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BC Conservation Data Centre: Species Summary


Aegolius acadicus
Northern Saw-whet Owl

 
Scientific Name: Aegolius acadicus (Gmelin, 1788)
English Name: Northern Saw-whet 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: http://www.aou.org/.
Classification Level: Species
Species Group: Vertebrate Animal
Species Code: B-NSWO
Kingdom Phylum Class Order Family
Animalia Craniata Aves Strigiformes Strigidae
   
Conservation Status / Legal Designation
Global Status: G5 (Apr 2016)
Provincial Status: S5B,S5N (Jan 2009)
BC List: Yellow
Provincial FRPA list:   
Provincial Wildlife Act:
COSEWIC Status:
SARA Schedule:
General Status Canada: 4 - Secure (2005)
Migratory Bird Convention Act:
   
Ecology & Life History
General Description:
Global Reproduction Comments: Nesting March-July (mainly April-May) in northeastern U.S. and southeastern Canada. Clutch size usually is about 5-6. Incubation, by female, lasts 26-28 days. Young first fly at 4-5 weeks (Johnsgard 1988).
Global Ecology Comments: Studies of a few birds yielded seasonal home range estimates of about 75-150 ha. Two breeding males had home ranges of 142 and 159 hectares (Cannings 1987). Limited data on breeding density suggests maximum of a few pairs per sq km (Johnsgard 1988); singing males can be as close as about 250 meters apart (Swengel 1990). However, most breeding habitat probably supports a maximum of about 1 pair/square kilometer, often much less (Cannings 1993).
Migration Characteristics:
(Global / Provincial)		 
    Nonmigrant:
    Local Migrant:
    Distant Migrant:
    Within Borders Migrant: 		Y /
Y /
N /
na /
Global Migration Comments: Probably makes local elevational migrations in the mountains of the western U.S. and possibly the Appalachians; fairly extensive north-south movement in east and north. Apparently two main migration corridors exist in the east: Ohio River valley and Atlantic coastal lowlands (Johnsgard 1988). At Cape May Point, New Jersey, 90% of fall migration was completed between mid-October and mid-November (Duffy and Kerlinger 1992). See also Russell et al. (1991) for an account of fall migration at Cape May Point, New Jersey. At Whitefish Point, Michigan, begins arriving in early April; migration peaks in mid- to late April, with a secondary peak in late May (Wilson Bull. 105:356-359).
Habitats:
(Type / Subtype / Dependence) 		Agriculture / Cultivated Field / Unknown
Agriculture / Hedgerow / Unknown
Agriculture / Pasture/Old Field / Unknown
Alpine/Tundra / Alpine/Subalpine Meadow / Unknown
Anthropogenic / Urban/Suburban / Unknown
Forest / Conifer Forest - Dry / Unknown
Forest / Conifer Forest - Mesic (average) / Unknown
Forest / Conifer Forest - Moist/wet / Unknown
Forest / Deciduous/Broadleaf Forest / Unknown
Forest / Mixed Forest (deciduous/coniferous mix) / Unknown
Grassland/Shrub / Meadow / Unknown
Grassland/Shrub / Shrub - Natural / Unknown
Lakes / Lake / Unknown
Riparian / Riparian Forest / Unknown
Wetland / Bog / Unknown
Wetland / Fen / Unknown
Wetland / Marsh / Unknown
Wetland / Swamp / Unknown
Global Habitat Comments: Dense coniferous or mixed forest, cedar groves, alder thickets, swamps, and tamarack bogs; also, when not breeding, in dense second growth, brushy areas, arid scrub, and open buildings. Often roosts in dense evergreens in winter, at various heights and usually close to the trunk (Swengel and Swengel 1992a). Nests usually in old woodpecker hole, also in other tree cavity, or in nest box. Roosts during daylight in or near nest hole during breeding season (NGS 1983). Suitable holes have diameter of 7 cm or more.
Food Habits: Carnivore: Adult, Immature
Invertivore: Adult, Immature
Global Food Habits Comments: Eats mainly small mammals (e.g., PEROMYSCUS, MICROTUS, shrews) (e.g., see Swengel and Swengel 1992b); sometimes birds and insects. In the Queen Charlotte Islands, British Columbia, nonbreeding owls may include marine intertidal invertebrates (amphipods) in the diet. Apparently obtains prey mainly by pouncing on it from above, after short flight from elevated perch. May hunt in areas with thick shrub cover.
Global Phenology: Crepuscular: Adult, Immature
Nocturnal: Adult, Immature
Provincial Phenology:
(1st half of month/
2nd half of month)
Colonial Breeder: N
Length(cm)/width(cm)/Weight(g): 20/ / 91
Elevation (m) (min / max): Global: 
Provincial: 
   
