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BC Conservation Data Centre: Species Summary

Strix nebulosa
Great Gray Owl

Scientific Name: Strix nebulosa Forster, 1772
English Name: Great Gray Owl
Classification / Taxonomy
Scientific Name - Concept Reference: American Ornithologists' Union (AOU). 1998. Check-list of North American birds. Seventh edition. American Ornithologists' Union, Washington, D.C. [as modified by subsequent supplements and corrections published in The Auk]. Also available online:
Classification Level: Species
Species Group: Vertebrate Animal
Species Code: B-GGOW
Kingdom Phylum Class Order Family
Animalia Craniata Aves Strigiformes Strigidae
Conservation Status / Legal Designation
Global Status: G5 (Apr 2016)
Provincial Status: S4 (Mar 2015)
BC List: Yellow
Provincial FRPA list:   
Provincial Wildlife Act:
COSEWIC Status: Not at Risk (May 1996)
SARA Schedule:
General Status Canada: 4 - Secure (2005)
Migratory Bird Convention Act:
Ecology & Life History
General Description:
Global Reproduction Comments: Egg dates: late March-May in Alberta, late April-early June in Ontario, peak mid-April to late May in California, mean date of first egg 5 May in southern Idaho and northwestern Wyoming; eggs laying may be delayed in years with deep snow (Franklin 1988). Clutch size is 2-5 (usually 2-3 or 3-4). Incubation lasts 28-29 days, by female (male brings food). Young begin to leave nest at 3-4 weeks (4 weeks in Idaho/Wyoming), fly well at 5-6 weeks (6 weeks in Idaho/Wyoming), independent at about 4-5 months (Idaho/Wyoming: Franklin 1988). Usually first breeds at 3-4 years. Pair bond is not maintained outside breeding season, but bond may reform if both birds return to the same breeding territory. Some pairs may not breed in years of low prey abundance.
Global Ecology Comments: Some may remain on breeding territory all year; others may move irregularly in search of favorable foraging conditions. In Oregon, radio-tagged juveniles moved 9-31 km from nest over period of 1 year, adults moved 3-43 km during same period (see Johnsgard 1988). Predation by great horned owl was greatest known mortality factor in northern Minnesota and southeastern Manitoba (Duncan 1987).
Migration Characteristics:
(Global / Provincial)
    Local Migrant:
    Distant Migrant:
    Within Borders Migrant:
Y /
N /
N /
na /
Global Migration Comments: Greater mobility exhibited in years when food scarce (Duncan 1987). Food scarcity or unavailability may cause post-breeding movement upslope and downslope movement in winter (California Department of Fish and Game 1990). May move several hundred km southward for winter; in some areas, longest movements made by immatures (but see ECOLCOM).
(Type / Subtype / Dependence)
Global Habitat Comments: Dense coniferous and hardwood forest, especially pine, spruce, paper birch, poplar; also second growth, especially near water, foraging in wet meadows; boreal forest and spruce-tamarack bogs in far north, coniferous forest and meadows in mountains.

