficiency of the
procedures at hand. This may have
occurred in the case of the pintail
duck eaten by an eagle in January.
Whether this duck was an over-
looked victim of a hunt or the prey
of the eagle cannot be determined
from the stomach contents. Like-
wise, under modern conditions,
there may be honest doubts as to
whether the remains of a jackrabbit
is indicative of eagle ])re(lation or
of highway hazards, (ieiierally, it
is safe to assume, from tlic known
predilections of the golden eagle,
that the gre;d niajority of the rab-
bits and rodents were taken alive.
Mention should be made of the 19
instances of ])heasants eaten in the
month of February. Circumstances
connected with 1 heir coHect ing ai'e
discussed undci- Pheasant on pagt's
22 and 23.

CARRION AS FOOD

It has been a popular conception
for many years that the bald eagle
is principally a scavenger, but that
the golden eagle takes carrion only
when compelled by necessity. Data
assembled in this study indicate
that carrion is frequently taken by
the golden eagle even when living-
prey is available. Substantiating
this contention are the fodowing
recorded incidents.

,1. Stokley Ligon. in Socorro
County, X. Mex., March 1915, noted
that golden eagles fed on the car-
casses of stock killed by wolves and
thought that "no doubt the destruc-
tion of the gray wolves will increase
the use fulness of the eagles by forc-
ing I hem to kill more of their meat
. . . rabbits."- (Bailey 1928.)
Murie ( l'.»44) ob.served in Mount
McKinley National Park that
golden eagles assembled at anv car-

12

rioii they could find althoimli
ground squirrels were available
most of the time.

An experiment conducted by
C. C. Sperry (field notes) in the
vicinity of Fort Davis. Tex., proved
that the carcass of a jackrabbit or of
a lamb which had been dead for 2
days or more was preferred even
thouoh live lambs of all ages were
in the immediate vicinity. As late
as April 12, when sheep carrion was
abundant and eagles scarce. Sperry
trapped an eagle at the carcass of a
stillborn lamb that had been dead
4S hours. This is common ]n-oce-
dure among stockmen in the South-
west in their attempts to trap or
poison golden eagles. A number of
ranchers interviewed during this
study remarked that when fresh
carrion is available, golden eagles
devour it instead of catching live
animals.

One also oljserves. in areas of rab-
bit concentration in the West, a sub-
stantial number of golden eagles
destroyed along highways to which
these birds have been attracted by
rabbits killed by automobiles.
Also, their predilection for carrion
is revealed in their own misfortune
when they die from eating rodents
that have been killed by poisoned
grain used in rodent control.

One might even surmise that simi-
lar carrion-feeding habits are re-
flected by the evidence found at the
|)rehistoric tar pools of LaBrea,
Calif. Howard (1930) determined
that in these deposits remains of the
golden eagle exceeded those of all
other hawklike birds, including the
carrion-eating vultures. That these
l)irds w^ere attracted to the area by

the animals which died as a result
of miring down in the pools of tar
is a logical assumption.

Thus, the conclusion is drawn
tliat the interrelation of the eagle
and game or domestic animals is
affected by the presence or absence
of carrion as emphatically as by the
relative populations of live buffer
or prey species.

THE GOLDEN EAGLE
AND ITS PREY

RABBITS AND RODENTS

Based on the findings of qualified
wildlife technicians in nine western
States, Canada, and Alaska, rabbits
and rodents are the dominant food
of the golden eagle over its wide
range in North America. In a
study of eagle food preferences in
June 1943 in Colorado and Wyo-
ming, R. H. Imler found that at
nine active nests approximately 77
percent of the food items came from
these sources (table 3).

On two study areas established
in northern Colorado by the author
in 1947 (pp. 17, 18) to determine
food preferences of the golden
eagle, many kinds of acceptable
prey were available to the nesting
eagles, yet most of the animals eaten
by them in that region were rodents
or rabbits (fig. 3). Of 138 such
animals recorded, 103, or 74.6 per-
cent, were rabbits, 32, or 23.2 per-
cent were prairie dogs, and 3, or 2.2
percent, were rats and mice. No
ground squirrels or pocket gophers
were found.

Although these studies show that
the golden eagle feeds extensively
on rabbits and rodents, it does not

302446—54-

13

Table 3. — Food items found near 9 golden-eagle nests in Colorado and Wyoming, I94S

Location of nest

Date
observed

Age of
young
in nest
(weeks)

Jack-
rabbit

Cot-
ton-
tail

Ground
squir-
rel

Wood
rat

Sheep
(bones)

Sage
ben

Water-
fowl

Uni-
denti-
fied

Colorado:

Loveland

June 5
...do

2-7

"Large"

1-8

2-3

(Same nest)

No data

2-3

1-7

(Same nest)

No data

1-7

1
..

..
..

3

10
9

2
6

1

Pawnee Butte

Orover

June 6

June 10
June 19
June 10
June 11
June 13
June 19
June 18
June 15

Wyoming:

Wolcott

9
2
9
11
6
2
2
4

3

1

Do

2
4

1
1

Point of Rock

8

Do

1

2

Parson

2
3

i 4
U

Do

Do

3

1

2

Rock Springs

1

1

Total

26

53

11

2

4

21

2

12

give the ultimate answer to the eco-
nomic considerations involved. The
simple fact that rabbits and/or
squirrels are considered desirable
game species in some areas and in
other localities pests, pointedly sets
forth the complexity of the prob-
lem. In the West, where the golden
eagle is resident, rabbits and ro-
dents often are considered economic
liabilities; consequently, the pres-
sure exerted on their populations by
the golden eagle is favorable to live-
stock, game, and forest manage-
ment.

Rabbits were not abundant on
the two study areas established in
northern Colorado during the
spring and summer of 1947. On
September 3 and 4, 1947, during
a 60-mile automobile census on botli
areas, one cottontail but no live
jackrabbits were observed. The
fact that the only jackrabbit seen
was being eaten by two eagles may
be indicative of food preference de-
spite the relative scarcity of rabbits
at the time.

Corroborating this apparent
preference of the golden eagle for
rabbits was the fiiuliiiir at a nest on

one of the study areas of the re-
mains of 60 rabbits as compared
with 28 prairie dogs, even though
there was a colony of prairie dogs
within 500 yards of the nest site.
The fact that during the first part
of the period, when young were
present in another nest, cottontail
rabbits predominated as food and
later more jackrabbit remains were
found there, may be indicative of
varying food selectivity^ as the
young eagles m a t u r e. Couey
(1944) in Montana and others else-
where have made similar observa-
tions.

Since manimalian predators had
been drastically controlled in the
Colorado study areas, tlie influence
of eagles on the rabbit population
ma}' have been substantial. Evi-
dence indicated that the eagles had
to hunt the rabbits they captured,
and that the rabbits taken were
"seed stock" and not part of a sur-
plus population crowded out into a
precarious, marginal existence.

