BIOLOGICAL DATA AND HABITAT REQUIREMENTS
WILDLIFE SPECIES: Haliaeetus leucocephalus | Bald Eagle 



TIMING OF MAJOR LIFE HISTORY EVENTS : 
Mate - late September through November in the South; January through
       March in the central states; late March to early April in
       Alaska; can vary with elevation as well as latitude; usually
       mate for life
Maturity - 4 to 5 years
Clutch - two eggs
Incubation - 35 days
Fledge - 10 to 12 weeks
Longevity - up to 36 years in captivity [12,16]


PREFERRED HABITAT : 
Bald eagles prefer habitat near seacoasts, rivers, large lakes, and
other large areas of open water [25].  They prefer to nest, perch, and
roost primarily in old-growth and mature stands of conifers or
hardwoods.  Eagles usually select the oldest and tallest trees that have
good visibility, an open struture, and are near prey [9,11,16,18,26].  A
study in Maine showed a preference for areas with "superdominant" trees.
It also showed bald eagles avoided lakes surrounded by dense forest or
inhabited by cold-water fishes.  They used areas away from human
disturbance and selected nesting sites near lakes with an abundance of
warm-water fishes [21].  Another study showed a preference for nesting
near lakes with a circumference greater than 7-mile (11-km).  The
smallest body of water supporting a nesting pair of bald eagles was 20
acres (8 ha) [25].

Eagles choose sites more than 0.75 miles (1.2 km) from low-density human
disturbance and more than 1.2 miles (1.8 km) from medium- to
high-density human disturbance [25].  Wintering bald eagles in New
Mexico and Arizona used a disproportionate amount of snags in the
largest class size (no d.b.h. given) for perching, and usually perched
in the top one-third of these trees.  For roosting, eagles preferred
the largest live trees with open structures for visibility [13].


COVER REQUIREMENTS : 
Habitat suitability index models have been developed for wintering bald
eagles in lacustrine and estuarine habitats of the central and northern
states [25].  Bald eagles need old-growth or late-successional forests
for nesting and roosting [20].  Nest snags must be sturdy to support
nests.  Tree height or species is not as important as the abundance of
comparatively large trees near feeding areas [11].  Lakes greater than
3.8 square miles (10 sq km) may be optimal for breeding bald eagles,
although longer and narrower bodies of water can support breeding pairs.
Nest trees should have an open form and sturdy branches in the upper
one-third of the tree.  Eagles nest in the overstory.  Forests used for
nesting should have a canopy cover of less than 60 percent (may be as
low as 20 percent) and be near water.  In treeless areas, bald eagles
nest on cliffs or on the ground [25].

Roosting sites need not be as near to water as nesting sites.  It is
more important that roosting sites are in dense stands of old growth
that offer protection from weather.  Eagles usually arrive at roost
sites after dark and depart roost sites before dawn.  It is therefore is
difficult to determine important roost sites through daytime observation
[13].

Average home ranges for eight pairs of bald eagles in Oregon were 1,650
acres (660 ha), with an average distance between nest territories of 2
miles (3.2 km), and an average of 0.3 miles (0.5 km) of shoreline per
pair [16].  In Arizona, the estimate was 24.6 square miles (64 sq km) of
home range, with 9.4 to 11.2 miles (15-18 km) of shoreline for each pair.


FOOD HABITS : 
Bald eagles eat fish, reptiles, birds, mammals, invertebrates and
carrion, including that of livestock.  Some food species of eagles
include bullhead fish (Ictalurus spp.), alewife (Alosa pseudoharengus),
chain pickerel (Esox niger), sucker (Catostomus spp.), salmon
(Oncorhyncus spp.), white perch (Morone americana), smallmouth bass
(Micropterus dolomieui), eel (Anguilla rostrata), sea otter (Enhydra
lutris), grebe (Podilymbus podiceps), Canada goose (Branta canadensis),
American coot (Fulica americana), mallard (Anas platyrhynchos), pintail
(A. acuta), hare (Lepus spp.), and prairie dog (Cynomys spp.) [17,18,21,25].


PREDATORS : 
NO-ENTRY


MANAGEMENT CONSIDERATIONS : 
Humans pose the greatest threat to bald eagles through habitat
destruction, pesticide use, and poaching [3,8].

In order of increasing ease, bald eagles are flushed from perches,
nests, and foraging areas by human disturbance [14].  They are most
easily disturbed by pedestrian traffic and least disturbed by aircraft.
Establishing buffer zones of 148 to 296 feet (400-800 m) in Oregon and
167 to 592 feet (450-1,600 m) in the Southeast was recommended to
reduce the impact of human disturbance on nesting pairs [14].

Silvicultural treatments for maintaining eagle habitat in ponderosa pine
(Pinus ponderosa) of various age and structure, subclimax mixed conifer,
Douglas-fir (Pseudotsuga menziesii) , and oak (Quercus lobata; Q.
kellogii) stands in northeastern California are detailed [4].



REFERENCES : 
NO-ENTRY

Related categories for Wildlife Species: Haliaeetus leucocephalus | Bald Eagle