Asio flammeus - (Pontoppidan, 1763)
Short-eared Owl
Other English Common Names: short-eared owl
Other Common Names: Coruja-do-Banhado, Mocho-do-Campo
Taxonomic Status: Accepted
Related ITIS Name(s): Asio flammeus (Pontoppidan, 1763) (TSN 177935)
French Common Names: hibou des marais
Spanish Common Names: Buho Cuerno Corto, Lechuzón Campestre
Unique Identifier: ELEMENT_GLOBAL.2.100351
Element Code: ABNSB13040
Informal Taxonomy: Animals, Vertebrates - Birds - Other Birds
 
Kingdom Phylum Class Order Family Genus
Animalia Craniata Aves Strigiformes Strigidae Asio
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: Asio flammeus
Taxonomic Comments: The genetic distance (based on allozyme data) between A. otus and A. flammeus is unusually large for congeneric bird species; further study of their phylogenetic relationships is warranted. Eight or nine subspecies are recognized, of which five or six are island endemics. Asio f. flammeus, the nominate form, is the only subspecies recognized in North America (Holt and Leasure 1993).
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
Reasons: Secure due mainly to extensive range; declining in some areas; trends are uncertain in many areas.
Nation: United States
National Status: N5B,N5N (05Jan1997)
Nation: Canada
National Status: N4B,N3N (13Feb2012)

U.S. & Canada State/Province Status
United States Alabama (S2N), Alaska (S4B), Arizona (SNR), Arkansas (S3N), California (S3), Colorado (S2B), Connecticut (SHB,S1N), Delaware (SHB,S2N), District of Columbia (S1N,SHB), Florida (SNA), Georgia (S4), Hawaii (S2), Idaho (S4), Illinois (S1B,S2S3N), Indiana (S2), Iowa (S1B,S2N), Kansas (S2B,S3N), Kentucky (S1B,S2N), Louisiana (S3N), Maine (S1B,S1N), Maryland (S1B), Massachusetts (S1B,S3N), Michigan (S1), Minnesota (S3B), Mississippi (S3N), Missouri (S2), Montana (S4), Nebraska (S2), Nevada (S4), New Hampshire (SNA), New Jersey (S1B,S3N), New Mexico (S2N), New York (S2), North Carolina (SUB,S3N), North Dakota (SNRB,SNRN), Ohio (S1S2), Oklahoma (S3N), Oregon (S3), Pennsylvania (S1B,S3N), Rhode Island (S1N), South Carolina (SNRN), South Dakota (S3B,S3N), Tennessee (S3N), Texas (S4N), Utah (S4), Vermont (S1B,S1N), Virginia (S1B,S3N), Washington (S2S3B,S3N), West Virginia (S1B,S1N), Wisconsin (S1B), Wyoming (S2)
Canada Alberta (S3), British Columbia (S3B,S2N), Labrador (S3S4B), Manitoba (S2S3B), New Brunswick (S3B), Newfoundland Island (S3B), Northwest Territories (S3S4B), Nova Scotia (S1S2), Nunavut (SNRB), Ontario (S2N,S4B), Prince Edward Island (S1S2B), Quebec (S3S4), Saskatchewan (S3B,S2N), Yukon Territory (S3B)

Other Statuses

Canadian Species at Risk Act (SARA) Schedule 1/Annexe 1 Status: SC (20Jun2012)
Committee on the Status of Endangered Wildlife in Canada (COSEWIC): Special Concern (25Apr2008)
Comments on COSEWIC: This owl has suffered a continuing population decline over the past 40 years, including a loss of 23% in the last decade alone. Habitat loss and degradation on its wintering grounds are most likely the major threat, while continuing habitat loss and degradation on its breeding grounds in southern Canada and pesticide use are secondary threats. This species nearly meets the criteria for Threatened status.

Designated Special Concern in April 1994 and April 2008.

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: >2,500,000 square km (greater than 1,000,000 square miles)
Range Extent Comments: The breeding range in North America extends from northern Alaska to northern Labrador, south to California, Utah, Colorado, Missouri, Illinois, Ohio, and Virginia. The species breeds in small numbers in every province and territory in Canada (Cadman and Page 1994). It is more numerous in western and central North America than in eastern North America. In the northeastern United States, it currently nests in Vermont, New York, Massachusetts, and Pennsylvania (Tate 1992). In Eurasia the short-eared owl ranges from Iceland, British Isles, Scandinavia, northern Russia, and northern Siberia south to southern Europe, Afghanistan, northern Mongolia, the northern Kurile Islands, and Kamchatka. The species also occurs in the Hawaiian Islands, Caroline Islands (Ponape), and Greater Antilles (Cuba, Hispaniola, Puerto Rico) (AOU 1983). During the nonbreeding season, this owl occurs mostly in the southern parts of most Canadian provinces and southward to southern Baja California, southern Mexico, the Gulf Coast, and Florida; also Hawaii (resident on all main islands) and the Greater Antilles (uncommon in Puerto Rico, including Isla Culebra). In the Old World, nonbreeding occurrences extend from the breeding range south to northwestern Africa, Mediterranean region, Ceylon, southern China, and Japan (AOU 1983).

Area of Occupancy: >12,500 4-km2 grid cells
Area of Occupancy Comments: Birdlife International (2014) gives an estimate of almost 30 million square kilometers for this speices

Number of Occurrences: 81 to >300
Number of Occurrences Comments: This species is represented by a large number of occurrences (subpopulations), with an estimated 3 million individuals by Partners in Flight (2013).

Population Size: >1,000,000 individuals
Population Size Comments: Partners in Flight estimates the global population at 3 million and U.S. population at 200,000. In the mid-1980s, estimated number of breeding pairs in the northeastern U.S. was less than 55 (see Tate [1992] for information on status in particular states). Estimated number of breeding pairs in Canada in the early 1990s was 20,000-40,000 (Kirk et al. 1995). Estimates from other regions are unknown. Analysis of North American Breeding Bird Survey (BBS) data for 1966-2003 resulted in average observed abundances of 0.18 birds/route survey-wide, 0.13 birds/route in Canada, and 0.2 birds/route in the U.S. for this species (Sauer et al. 2004).

Number of Occurrences with Good Viability/Integrity: Very many (>125)
Viability/Integrity Comments: With an estimated global population of three million, there should be at least 125 good element occurrences.

Overall Threat Impact: High
Overall Threat Impact Comments: Habitat loss is the biggest problem. The species is declining in many parts of the range due to destruction and degradation of marshes, grasslands, and low-use pastures (Ehrlich et al. 1992). This may be a result of development, changing land-use patterns (e.g., farmlands to woodlands, or to development), changing farming practices (e.g., hay fields to row crops), reforestation, wetland loss, or a combination of these factors. Populations have declined due to reforestation of farmlands and fragmentation and development of coastal grasslands (see Holt 1992). Loss of open grasslands to later successional stages of community development reduces available hunting and breeding habitat. On Nantucket Island, succession of maritime heathland to scrub oak may be reducing available habitat (Tate 1991). Prey abundance may be a limiting factor in the owl's distribution and breeding success (Melvin et al. 1989). The owl's reported reliance on microtine rodents emphasizes the importance of open habitats favored by these mammals (Lockie 1955, Hagen 1969, Clark 1975).

