Aegolius acadicus - (Gmelin, 1788)
Northern Saw-whet Owl
Other English Common Names: northern saw-whet owl
Taxonomic Status: Accepted
Related ITIS Name(s): Aegolius acadicus (Gmelin, 1788) (TSN 177942)
French Common Names: petite nyctale
Spanish Common Names: Tecolote Afilador
Unique Identifier: ELEMENT_GLOBAL.2.106412
Element Code: ABNSB15020
Informal Taxonomy: Animals, Vertebrates - Birds - Other Birds
Image 7699

© Larry Master

 
Kingdom Phylum Class Order Family Genus
Animalia Craniata Aves Strigiformes Strigidae Aegolius
Genus Size: B - Very small genus (2-5 species)
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Concept Reference
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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/.
Concept Reference Code: B98AOU01NAUS
Name Used in Concept Reference: Aegolius acadicus
Taxonomic Comments: Constitutes a superspecies with and may be conspecific with Middle American A.ridgwayi (AOU 1998).
Conservation Status
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NatureServe Status

Global Status: G5
Global Status Last Reviewed: 06Apr2016
Global Status Last Changed: 27Nov1996
Ranking Methodology Used: Ranked by inspection
Rounded Global Status: G5 - Secure
Nation: United States
National Status: N5B,N5N (05Jan1997)
Nation: Canada
National Status: N5B,N5N,N5M (08Jan2018)

U.S. & Canada State/Province Status
Due to latency between updates made in state, provincial or other NatureServe Network databases and when they appear on NatureServe Explorer, for state or provincial information you may wish to contact the data steward in your jurisdiction to obtain the most current data. Please refer to our Distribution Data Sources to find contact information for your jurisdiction.
United States Alabama (S2N), Alaska (S3), Arizona (S4), Arkansas (SU), California (SNR), Colorado (S5), Connecticut (S2S3B), Delaware (SNA), District of Columbia (S1N), Georgia (S3), Idaho (S4), Illinois (S1?), Indiana (SHB), Iowa (SNA), Kansas (SNA), Kentucky (SNA), Maine (S4S5N,S5B), Maryland (S1B), Massachusetts (S3B,S5N), Michigan (S3S4), Minnesota (SNRB,SNRN), Montana (S4), Navajo Nation (SNR), Nebraska (SNRN), Nevada (S4), New Hampshire (S4), New Jersey (SU,S4N), New Mexico (S4B,S4N), New York (S3), North Carolina (S2B,S2N), North Dakota (SNA), Oregon (S4?), Pennsylvania (S4), Rhode Island (S1B,S1N), South Carolina (S2N), South Dakota (S3B,S3N), Tennessee (S1), Utah (S3), Vermont (S3B,S3N), Virginia (S1B,S2N), Washington (S4B,S4N), West Virginia (S2B,S1N), Wisconsin (S4B,S4N), Wyoming (S4)
Canada Alberta (S5), British Columbia (S5B,S5N), Manitoba (S4S5B), New Brunswick (S5B,S5M), Newfoundland Island (S3?), Nova Scotia (S4B), Ontario (S4), Prince Edward Island (S4B), Quebec (S4S5B), Saskatchewan (S5B,S4N)

Other Statuses

Implied Status under the Committee on the Status of Endangered Wildlife in Canada (COSEWIC):PS:T
Comments on COSEWIC: Subspecies brooksi is designated Threatened.
IUCN Red List Category: LC - Least concern
Convention on International Trade in Endangered Species Protection Status (CITES): Appendix II

NatureServe Global Conservation Status Factors

Range Extent Comments: 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.

Population Size Comments: Guesstimated number of breeding pairs in Canada in the early 1990s was 50,000-150,000 (Kirk et al. 1995).

Short-term Trend Comments: Trend in Canada was reported by Kirk et al. (1995) as "?stable."

Other NatureServe Conservation Status Information

Distribution
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Global Range: 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.