DesjDite the frequency with which
the golden eagle preys on rabbits
and rodents there are few refer-
ences in the literature describing

14

Figure 3. — Food remains found at nest of golden eagle on Colorado State Antelope
Refuge in 1947. They include the skull of a prairie dog, 26 hind feet of cottontails,
and 21 hind feet of jackrabbits. (Photograph by E. R. Kalmbach.)

the act. H. N. Elliott, a Imiiter for
the former Bureau of Biological
Survey cited the following incident
that occurred in May 193(3 in Jeff
Davis County, Tex.:

The eagle was seen flying at a height
of approximately 200 feet. At a certain
point the bird folded its wings and went
into a dive. When about 20 feet from
the ground it spread its wings and con-
tinued toward the ground. When within
a few inches of the surface its feet were
lowered just enough to strike a prairie
dog that was feeding some 10 feet from

its hole. The eagle then cii'cled and re-
turned to the point where the pi-airie dog
had been struck and its back broken.

BIG GAME

Pronghorn Antelope. — G olden
eagles have been known to kill both
young and adult antelope. Attacks
on athilt antelope occur usually in
severe winter weather or during pe-
riods of food scarcity or distress for
the antelope, the eagles, or both.
Such incidents have been reported

15

more f req 1 It'll 1 1 y than those of ea^^les
attacking antelope kids.

E. S. Cameron ( lU(is) has jjfiven
this graphic acctnuit of the attack
of several golden eagles on an adnlt
antelope in Montana:

The ea.iiles had obviously .stampeclod a
bunch of antelope and then cut out a
victim by a combined jittack. Altogether
the antelope could barely have covered
three hundred yards afti-r the tirst attack
by the eagles.

The following observation was
made by Willard W. Lahninn, biol-
ogist. United States Fish and Wild-
life Service, on the Garcia Ranch
near Magdalena, N. Mex., on June
19, 1943:

Milton H. Webster and I jtimped an
antelope and two kids this morning, and
on the way back we passed over the same
road. In the wheel track was a dead
antelope kid with an adult golden eagle
feeding on the carcass. About one-quar-
ter mile from where the carcass of the

kid and tlie eagle were seen, were a
female anteloiH^ and one kid. \ot over
one-half hour had passed since we had
previously seen the female and the two
kids.

Figure 4 pictures the Aictim of this
episode.

Despite the authenticity of such
re])orts. determining the importance
of t'agh' predation in anteloj)e sur-
vival is not easy. This becomes ob-
vious if one considers that compe-
tent observers (Williams and Mat-
teson 1948) believe there is a greater
al)un(lance of breeding golden eagles
in AVyoming on the basis of com-
parable area, than in any other west-
ern State: yet, through various
management practices which placed
litth' or no weight on the influence
of the golden eagle, a remnant ante-
lope p()j)iihition of fewer than 5,000
in 1900 was increased to a point
where more than 41,000 were har-
vested in 1952.

*'-^: v^ip?^.T?f

FioiKK 4. — Keniaius nf ;nilcl(iiPf kid killed l)y a golden eagle near .Magilaleiia. .\. .Me\.
June lit, I'Jlo. (Photograph l)y W. W. Lahinim.)

16

To ()l)tain (luaiititative data con-
cerning the o()l(]en eai»le-antelope
relationship, two areas in north-
central Colorado bounded on the
north by the Wyomino; boundary
"svere selected as study areas in the
spring of 1947. One was the Colo-
rado State Antelope Refuge, of ap-
pi-oxiniately 114 square miles, and
the other an are." of similar size
some 14 miles to tl e east. Although
the refuge was adi littedly the more
suitable for ant^elope, ap})roxi-
mately one-half of the other area
compared favorably with the refuge
in forage, teri-ain, and lack of bar-
riers that would inhibit antelope
movement. Xest sites and hunting-
territories for eagles were about the
same on both areas. The principal
economic use of each area was graz-
ing of sheep and/or cattle. The
study on the refuge was conducted
cooperatively by the United States
Fish and Wildlife Service and the
Colorado Game and Fish Dei)art-
ment, represented by Biologist
Robert R. Elliott, who was con-
ducting fawning studies at the time.

Between June C and 18, 1947. four
occupied eagle nests were found on
the refuge and two on the area to the
east. An aerial survey of the areas
at a later date failed to disclose
additional nests. The activities of
the six pairs of eagles and their
young were followed at intervals
until October 1(). During the fol-
lowing winter, P^lliott maintained
records and determined the year-
round presence of eagles in the vi-
cinity of certain nests on the refuge.
In April 1948, the writer again
visited each nesting territory to de-

termine occupancy during the 1948
nesting season.

Tnfoi-mation supplied by the
Colorado Game and Fish Depart-
ment indicated that approximately
548 adult antelope were on the
refuge during the 1947 eagle nesting-
period. The antelope population on
the other area was estimated to be
not more than 50. Relatively few
white-tailed and black-tailed jack-
rabbits or cottontails were ob-
served on either area. Two prairie-
dog "towns'- of several dozen bur-
rows each were located within the
radius of influence of one nest on
the refuge area and another "town"
was within a few hundred yards of
one of the nests on the other area.
There may have been other undis-
covered towns on either or both
areas. A scattered population of
mide deer was present in suitable
habitat on each area.

In addition to these potential
]n-ey species, each area supported
numerous other acceptable food
species including small rodents,
small mammalian predators, and
several species of birds. Scarcity
of sign indicated low coyote and
bobcat populations, due no doubt to
intensive control for several years.
Fresh carrion was found on one
occasion on each of the areas dur-
ing the 1947 nesting season. Eagles
were observed feeding on it in the
refuge. Although a carcass on the
other area gave evidence of having
been fed on, none of the large birds
was observed feeding on it.

All golden-eagle nests under study
on the two areas were located on
rock ledges adjacent to open country
iidiabited by antelope. Two nests

17

were situated so as to afford a clear
view of several square miles of ante-
lope range. Althoiio;h anoilu-i- nest
had a more restricted view, a newly
dropped fawn was obsei'ved by
Elliott within siglit of it. Tlu'
fourth nest on the refuge was jjlaced
on the ])recipitous face of a small
cany(m. Although it was sliut off
from the open country, the rock
ledge above the nest afforded a clear
view of the open antelope range.
In two of these four nests two young
eaglets each Avere raised to flight
stage; another nest was probably
successful; and at the time of dis-
covery on June 10, the fourth nest
contained two recently dead eaglets
approximately 6 Aveeks old.

Nest contents, animal remains,
and pellets at these nests were ana-
lyzed for evidence of golden-eagle
predation on antelope kids. Al-
though a portion of one antelope
kid found beneath a nest indicated
possible predation by eagles, El-
liott's field observations revealed
little predation of any sort on young-
antelope during the 1947 kidding
season. The two active eagle nests
on the eastern area were inaccessible
to the Avriter, but remains only of
rabbits and prairie dogs were dis-
covered below them.

According to Robert Niedrach of
the Denver Museum of Natural
History, the 1017 caglf pojjulat ion
for the eastern area was ai)|)i'()xi-
mately one-half of that present be
tween 1930 and 19o5. lianchers in
the vicinity stated the antelope pop-
ulation had shown no noticeable
increase. In contrast, at the time
of this study the refuge was believed
to support close to the maxinuuu

mnul)er of eagles for an area of its
type, and according to the Colorado
Game and Fish Department the
antelope population had increased
from 250 in 19:]9 to more than 500
in 1947. It woidd api)eai' that the
number of nesting gohh'n eagles on
these areas at kidding time had no
appreciable effect on antelope ])()pu-
lations.

