BIOLOGICAL DATA AND HABITAT REQUIREMENTS
WILDLIFE SPECIES: Aquila chrysaetos | Golden Eagle 



TIMING OF MAJOR LIFE HISTORY EVENTS : 
Age at sexual maturity -  Golden eagles are sexually mature at
4 or more years of age [16].

Breeding season - The golden eagle breeding season generally occurs from
mid-January to mid-September, but varies according to geographic area
[22,27].

Clutch size and incubation - The golden eagle lays one to three eggs,
with two eggs most common [9,21,27].  The eggs are incubated for 35 to
45 days [9].

Fledging - Nestlings fledge at 9 to 10 weeks and remain in the vicinity
of the nest.  The parents provide food for the fledglings until they are
about 14 weeks old or older [9].

Migration - Migration varies with population and cohort and is a
function of both food supply and climate.  Golden eagles in the
subarctic and at least some golden eagles of all ages in northern boreal
areas migrate.  They travel south along high ridges in the Intermountain
West during September and October.  In the East they traverse the ridges
of the Appalachians to the southern highlands from September through
November.  In a zone near the United States-Canada boundary, resident
breeders and older prebreeders migrate short distances in severe winters
and/or when food is scarce [21].  In the mountainous West, golden eagles
often move down from the mountains onto the plains and valleys during
the winter [8].  Breeding golden eagles prefer to maintain their
nesting-hunting territories or travel the shortest distance necessary to
survive prolonged cold or heat, while older prebreeders may be less tied
to specific locations.  Birds of the youngest cohort are often
migratory.  In the arid Southwest, golden eagles move to high elevations
after breeding [21].

Longevity - Golden eagles in captivity have lived 41 to 48 years, but it
is unlikely that many live that long in the wild [9].


PREFERRED HABITAT : 
The golden eagle inhabits open country from barren areas to open
coniferous forests.  They are primarily in hilly and mountainous
regions, but also in rugged deserts, on the plains, and in tundra.  The
golden eagle prefers cliffs and large trees with large horizontal
branches and for roosting and perching [8].

Nesting habitat - The golden eagle nests on cliff ledges, preferably
overlooking grasslands; 10 to 100 feet (3-30 m) above ground in dead or
live trees; in artifical structures; or on the ground [8,7,27].  In
western mountains, golden eagles nest at elevations of 4,000 to 10,000
feet (1,219-3,048 m).  Pairs may use the same nest year after year or
use alternate nests in successive years [8].

Golden eagles are most likely to use trees for nesting if cliff sites
are unavailable.  In the Powder River Basin of Wyoming, 67 percent of
golden eagle nests were found in deciduous trees; 22 percent in
ponderosa pine (Pinus ponderosa); and 4 percent on the ground [19].
Near Medicine Bow, Wyoming, 60 percent of golden eagle nests were on
cliffs [17].  In Campbell and Converse counties, Wyoming, 57 percent of
occupied nests were found in deciduous trees along drainages and 25
percent were in ponderosa pine trees.  The remaining nests were on rock
outcrops and peaks (8%), artifical structures (7%), and creekbanks (3%).
In Campbell and Converse counties golden eagles preferred to nest in
large pines when both cottonwoods and pines were available.  Large dense
stands of both cottonwoods and pines were avoided as nest areas.
Isolated or scattered trees were preferred [22].  In the Coast Ranges
of California, the golden eagle nests almost exclusively in trees [21].

Foraging habitat - The golden eagle generally forages in open habitats
where rabbits and small rodents are available.  During the nesting
season the golden eagle usually forages within 4.4 miles (7 km) of the
nest [7].  Trees, live or dead, are often used for perches if they are
near open areas where prey can be easily seen [30].

Winter habitat - Winter habitat requirements for the golden eagle are
very similar to nesting habitat requirements.  In the East the golden
eagle generally winters on coastal plains and wetlands [7].


COVER REQUIREMENTS : 
Golden eagles use elevated nest sites, especially sheltered ledges on
secluded cliffs, that are isolated from human disturbance and are close
to hunting areas [8,24].  Golden eagles are most efficient predators in
open areas where winds and thermal updrafts aid flying.  They are less
efficient where shrub and/or tree cover increases.  Abundant shrub cover
provides hiding and escape cover for prey.  Physical obstructions close
to the ground make hunting difficult [18].