PREDATION: As a ground-nesting species, eggs and young are vulnerable to various mammalian ground predators such as foxes, raccoons, and mustelids, populations of which have been augmented because of human-caused increases in food resources. Predation by the striped skunk may be one of the reasons for the extirpation of the short-eared owl as a breeding bird on Martha's Vineyard (Melvin et al. 1989). Domestic cats and dogs have been known to disturb owl nests on Nantucket Island (Tate 1991). The potential for an increase in the threat of predation or disturbance by domestic or feral cats and dogs may be high.

OTHER FACTORS: Clark (1975) reported mortality caused by collisions or entanglement with trains, cars, aircraft, farm machinery, and wire fencing, and collisions with radio antennas and guy wires are likely, but these probably do not pose a major threat compared to habitat loss. Short-eared owls have often been subjected to shooting by humans (Bent 1938; Clark 1975; Remsen 1978; J. C. Andrews, pers. comm.). Remsen (1978) mentioned the owl's vulnerability to shooting as a factor in its decline in California.

Short-term Trend: Decline of 10-30%
Short-term Trend Comments: Area of occupancy and population size appear to be declining.

Long-term Trend: Decline of >50%
Long-term Trend Comments: As of the early 1990s, this species was reported as declining in many parts of the range (Ehrlich et al. 1992). Christmas Bird Count data indicate a significant decline in North America between 1960 and 1989. Breeding Bird Survey data indicate a significant, long-term decline in much of North America between 1966 and 1989, though the population trend is unknown in remote northern Canada (Cadman and Page 1994). Analysis of North American Breeding Bird Survey results for 1966-2003 showed a survey-wide decline of -4.3% per year (P=0.01) (Sauer et al. 2004). The estimated 1980-2003 trend for Canada was -9.7% per year (P=0.07) and in the United States was -4.3% per year (P=0.03) (Sauer et al. 2004). Kirk and Hyslop (1998) concluded that he population in Canada is in a long-term decline. However, erratic population fluctuations make trend detection difficult.

NORTH AMERICA: Bent (1938) first noted diminishing numbers, and attributed this to shooting. Although never an abundant breeder in the Midwest, apparently in decline in this region. Various observers relate the decline to loss of habitat, specifically loss of native prairies. Throughout the Midwest, this owl is more commonly seen during migration and in winter. In southern Ontario, it is limited in distribution as a breeder and has declined during this century (Cadman et al. 1987). This decline may be related to the loss of wetlands to agriculture and housing developments. The species may be more abundant in northern Ontario (Cadman et al. 1987). Breeding occurs along the coasts of Hudson and James Bays and in some southern agricultural areas.

Numbers of breeding owls appear to fluctuate considerably in the Maritime Provinces of Canada. Such fluctuations have led to the conclusion that numbers of breeders are no more or less abundant than in the past in this area.

In the Great Plains states and into southern Canada and westward this species is still an abundant nester where there is suitable habitat. However, in some western areas, local and regional declines have been noted; it is a rare and local breeder in Kansas where it was formerly more common; in California the owl is now absent as a breeder from many former nesting locations, particularly along the southern coast. This decline, as with others, is tied to destruction of habitat; in California, marsh and tall grassland particularly are being lost (Remsen 1978). Remsen (1978) also mentioned the owl's vulnerability to shooting as a factor in its decline in California. In more northerly areas, such as northern Canada and Alaska, owls may occur irregularly in relation to the abundance of prey (Pitelka et al. 1955).

In the northeastern United States, this species has never been an abundant breeder. Its numbers, nonetheless, are definitely declining and this decline may be tied to habitat loss (Melvin et al. 1989). Birdlife International (2014) notes a 71.2% decline over the last 40 years.

Intrinsic Vulnerability: Moderately vulnerable
Intrinsic Vulnerability Comments: This species has a strong link with mammalian outbreaks so the population of this species correlates with that of the small mammals on which it preys (Wiggins, Holt, and Leasure, 2006).

Environmental Specificity: Moderate to broad.
Environmental Specificity Comments: Requires open terrain but otherwise from in agricultural areas to the high Arctic (Wiggins, Holt, and Leasure, 2006).

Other NatureServe Conservation Status Information

Inventory Needs: Population status difficult to assess because of nomadic nature of this species along with annual fluctuations. Nationwide inventories are necessary but difficult to coordinate.

Protection Needs: Short-eared Owls appear particularly sensitive to habitat loss and fragmentation, as they require relatively large tracts of grassland and are ground nesters, making them susceptible to the increased predation pressure that is typical within fragmented habitats and near rural developments. The development of conservation/management plans for this owl has been hampered by difficulty in accurately assessing their local and regional status, and by a lack of information on reproductive success. Although they are listed as a Bird of Conservation Concern by the U.S. Fish and Wildlife Service, as well as a Priority species within many state and regional Partners in Flight bird conservation plans, no research programs on the conservation status of short-eared owls are currently underway. The loss of open grassland habitats on the Great Plains and along the Pacific and northern Atlantic coasts has been cited in a number of studies as the primary causative factor behind recent declines in Short-eared Owls in those areas. On the Great Plains, the primary sources of habitat loss have been the conversion of native prairie to agricultural use and overgrazing of existing grasslands. Along coastal areas, which include many wintering sites, recreational use and land development have caused losses of nearshore marsh and oldfield habitats. Habitat restoration programs, such as the Conservation and Wetland Reserve Programs, have shown some success in restoring suitable habitat for short-eared owls on private land. Such programs not only provide suitable nesting and wintering habitat, but they may also help to restore small mammal populations, which are the key resource responsible for population fluctuations of owls. However, it is important to note that large blocks of habitat are essential for short-eared owls, and habitat preservation/restoration programs should aim to conserve large blocks of habitat (>100 ha) (Wiggins, Holt, and Leasure, 2006).

Distribution
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Global Range: (>2,500,000 square km (greater than 1,000,000 square miles)) The breeding range in North America extends from northern Alaska to northern Labrador, south to California, Utah, Colorado, Missouri, Illinois, Ohio, and Virginia. The species breeds in small numbers in every province and territory in Canada (Cadman and Page 1994). It is more numerous in western and central North America than in eastern North America. In the northeastern United States, it currently nests in Vermont, New York, Massachusetts, and Pennsylvania (Tate 1992). In Eurasia the short-eared owl ranges from Iceland, British Isles, Scandinavia, northern Russia, and northern Siberia south to southern Europe, Afghanistan, northern Mongolia, the northern Kurile Islands, and Kamchatka. The species also occurs in the Hawaiian Islands, Caroline Islands (Ponape), and Greater Antilles (Cuba, Hispaniola, Puerto Rico) (AOU 1983). During the nonbreeding season, this owl occurs mostly in the southern parts of most Canadian provinces and southward to southern Baja California, southern Mexico, the Gulf Coast, and Florida; also Hawaii (resident on all main islands) and the Greater Antilles (uncommon in Puerto Rico, including Isla Culebra). In the Old World, nonbreeding occurrences extend from the breeding range south to northwestern Africa, Mediterranean region, Ceylon, southern China, and Japan (AOU 1983).