Elliott reported three instances
ill which eagles may have caused
the death of adult anteloi)e during
the winter of 1947-48. Lehti
(1947) also reported one highly
probable eagle kill on the refuge on
February 21, 1947. Although from
the spring of 1947 to the spring of
1948. golden eagles exerted some in-
fluence on the antelope, evidence
indicates that this was detrimental
only in a minor way. Under a four-
pliase utilization program involv-
ing sheep, cattle, antelope, and to a
less degree deer, there was competi-
tion for forage. Therefore, in the
overall analysis of the situation in
1947. it is believed that the destruc-
tion by the golden eagle of rabbits
and prairie dogs which were in
direct competition for forage with
the four major species, outweighed
whatever minor negative influence
there might have been.

This brief field study does not
solve th(» eagle-antel()i)e pi'oblem
lliroiighoiil the wide overla]iping
range of the two species. Under
othei- conditions the situation as it
existt'd during the 1947-48 season
iiiiglit be subject to different inter-
pretation, even in northern Colo-
rado.

Deer. — Under favorable condi-
tions the golden eagle may kill

18

adult or young deer. Somewhat
typical of the evidence concerning
such activities is the following ob-
servation made in September 1939
in southeastern Arizona by Glen
Taylor, a hunter for the former Bu-
reau of Biological Survey. The
animal under attack was a white-
tailed fawn.

While huuting lions on the south end
of the Galiuro Mountains, I was walk-
ing up a very rough canj-on. As I
ueared the head I heard a noise like a
liaby crying in pain and looking up to
the rim of the canyon, saw a Mexican
(golden) eagle swoop down and then
rise very fast. I then noticed an old
doe deer standing on her hind legs and
])awing at the eagle and a fawn was
lying on the ground under the doe. After
the eagle had swooped six times, the
doe struck it on cue wing, and it flew
over in the top of a juniper, where I
shot it. Upon returning to camp that
evening I came back by the place where
the fight took place and there lay the
fawn nearly dead. It could not control
its back legs. The eagle had injured its
hack and no doubt it died later.

In contrast, is an incident observed
by Philip Wells of the Arizona
Game and Fish Commission during
the spring of 1945 in northern Ari-
zona, in which a doe was able to pro-
tect twin fawns from eagle attack.

The following account from
Adolph S. Hamm, Cheyenne, Wyo.,
is illustrative of eagle depredations
on adult deer :

J. W. Yerplancke, and his companion
Arthur Vany, while running their trap
lines in southern Carbon County in De-
cember 1938, were 300 to 400 yards from
a small group of mule deer when sud-
denly a large golden eagle swooped down
and attacked a five-point buck in this
herd. The eagle caught the deer in the
back with its talons and within a hun-
dred yards in snow 2 feet deep brought

it to the ground. In a few seconds 7
more eagles swarmed on the deer and
started ripping him open. It took the
boys about fifteen minutes to work their
way through the deep snow to where this
deer was down and during that time the
eagles had completely disemboweled the
deer and, of course, he was dead. When
the men returned 2 days later, the eagles
had practically devoured the entire car-
cass as there were no signs of any other
animals having fed upon it.

These records and others indicate
that under certain conditions eagles
may kill even adult deer. Here
again, as in the case of the antelope,
the importance of this factor is diffi-
cult for the game manager to as-
certain. Often golden eagles swoop
at a wide variety of animals ranging
in size from ducks to grizzly bears
(Murie 1944) merely to harass
them. An example of this was re-
ported in 1948 by Refuge Manager
Greenwalt of the Wichita Mountain
Wildlife Eef uge in Oklahoma :

On the 8th Shrader saw an eagle feint
three times at an adult* doe deer within
a distance of a half a mile while the
animal was running for cover. He said
the eagle did not strike the deer but
came close each time.

The following account, narrated
in a letter by Jack A. Parsell, Forest
Service employee of the Nezperce
National Forest in Idaho, indicates
that at times these passes at prey
may be of more serious intent. He
stated :

On one occasion, in the spring of 1936
I personally observed an eagle in the act
of separating a yearling mule deer from
a band of fifteen others. The eagle, after
thoroughly frightening the deer by swoop-
ing down and flagging the animal with
its wings, proceeded to direct the course
of the deer through an exceedingly pre-
cipitous area to the river some 1,000 or

19

1, .">()() t'cet below. There was no mistak-
ing the intent of tlie eagle. Il diiccted
its efforts toward forcing the deer over
the sheer bluffs, thereby either killing the
deer or crippling it so badly that it could
offer no further resistance to the attack
of the eagle.

Sutton (liJ-!8) ie{)<)rts a similar
case of a golden eagle pursuing a
fawn until it was driven over a
sharp declivity. The deer's leg wan
broken in the fall, whereupon it be-
came easy prey for the large bird.
Anderson (1940) also reports two
instances where he thought golden
eagles were intentionally trying to
knock mountain goats from ledges.
In one of these the eagle actually
knocked a yearling goat off the ledge
but the latter landed on a ledge K)
feet below with no apparent ill
effects.

To what extent such observations
portray the unusual or the connnon-
place is not possible to state. Pend-
ing the time when adequate field
appraisal of the deer-eagle relation-
ship can be made, available evidenc?
indicates that the golden eagle has
only a minor influence on deer. .Vl-
tliough more than UK) years havi'
elapsed since Audubon (IS-'U)
placed "young deer'' at the top of
the golden eagle's food list, there
still is almost as much need foi-
factual data on this specific trait as
there was in bS^U.

B}(/h(}rn Shi'( j). — In u study of
the bighorn in .Vi'izona. cooix'ra-
tively conducted by the National
Association of Auduljon Societies,
the Arizona Game and Fish Com-
mission, and the I'niversity of Ari-
zona in 10.")T. A. A. Xichol (corre-
spondence) found that the thnH>
major factors operat ing to the det ri

meiU of the species at that time were
I)oaching, roads, and drongiit. and
the greatest of these was poaching.
Xo eagle depredations on bighorn
sheep were observed during the
investigation.

Since Xichol's survey, this species
has been subjected to research in
practically every State in the AVest,
bighorn-sheep refuges have been
established, and technically trained
wildlife managers have been as-
signed to them. Even with this in-
creased emphasis on bighorn-sheep
restoration, authentic information
is still sketchy concerning the etfect
of golden eagles on bighorn sheep
with which they often share the
same range.

Great interest, however, was man-
ifested when Allen (lOoS)) in his
account of the ecology and manage-
ment of Nelson's bighorn, consid-
ered the eagle a serious threat to
bighorns in southern N^evada. He
expressed the opinion that golden
eagles probably killed far more
newborn lambs than did mam-
malian predators, and stated that
he had personally observed 17 kills
of bighorn lambs by eagles.

Ivefnge^SIanager Kennedy ( 1948)
of the San Andi'es Xational Wild-
life Kefuge, X". Mex., n'corded a
highly probable case of a golden
eagle's killing a desert bighorn
lamb. In this instance the ewe was
observed in the process of giving
biilh to I he lanib. and she was seen
wit h the hinib -1 days later. On the
thii'd day a golden eagle was ob-
served feeding on the lamb, and
circuinstances attending tlie obser-
Nalion indicated that the eagle had
Ivilled the lamb. It may be signifi-

20

cant that although a study has boon
nui(U' by personnel of the San
Andres Kefuge of six <j;()lden ea<ile
nests, no further evidence of pre:la-
tion on bighorn sheep by eagles has
been encountered.