U.S. States and Canadian Provinces

Due to latency between updates made in state, provincial or other NatureServe Network databases and when they appear on NatureServe Explorer, for state or provincial information you may wish to contact the data steward in your jurisdiction to obtain the most current data. Please refer to our Distribution Data Sources to find contact information for your jurisdiction.
Color legend for Distribution Map
NOTE: The maps for birds represent the breeding status by state and province. In some jurisdictions, the subnational statuses for common species have not been assessed and the status is shown as not-assessed (SNR). In some jurisdictions, the subnational status refers to the status as a non-breeder; these errors will be corrected in future versions of these maps. A species is not shown in a jurisdiction if it is not known to breed in the jurisdiction or if it occurs only accidentally or casually in the jurisdiction. Thus, the species may occur in a jurisdiction as a seasonal non-breeding resident or as a migratory transient but this will not be indicated on these maps. See other maps on this web site that depict the Western Hemisphere ranges of these species at all seasons of the year.
Endemism: occurs (regularly, as a native taxon) in multiple nations

U.S. & Canada State/Province Distribution
United States AK, AL, AR, AZ, CA, CO, CT, DC, DE, GA, IA, ID, IL, IN, KS, KY, MA, MD, ME, MI, MN, MT, NC, ND, NE, NH, NJ, NM, NN, NV, NY, OR, PA, RI, SC, SD, TN, UT, VA, VT, WA, WI, WV, WY
Canada AB, BC, MB, NB, NF, NS, ON, PE, QC, SK

Range Map
Note: Range depicted for New World only. The scale of the maps may cause narrow coastal ranges or ranges on small islands not to appear. Not all vagrant or small disjunct occurrences are depicted. For migratory birds, some individuals occur outside of the passage migrant range depicted. For information on how to obtain shapefiles of species ranges see our Species Mapping pages at www.natureserve.org/conservation-tools/data-maps-tools.

Range Map Compilers: WILDSPACETM 2002


U.S. Distribution by County Help
State County Name (FIPS Code)
CT Fairfield (09001), Hartford (09003)*, Litchfield (09005), Tolland (09013), Windham (09015)*
ID Bannock (16005), Boise (16015), Bonner (16017), Boundary (16021), Cassia (16031), Idaho (16049), Lemhi (16059), Valley (16085)
MD Allegany (24001), Garrett (24023)
NC Avery (37011), Buncombe (37021), Cherokee (37039)*, Graham (37075), Haywood (37087), Jackson (37099), Macon (37113), Madison (37115), Mitchell (37121), Swain (37173), Transylvania (37175), Watauga (37189), Yancey (37199)
NE Antelope (31003), Banner (31007), Blaine (31009), Dawes (31045), Scotts Bluff (31157), Thomas (31171)
NJ Sussex (34037)
PA Luzerne (42079), Potter (42105), Sullivan (42113), Wyoming (42131)
RI Washington (44009)
SD Custer (46033), Harding (46063), Meade (46093), Pennington (46103), Roberts (46109)
TN Carter (47019), Claiborne (47025), Monroe (47123), Unicoi (47171)
VA Bland (51021)*, Grayson (51077), Highland (51091), Russell (51167), Smyth (51173)*, Tazewell (51185), Washington (51191)*
WV Preston (54077), Randolph (54083), Tucker (54093)
WY Albany (56001), Teton (56039)*
* Extirpated/possibly extirpated
U.S. Distribution by Watershed Help
Watershed Region Help Watershed Name (Watershed Code)
01 Farmington (01080207)+*, Pawcatuck-Wood (01090005)+, Shetucket (01100002)+, Housatonic (01100005)+, Saugatuck (01100006)+
02 Rondout (02020007)+, Lehigh (02040106)+, Upper Susquehanna-Tunkhannock (02050106)+, Sinnemahoning (02050202)+, Lower West Branch Susquehanna (02050206)+, South Branch Potomac (02070001)+, North Branch Potomac (02070002)+
03 Upper Catawba (03050101)+, Tugaloo (03060102)+
05 Tygart Valley (05020001)+, Cheat (05020004)+, Youghiogheny (05020006)+, Upper New (05050001)+, Middle New (05050002)+*
06 North Fork Holston (06010101)+, South Fork Holston (06010102)+*, Watauga (06010103)+, Upper French Broad (06010105)+, Pigeon (06010106)+, Lower French Broad (06010107)+, Nolichucky (06010108)+, Watts Bar Lake (06010201)+, Upper Little Tennessee (06010202)+, Tuckasegee (06010203)+, Lower Little Tennessee (06010204)+, Upper Clinch (06010205)+*, Powell (06010206)+, Hiwassee (06020002)+*
07 Upper Minnesota (07020001)+
10 Upper Little Missouri (10110201)+, Angostura Reservoir (10120106)+, Beaver (10120107)+, Middle Cheyenne-Spring (10120109)+, Rapid (10120110)+, Middle Cheyenne-Elk (10120111)+*, Lower Cheyenne (10120112)+, Lower Belle Fourche (10120202)+, North Fork Grand (10130301)+, South Fork Grand (10130302)+, South Fork Moreau (10130304)+, Upper Moreau (10130305)+, Upper White (10140201)+, Upper Niobrara (10150003)+, Lower Niobrara (10150007)+, Upper North Platte (10180002)+, Middle North Platte-Scotts Bluff (10180009)+, Pumpkin (10180013)+, Upper Middle Loup (10210001)+
16 Curlew Valley (16020309)+
17 Moyie (17010105)+, Priest (17010215)+, Snake headwaters (17040101)+*, Gros Ventre (17040102)+*, Greys-Hobock (17040103)+*, Portneuf (17040208)+, Boise-Mores (17050112)+, North Fork Payette (17050123)+, Middle Salmon-Panther (17060203)+, Lemhi (17060204)+, Middle Salmon-Chamberlain (17060207)+
+ Natural heritage record(s) exist for this watershed
* Extirpated/possibly extirpated
Ecology & Life History
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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).
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).
Non-Migrant: Y
Locally Migrant: Y
Long Distance Migrant: N
Mobility and 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).
Terrestrial Habitat(s): Forest - Conifer, Forest - Mixed
Special Habitat Factors: Standing snag/hollow tree
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.
Adult Food Habits: Carnivore, Invertivore
Immature Food Habits: Carnivore, Invertivore
Food 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.
Adult Phenology: Crepuscular, Nocturnal
Immature Phenology: Crepuscular, Nocturnal
Length: 20 centimeters
Weight: 91 grams
Economic Attributes Not yet assessed
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Management Summary
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Monitoring Requirements: To detect owls in Rocky Mountains: biweekly surveys in March-April; minimum of 3 years of censusing may be needed because of low vocal activity in some years; census on clear calm nights (Palmer 1987). See Bull (1987) for information on capture techniques.
Population/Occurrence Delineation
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Group Name: Small and Medium Owls