U.S. States and Canadian Provinces
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, FL, GA, HI, IA, ID, IL, IN, KS, KY, LA, MA, MD, ME, MI, MN, MO, MS, MT, NC, ND, NE, NH, NJ, NM, NV, NY, OH, OK, OR, PA, RI, SC, SD, TN, TX, UT, VA, VT, WA, WI, WV, WY
Canada AB, BC, LB, MB, NB, NF, NS, NT, NU, ON, PE, QC, SK, YT

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: NatureServe, 2002; WILDSPACETM 2002; WWF-US, 2000


U.S. Distribution by County Help
State County Name (FIPS Code)
CA Alameda (06001), Contra Costa (06013), Fresno (06019), Imperial (06025)*, Los Angeles (06037)*, Modoc (06049)*, Monterey (06053)*, San Mateo (06081)*, Solano (06095)
CO Alamosa (08003), Conejos (08021), Delta (08029)*, Eagle (08037)*, Jackson (08057)*, Mesa (08077)*, Moffat (08081), Montezuma (08083)*, Rio Grande (08105)*, Routt (08107)*, Saguache (08109), San Miguel (08113)
CT Fairfield (09001)*, Hartford (09003)*, New Haven (09009)*, New London (09011)*
DE Kent (10001)*, Sussex (10005)*
HI Honolulu (15003)
IA Bremer (19017), Emmet (19063), Guthrie (19077), Howard (19089), Jasper (19099), Kossuth (19109), Palo Alto (19147), Ringgold (19159), Tama (19171), Van Buren (19177), Warren (19181)
ID Ada (16001), Blaine (16013), Clark (16033), Owyhee (16073)
IL Brown (17009), DuPage (17043), Fulton (17057), Jasper (17079), Lee (17103), Marion (17121), Morgan (17137), Perry (17145), Pulaski (17153), Randolph (17157), Richland (17159), Saline (17165)*, Schuyler (17169), St. Clair (17163), Tazewell (17179), Vermilion (17183), Will (17197)
IN Allen (18003)*, Benton (18007), Greene (18055), Knox (18083), Pike (18125), Sullivan (18153), Tippecanoe (18157), Warrick (18173)
KS Hamilton (20075), Logan (20109), Pawnee (20145), Russell (20167), Stevens (20189)
KY Muhlenberg (21177), Ohio (21183)
LA Caldwell (22021), Catahoula (22025), Evangeline (22039)*, Franklin (22041), La Salle (22059)
MA Barnstable (25001), Bristol (25005)*, Dukes (25007), Essex (25009)*, Hampden (25013)*, Nantucket (25019)
MD Queen Annes (24035)*
ME Aroostook (23003)
MI Chippewa (26033)*, Hillsdale (26059), Missaukee (26113)*, Osceola (26133)*
MN Aitkin (27001), Becker (27005)*, Beltrami (27007), Big Stone (27011), Chippewa (27023), Crow Wing (27035), Hubbard (27057)*, Kandiyohi (27067), Lac Qui Parle (27073), Lake of the Woods (27077), Mahnomen (27087)*, Marshall (27089), Otter Tail (27111), Pennington (27113), Polk (27119), Red Lake (27125), Rock (27133), Roseau (27135), Steele (27147), Wilkin (27167), Yellow Medicine (27173)
MO Barton (29011), Carroll (29033), Grundy (29079), Harrison (29081), Knox (29103), Macon (29121), Putnam (29171), St. Charles (29183), St. Clair (29185), Sullivan (29211)
NE Cherry (31031), Garden (31069), Perkins (31135), Sheridan (31161)
NJ Bergen (34003), Cape May (34009), Hudson (34017), Somerset (34035), Warren (34041)
NY Allegany (36003), Cayuga (36011), Chautauqua (36013), Chemung (36015), Clinton (36019), Erie (36029), Essex (36031), Franklin (36033), Genesee (36037), Greene (36039), Herkimer (36043), Jefferson (36045), Kings (36047), Livingston (36051), Madison (36053), Monroe (36055), Montgomery (36057), Nassau (36059), Niagara (36063), Oneida (36065), Onondaga (36067), Ontario (36069), Orange (36071), Orleans (36073), Queens (36081), Richmond (36085)*, Saratoga (36091), Schoharie (36095), Schuyler (36097), Seneca (36099), St. Lawrence (36089), Suffolk (36103), Tompkins (36109), Ulster (36111), Washington (36115), Wayne (36117), Westchester (36119), Wyoming (36121), Yates (36123)
PA Adams (42001)*, Allegheny (42003), Berks (42011)*, Cambria (42021), Chester (42029), Clarion (42031), Crawford (42039)*, Delaware (42045), Lawrence (42073), Lehigh (42077)*, Philadelphia (42101)
UT Beaver (49001), Box Elder (49003), Cache (49005), Daggett (49009), Davis (49011), Duchesne (49013), Garfield (49017), Iron (49021)*, Juab (49023), Millard (49027), Piute (49031)*, Rich (49033)*, Salt Lake (49035), San Juan (49037), Sevier (49041), Summit (49043), Tooele (49045), Uintah (49047), Utah (49049), Wasatch (49051), Washington (49053)*, Wayne (49055), Weber (49057)
VA Mathews (51115)*
VT Addison (50001), Chittenden (50007)*, Grand Isle (50013)
WI Adams (55001), Burnett (55013), Portage (55097)
WY Albany (56001), Big Horn (56003), Campbell (56005), Carbon (56007), Converse (56009), Fremont (56013), Goshen (56015), Hot Springs (56017), Johnson (56019), Laramie (56021), Lincoln (56023), Natrona (56025), Niobrara (56027), Park (56029), Platte (56031), Sheridan (56033), Sublette (56035), Sweetwater (56037), Teton (56039), Uinta (56041), Weston (56045)
* Extirpated/possibly extirpated
U.S. Distribution by Watershed Help
Watershed Region Help Watershed Name (Watershed Code)
01 Meduxnekeag (01010005)+, Maine Coastal (01050002)+, Lower Connecticut (01080205)+*, Cape Cod (01090002)+, Thames (01100003)+*, Quinnipiac (01100004)+*, Housatonic (01100005)+*, Saugatuck (01100006)+*
02 Hudson-Hoosic (02020003)+, Mohawk (02020004)+, Middle Hudson (02020006)+, Rondout (02020007)+, Lower Hudson (02030101)+, Hackensack-Passaic (02030103)+, Sandy Hook-Staten Island (02030104)+*, Raritan (02030105)+, Southern Long Island (02030202)+, Long Island Sound (02030203)+*, Middle Delaware-Musconetcong (02040105)+, Lehigh (02040106)+*, Lower Delaware (02040202)+, Schuylkill (02040203)+*, Brandywine-Christina (02040205)+, Cohansey-Maurice (02040206)+, Broadkill-Smyrna (02040207)+*, Chemung (02050105)+, Chester-Sassafras (02060002)+*, Monocacy (02070009)+*, Great Wicomico-Piankatank (02080102)+*
04 Muskegon (04060102)+*, St. Marys (04070001)+*, St. Joseph (04100003)+, Upper Maumee (04100005)+*, Auglaize (04100007)+*, Chautauqua-Conneaut (04120101)+, Buffalo-Eighteenmile (04120103)+, Niagara (04120104)+, Oak Orchard-Twelvemile (04130001)+, Upper Genesee (04130002)+, Lower Genesee (04130003)+, Seneca (04140201)+, Oneida (04140202)+, Black (04150101)+, Chaumont-Perch (04150102)+, Upper St. Lawrence (04150301)+, Indian (04150303)+, Raquette (04150305)+, St. Regis (04150306)+, Mettawee River (04150401)+, Otter Creek (04150402)+, Lake Champlain (04150408)+