 
Distribution
Endemic: N
Global Range Comment: BREEDS: southern Alaska to central Saskatchewan and northern New Brunswick, south to southern California, southern Arizona, southern Mexico, western Texas, Missouri, southern Michigan, Maryland; also in Great Smoky Mountains. WINTERS: generally throughout breeding range (some southward withdrawal), irregularly or casually south to southern U.S.
 
Authors / Contributors
Global Information Author: HAMMERSON, G.
Last Updated: Mar 03, 1994
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. 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.
Campbell, R.W., et al. 1988. Species Notes for Selected Birds, Vol. 2 in A.P. Harcombe, tech. ed. 1988. B.C. Minist. Environ., Lands and Parks, Wildl. Branch. Rep. R-16. 131pp.
Campbell, R.W., N.K. Dawe, I. McTaggart-Cowan, et al. 1990b. The Birds of British Columbia Vol. 2: Nonpasserines: Diurnal Birds of Prey through Woodpeckers. Royal British Columbia Museum, Victoria, BC.
Cannings, R. J. 1987. The breeding biology of Northern Saw-whet Owls in southern British Columbia. Pages 193-198 IN Nero, R.W., R. J. Clark, R. J. Knapton, and H. Hamre, editors. 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.
Cannings, R. J. 1993. Northern Saw-whet Owl (Aegolius acadicus). No. 42 IN A. Poole and F. Gill, editors. The birds of North America. The Academy of Natural Sciences, Philadelphia; The American Ornithologists' Union, Washington, DC. 20pp.
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.
Demarchi, M.W. and M.D. Bently. 2005. Best Management Practices for Raptor Conservation during Urban and Rural Land Development in British Columbia. B.C. Minist. of Environ., Victoria, B.C. MoE BMP Series.
Duffy, K., and P. Kerlinger. 1992. Autumn owl migration at Cape May Point, New Jersey. Wilson Bull. 104:312-320.
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.
Harrison, C. 1978. A Field Guide to the Nests, Eggs and Nestlings of North American Birds. Collins, Cleveland, Ohio.
Harrison, H. H. 1979. A field guide to western birds' nests. Houghton Mifflin Company, Boston. 279 pp.
Johnsgard, P. 1988. North American owls: biology and natural history. Smithsonian Inst. Press. 336 pp.
National Geographic Society (NGS). 1983. Field guide to the birds of North America. National Geographic Society, Washington, DC.
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.
Palmer, D. A. 1987. Annual, seasonal, and nightly variation in calling activity of boreal and northern saw-whet owls. Pp. 162-168 in Nero, R.W., et al., eds. Biol. & Cons. of n. forest owls. U.S. For. Serv., 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.
Russell, R. W., et al. 1991. A visual study of migrating owls at Cape May Point, New Jersey. Condor 93:55-61.
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.
Swengel, S. R. 1990. How to find Saw-whet Owls. Bird Watcher's Digest 12:68-75.
Terres, J. K. 1980. The Audubon Society encyclopedia of North American birds. Alfred A. Knopf, New York.
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. 1994. Species Summary: Aegolius acadicus. B.C. Minist. of Environment. Available: https://a100.gov.bc.ca/pub/eswp/ (accessed Oct 22, 2026).