Written by: C. Polite
Reviewed by:L. Kiff
Edited by: L. Kiff

DISTRIBUTION, ABUNDANCE, AND SEASONALITY

     A common, permanent resident throughout the state from sea level to 2100 m (0-7000 ft),
occasionally to 3200 m (10,500 ft).  Exploits a variety of forests with meadows and other
openings, extending from valley foothill hardwood to mixed conifer habitats.  Commonly feeds
and breeds in riparian, conifer, chaparral, and desert habitats.

SPECIFIC HABITAT REQUIREMENTS

   Feeding:    Usually makes low, rapid flight from perch to capture prey on ground.  Rabbits,
rodents, and other small to medium-sized mammals usually make up 90% of the diet.  Also
eats birds (occasionally smaller or young raptors; Wiley 1975b), amphibians, reptiles, fish,
and arthropods.  Frequently forages in meadows and woodland or forest openings, or along
edges.

   Cover:    Requires trees with dense foliage for roosting; often uses thickly wooded canyons.

   Reproduction:    Nests in abandoned hawk, crow, raven, or squirrel nest, in cave or crevice,
on cliff ledge, occasionally in snag or tree cavity (Call 1978).  Nests in trees usually 12-21 m
(40-70 ft) above ground.

   Water:    Most water requirements probably met from prey (Bartholomew and Cade 1963).
Will drink water in captivity.

   Pattern:    Frequents forested habitats; feeds especially in edges, openings, and meadows.

SPECIES LIFE HISTORY

   Activity Patterns:    Yearlong, nocturnal and crepuscular activity.

   Seasonal Movements/Migration:    Mostly not migratory, but will move upslope and
downslope in response to weather conditions.

   Home Range:    In Wyoming, home range varied from 1.2 to 2.9 km² (0.4 to 1.1 mi²), with an
average of 2.1 km² (0.8 mi²).  In eastern Oregon, home range averaged 12.1 km² (4.7 mi²).  In
Michigan farmland, nesting density varied from 0.04 to 0.08 pair per km² (0.1 to 0.2 per mi²),
and wintering density varied from 0.12 to 0.15 individuals per km² (0.3 to 0.4 per mi²)
(Craighead and Craighead 1956).

   Territory:    Average territory was 65 ha (160 ac) in oak habitats in Kansas (Fitch 1958).
Male defends territory throughout breeding season more aggressively than female.

   Reproduction:    Breeds from mid-January through June, peak usually March through May.
Clutch size 1-6; average 3; often laid in February or March.  Incubation 26-35 days,
semialtricial young fledge in 35-56 days.  Male may assist with nest activities.  Craighead and
Craighead (1956) reported fledging success (young fledged/eggs laid) of 27% and 50% in
Michigan, and 89% in Wyoming.

   Niche:    Golden eagles and humans may be the only predators (Hoechlin 1976).
Competitors for food include Cooper's hawks, American kestrels, and other large owls.
Population numbers respond to prey abundance.

REFERENCES

Bartholomew, G. A., and T. J. Cade.  1963.  The water economy of land birds.  Auk 80:504-
     539.
Bent, A. C.  1938.  Life histories of North American birds of prey.  Part 2.  U.S. Natl. Mus. Bull.
     170.  482pp.
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.
Craighead, J. J., and F. C. Craighead, Jr.  1956.  Hawks, owls and wildlife.  Stackpole Books,
     Harrisburg, PA.  443pp.
Ehrlich, P. R., D. S. Dobkin, and D. Wheye.  1988.  The birder's handbook.  Simon and
     Schuster, New York.  785pp.
Fitch, H. S. 1947.  Predation by owls in the sierran foothills of California.  Condor  49:137-151.
Fitch, H. S. 1958.  Home ranges, territories, and seasonal movements of vertebrates of
     the Natural History Reservation.  Univ. Kans., Lawrence. Publ. Mus. Nat. Hist. 11:63-
     326.
Grinnell, J., and A. H. Miller.  1944.  The distribution of the birds of California.  Pac. Coast
     Avifauna No. 27.  608pp.
Guiguet, C. J.  1960.  The Birds of British Columbia (7).  The owls.  Brit. Col. Prov. Mus.,
     Vancouver.  Handb. No. 18.  62pp.
Harrison, C.  1978.  A field guide to the nests, eggs and nestlings of north American birds.  W.
     Collins Sons and Co., Cleveland, OH.  416pp.
Hoechlin, D. R.  1976.  Development of golden eaglets in southern California.  West. Birds
     7:137-152.
Karalus, K. E., A. W. Eckert.  1974.  The owls of North America. Doubleday Co., Garden City
     NY.  278pp.
Marti, C. D.  1974.  Feeding ecology of four sympatric owls.  Condor  76:45-61.
Murray, G. A.  1976.  Geographic variation in the clutch size of seven owl species.  Auk
     93:602-613.
Wiley, J. W.  1975b.  Relationships of nesting hawks with great horned owl.  Auk  92:157-159.
 
Compiled from information from California Department of Fish and Game - California Interagency Wildlife Task Group