Use Class: Breeding
Subtype(s): Nest site
Minimum Criteria for an Occurrence: Evidence of historical breeding, or current and likely recurring breeding, at a given location, minimally a reliable observation of one or more breeding pairs in appropriate habitat. Be cautious about creating EOs for observations that may represent single breeding events outside the normal breeding distribution.
Separation Barriers: None.
Separation Distance for Unsuitable Habitat: 5 km
Separation Distance for Suitable Habitat: 5 km
Separation Justification: Separation distance is not intended to delineate demographically independent populations or metapopulations (such units would be quite large) but rather serves to circumscribe breeding occurrences that are of practical size for conservation/management use.

Separation distance is larger than three times the diameter of an average home range for these volant species; based the diameter of larger home ranges of males, e.g. those of Northern Pygmy-Owls given below.

Ferruginous Pygmy-Owl: post-fledging families used 9.3 to about 60 hectares until the young dispersed (Proudfoot and Johnson 2000).

Northern Pygmy-Owl: territory in Colorado estimated to be about 75 hectares (Rashid 1999, cited in Holt and Petersen 2000); home ranges of breeding males in Washington 170-230 hectares (A. Giese, pers. comm., cited in Holt and Petersen 2000); home ranges of males in Sweden averaged 231 hectares (Kullberg 1995).

Northern Saw-whet Owl: Two breeding males had home ranges of 142 and 159 hectares (Cannings 1987). Most breeding habitat probably supports a maximum of about 1 pair/square kilometer, often much less (Cannings 1993); singing males can be as close as about 250 meters apart (Swengel 1990).

Elf Owl: home ranges smaller, range 0.2-2.6, mean 1.0 hectares (Gamel 1997).

Flammulated Owl males had mean home ranges of about 14 hectares in Colorado (Linkhart 1984) and about 16 hectares in Oregon (during the incubation period; Goggans 1986). DNA data indicate very low differentiation among populations in different mountain ranges in New Mexico and Utah; evidently the species exhibits long-distance natal dispersal and frequent intermountain dispersal (Arsenault et al. 2005).

Whiskered Screech-Owls had home ranges about 1550 meters long, along permanent creek (Gehlbach and Gehlbach 2000).

Burrowing Owl: In Saskatchewan, the average home range was about 1.2 kilometers in diameter (Haug and Oliphant 1990).

