Written by: C. Polite, J. Pratt
Reviewed by: L. Kiff
Edited by: L. Kiff
DISTRIBUTION, ABUNDANCE, AND SEASONALITY
Permanent resident, and uncommon winter migrant,
now restricted to breeding mostly in
Butte, Lake, Lassen, Modoc, Plumas, Shasta, Siskiyou, and Trinity cos.
About half of the
wintering population is in the Klamath Basin. More common at
lower elevations; not found in
the high Sierra Nevada. Fairly common as a local winter migrant
at a few favored inland
waters in southern California. Largest numbers occur at Big Bear
Lake, Cachuma Lake, Lake
Mathews, Nacimiento Reservoir, San Antonio Reservoir, and along the
SPECIFIC HABITAT REQUIREMENTS
Feeding: Requires large bodies of water,
or free flowing rivers with abundant fish, and
adjacent snags or other perches. Swoops from hunting perches,
or soaring flight, to pluck
fish from water. Will wade into shallow water to pursue fish.
Pounces on, or chases, injured
or ice-bound water birds. In flooded fields, occasionally pounces
on displaced voles, or other
small mammals. Groups may feed gregariously, especially on spawning
dead fish, water birds, and mammals. Open, easily approached
hunting perches and feeding
areas used most frequently.
Cover: Perches high in large, stoutly
limbed trees, on snags or broken-topped trees, or on
rocks near water. Roosts communally in winter in dense, sheltered,
remote conifer stands. In
Klamath National Forest, winter roosts were 16-19 km (10-12 mi) from
Reproduction: Nests in large, old-growth,
or dominant live tree with open branchwork,
especially ponderosa pine. Nests most frequently in stands with
less than 40% canopy, but
usually some foliage shading the nest (Call 1978). Often chooses
largest tree in a stand on
which to build stick platform nest. Nest located 16-61 m (50-200
ft) above ground, usually
below tree crown. Species of tree apparently not so important
as height and size. Nest
usually located near a permanent water source.
Water: In California, 87% of nest sites
were within 1.6 km (1 mi) of water.
Pattern: Requires large, old-growth trees
or snags in remote, mixed stands near water.
SPECIES LIFE HISTORY
Activity Patterns: Yearlong, diurnal
activity. Winter feeding usually occurs immediately
after dawn and in late afternoon.
Seasonal Movements/Migration: Individuals
that breed in California may make only local
winter movements in search of food. Winter migrants move from
north to south.
Home Range: No data found.
Territory: Breeding territory in Alaska
(n = 14), varied from 11-45 ha (28-112 ac), and
averaged 23 ha (57 ac) (Hensel and Troyer 1964). Breeding territory
defended from mating
through fledging. Minimum distances between nests were 1 km (0.6
mi) in Alaska, and 17 km
(10 mi) in Washington.
Reproduction: Breeds February through
July; peak activity March to June. Clutch size
usually 2; range 1-3. Incubation usually 34-36 days. Semialtricial
asynchronously (Ehrlich et al. 1988). Monogamous, and breeds
first at 4-5 yr.
Niche: Highly vulnerable to DDE-induced
eggshell thinning. Competes with, and steals
prey from osprey. Territories have been abandoned after disturbance
recreational development, and other human activities near nests (Thelander
does not begin nesting if human disturbance is evident.
Brown, L., and D. Amadon. 1968. Eagles, hawks and falcons
of the world. 2 Vols. Country
Life Books, London. 945pp.
Call, M. W. 1978. Nesting habits and survey techniques
for common western raptors.
U. S. Dep. Inter., Bur. Land Manage., Portland,
OR. Tech. Note No. 316. 115pp.
Detrich, P. J. 1979. Bald eagle winter habitat on BLM lands
in California. U.S. Dep. Inter.,
Bur. Land Manage., Sacramento. Tech. Rep.
Ehrlich, P. R., D. S. Dobkin, and D. Wheye. 1988. The birder's
handbook. Simon and
Schuster, New York. 785pp.
Hensel, R. J. , and W. A. Troyer. 1964. Nesting studies
of the bald eagle in Alaska. Condor
Lehman, R. N. 1979. A survey of selected habitat feature
of 95 bald eagle nest sites in
California. Calif. Dep. Fish and Game,
Sacramento, Wildl. Manage. Branch Admin. Rep.
No. 79-1. 23pp.
Snow, C. 1973. Southern bald eagle, Haliaeetus leucocephalus
leucocephalus, and northern
bald eagle, Haliaeetus leucocephalus, alascanus.
U.S. Dep. Inter., Bur. Land Manage.,
Wash. DC. Tech. Note No. 171. 58pp.
Spencer, D. A., ed. 1976b. Wintering of the migrant bald
eagle in the lower 48 states. Natl.
Agric. Chem. Assoc. Publ., Wash. DC.
Steenhof, K. 1978. Management of wintering bald eagles.
U.S. Dep. Inter., Fish and Wildl.
Serv., Wash. DC. OBS 78/79. 59pp.
Thelander, C. G. 1973. Bald eagle reproduction in California,
1972-1973. Calif. Dept. Fish
and Game, Sacramento. Wildl. Manage.
Branch Admin. Rep. 73-5. 17pp.
Compiled from information from California Department of Fish and Game - California Interagency Wildlife Task Group