05 French (05010004)+*, Clarion (05010005)+, Middle Allegheny-Redbank (05010006)+, Conemaugh (05010007)+, Upper Ohio (05030101)+, Shenango (05030102)+*, Connoquenessing (05030105)+, Middle Green (05110003)+, Middle Wabash-Little Vermilion (05120108)+, Vermilion (05120109)+, Middle Wabash-Busseron (05120111)+, Little Wabash (05120114)+, Skillet (05120115)+, Lower White (05120202)+, Patoka (05120209)+, Lower Ohio-Little Pigeon (05140201)+, Highland-Pigeon (05140202)+, Saline (05140204)+*
07 Mississippi Headwaters (07010101)+, Prairie-Willow (07010103)+, Elk-Nokasippi (07010104)+, Redeye (07010107)+, South Fork Crow (07010205)+, Upper Minnesota (07020001)+, Lac Qui Parle (07020003)+, Hawk-Yellow Medicine (07020004)+, Blue Earth (07020009)+, Lower St. Croix (07030005)+, Zumbro (07040004)+, Upper Iowa (07060002)+, Castle Rock (07070003)+, Upper Wapsipinicon (07080102)+, Middle Iowa (07080208)+, Green (07090007)+, Upper Des Moines (07100002)+, East Fork Des Moines (07100003)+, South Raccoon (07100007)+, Lake Red Rock (07100008)+, Lower Des Moines (07100009)+, Bear-Wyaconda (07110001)+, North Fork Salt (07110005)+, Peruque-Piasa (07110009)+, Iroquois (07120002)+, Des Plaines (07120004)+, Lower Fox (07120007)+, Lower Illinois-Lake Chautauqua (07130003)+, Mackinaw (07130004)+, La Moine (07130010)+, Lower Illinois (07130011)+, Big Muddy (07140106)+, Cache (07140108)+, Middle Kaskaskia (07140202)+, Lower Kaskaskia (07140204)+
08 Lower Ouachita (08040207)+, Castor (08040302)+, Little (08040304)+, Boeuf (08050001)+, Mermentau Headwaters (08080201)+*, Eastern Louisiana Coastal (08090203)+
09 Otter Tail (09020103)+, Upper Red (09020104)+, Eastern Wild Rice (09020108)+*, Red Lake (09020303)+, Thief (09020304)+, Clearwater (09020305)+, Snake (09020309)+, Two Rivers (09020312)+, Roseau (09020314)+, Rapid (09030007)+, Lower Rainy (09030008)+, Lake of the Woods (09030009)+
10 Clarks Fork Yellowstone (10070006)+, Upper Wind (10080001)+, Little Wind (10080002)+, Muskrat (10080004)+, Badwater (10080006)+, Upper Bighorn (10080007)+, Shoshone (10080014)+, Little Bighorn (10080016)+, Upper Tongue (10090101)+, Middle Fork Powder (10090201)+, Upper Powder (10090202)+, South Fork Powder (10090203)+, Salt (10090204)+, Crazy Woman (10090205)+, Clear (10090206)+, Middle Powder (10090207)+, Little Powder (10090208)+, Antelope (10120101)+, Dry Fork Cheyenne (10120102)+, Upper Cheyenne (10120103)+, Lance (10120104)+, Lightning (10120105)+, Hat (10120108)+, Upper Belle Fourche (10120201)+, Upper Niobrara (10150003)+, Lower Big Sioux (10170203)+, North Platte Headwaters (10180001)+*, Upper North Platte (10180002)+, Middle North Platte-Casper (10180007)+, Glendo Reservoir (10180008)+, Middle North Platte-Scotts Bluff (10180009)+, Upper Laramie (10180010)+, Lower Laramie (10180011)+, Horse (10180012)+, Upper Lodgepole (10190015)+, Upper North Loup (10210006)+, Little Sioux (10230003)+, Stinking Water (10250006)+, Ladder (10260004)+, Lower Saline (10260010)+, Upper Grand (10280101)+, Thompson (10280102)+, Lower Grand (10280103)+, Lower Chariton (10280202)+, Harry S. Missouri (10290105)+, Lower Missouri-Crooked (10300101)+
11 Middle Arkansas-Lake Mckinney (11030001)+, Coon-Pickerel (11030004)+, Bear (11040005)+, Upper Cimarron-Liberal (11040006)+
13 Alamosa-Trinchera (13010002)+, San Luis (13010003)+, Saguache (13010004)+, Conejos (13010005)+
14 Colorado headwaters (14010001)+*, Colorado headwaters-Plateau (14010005)+*, Lower Gunnison (14020005)+*, Upper Dolores (14030002)+, Upper Green (14040101)+, New Fork (14040102)+, Upper Green-Slate (14040103)+, Big Sandy (14040104)+, Bitter (14040105)+, Upper Green-Flaming Gorge Reservoir (14040106)+, Blacks Fork (14040107)+, Muddy (14040108)+, Vermilion (14040109)+, Great Divide closed basin (14040200)+, Lower Yampa (14050002)+, Little Snake (14050003)+, Lower White (14050007)+, Lower Green-Diamond (14060001)+, Duchesne (14060003)+, Lower Green-Desolation Canyon (14060005)+, Upper Lake Powell (14070001)+, Fremont (14070003)+, Escalante (14070005)+, Paria (14070007)+, Mcelmo (14080202)+*
15 Lower Virgin (15010010)+*
16 Upper Bear (16010101)+*, Central Bear (16010102)+, Middle Bear (16010202)+, Little Bear-Logan (16010203)+, Lower Bear-Malad (16010204)+, Upper Weber (16020101)+, Lower Weber (16020102)+, Utah Lake (16020201)+, Spanish Fork (16020202)+, Provo (16020203)+, Jordan (16020204)+, Hamlin-Snake Valleys (16020301)+*, Pine Valley (16020302)+, Rush-Tooele Valleys (16020304)+, Skull Valley (16020305)+, Southern Great Salt Lake Desert (16020306)+, Northern Great Salt Lake Desert (16020308)+, Curlew Valley (16020309)+, Great Salt Lake (16020310)+, East Fork Sevier (16030002)+, Lower Sevier (16030005)+, Beaver Bottoms-Upper Beaver (16030007)+*, Lower Beaver (16030008)+, Sevier Lake (16030009)+
17 Snake headwaters (17040101)+, Lake Walcott (17040209)+, Beaver-Camas (17040214)+, Bruneau (17050102)+, Lower Boise (17050114)+
18 Lost (18010204)+*, Upper Dry (18030009)+, San Joaquin Delta (18040003)+, Suisun Bay (18050001)+, San Pablo Bay (18050002)+, San Francisco Bay (18050004)+*, Alisal-Elkhorn Sloughs (18060011)+*, Antelope-Fremont Valleys (18090206)+*, Salton Sea (18100204)+*
20 Oahu (20060000)+
CA CAPE COD (CAPE COD)+*
+ Natural heritage record(s) exist for this watershed
* Extirpated/possibly extirpated
Ecology & Life History
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Basic Description: A medium-sized owl; 34-42 cm in length with wing span of 95-110 cm. Females larger and heavier than males. Back and upper wing are tawny brown to buff with heavy streaking. Underside is much lighter with bold, vertical brown streaking on the breast. Birds have ear tufts at the top of the facial disk and a dark patch at the base of the primaries.
General Description: A small to medium-sized owl. Published lengths range from 37-39 cm (Cramp 1985) to 34-42 cm (Mikkola 1983), with females slightly larger than males and considerably heavier, averaging 411 g compared to 350 g for males (Mikkola 1983). They are excellent flyers with long wings (95-110 cm) (Cramp 1985), and light wing-loading (0.333 g/cm squared) (Clark 1975). There is little difference in wing length between the sexes (Clark and Ward 1974).