Nests in top of large broken-off tree trunks (especially in south), in old nests of other large birds (e.g., hawk nest) (especially in north), or in debris platforms from dwarf mistletoe; frequently near bogs or clearings. Nests frequently reused (Franklin 1988). Same pair often nests in same area in successive years.
Food Habits: Carnivore: Adult, Immature
Global Food Habits Comments: Diet in North America dominated by pocket gophers and voles. Forages usually in open area where scattered trees or forest margin provides suitable sites for visual searching; also uses sound to locate prey under snow cover.
Global Phenology: Circadian: Adult, Immature
Global Phenology Comments: In winter, hunts primarily in early morning and from late afternoon until dusk. When nesting, may hunt day or night.
Provincial Phenology:
(1st half of month/
2nd half of month)
Colonial Breeder: N
Length(cm)/width(cm)/Weight(g): 69/ / 1298
Elevation (m) (min / max): Global: 
Endemic: N
Global Range Comment: BREEDS: central Alaska to northern Ontario, south locally in mountains to California (vicinity of Yosemite), Idaho, Montana, Wyoming, central Saskatchewan, northern Minnesota, and south-central Ontario. WINTERS: generally throughout breeding range, wandering south irregularly to northern U.S. Also in Old World. Usually uncommon, but sometimes may be locally abundant.
Authors / Contributors
Global Information Author: HAMMERSON, G.
Last Updated: Mar 31, 1995
Provincial Information Author:
Last Updated:
References and Related Literature
American Ornithologists' Union (AOU). 1983. Check-list of North American Birds, 6th edition. Allen Press, Inc., Lawrence, Kansas. 877 pp.
Bent, A. C. 1938. Life histories of North American birds of prey. Part 2. U.S. Nat. Mus. Bull. 170. 482 pp., 92 pls.
Bull, E. L., et al. 1987. Nest platforms for great gray owls. Pp. 87-90 in Nero, R. W., et al., eds. Biology and conservation of northern forest owls. USDA Forest Service, Gen.Tech. Rep. RM-142.
Bull, E.L. 1987. Capture techniques for owls. Pages 291-293 in R.W. Nero, R.J. Clark, R.J. Knapton, and R.H. Hamre, editors. Biology and conservation of northern forest owls. USDA Forest Service, Gen. Tech. Rep. RM-142.
California Department of Fish and Game (CDF&G). 1990. 1989 annual report on the status of California's state listed threatened and endangered plants and animals. 188 pp.
Campbell, R.W., N.K. Dawe, I. McTaggart-Cowan, J.M. Cooper, G.W. Kaiser, and M.C.E. McNall. 1990b. The Birds of British Columbia Vol. 2: Nonpasserines: Diurnal Birds of Prey through Woodpeckers. Royal British Columbia Museum, Victoria, BC.
Clark, R. J., D. G. Smith, and L. H. Kelso. 1978. Working bibliography of owls of the world. National Wildlife Federation, Sci. & Tech. Ser. No. 1. 336 pp.
Duncan, J. R. 1987. Movement strategies, mortality, and behavior of radio-marked great gray owls. Pp. 101-107 IN Nero, R.W., R. J. Clark, R. J. Knapton, and H. Hamre, eds. Biology and conservation of northern forest owls. USDA For. Serv. Gen. Tech. Rep. RM-142, USDA Forest Service, Rocky Mountain Forest and Range Experiment Station, Fort Collins, CO.
Duncan, J., and P. Duncan. 1994/95. Nocturnal owl surveys. Bird Trends (Canadian Wildlife Service) (4):24-25.
Eckert, Allan W. 1978. The Owls of North America. Weather-vane Books, New York. 278 pp.
Fisher, A.K. 1893. The hawks and owls of the United States in their relation to agriculture. Washington U.S. Dept. of Agriculture Bull. no. 6. 210 pp.
Franklin, A. B. 1988. Breeding biology of the great gray owl in southeastern Idaho and northwestern Wyoming. Condor 90:689-696.
Harrison, C. 1978. A Field Guide to the Nests, Eggs and Nestlings of North American Birds. Collins, Cleveland, Ohio.
Hayward, G. D., and J. Verner, editors. 1994. Flammulated, boreal, and great gray owls in the United States: a technical conservation assessment. USDA Forest Service, General Technical Report RM-253. Fort Collins, Colorado.
Johnsgard, P. 1988. North American owls: biology and natural history. Smithsonian Inst. Press. 336 pp.
Kirk, D. A., D. Hussell, and E. Dunn. 1995. Raptor population status and trends in Canada. Bird Trends (Canadian Wildlife Service) 4:2-9.
National Geographic Society (NGS). 1983. Field guide to the birds of North America. National Geographic Society, Washington, DC.
Nero, R. W. 1980. The great gray owl: phantom of the northern forest. Smithsonian Institution Press, Blue Ridge Summit, PA. 168 pp.
Nicholls, T. H., and M. R. Fuller. 1987. Owl telemetry techniques. Pages 294-301 IN R.W. Nero, R.J. Clark, R.J. Knapton, and R.H. Hamre, editors. Biology and conservation of northern forest owls. USDA Forest Service, Gen. Tech. Rep. RM-142.
Pendleton, B. A. G., B. A. Millsap, K. W. Cline, and D. M. Bird. 1987. Raptor management techniques manual. National Wildlife Federation, Sci. and Tech. Ser. No. 10. 420 pp.
Quinton, M. S. 1988. Ghost of the forest: the great gray owl. Northland. 99 pp.
Servos, M. C. 1987. Summer habitat use by great gray owls in southeastern Manitoba. Pp. 108-114 in Nero, R. W., et al., eds. Biology and conservation of northern forest owls. USDA For. Serv., Gen. Tech. Rep. RM-142.
Smith, D.G. 1987b. Owl census techniques. Pages 304-307 in R.W. Nero, R.J. Clark, R.J. Knapton, and R.H. Hamre, editors. Biology and conservation of northern forest owls. USDA Forest Service, Gen. Tech. Rep. RM-142.
Spahr, R., L. Armstrong, D. Atwood, and M. Rath. 1991. Threatened, endangered, and sensitive species of the Intermountain Region. U.S. Forest Service, Ogden, Utah.
Terres, J. K. 1980. The Audubon Society encyclopedia of North American birds. Alfred A. Knopf, New York.
Thomas, J. W., Ward, J., Raphael, M.G., Anthony, R.G., Forsman, E.D., Gunderson, A.G., Holthausen, R.S., Marcot, B.G., Reeves, G.H., Sedell, J.R. and Solis, D.M. 1993. Viability assessments and management considerations for species associated with late-successional and old-growth forests of the Pacific Northwest. The report of the Scientific Analysis Team. USDA Forest Service, Spotted Owl EIS Team, Portland Oregon. 530 pp.
U.S. Forest Service (USFS), et al. 1993. Draft supplemental environmental impact statement on management of habitat for late-successional and old-growth forest related species within the range of the northern spotted owl. Published separately is Appendix A: Forest Ecosystem Management Assessment Team. 1993. Forest ecosystem management: an ecological, economic, and social assessment (FEMAT Report).
Voous, K. H., and A. Cameron. 1989. Owls of the Northern Hemisphere. MIT Press, Cambridge, Massachusetts. 320 pp.
Walker, L.W. 1974. The book of owls. Alfred A. Knopf, Inc. New York. 255 pp.

Please visit the website Conservation Status Ranks for definitions of the data fields used in this summary report.

Suggested Citation:

B.C. Conservation Data Centre. 1995. Species Summary: Strix nebulosa. B.C. Minist. of Environment. Available: (accessed Jan 24, 2022).