C. C. Spencer (15)4:*)) , in his study
of bighorns in the Tarryall Moun-
(ains of Colorado, failed to observe
eagles attack or molest the sheep in
any manner. He did note that the
sheep were not alarmed when eagles
came near, although the ewes were
alert even when a raven came close
to the lambing grounds. As a re-
sult of his studies he felt that al-
though his observations were not
conclusive, they were at least in-
dicative that in the Tarryall Moun-
tains the eagle is a minor factor in
the well-being of the bighorn.

Packard (1940), who stndied
eagle-bighorn relationshi})s in
Rocky Mountain National Park,
also found no evidence to indicate
that golden eagles preyed on big-
horn sheep. Supporting this con-
tention was the observation that
eagles were seen soaring low over
l)anks that contained lambs without
I)aying any noticeable attention to
the young animals.

Honess and Frost (1942), study-
ing the factors responsible for the
decline of bighorns in Wyoming,
made observations June 1 to August
1, 1940, on an eagle's nest in the
very heart of the lambing grounds
but found no remains of lamb or
adult bighorns. They also stated
that no predation by eagles on big-
horns had been seen by any survey
member nor had one been reported
during the time of the study.

Therefore, they concluded that
eagles could be exonerated of any
serious blame for the decline of the
Crystal Creek bighorn herd.

Coney (1944) reports that in the
Sun River area, in ^[ontana, big-
horn ewes with small lambs were
seen in the vicinity of an eagle's
nest but that the sheej) were uncon-
cerned even when the eagles flew
over them in search of food.

The Idaho mountain-sheep sur-
vey (Ellis 1941) also revealed no
reliable evidence of predation by
eagles on lambs or mature bighorns
during the year-long study. It was
concluded that, although the eagles
are capable of killing young lambs,
"the survival of the lambs through
the yearling stage would seem to
discredit the menace of the
eagle * * *.''

With regard to the relation of the
golden eagle to the Dall sheep of
Mount McKinley National Park,
Murie (1944) reported that no au-
thentic case of an eagle's having
killed a lamb came to his attention
although he did find pellets indicat-
ing that the bird had eaten lamb.
His statement that ''it is apparent
that their (golden eagles'") preda-
tion on sheep is negligible'' is based
on 3 yeai-s intensive field study.

AVhen the overall problem is ana-
lyzed in the light of available data,
it is the writer's opinion that the
influence exerted by the golden
eagle in either decimating the for-
mer populations of bighorns or in-
hibiting their restoration has been
relatively minor when compared
with other factors controlling big-
horn sheep populations.

21

GAME BIRDS

The relationship of the golden
eagle to upland game birds has long
been a matter of debate. In Eng-
land and on the continent, the black
grouse {Lyrwrus tetrix) and other
gallinaceous birds have been re-
ported preyed on by the eagle.
During the 19th century this one
factor Avas considered responsible
for the serious depletion of game-
bird populations in some European
areas (Oberholser 1906).

In this country, little regard lias
been given to the possible effect of
this large bird on various species of
grouse until recent years. Among
earlier workers, Ridgway (1877)
reported a pair of golden eagles
giving chase to and capturing a sage
lien. In this instance the eagles
pursued the grouse on the wing
until it dropped to the ground from
exhaustion, where it was picked up
by the foremost of the large birds.

Sharp-tailed G r on s e. — That
golden eagles at times may levy a
substantial toll upon sharp-tailed
grouse first gained emphasis when
Cameron (1905) reported that one
eagle nest under observation in
Montana always had the remains of
grouse in it when visited. He also
noted that when the yoving eagles
were nearly grown they were fed
almost exclusively on this game
bird. Later, C a m e r o n (1908)
pointed out that eagles nesting in
territory wliere grouse were not
plentiful fed their young largely on
jackrabbits and prairie dogs.

Tlio etrectiveness of cover in })ro-
tectiug prey species from attack by
the gohlen eagle was recognized by
Barrows ( 1912 ) . He tells of three

instances in which golden eagles
were caught alive after becoming
entangled in bushes and vines where
evidently, they had plunged after
some quarry they had failed to cap-
ture. A similar case was recorded
by Prudy (1898) near Northville,
Mich., in which a golden eagle was
so intent on its pursuit of a covey
of bobwhites that it entangled itself
in a thicket of raspberry bushes.

PheoJiOnt. — The golden eagle's in-
fluence on pheasant populations
varies with local conditions. Illus-
trative of this is the somewhat ex-
treme situation that existed at a
game farm near Dawson, N. Dak.,
late in the winters of 1939^0 and
1940-41. The North Dakota Game
Department had sanctioned the kill-
ing of eagles on this area of pheas-
ant concentration during the 2
winters. This decision was based
on investigations which disclosed
definite predation on and disturb-
ance of the pheasant po])uhition by
eagles. The game farm had an es-
timated population of 15,000 pheas-
ants, and cover was not dense over
most of the area.

The depredations by the eagles
were described as follows by E. M.
Lee, chief game warden :

As soon as the eagles had finished their
meal they would perch in tall Cottonwood
trees which are growing in scattered
places over the farm. Game birds noting
tlie perching eagles would remain in
liiding for hours. After one pair of eagles
li.id been Ivilled everything was quiet for
I wo or three days, and then another pair
would invade the ranch. At times a
week would intervene before the succes-
sors came. * * * i have personally ob-
served eagles at two different times take
plieasants, and the pheasants taken were
both feeding. Apparently they do not see

22

the oncoming enemy until it is too late
to fly, and they squat on open ground
where the eagle lias no trouble in grab-
bing its prey on the first attempt.

Fourteen golden eagles were
killed between January 1 and
March 15, 1940, and 15 were taken
during a similar period in 191:1.
The eagles killed in 1940 were with-
out exception in good physical coii-
(litiou. Tlie crop and stomach
coutents of all 29 were examined at
the Wildlife Research Laboratory
of the Fish and Wildlife Service at
Denver, Colo. Eight of the crops
and gizzards were empty; 3 con-
tained only jackrabbits; 1, a cot-
tontail rabbit; 14, pheasants; and
o sliowed evidence of the eagles hav-
ing taken both a jackrabbit and a
])heasant. In short, of the 21
golden eagles which contained food,
approximately 81 percent had eaten
pheasant.

A somewhat similar situation
arose in the winter of 1947-48 on the
Lacreek National Wildlife Refuge
in South Dakota. A report from
that area stated that —

tlH' |)heasants survived the winter
with little loss except predation by golden
eagles. The eagles appeared unusually
aggressive this season in attacking pheas-
ants, and refuge personnel witnessed four
birds seized by them in a single day.

Besides showing the capabilities
of the golden eagle under peculiar
local conditions, the foregoing inci-
dents reveal one of the weaknesses
of generalizations as to wildlife
food habits when appraised solely
through stomach analysis unsup-
ported with associated evidence of
field conditions. Without such
knowledge, deductions based on
these crop and stomach contents

would make it appear that the ring-
necked pheasant ranked second to
jackrabbits as a food item of the
golden eagle (see table 2). Over
the general range of the two birds
this would not be a true picture.
Inadequate data, no matter how sin-
cerely presented, can thus be as
great a perjurer of wildlife testi-
mony as can circumstantial evi-
dence in the hands of one attempt-
ing to "prove" a preconceived point.