The back and upper wing surfaces are tawny brown to buff-colored with heavy but indistinct streaking. The ventral surfaces are much lighter, with bold, vertical brown streaking on the breast, and a pair of barely visible "ear" tufts close together at the top of the facial disk; belly is pale, lightly streaked; wings are long and have a buffy patch beyond the wrist above and a dark patch at the base of the primaries below; dark facial disk contrasts with yellow eyes; legs and feet are feathered (NGS 1983). Mature males are bright white on the underwing, while mature females show somewhat more buff coloration (Bent 1938, Village 1987). It is, nonetheless, difficult to sex or age these birds in the field. Females are generally darker than males but young birds are also darker than older ones (Mikkola 1983), thus a young male may be darker than an old female. Both sexes have a distinct, black carpal bar and dark wingtips. Juveniles possess full adult plumage by October of the first year (Bent 1938, Cramp 1985).

The facial disc is circular and whitish with dark areas around the bright yellow eyes. Recently fledged and juvenile owls show much darker coloration overall and a much darker facial disc which whitens with age. The owl gets its common name from the small ear-tufts over the eyes. These tufts are part of the facial disc and are erected when the bird is annoyed or alert. They may possibly aid in making birds more cryptic when in vegetation by breaking the line of the circular facial disc.

VOCALIZATIONS: The bird is generally silent but does vocalize in courtship (a low, repeated, hooting: "voo, hoo, hoo, hoo," or in conjunction with defensive behavior or annoyance: "yaps" or "barks"). Young owls give a food-begging call ("pssssip") that apparently aids adults in locating them from the time they leave the nest until after fledging. Adult owls may squeal while feigning injury during broken-wing acts to distract intruders from nests or young. Both young and adults will clack their bills when annoyed or in defense. Apparently, no data exist on the use of broadcasting tape-recorded vocalizations for detection or monitoring purposes.

Diagnostic Characteristics: These are probably the most diurnal of owls (Lockie 1955, Clark 1975) and may often be observed from late afternoon until nightfall, or at dawn. A crow-sized owl abroad during daylight in open country will most likely be a short-eared owl. However, they also hunt at night. Easily recognized by its blunt-headed profile and the fact that it glides with its wings held horizontally. This contrasts with the shallow V-shape of the northern harrier (Circus cyaneus) with which the owl often shares habitat and may be confused. Harriers may also be distinguished by their white rump patch. Habitat is useful in separating short-eared owls from long-eared owls (Asio otis), the latter being predominantly a woodland dweller. The long-eared owl is also more slender with much longer ear tufts. Burrowing owl also inhabits open country but is smaller (24 cm vs. 38 cm), has relatively longer legs, and (in adults) has at least some horizontal barring on the breast. The short-eared owl's style of flight is unique and has at times been called mechanical, moth-like, or even "slovenly" (Peterson 1934).
Reproduction Comments: See Johnsgard (1988) for egg dates (timing of nesting varies with latitude and prey abundance). Often only the oldest chicks survive.

COURTSHIP AND TERRITORIAL DEFENSE: Wing-clapping, exaggerated or deep wing-beats, and skirmishing are three displays seen predominantly during the breeding season (Lockie 1955, Clark 1975). Short-eared owls wing-clap along territorial boundaries or during flights within a territory, in aggressive displays to other birds or to human observers, and in courtship flight. When wing-clapping, the owl's wings are brought below the body and clapped together in short, rapid bursts. Both males and females may wing-clap. The courtship flight is unique and involves song, a spiraling flight, and wing-clapping by the male (DuBois 1924, Mikkola 1983, Holt 1985). Exaggerated wing-beats also occur in the same contexts as wing-claps. In this behavior the owl brings its wings high over its body, prominently displaying the underwing. Owls often patrol territorial boundaries using exaggerated wing-beats. Skirmishing involves other neighboring owls, usually along territorial boundaries, and is aggressive and territorial in nature. Exposure of talons, hovering, and sometimes actual striking of the other bird is involved. Any of these displays observed during the breeding season may signify a territorial bird. Observation and mapping of these behaviors over a nesting season is the best way to delineate an owl's breeding territory (Lockie 1955, Village 1987, Tate 1991).

Generally begin courtship in mid- to late March on Nantucket Island along the coast of Massachusetts (Holt and Melvin 1986; Tate and Melvin 1987, 1988). Courtship has been reported as occurring in mid-March in Montana (Dubois 1924) and as early as late February in Jefferson County, New York (G. Smith, pers. comm.). Pitelka et al. (1955) reported initial courtship activity in the first week of June at Barrow, Alaska. Unpaired males may engage in courtship flights well into the breeding season (Clark 1975; G. Tate, pers. obs.). The breeding season is often reported to commence in direct relation to vole abundance with a larger prey population yielding an earlier start to breeding activities (Randall 1925, Snyder and Hope 1938, Lockie 1955, Mikkola 1983).