FOOD HABITS : 
The golden eagle feeds primarily on mammals.  It feeds mainly on
lagomorphs and small rodents, but also on marmots (Marmota spp.),
prairie dogs (Cynomys spp.), ground squirrels (Spermophilus spp.),
weasels (Mustela spp.), woodrats (Neotoma spp.), skunks, mice, and
rarely, large mammals.  The golden eagle also eats grouse, pheasants
(Phasianus spp.), owls, hawks, rock dove (Columba livia), magpies (Pica
spp.), and other birds as well as rattlesnakes, frogs, carrion, and
occasionally, fish [4,8,9,21,27].


PREDATORS : 
NO-ENTRY


MANAGEMENT CONSIDERATIONS : 
Direct and indirect human-caused mortality, disturbance, and the
elimination of prey by habitat alteration are the main factors limiting
golden eagle populations [28].  Shooting, poisoning, trapping,
electrocution and/or collision with powerlines, and pesticide
contamination have all been identified as causes of the decline of
golden eagle populations.  In addition, recreational activities may
disturb breeding, wintering, and migration activities, disrupting and
often reducing the population [9].

Habitat management for the golden eagle primarily consists of protecting
areas used for nesting, resting, and foraging, and protecting habitat
used by the prey base [9].  Some researchers suggest placing 0.25- to
2-mile (0.4-3.2 km) buffer zones around nest sites in areas undergoing
energy development or increased recreational use.  Nest-site protection
is only advantageous if the prey base remains adequate following
development.  Many types of development such as oil, gas, and geothermal
exploration; pipeline and road construction; and development of
campgrounds and interpretive facilities on public lands remove
vegetation from small areas.  If important prey concentrations such as
ground squirrel colonies are avoided, golden eagles should be able to
coexist with these developments provided nest sites are undisturbed
[25].  Nesting habitat can be enhanced by providing artifical nest
structures in areas where natural nesting sites have been eliminated.
Population enhancement through captive breeding, foster parenting, and
rehabilitation and reintroduction are feasible techniques where suitable
habitat for golden eagles is unoccupied [9].

Golden eagles are sensitive to human disturbance and are likely to
abandon their nests during the incubation period if disturbed [9,21].
Human disturbance was responsible for 85 percent of golden eagle nesting
failures along the Front Range of the Rockies in Wyoming, Colorado, and
in New Mexico [21].  Placing seasonal restrictions on recreational
activities and limiting human access in nesting areas can minimize the
chance of disturbance [5,9].

Some current laws have reduced human-caused hazards to golden eagles.
As of February 1972, use of poisons on public lands has been banned by
Executive Order.  Some animal trapping groups have established policies
against placing leg-hold traps near open bait, and some states have laws
prohibiting open bait trapping [9].  The problem of golden eagles being
electrocuted by powerlines has been greatly reduced during the past
decade through cooperative efforts of government agencies, conservation
organizations, and the electric industry.  This cooperation is now being
extended into positive golden eagle habitat management by power
companies [20].

Golden eagles are very susceptible to organochlorine pesticides and many
other environmental contaminants.  Since jackrabbits and other
herbivores eaten by golden eagles accumulate low pesticide levels,
golden eagles accumulate higher levels via food-chain concentration.
Another major threat to golden eagle populations is lead toxicosis,
which has been identified as a cause of golden eagle deaths.  A
preliminary study of a population in southern California reported that
26 of 66 golden eagles (39%) had blood lead levels greater than 0.2 ppm,
indicating exposure to environmental lead [13].

Serious golden eagle depredation of livestock is usually infrequent and
localized; however, livestock predation has sometimes become a problem
for ranchers [18].  While a potential problem may occur anywhere golden
eagles and livestock coexist, depredation is most severe on lambs in
open range, most notably in Montana and New Mexico.  Because golden
eagles are protected under federal law, options for damage control
efforts are limited and highly restricted [23].  In other areas, such as
California, golden eagle depredation of livestock appears minor [13].
Some researchers suggest that golden eagles are beneficial to livestock
interests because a large percentage of their diet is made up of
rabbits, which compete with livestock for forage.  Eight to twelve
jackrabbits consume enough forage to support one sheep.  The number of
rabbits and rodents killed by golden eagles translates into a sizeable
quantity of forage [18].


REFERENCES : 
NO-ENTRY

Related categories for Wildlife Species: Aquila chrysaetos | Golden Eagle