Sage Grouse. — More recently,
Batterson and Morse (1948) con-
tended that in an Oregon area
studied, the chief predator of sage
grouse during the strutting season
was the golden eagle. They tell of
the killing of two male grouse by
this eagle on a strutting area dur-
ing the 1942 season when the maxi-
mum number of males present
was 67.

Scott (1942) observed golden
eagles disrupting sage-grouse strut-
ting and mating activities, but
stated that the time of day at which
mating occurs is probably a helpful
adaptation for protection against
the "most dreaded of all enemies,
the golden eagle.'' He noted that
golden eagles seldom flew over the
strutting grounds before sunrise
and that more than 50 percent of all
matings recorded occurred before
that time of clay.

Wild Turhcy. — This study sheds
no new light on the relation of the
golden eagle to the wild turkey,
but the following previously un-
published testimony' is presented.

W. C. Glazener, of the Texas
(rame and E'ish Commission, re-
ports :

On January 11, 194.5, I flushed an im-
mature golden eagle from a live oak mott

23

approximately IS miles southwest of Fal-
furrias, Brooks Coniity, 'IVxas. Upon
going into the mott. I found the remains
of a freshly killed tuikey hen, with a
number of large tracks around in the
loose sand. The breast of the turkey
had been pretty well eaten. Xo further
sight or record of the eagh' li.-id Ikmmi
secured, but it was evident that this liird
had been the one tliat iiad fed on tlic
turkey. Whether it did the killing. I
cannot say, but the eircunistantial evi-
dence was very strong, with no indication
of any other predator having been pre.'^-
ent. The site was at a turkey baiting
station.

Another golden eagle-wild tur-
key episode was recorded by Brown -
low Wilson of Colfax County, X.
Mex., on April 27, 1948. He relates :

This week I was riding in the Cerro-
soso Canyon and observed a golden eagle
soaring overhead as if it had something
located. All at once it disappeared from
view and apparently dived on its prey,
although I did not see this actually hap-
pen. I then started up a trail onto the
hill top. When about 300 feet up I came
upon a sight such as I have never seen
before. Here was the golden eagle
perched on the back of a large turkey
gobbler feeding on it. The gobbler, still
alive, seemed paralyzed all except its
head and neck.

Biologist C. M. Aldous, United
States Fish and Wildlife Service,
reported tlie following observation
made on tlie Mescaleio Indian
Reservation, N. Mex. :

On about the first of October 104.",
superintendent Robert I). Iloltz, regional
forester William H. Zeh. and reservation
f(n-ester Bert Shields were traveling by
car going northeast from Snake Wells
when they saw a golden eagle plunuiit't
earthward at a terrific speed about one-
half to 1 mile away. When tlu'y reached
the point where they judged the eagle
had landed, they flushed the bird from
a freshly killed full-grown turkey. The
eagle had consunied almost Hie entire

edible portion of the carcass by the time
they arrived.

Siicii is the iiatiifc of t lie dat a coii-
cerniug depivdat ions on wikl tur-
key by the golden eagle. Tlie i)re-
ceding qtiotations and |)iiblishe(l
I'ecofds dating even to the pi'c-
Aiidiibon pt'i'iod substantiate tlii'
fticf that on occasion the golden
eagle kills wild turkeys. The quan-
titative significance remains to be
determined.

In general, the jjroblenis of inter-
relationship of upland game birds
;ind eagles are as varied iis the
habitats and species involved. A
C()m|)lex ])roblem is made even more
coin|)licated by the fact that the
gohh^n eagle also preys on other ani-
mals such as skunks and snakes
wliich nuiy at times exert pressure
on tipland-game-bird ])optdations.
In short, the relationship presents ti
difficult ecological problem wliich
can l)e solved oidy locally by quali-
fied wildlife technicians.

Waterfowl. — As both the eagle
and waterfowl are migratory, their
interrelationship is luiique. The
simultaneous appearance of golden
eagles and waterfowl in an area in
fall and winter often leads to the
deduction that the eagles are follow-
ing the waterfowl.

That the golden eagle, on occa-
sion, may kill ducks or geese is be-
yond dispute. Records of gohh'ii
eagles' "stooping'' on waterfowl or
feeding on detid ducks are numerous
and of theif catching live water-
fowl are occasional. Whether the
ducks they catch are chiefly sick oi'
iiijuicd bii'ds still is ;m ummswered
(|uest ion.

Sevei'id methods were utilized to

24

obtain infonnation on the relative
importance of golden-eagle preda-
tion on waterfowl. Managers of
migratory waterfowl refuges were
solicited ; files of the United States
Fisli and Wildlife Service in Wash-
ington, D. C., were reviewed; and
sportsmen, game-law-enforcement
officers, and waterfowl specialists
were consulted.

The following comments liave
been selected from the reports of
managers of Federal refuges as
being representative of the facts
;ind opinions held on the relative
importance of golden-eagle preda-
tion:

BowDoiN Refuge, Mont. — As many as
six golden eagles are commonly observed
during the fall and winter, especially
when the lake freezes over, at which time
they prey on the wounded and crippled
birds left over from the hunting season
and continue to feed on the frozen car-
casses well into the winter. (B. M.
Hazeltine.)

Medicine Lake Refuge, Mont. — The
fall migrants feed on rabbits, muskrats,
and waterfowl. No observations were
made on the actual kills of rabbits or
waterfowl, but on one occasion, in No-
vember, an eagle was seen to take a live
muskrat off the edge of the ice. Remains
of three muskrats were found on the land-
ings of the subheadquarters tower where
they had been carried for devouring.
(T. C. Horn.)

Red Rock Lakes Refuge, Mont. — In
the fall of the year when they are most
common on the refuge, golden eagles have
t)een observed feeding on dead or wounded
ducks that were not retrieved by hunters.
They have also been observed feeding on
dead animal carcasses. We have never
observed eagles feeding on or attacking
liealthy individual ducks or other forms
of bird life on tlie refuge. (A. V. Hull.)

Sacramento Refuge, Calif. — It is be-
lieved . . . that they feed to a large ex-
tent on weak and crippled birds. Most

of tiieir food is waterfowl, at least in the
fall, based on their actions and the loca-
tions frequented. Records in 1938 showed
an eagle pursuing a cackling goose on
two occasions but in each case it missed
its prey. (P. J. Van Huizen.)

Sand Lake Refuge, S. Dak. — During
cold, snowy weather, most of the food of
the golden eagle on this refuge consists
of wild ducks ; at least this was the case
last winter (1939^0). Many of the wild
mallards on the refuge last winter suf-
fered from lead poisoning and it is pos-
sible that some of the ducks eaten Iiy
eagles were ill. (R. C. Winslow.)

Wichita Mountains Refuge, Okla. —
Golden eagles have Iteen noticed feeding
on tlie carcass of a deer. Hying low over
jackrabbits, and chasing ducks in the
Rush Lake area. Ranger William E.
Drummond observed a golden eagle chase
a skunk into a thicket in the spring of
19.39 and watched the bird beat around
the edges of the brush until it was driven
off. (E. J. Greenwalt.)

In addition to these comments
from refuge administrators, the re-
sults of a one-season nesting study
of tlie golden eagle carried out on
tlie Malheur National Wildlife
Refuge in Oregon by Frank W.
Groves are available.