NESTING: Depending on latitude, nesting activities generally begin in late winter to early spring across the owl's distribution. Timing of nesting may be correlated with latitude and prey abundance (Mikkola 1983, Cramp 1985). The nesting cycle from nest initiation to fledging of young takes approximately seven to nine weeks in temperate zones lasting from mid-March to mid-September in the Northeast Region. During a four-year study of breeding ecology on Nantucket Island, egg-laying began in April each year (as early as the first week) and all young were fledged by the first week of September (Holt and Melvin 1986; Tate and Melvin 1987, 1988; Combs and Melvin 1989). Late nests or renests accounted for young fledging in late August and September (Tate and Melvin 1987, 1988). Polygyny may result in two nests within one short-eared owl territory. On Nantucket, two broods from different females that overlapped temporally were raised within a territory defended by a single male (Tate 1991).

Unlike most owls that nest in holes or take over the abandoned nests of crows or other birds, the short-eared owl is unique within its family (Strigidae) in building a nest, albeit a crude one, on the ground. The female makes a small scrape in the ground with her body and lines it with nearby material. Nests may be lined with grass, leaves, twigs or feathers (Bent 1938, Clark 1975). These small nest depressions do not last long after the young have dispersed from the site (G. Tate, pers. obs.).

Generally between four and nine eggs are laid, and sometimes more (Bent 1938), although Mikkola (1983) reported a range of two to 13 from 121 European records. Murray (1976) reported a mean clutch size of 5.61 from 186 nests in North America. A trend for mean clutch size to increase from south to north was also noted in this sample. The largest clutch ever reported in the literature is 16 from Finland (Mikkola 1983). Large clutches of 14 in Scotland (Adair 1982) and 13 from Finland (Mikkola and Sulkara 1969) have also been reported. All exceptionally large clutches were laid in years of peak vole abundance in these areas.

Clark (1975) reported a mean clutch of 8.6 from five clutches in 1969 in Manitoba, Canada. Pitelka et al. (1955) reported a range in clutch size of four to eight with a mean of 6.3 from 22 nests in Alaska. A four-year study of nesting owls on Nantucket reported clutch sizes of 5.8 (n = 6), 7.7 (n = 9), 6.8 (n = 8), and 5.2 (n = 8) in 1985-88 respectively, with an inclusive range of four to nine (Holt and Melvin 1986; Tate and Melvin 1987, 1988; Combs and Melvin 1989).

Two broods are sometimes raised and, if the nest is destroyed or depredated, the female may renest (Lockie 1955, Mikkola 1983). Pitelka et al. (1955) saw no evidence of renesting by short-eared owls in Alaska; this was apparently tied to the shorter season. In 1986 and 1987, single late nests with eggs were found on Nantucket in mid-July (G. Tate, unpubl. data). These were suspected to be either second broods or renests.

Witherby et al. (1938) reported an incubation period of 24-28 days in temperate zones. With data from six eggs in four nests, Pitelka et al. (1955) reported an incubation period for Barrow, Alaska, that ranges from 26-37 days (mean = 30). He saw no evidence that incubation takes longer there than at lower latitudes. From a Finnish study of four nests, Gronlund and Mikkola (1969) reported an incubation period of 24-29 days (mean = 25.7). In 1986, three eggs, each from separate nests on Nantucket, were documented as having 29-, 30-, and 31-day incubation periods (mean = 30) (Tate 1991).

Normally the female does all of the incubation (Witherby et al. 1938, Dement'ev et al. 1951, Pitelka et al. 1955, Clark 1975) and lays at approximately 24-hour intervals (Mikkola 1983). She begins incubation with the first egg laid and hatching is therefore asynchronous. According to Mikkola (1983), the first and last eggs laid take the same length of time to incubate. Young owls leave the nest before fledging and wander into the surrounding area at about two weeks of age (Lockie 1955, Clark 1975). The young owlets stay concealed but continue to wander and are found and fed by both parents by means of the food-begging call given by the young. Fledging has been reported variously at 24-27 days (Witherby et al. 1938) and 31-36 days (Urner 1923). On Nantucket, young owls dispersed from the nest at 14-17 days and fledged when about 30 days old (Holt and Melvin 1986).

Age of first breeding is reported as one year or less (Mebs 1966, cited by Mikkola 1983; Glutz von Blotzheim and Bauer 1980). Field evidence of breeding at one year has been obtained on Nantucket in 1990, when a sitting female that had been banded as a nestling in 1989 was trapped. This female was brooding on a nest only 98 m from her natal nest site (K.P. Combs unpubl. data). These owls have been known to live as long as 12.5 years (Mebs 1966, cited by Mikkola 1983).

Short-eared owls usually offer little defense of the nest from human intruders. Wing-clapping, circling overhead with deep wing beats, "barks" or "yaps," and broken-wing acts are employed when any defense is attempted. Adults perform a distraction display that is a dramatic broken-wing act accompanied by vocalization. It is most often used by the male when an observer is at, or near, a nest or dispersed young (Clark 1975; G. Tate, pers. obs.). However, often both owls vacate the vicinity of the nest site while an intruder is present. At times the female may desert the area, retreating to another part of the breeding territory, while the male remains nearby. Females may return to the nest by flying low and remaining inconspicuous (G. Tate, pers. obs.).

While short-eared owls have been observed diving at house cats (G. Tate, pers. obs.), the best defense is their cryptic coloration and the fact that the female sits tightly on the nest. On Nantucket, some females remained on the nest while observers passed within two meters, and on Tuckernuck Island, a female on a nest would not budge in spite of repeated attempts from as close as one meter to flush her (G. Tate, pers. obs.). These behaviors make it extremely difficult to find nests.

Ecology Comments: Somewhat gregarious in winter; groups may gather where prey is abundant (NGS 1983, Tate 1992). Breeding density in different areas 0.6-6 pairs per sq km. May defend feeding territory in winter (where prey is sufficient). Reported average home range size: 15-200 ha. In coastal Massachusetts, 10 territories averaged 64 ha (48-126 ha) (Holt 1992). In Manitoba, mean size of five territories was 73.9 hectares (Clark 1975).

Local abundance varies with vole abundance. In the winter, short-eared owls congregate at sites that provide good foraging (Craighead and Craighead 1956). Congregations of up to 200 birds have been reported (Bent 1938). Assemblage sites usually provide shelter and are within, or adjacent to, hunting areas (Clark 1975). In wintering areas in New York where vole densities were high, Clark (1975) saw owls establish and defend hunting territories. Territories were less distinct when vole numbers were low.

