Bald Eagles have long rounded wings, large hooked bills, sharp
talons, and are the largest birds of prey in the United States. They swoop down
on their prey at high speeds, and their diet varies by species and considerably
by habitat. In most species, the male is smaller than the female, but
otherwise, the sexes are similar in appearance. This family also includes kites
and hawks.
The bald eagle (Haliaeetus
leucocephalus), is U.S. national symbol. It is a federally designated
endangered species. Relatively common in Alaska, populations in the lower 48
States have been seriously diminished, although they are recovering in some
areas. Bald eagles are most commonly sighted in coastal areas or near rivers or
lakes.
Bald eagles are primarily
carrion feeders. Perhaps Bald Eagle sound is not good in listening. Normally
they emit a sort of high-pitched giggle or a weak scream showing the classics
symbol of adventure. Habitually, Bald Eagle is a very romantic bird of
prey, tend to pair for lifetime. They like to share parenting responsibilities
with the female. You can listen Bald Eagle sound here
Body
Size
Females are significantly
larger than males, but otherwise, the sexes look alike. Body size increases
with latitude and is the sole basis by which the northern and southern
subspecies are divided. Length from bill tip to tail tip averages 81 cm in the
more northerly populations. There may be the reason those female needs extra
food reserves to produce her eggs. This is scariest eagle is pretty much always
the lady.
Bald
Eagle Habitat
Bald eagles generally are
restricted to coastal areas, lakes, and rivers. However, in winter areas it is
not associated with water. Preferred breeding sites include proximity to large
bodies of open water and large nest trees with sturdy branches (often conifers)
and areas of old-growth timber with an open and discontinuous canopy.
In a study shows, more than
200 nests, found 55 % within 46 m of shoreline and 92 percent within 183 m of
shore. During migration and in winter, conifers often are used for communal
roosting both during the day and at night, perhaps to minimize heat loss.
Mature trees with large open crowns and stout, horizontal perching limbs are
preferred for roosting in general. Bald eagles reach maximum densities in areas
of minimal human activity and are almost never found in areas of heavy human
use.
Food
Habits
Bald Eagle primarily
carrion feeders eat dead or dying fish when available but also will catch live
fish swimming near the surface or fish in shallow waters. In general, bald
eagles can be described as opportunistic feeders, taking advantage of whatever
food source is most plentiful. Also, it is easy to scavenge or to capture,
including birds and mammals. In many areas, particularly in winter, waterfowl,
killed or injured by hunters, and shore birds are an important food source.
Usually, eagles forage in
an upland area in the winter season. when surface waters are frozen over,
consuming carrion including rabbits, squirrels, and dead domestic livestock
such as pigs and chickens. The Bald eagles is also famous in to steal food from
other members of their own species as well as from hawks, osprey, gulls, and
mergansers. This Bald Eagle may occur when there is a shortage of a primary
food source, such as fish, and an abundance of other prey such as waterfowl
being used by other predatory birds.
Some prey is important to a
few populations; for example, in the Chesapeake Bay region, turtles are
consumed during the breeding season, and at Amchitka Island in Alaska, sea
otter pups are found regularly in bald eagle nests. In the Pacific Northwest
during the breeding season, that bald eagles hunted live prey 57 percent of the
time, scavenged for 24 percent of their prey, and pirated 19 percent (mostly
from gulls or other eagles).
Because bald eagles
scavenge dead or dying prey, they are particularly vulnerable to environmental
contaminants and pesticides (e.g., from feeding on birds that died from
pesticides, consuming lead shot from waterfowl killed or disabled by hunters.
Bald eagles also are vulnerable to biomagnification of contaminants in food
chains.
At the close of Lake
Superior (WI), herring gulls, which were consumed by over 20 percent of nesting
bald eagle pairs, were found to be a significant source of DDE and PCB intake
by the eagles. The gulls contained higher contaminant levels than the local
fish because of their higher trophic level.
Molt
Adult eagles molt yearly.
In northern populations, molting occurs from late spring to early fall; in
southern populations, molting may be initiated earlier. It is likely that the
molt is not complete, and that some feathers are retained for 2 years. Young
bald eagles generally molt into their adult plumage by their fifth year.