During the nesting season of 19-10,
Groves made a study of the food
utilized by four pairs of golden
eagles. For purposes of compari-
son these nests are grouped into two
categories. Three nests located a
mile or more from the duck nesting
area will be considered jointly as
contrasted with one nest situated
ai)proxiniately 100 yards from the
water. Only those animal remains
found in the nests and identified
in the field were considered. Food
remains found at the three nests a
mile or more from the water area
included more than 40 jackrabbits,
1 cottontail, and 1 mallard duck.

25

The debris in the nest near water
inchided 10 ducks, 1 coot, 1 jack-
rabbit, 1 cottontail, and 2 marmots.
Tlri-eeo-f tl-te- clucks, 2 mallards, and
1 cinnamon teal, were examined for
evidence of cause of death, and
Groves states tliat "as nearly as
could be determined, all three had
l)ecn liealthy individuals. Two of
the birds showed talon marks on the
shoulders and neck."' He added
that—

with the small number of nests under
observation and the limited amount of
time spent on this study it would be
impossible to draw any definite conclu-
sions as to the economic status of the
golden easle on the Malheur National
Wildlife Kefuge. Indications point to
the fact that the eagles are probably
much more beneficial than harmful.

Whereas the foregoing testimony
indicates a relation between the
golden eagle and waterfowl, the ef-
fect can best be determined by those
who actually manage waterfowl
areas and thus are in constant touch
M'ith the ever-changing picture.

OTHER BIRDS

The capture of and feeding on
lesser raptors by golden eagles has
been recorded on several occasions.
Maurice Broun of the Hawk INIoun-
taiii Saiicliiarv in Pennsylvania
witnessed the capture in midaii' ot"
a led-slionldcrcd hawk by a golden
eagle il had been harassing (Broun
I'.»I7). The smaller bird persisted
ill annoying its fellow traveller un-
I il the golden eagle

* * * made a su(hlen thrust ,f(irwar(l,
executed an "Imnielmann turn" * * *
and then seized the .smaller hawk which
seemed to iiul up a mnineiitary, hopeless
strniiule. I>nwii came I lie two birds pre-

cipitously, the eagle with set wings and
clutching its victim.

Oscar T. Thordarson, making a
study of the food of predatory
species on the I'pper Souris Wild-
life Eefuge, N. Dak., shot and
wounded a great horned owl. Be-
fore he could arrive at the point
wdiere the owl had come to earth a
piuv of golden eagles appeared and
one picked up and carried away the
still-struggling owl (Henry 1939).
H. H. Brimley (correspondence) in
Nash County, N. C, reports he
found the remains of a crow in the
stomach of a golden eagle.

With respect to domestic poultry,
the golden eagle is only an oc-
casional in-edator. Such preclation
is most likely to occur during the
winter months when the large birds,
pressed for food, concentrate in the
vicinity of unprotected poultry.
The remains of a single chicken in
the stomach of 1 of the 102 eagles
examined (talile li) attest to the
infrequency of such feeding.

LIVESTOCK

Sheep. — The domestic sheep is a
highly bred, man-controlled exotic
without the defenses against hostile
elements in its environment found
in native sjiecies. Furlhennore,
there has been a growing tendency
in recent years to replace sheep
herding with large, fenced pastures
in which sliee|) aic pefniitti'd to
roam.

As in e\ery other pfoblein of eco-
noniii-s. \\\v eleineiil of |)r()fit is the
yai'dstirk. W'hichexcr proves the
nioic piohlalile techni(iiie — that of
herding oi' thai of fencing and
rii:(irou>-l \' coiii lollini:' 'he eiix'iron-

26

nient — is likely to be the one used.
Consequently, methods vary con-
siderably from one section of the
country to another. When factors
such as range utilization, relative
abundance of ground predators,
time of lambing, presence and ab-
sence of buffer species, availability
of carrion, unseasonal freezes or ex-
tremely hot weather, screw worms,
disease, and poisonous plants are
taken into account, any attempt to
fit the golden eagle into the picture
becomes a complicated problem.

During this study, two areas in
Avhich combined cattle and sheep
raising was the principal land use
were compared. One of these was
country north of Fort Collins, Colo.,
on the eastern piedmont plain of
the Rocky Mountains in northern
Colorado and southern Wyoming;
the other the sheep-raising country
of west Texas.

The Colorado-Wyoming area in-
cludes rolling foothills, scattered
blutl's and buttes, and open prairie.
In general, it is Upper Sonoran
})i'airie grassland with brushy cover
on the slopes. The resident eagle
population varies from place to
place depending on the availability
of suitable nesting territories, but
it approximates one pair to a town-
ship. Sheep usually are herded in
flocks of about GOO to the herder
(hiring the late-winter and prelamb-
ing season. Lambing is from
March 25 to mid-May, and usually
occurs in sheds with the ewes and
lambs being confined for 10 days.
The flocks are kept under close su-
pei'visioii until summer herds of ap-
proximately IjoOO lambs and ewes

are formed. Grazing pressure va-
ries from moderate to heavy.

In this region, sheepmen feel that
the golden eagle is no particular
problem. W. H. Delvin, foreman
for one outfit in the Colorado area,
stated that he has neither seen nor
lieard of an eagle's killing a lamb
or a sheep in this area during his
20 years of experience. On the
other hand, his observations lead
him to believe that they are quick
to find and devour any sheep dying
from other causes.

The Texas area west of the Pecos
is devoted to cattle (GO percent) and
to sheep and goats (40 percent).
Topographically, this region is
characterized by scattered moun-
tain ranges sejDarated by rolling-
hills and flat valleys. The flora is
semiarid grassland or scrub in the
lowlands, diffusing into scattered
brushy cover on the steeper slopes.
Although the eagle j)<)pulation has
been disrupted in recent years, early
observations indicate that before
control operations were initiated the
golden eagle population compared
favorably in numbers with that in
the Colorado- Wyoming area. Sheep
are restricted to fenced areas. The
peak of the lambing season is about
March 15, although some young are
born as early as December. For the
most i^art, lambing is in pastures
rather than in sheds. ( Irazing pres-
sure varies from heavy to extremely
heavy, and land use may be abusive.

In the Texas area, many ranchers
consider the golden eagle one of the
most detrimental factors with which
they have to contend in raising
sheep. Even though observations of

27

ea<^]es kiirni<j: laiulis arc lai'e. this
may not be si<i:iiilicaiit when one
considers tlie wariness of these lar<i:e
birds of prey and the wide ran<ze of
the sheej) at lanil)iiio- time. "When
C. C. Sperry * worked in tlie area in
1937, all rancliers interviewed liad
seen eagles feediiio- on dead ]aml)s,
and many had examined tlie car-
casses to determine the cause of
death. The general conchision was
that death resulted from claw punc-
tures at the base of the skull. Hie
observers agreed that eagles seldom
bother lambs more than a week oi-
10 days old and that the most vul-
nerable pei'iod for the lambs is the
first few hours of life.