DISEASES, PARASITES, AND PREDATION: Disease is presently not known to limit populations. Harrison (1943) reported an owl infected with Mycobacterium tuberculosis avium In 1987, four young owls from two widely separated nests on Nantucket Island were discovered to be suffering from a feather disorder of unknown cause (Tate 1991), in which the juvenal plumage was not developing properly and the emerging feathers were twisted or malformed. All of these young had developed open sores, apparently from picking at the skin around these feather shafts with their beaks. This problem is not known to have been reported previously in the literature and no cause was determined. Avian predation is known from: great horned owl (Bubo virginianus), snowy owl (Nyctea scandiaca), peregrine falcon (Falco peregrinus), and marsh harrier (Circus aeruginosus) (Clark 1975). Northern harrier, American crow (Corvus brachyrhynchos), and European kestrel (Falco tinnunculus) have been known to steal prey from short-eared owls (Village 1987, Tate 1991).

Habitat Type: Terrestrial
Non-Migrant: Y
Locally Migrant: Y
Long Distance Migrant: Y
Mobility and Migration Comments: Breeding populations throughout most of Canada and north-central U.S. move south for winter. Somewhat nomadic. Arrives in northern breeding areas mid-May to early June (Johnson and Herter 1989). Migrational patterns are not well known. Apparently more northerly parts of the range are vacated in the fall and the owls move southward (Craighead and Craighead 1956, Clark 1975). In North America the movement is mostly from Canada and Alaska as far south as the southern U.S. and even Mexico (Cramp 1985). Toward the central part of the species' range (temperate zones) owls are seen year-round. Because breeding birds move south in fall and winter and are replaced by migrants from more northerly areas, Clark (1975) suggests that separate populations may occupy these areas during the different seasons.

It is also possible that the owl migrates only in search of food and therefore may remain year-round in an area that provides sufficient resources. The owl congregates in areas where prey is plentiful (Bent 1938, Mikkola 1983) and may migrate accordingly. This feature of the biology has earned it a reputation as an "irregular migrant," or as "nomadic," "irruptive," or "vagrant" (Clark 1975, Mikkola 1983).

Estuarine Habitat(s): Herbaceous wetland
Palustrine Habitat(s): Bog/fen, HERBACEOUS WETLAND
Terrestrial Habitat(s): Cropland/hedgerow, Grassland/herbaceous, Old field, Savanna, Tundra
Habitat Comments: BREEDING: Broad expanses of open land with low vegetation for nesting and foraging are required. Habitat types frequently mentioned as suitable include fresh and saltwater marshes, bogs, dunes, prairies, grassy plains, old fields, tundra, moorlands, river valleys, meadows, savanna, open woodland, and heathland (Dement'ev et al. 1951, Clark 1975, Mikkola 1983, Holt and Melvin 1986). In general, any area that is large enough, has low vegetation with some dry upland for nesting, and that supports suitable prey may be considered potential breeding habitat, although many will not have breeding short-eared owls. Dement'ev and Gladkov (1951) assert that "nearby water" is a requirement for nesting habitat. Roosts by day on ground, on low open perch, under low shrub, or in conifer. Reported from "forest" habitats in Hawaii.

Nests on ground, generally in slight depression (Terres 1980), often beside or beneath a bush or clump of grass. Many nests are near water but generally are on dry sites. In coastal Massachusetts, nested in secondary herbaceous grass/sand dune vegetation dominated by Ammophila (Holt 1992). Same nest site may be used in successive years. Moves into and breeds in areas with high rodent densities.

Generally nest on high ground or upland sites (Pitelka et al. 1955; Clark 1975; Holt and Melvin 1986; Tate and Melvin 1987, 1988; Combs and Melvin 1989). Urner (1925) reported nests in a saltmarsh, one of which was subsequently flooded by a high tide, but in general, drier sites are preferred. During five years of study on Nantucket and Tuckernuck islands, all 41 nests found were in dry upland areas, though wetter sites were available (Holt and Melvin 1986; Tate and Melvin 1987, 1988; Combs and Melvin 1989; Combs and Griffin 1990). Eight nest sites at Monomoy National Wildlife Refuge, east of Nantucket, found between 1982 and 1985, were also all on dry upland sites (Holt and Melvin 1986).

Using a line-intercept technique (Brower and Zar 1977, Holt and Melvin 1986), vegetation characteristics of 15 nest sites on Nantucket were evaluated in 1986 and 1987. This analysis showed that low dense shrubs, mainly black huckleberry (Gaylussacia baccata) and bayberry (Myrica pennsylvanica), that were less than 0.5 m comprised 40.4%, and high dense shrubs (same species, >= 0.5 m) comprised 37.14% of the cover within five meters of the nest (Tate and Melvin 1987, 1988). Other vegetation included low sparse shrubs (11.1%), low dense grass (8.1%), and high dense grass (3.0%, mostly Andropogon scoparius and Ammophila breviligulata). These data demonstrate that in choosing nest sites on Nantucket, dense shrub cover is usually sought.

NON-BREEDING: Suitable breeding habitat may also be occupied by wintering birds. Conversely, Clark (1975) noted two occasions when winter territories became breeding territories. Short-eared owls tend to congregate and roost communally in the winter (Banfield 1947, Craighead and Craighead 1956, Clark 1975), often in sheltered sites near hunting areas. Winter roosts have been reported in abandoned dumps, quarries, gravel pits, storage yards, stump piles, old fields, small evergreen groves, bayberry thickets, dunes, and open, abandoned cellars (Clark 1975, Bosakowski 1986). May also roost directly on the ground in tall grasses, possibly choosing vegetation of a coloration that blends with their plumage (Craighead and Craighead 1956).

In winter the ground roosting habit may be abandoned for trees, possibly in response to deep snow (Banfield 1947, Bosakowski 1986). Smith (1989) noted drastic decreases in numbers of short- eared owls at known winter roosts on Point Peninsula in Jefferson County, New York, after a heavy snowfall created deep cover.

Adult Food Habits: Carnivore
Immature Food Habits: Carnivore
Food Comments: Eats mainly rodents (commonly Microtus); also regularly other small mammals, small birds (especially in coastal areas), and insects (Terres 1980, Holt 1993a, Holt 1993b). Forages primarily by flying low, typically into wind, and dropping down onto prey, sometimes after brief hover. Sibling cannibalism may occur. Sometimes caches food. Prey is small mammals and some small birds; unfledged young may also take some insects. The preferred prey is often reported as microtine rodents (Goddard 1935, Lockie 1955, Mikkola 1983). Clark (1975) reported meadow voles (Microtus pennsylvanicus) in ? 91% of pellets analyzed from a winter roost in New York between 1967 and 1970. Pitelka et al. (1955) found that short-eared owls breeding in Barrow, Alaska, fed solely on brown lemmings (Lemmus sibiricus). Mikkola (1983) summarized studies of prey items taken in the breeding season in Finland, Norway, Germany, and Hungary and found that voles (Microtus spp.) made up 78.9%, 65.1%, 94.6%, and 21.1% of the diet respectively. In Hungary, shrews (Soricidae) predominated in 69.9% of the diet while in Finland and Norway, voles (Clethrionomys spp.) and shrews accounted for most of the other identifiable prey items. Two voles, Microtus agrestis and M. arvalis, comprised 98% of all prey species in a Finnish study in 1977 (Korpimaki 1984).