Long-eared Owl: In Wyoming, breeding home range in riparian habitat varied from 34-106 hectares and averaged 51 hectares (Craighead and Craighead 1956).

Short-eared Owl: Breeding territories average 64 -74 hectares (Holt 1992, Clark 1975).

Inferred Minimum Extent of Habitat Use (when actual extent is unknown): .6 km
Inferred Minimum Extent Justification: Conservatively based on an average home range of 27 hectares for a Ferruginous Pygmy-Owl family (Proudfoot and Johnson 2000). A breeding male Northern Saw-whet Owl spent most of its active time in a core area of only 27 hectares (Cannings 1987).

Long-eared Owl: May use an IE of 0.8 km, which is the diameter of an average home range (Craighead and Craighead 1956).

Short-eared Owl: May use an IE of 0.9 km, which is based on an average breeding home range of 65 hectares.

Date: 26Feb2005
Author: Cannings, S., and G. Hammerson
Notes: Contains owls in the genera Otus, Glaucidium, Aegolius, Asio and Athene.

Use Class: Nonbreeding
Minimum Criteria for an Occurrence: Evidence of recurring presence of wintering individuals (including historical); and potential recurring presence at a given location. Occurrences should be locations where the species is resident for some time during the appropriate season; it is preferable to have observations documenting presence over at least 20 days annually. Be cautious about creating EOs for observations that may represent single events.
Separation Barriers: None.
Separation Distance for Unsuitable Habitat: 5 km
Separation Distance for Suitable Habitat: 5 km
Separation Justification: Separation distance larger than three times the diameter of an average home range for these volant species; based the diameter of larger home ranges of males, e.g. those of Northern Pygmy-Owls: in Washington 170-230 hectares (A. Giese, pers. comm., cited in Holt and Petersen 2000); in Sweden, averaged 231 hectares (Kullberg 1995).
Whiskered Screech-Owls had home ranges about 1550 meters long, along permanent creek (Gehlbach and Gehlbach 2000).

Inferred Minimum Extent of Habitat Use (when actual extent is unknown): .6 km
Inferred Minimum Extent Justification: Conservatively based on a home range of 27 hectares; for example, a breeding male Northern Saw-whet Owl spent most of its active time in a 27-hectare core area (Cannings 1987).
Date: 16Apr2002
Author: Cannings, S.

Use Class: Roost
Minimum Criteria for an Occurrence: Evidence of recurring, nonbreeding, communal roosting at a given location; reliable observation of multiple individuals roosting in a distinct habitat patch in multiple years. To avoid creating EOs for ephemeral situations, there should be evidence of communal roosting over at least two different (though not necessarily consecutive) nonbreeding seasons.
Separation Barriers: None.
Separation Distance for Unsuitable Habitat: 5 km
Separation Distance for Suitable Habitat: 5 km
Separation Justification: Separation distance is arbitrary. Pertinent biologically based separation criteria do not exist.
Date: 25Oct2012
Author: Hammerson, G.
Population/Occurrence Viability
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U.S. Invasive Species Impact Rank (I-Rank) Not yet assessed
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Authors/Contributors
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Element Ecology & Life History Edition Date: 03Mar1994
Element Ecology & Life History Author(s): HAMMERSON, G.

Zoological data developed by NatureServe and its network of natural heritage programs (see Local Programs) and other contributors and cooperators (see Sources).

References
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  • 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.

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Note: All species and ecological community data presented in NatureServe Explorer at http://explorer.natureserve.org were updated to be current with NatureServe's central databases as of March 2018.
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Citation for Bird Range Maps of North America:
Ridgely, R.S., T.F. Allnutt, T. Brooks, D.K. McNicol, D.W. Mehlman, B.E. Young, and J.R. Zook. 2003. Digital Distribution Maps of the Birds of the Western Hemisphere, version 1.0. NatureServe, Arlington, Virginia, USA.

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Citation for Mammal Range Maps of North America:
Patterson, B.D., G. Ceballos, W. Sechrest, M.F. Tognelli, T. Brooks, L. Luna, P. Ortega, I. Salazar, and B.E. Young. 2003. Digital Distribution Maps of the Mammals of the Western Hemisphere, version 1.0. NatureServe, Arlington, Virginia, USA.

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IUCN, Conservation International, and NatureServe. 2004. Global Amphibian Assessment. IUCN, Conservation International, and NatureServe, Washington, DC and Arlington, Virginia, USA.

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