The following episodes, reported
to the writer during a short stay in
the Texas area in 1948, illustrate the
type of evidence leading to ranchei'
sujijiort of locally organized eagle
control. E. G. Po])e, assistant dis-
trict agent. Tnited States Fish and
Wildlife Service, Lubbock, Tex.,
stated that dttring the spring of
1935, wliile Hying over the "HO"
pasture at the foot of the (xuada-
lupe Mountains in west Texas, he
noted a golden eagle flying from the
foothills toward tlie valley. Latei'
he saw a lamb and a ewe standing
close together in the valh'y. The
eagle flew overtlie two. ma(h' a small
circle, and (lroj)j)ed on I he hi mb wit h
such force that it actually a|)peared
to bounce. During that spi-ing it
was i-epoi'ted to r'o|)e that eagles in
the general area were eating from
15 to 20 lambs a day, but he ob-

M-:agles vs. iMuihs in \vi:ntci-u Tfx.-is, 1!t:!T
•MS. in files of United States Fish .ind Wild
life Service, Washington, D. C.

served that at the time there was
little else for eagles to eat.

In the spring of 1946, M. E.
Bomar, of Marfa, Tex., saw an eagle
dive twice on a lamb, hitting the
animal both times. Although the
eagle was shot, the lamb died a few
minutes after the attack.

These records and others both in
this country and abroad establish
the fact that golden eagles are capa-
ble of killing lambs. The extent
of this loss under varying condi-
tions cannot be computed from the
(lata now at hand.

Most of the successful sheep rais-
ers in the area where intensive eagle
control is practiced are attempting
to control all factors limiting sheep
})roduction. These include such di-
vergent things as removing loco-
weed and trapping flies at water
holes to control screwworm. The
attitude of most ranchers paying the
bill for eagle control is that it is a
"necessary chore," and they are con-
vinced that the value received in in-
creased livestock crops is worth the
price. That control is an extensive,
annual i)rocess, is indicated by the
number of eagles killed under a
l)roject sponsored by the Big Bend
Eagle Club of west Texas. This or-
ganization of about 100 ranchmen
hire<l a |)ilot to shoot eagles from an
aii'plane. The numbers killed over
a Ci-year jteriod are as follows: (157
in 1!»41 4l\ (;t;7 in r.>42-4;5. l.OOS in
1943-44, cSOO in 1944-4.5, 8(')7 in 1945-
4(), and 819 in 194()-47, for a total
of 4,818 (Buechner 1950).

The extent of eagle damagi' under
foi'iner conditions of less I'igid con-
liol in this same area is reflected

28

ill Sperry's report^ in wliicli lie
stated :

Some more definite data on lamb losses
due to eagle depredations were obtained
from J. W. Lawhorn, manager of the
Thompson Brothers Ranch in Schleicher
County east of the Pecos lliver. For a
inunher of years "> or (} eagles have been
noted during the winter on that 2ri,0(KI-
acre ranch. They came late in Novem-
ber and stayed through January, but in-
variably left about February 1. For the
past 10 years such has been the case and.
as lambing did not start until February 1.
no losses were charged to eagles. This
year (1937), however, the eagles did udt
leave on schedule and there were about
-o present during February. Depreda-
tions on newborn lambs were soon noted
but no effective means of checking them
v.as found until late in February when
10 eagles were killed from an airplane.
A checkup late in March revealed a
heavy lamb loss chargeable to eagles.
Records of 5 or more years showed that
the average lamb markup for the Thomp-
son Brothers Ranch was 90 percent, and
that for 1937 it should have been well
above average because the spring was
extremely favorable for lambing. In
fact, a small group of ewes (47) moved
from a large pasture (later frequented
by eagles) to a small enclosure near the
ranch buildings actually gave a lamli
crop of 105 percent, while a markup from
178 ewes in the large pasture and 330 in
an adjacent one — in both of whicii lambs
wei-e exposed to eagle attack — was only
7r> and 87 percent, respectively.

It has not been possible in this
study to determine the magnitude of
the total daina<2;e done to sheep in
this area by the oolden ea<ile. Here,
again, the relative acceptability of
carrion to the bird prevents objec-
tive analvsis. This was broiie;ht out

^ Eagles vs. lambs in western Texas. 1937.
MS. in files of United States Fish and Wild-
life Service, Washington, D. C.

by R. H. Imler," who worked in the
sheep-raising area of southern New
Mexico and west Texas and obtained
29 crops and stomachs of golden
eagles, principally from birds killed
by local eagle lumters.

Although many of the birds had
been dead for months, the food
items were still readily identified
and the data regarding them were
obtained from those who had killed
the eagles. It was impossible, how-
ever, in most cases to determine
which items had been taken as
carrion.

Of the 29 stomachs, 14 contained
portions of domestic sheep or goats,
of which at least -f were classified as
carrion. Fourteen of the stomachs
contained remains of rabbits, of
which 3 were considered to be car-
rion. With respect to the remains
of skunks (3), bobcat (1), coyote
(1), wood rat (1), and turkey vul-
ture (1), there Avas no conclusive
evidence as to whether the items
were live prey or carrion.

It may be of interest that 6 of
these eagles were shot near Clover-
dale, N. Mex., on range occupied by
very young lambs and kids. Their
stomachs contained respectively,
skunk, 100 percent in 2 stomachs;
bobcat, 100 percent ; coyote, 100 per-
cent; skunk and rabbit, 60 and 40
percent; and rabbit and domestic
sheep or goat, 43 and 57 percent.
Wliat part of these items was car-
rion could not be determined.

Available information indicates
that losses of lambs as Avell as of
goat kids, attributable to eagles are

« Report on field trip to Texas and New-
Mexico in 1942. In files of the United States
Fish and Wildlife Service, Washington, D. C.

29

spasmodic in this area and may vary
considerably under cliangino; local
conditions. Comparison of the sit-
uation in the Texas area with tliat
in the Colorado-Wyoming area (p.
•27) appears to indicate tliat the
prc^blem is local in nature and one
to be handled locally as it occurs.

Cattle. — There are occasional rec-
ords of the golden eagle killing
calves. Most of the cattle ranchers
interviewed during this study felt
that such occurrences either were so
rare that they did not warrant eagle
control, or the losses were out-
weighed by tlie good done by the
s[)('cies. As with the sheepmen, the
cattlemen's primary interest is gov-
erned by economics. One example
of this attitude encountered near
Middlewater in the Texas Panhan-
dle should suffice. When ques-
tioned concerning the activities of
a certain pair of eagles nesting near
a cattle watering trough, the ranch
foreman stated :

The birds have been there for 5 or 6
yeai's. Year before last I destroyed their
eggs in an effort to discourage them, but
last year I let them raise young so I
could see for myself what they were do-
ing. During the season every time I
checked the nest there were rabbit feet
imder it. In all, I would say they had a
barrel full. I did not find any parts of
antelope even though I was looking for
them. I have heard that sometimes they
eat calves, but now I am beginning to
wonder if perhaps they do me more good
tban harm.

Xear (he j)lain of San Augustine,
Catron County, N. Mex., E. A. (lold-
man (field notes. United States Bi-

ological Survey) wrote in 1909,
''Some cattlemen believe that eagles
kill small calves. Several told me
they had seen them eating carcasses
but none had seen an eagle kill a
calf." E. G. Pope (field notes,
United States Biological Survey)
in 1905 reported that one of his as-
sistants in the moimtains near Ala-
mogordo, N. Mex., was attracted by
the frantic bleating of a young calf
which was being fiercely attacked by
a large eagle. The eagle was shot.

D. T. AVood (1940) writes of an
experienced cattleman from the
Lompoc area, Calif., who observed
an eagle perched on a newborn calf
estimated to weigh about 25 pounds.
When the observer arrived at the
spot, he found the calf near death
and bleeding considerably about the
back and head.