Migration
Bald eagles migrate out of
areas where lakes are completely frozen over in winter but will remain as far
north as the availability of open water and a reliable food supply allow. Areas
with ice-free waterways, such as the Columbia River estuary in Washington and
Oregon, may support both resident and migratory populations in the winter. The
far northern breeding populations migrate south for the winter and often
congregate in areas with abundant food, particularly the Mississippi Valley and
the northwestern States.
Some populations of eagles
that breed in southern latitudes (e.g., Arizona, Florida) show a reverse
migration and migrate north in midsummer (following breeding), returning south
in early autumn or winter. Bald eagles have been observed to nest successfully
at 4 years of age, but most do not breed until at least their fifth year.
Breeding pairs remain together if both are alive.
Nests
of Bald Eagle
Moreover, Bald Eagle is
famous for building a massive nest high in the treetops. Both male and female
play their role to construct their home to cement their lifelong bond. The
nests normally consist of grass and feathers and they used it year after year
spruce it up with a whopping foot or two of new material. The nests on average
is 2 to 4 feet deep and 5 to 6 feet wide.
Large stick nests
(approximately 1.5 m across and 0.6 m deep) are built near water and most often
in a large tree, but sometimes on rocky outcrops or even on the ground on some
islands. In the absence of disturbance, the same nest site may be used for many
years. In Florida, eggs are laid in late autumn or winter, while over the rest
of the eagle's range, mating and egg-laying occur in spring.
Clutch sizes are larger in
the north, and both sexes take responsibility for feeding the young. Young
fledge at about 10 to 12 weeks of age; after leaving the nest, they are still
dependent on their parents for several weeks and often return to the nest for
food. After nesting, large groups will often gather at sites with plentiful
food and resources, such as along rivers following a salmon spawn.
Bald
Eagle Range
During the breeding season,
eagles require large areas near open water, with an adequate supply of nesting
trees. Distance from human disturbance is an important factor in nest-site
selection, and nests have been reported to fail because of disturbance. During
incubation and brooding, eagles show territorial defense of an area around the
nest site. Following fledging, there is little need for nest defense, and
eagles are opportunistic in their search for abundant sources of prey.
During winter, eagles roost
communally in large aggregations and share a foraging home range. The
population of 150 eagles that fed on meadow voles in a 250-ha flooded field for
a 4-week period. This group also established a communal night roost in the
vicinity.
Bald
Eagle Population
Because population density
depends strongly on the configuration of the surface water bodies used for
foraging, few investigators have published explicit density estimates on an
area basis; most report breeding densities along a shoreline on a linear basis.
During the breeding season, 0.03 to 0.4 pairs have been recorded per km shore.
Eagles migrating south from
their summer territories in Canada have aggregated in communal roosts of up to
400 eagles in a 40-ha area. In the winter, communal roost sites may also
contain large numbers of eagles. A group of 150 eagles that roosted and foraged
together in the Klamath Basin, and communal night roosts of up to 300 eagles in
Oregon in late winter.
Not all adults in an area
are part of the breeding population. Some pairs may establish territories and
not breed, while others may not even pair. The percentage of adults breeding
and the breeding success of those that do vary with local food abundance,
weather, and habitat conditions.
The bioaccumulation of
organochlorine pollutants reduced the reproductive success of bald eagles. Now,
in many areas, these raptors are reproducing at rates like those prior to the
widespread use of these pesticides. Eagles lay one clutch per year, although
replacement clutches may be laid upon loss of the initial one. Very little is
known about mortality rates of bald eagles.
The population models that
adult survival is more important than the reproductive rate to the continued
success of bald eagle populations. In captivity, bald eagles have lived for up
to 50 years, and one wild eagle, banded and recaptured in Alaska, was estimated
to be almost 22 years old. Upon loss of an initial clutch, bald eagles may lay
replacement clutches if enough time remains. Moreover, the average life of bald
is around 20 years, however, the oldest confirmed life span is 38 years of age.
Similar
Species
The golden eagle (Aquila
chrysaetos) is similar in size (81 cm) to the bald eagle. Its range encompasses
all but the southeastern United States. Small mammals, snakes, birds, and
carrion are primary prey items, and golden eagles prefer mountainous or hilly
terrain.
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