Owen W. Morris, United States
Fish and Wildlife Service, reported
an incident in which an adult cow,
attacked by an eagle, lost its footing
on an ic}^ incline above a high ledge
and plunged to its death. Shortly
after, the eagle commenced to feed
on the cow.

Such is the nature of the general
evidence concerning the effect of the
golden eagle on cattle. The signifi-
cant fact is that in the average cat-
tleman's analysis of the situation
the bird is considered at least a neu-
tral if not a beneficial wildlife spe-
cies. AVith respect to the survival
of the golden eagle this is signifi-
cant, as the bird is afforded relative
security on many of the large cattle
ranches.

30

SUMMARY AND CONCLUSIONS

1. The golden eagle is widely dis-
tributed in mountains and adjacent
plains throughout nnich of tlie
Xorthern Hemisphere. Its princi-
pal breeding range in North Amer-
ica extends from the Arctic Ocean
south into Mexico, westward from
the 99th meridian. As it nests from
near sea level to timberline, it may
be found in a wide variety of hab-
itats, and in winter it occurs prac-
tically throughout this country. Its
food habits are as varied as the di-
versified habitats in which it lives.

'1. Tlie golden eagle has been
known to kill and eat more than 60
(lifl'erent kinds of animals ranging
from full-grown deer and antelope
to mice, birds, frogs, and insects.
Both living creatures and dead are
included in its diet, and at times it
accepts carrion even though living
prey is available.

3. Rabbits and rodents form the
staple diet of the golden eagle, the
proportion taken varying with local
conditions. During the nesting
season on a Colorado antelope
range, rabbits supplied most of the
golden eagles' food; under winter
conditions on a North Dakota
pheasant refuge, they comprised
approximately 19 percent.

4. On occasion, the bird will kill
adult and young antelope, although
in northern Colorado, where four
pairs of eagles nested in close prox-
imity to antelope at fawning time
sucli predation was negligible.

5. Although the golden eagle will
kill either the adult or the young
of deer, no evidence was found to
indicate that the bird is more than

a minor influence when compared
to other factors controlling deer
])opulations.

G. One fairly conclusive account
of golden-eagle predation on a big-
horn lamb is cited, but available in-
formation indicates that any danger
to bighorn sheep either in decimat-
ing populations or inhibiting their
restoration has been relatively
minor.

7. Depending on local conditions,
the golden eagle exerts a varying
pressure on upland game birds,
and at times this pressure may be
sufficient to warrant eagle control.
Harassment of upland game, thus
keeping it from feeding properly in
severe Aveather, may be more serious
than the actual killing activities of
the eagle. That being the case, it
appears that time and effort might
be wisely spent in developing cover
which will give permanent protec-
tion from the golden eagle rather
than in assuming the never-ending
task of control. Golden eagles kill
wild turkeys, but the significance of
this activity on present-day wild-
turkey populations was not deter-
mined in this study.

8. When nesting in the vicinity
of waterfowl areas, the golden eagle
may feed its young largely on water-
fowl. In one study cited, it was
shown that pressure on waterfowl
was applied principally by a pair of
eagles in whose nesting territory the
])rey was found.

9. Golden eagles at times kill do-
mestic lambs. The extent of this
damage varies with local conditions.
Conservative local control, properly

31

executed in areas of scA'ere dama<>-e,
should uot unduly influence llie
ovei'all status of the species. Jie-
cause the birds tend to congrejiate.
esj)ecially in winter, in areas where
carrion is available, it would be to
the slieep rancher's own advantaae
to detei'niine whether the eagles on
his ranch are preyina' <mi li\e lambs
or on those that died from other
causes that })erhaps could be
remedied.

10. On occasion, golden ea<iles
kill calves or may even contribute
to the death of full-fjrown cattle.
All evidence indicates tliat this is
an exceptional activity and the gen-
eral attitude of cattlemen intei'-
viewed (hiring this study lias not
been antagonistic to the eagle.

11. Golden eagles occur in vary-
ing numbers on more than 65 Fed-
eral wildlife refuges where, in gen-
eral, they serve a beneficial purpose
in consuming wounded, sick, or dead
ducks an<l forage-consuming jack-
rabbits and rodents. On those

areas where not detrimental, they
are given full protection.

I'-i. The golden eagle may \aiyin
influence, depending on its liabitat,
from the one exti-eme where it may
be endangering tlie young of the
rare trumpeter swan to the oi)posite
exti'enie whei'e it may })e a conti'ibut-
ing factor in saving some rnncht'i-
appreciable forage which would l)c
eaten by jackrabbits. Its harmful
activities should not be allowed to
go unbridled. Neither should its
l)eneHcial influence be dissipated for
want of insight into the complex-
ities of present-day wildlife ])i-ob-
lems. In the final analysis of any
wildlife situation in which the
golden eagle is involved, its man-
agement calls for local ai)])raisal
combined with an impartial and
thorougli understanding of the
broader aspects of its infltience.
Let it not be forgotten that the
golden eagle will always be looked
u[)()n as a noble and ])riceless heri-
tage of our mountains and western
])lains.

32

LITERATURE CITED

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1939. Ecology and managemejit of Xelson'.s bighorn on the Nevada mountain ranges.
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Anderson, Nillo A.

1940. Mountahi goat study. Washington Dept. Game, Biological Bull. 2, 21 pp.,
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Arnold, Lee W.

1948. Eagle attacks boy. Audubon Mag., vol. 50, pp. 256-257.
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1928. Birds of New Mexico. New Mexico Dept. Game and Fish in cooperation
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1948. Oregon sage grouse. Oregon State Game Commission, Fauna Series No. 3,
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1938. Life histories of North American Itirds of prey. Part 2. U. S. Natl. Mus.
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Broun, Maurice.

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1905. Nesting of the golden eagle in Montana. Auk, vol. 22, pp. 158-167.
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Couey, Fa ye.

1944. Golden eagle vs. bighorn sheep. Montana Wildlife lUiU., vol. 1, pp. 2-3.
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pp. 49-56, Illus, March-April.

33

Ellis, F. Gordon.

1941. Progress summary report, Idaho uiounlairi slioep survey. Federal aid to
wildlife project No. 7-R-C., 38 pp.

Errington, Paul L.
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1943. liaptor pellets as indicators of food habits. California Fish and Game,
vol. 29, No. 3, pp. 92-121. July.

Henry, C. J.

1939. Golden eagle takes wounded horned owl. Auk, vol. 56, No. 1. u. 75.
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HoNESs, Ralph F., and Nedward M. Frost.

1942. A Wyoming bighorn sheep study. Wyoming Game and Fish Dept., Bull. 1,
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Howard, Hildegakde.

1930. A census of the Pleistocene birds of Rancho LaBrea from the collections of
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1933. Bird remains from cave deposits in New Mexico. Condor, vol. 35, No. 1,
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JoixiE, Malcolm T.

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October.

Kennedy, Cecil A.

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Lehti, Robert W.

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1931. Check-list of birds of the world. Vol. 1. ,",45 pp. Harvard University Press,
Cambridge, Mass.

Pierce, Wright M.

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Poole, Earl L.

1938. Weights and wing ar(>as in North American birds. Auk, vol. 55, pp. 511-517.
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34

Scott, John W.

1942. Mating behavior of tlie sage grouse. AuU, vol. 59, pp. 477-498.
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35

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