On Nantucket Island, seven species of small mammals were identified from prey remains in 1,992 short-eared owl pellets collected over two years (1986-87), predominately during the spring and summer (Tate 1991). Of these, meadow voles (M. pennsylvanicus) were the most abundant, accounting for 89% of prey items. Short- tailed shrews (Blarina brevicauda) and white-footed mice (Peromyscus leucopus) each comprised 3% of the total, with birds and insects making up 2.5% and 1.0%, respectively. Analysis of 1,214 pellets collected on Nantucket in 1985 showed that meadow voles comprised 93.3% of total prey remains (Holt and Melvin 1986).

Short-eared owls are attracted to areas with abundant food resources, and may breed opportunistically and sporadically in such areas. When they do find areas of especially abundant resources they may breed in large numbers (Pitelka et al. 1955, Beske and Champion 1971, Larsen 1987) and produce super-normal clutches (Adair 1982, Goddard 1935).

Short-eared owls hunt predominantly by flying low over open areas in coursing flights much like those of northern harriers. Upon detecting prey the owl drops or pounces, sometimes briefly hovering beforehand. They may also hunt from a perch and dive directly on prey. At times they also hunt using a hovering flight similar to American kestrels (Falco sparverius). They hang in the air for protracted periods of time at considerable heights until prey is sighted. As Clark (1975) notes, this protracted hovering has often been reported in the European literature but has been seldom mentioned for North American birds. On Nantucket, they were most often observed hunting in this fashion over dunes of grasses (Ammophila breviligulata) (G. Tate, pers. obs.).

During the breeding season, food is sometimes cached (Young et al. 1988). On Nantucket Island three separate owls were observed caching food on four separate occasions. Each cache involved meadow voles that were taken short distances from the site of capture and placed beneath small shrubs. Each owl then resumed hunting (Tate 1991). Short-eared owls were observed caching food in Jefferson County, New York, during a winter when food resources appeared abundant (G. A. Smith, pers. comm.).

Adult Phenology: Circadian, Crepuscular, Diurnal
Immature Phenology: Circadian, Crepuscular, Diurnal
Phenology Comments: May forage day or night; may favor late afternoon and early evening (Johnsgard 1988). Hunts chiefly at dawn and dusk (National Geographic Society 1983). Active day or night in Hawaii (Pratt et al. 1987, Berger 1981).
Length: 38 centimeters
Weight: 378 grams
Economic Attributes Not yet assessed
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Management Summary
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Stewardship Overview: Have never been an abundant breeder in the Northeast, but fewer are now known from historical nesting sites. Today in the region, short-eared owls nest only in Vermont, New York, Massachusetts, and Pennsylvania. Populations traditionally fluctuate in response to the cycles of microtine rodents, their preferred food base, but loss of suitable breeding habitat to land-use changes appears to be the major limiting factor. Their ground-nesting habits in grasslands, saltmarshes, and on offshore islands renders the birds susceptible to mammalian predators, whose numbers are enhanced by human disturbance. Large tracts of open habitat are required for breeding and hunting. These must be maintained in order to enhance the regional population. The level of breeding success is unknown in fragmented habitats. Adequate monitoring techniques are currently lacking to track populations (Tate 1992).
Restoration Potential: Evidence that short-eared owls have begun to breed in recovered strip-mine areas of Pennsylvania and possibly Ohio is encouraging. Although breeding populations in the Northeast and the Midwest are declining, large breeding populations still exist in other parts of the country. Recovery of the Northeast population depends on restoration of large areas of open habitat and an influx of breeding birds (Tate 1992).
Preserve Selection & Design Considerations: Some useful data exist on which to base preserve designs for conservation. Acreage of breeding territories has been estimated in a few studies. These data should serve as guidelines for the minimum acreage necessary for breeding since nocturnal habitat use is seldom documented.

From the available data it is obvious that land preservation efforts must be aimed at protecting large tracts of open habitat with low vegetation. In areas where short-eared owls nest, observation of hunting flights and territorial displays during the breeding season will help to delineate areas used by resident owls. Any adjacent similar habitat not used by the birds should be considered potential habitat. Areas of approximately 50 ha or larger, of low, open grasslands or similar habitat with abundant small mammal populations should also be considered as potential breeding or wintering habitat. Because of the abundance of coastal sightings in the Northeast in winter, protection of large areas of coastal grassland, heaths, and saltmarshes for wintering owls is also recommended.

Management Requirements: Management procedures should address known and suspected limiting factors. Melvin et al. (1989) listed limiting factors in the Northeast as (1) availability of suitable habitat, (2) sufficient prey abundance, (3) predation, and (4) human-related disturbance.

Management for suitable habitat includes maintaining large tracts of open grassland, salt or freshwater marshes, or other appropriate habitat. Protection of such habitat is crucial to the persistence of breeding and wintering short-eared owls in the Northeast and elsewhere. Restoration or new establishment of grasslands (e.g., from strip-mined areas) may offer potential habitat.

Active maintenance of open habitat may be beneficial to short-eared owls where succession to woody vegetation occurs. Any management practice used to maintain open habitat and inhibit the growth of woody vegetation, such as mowing or burning, might be used. However, these management practices must be employed outside the nesting season to avoid the destruction of nests, eggs and young. In addition, care must be taken to allow for adequate build-up of the litter layer that provides habitat for microtine rodents. MICROTUS populations require adequate cover for several aspects of their ecology (Birney et al. 1976). Maintenance of an adequate prey base is essential since distribution and abundance seems to be tied to prey density (Adair 1892, Lockie 1955, Clark 1975, Melvin et al. 1989).

Management might include the control of predators in areas where the owls nest, where populations of potential ground predators are high, and where predators are known to have a significant impact on owl nesting success. However, trapping and removal of predators or elimination of predators by killing is seldom practical. Predator exclosures have apparently never been used at short-eared owl nests. Their design would have to take into account the dispersal of the young on foot and the type, or types, of ground predators to be excluded.

Educational programs on the natural history, ecology, and conservation of short-eared owls, other raptors, and grassland birds might help alleviate human-related disturbances, such as shooting and harassment by domestic pets. Education should address the need to legally protect declining species and the consequences and benefits of legal protection. Education could also lead to an increased willingness to preserve habitat. Although single-species protection is important, education aimed at increasing the awareness of the inclusive benefits of habitat protection is now needed. Preservation of open habitat in the form of grasslands, heathlands, marshes, etc., is a key component in the preservation of a number of declining birds. Such species as grasshopper sparrow (AMMODRAMUS SAVANNARUM), Henslow's sparrow (A. HENSLOWII), upland sandpiper (BARTRAMIA LONGICAUDA), loggerhead shrike (LANIUS LUDOVICIANUS), and northern harrier would also benefit from an increased effort to preserve or restore open habitat. This knowledge should be an added incentive to proponents for open habitat preservation (Tate 1992).

Monitoring Requirements: Adequate population monitoring techniques need to be developed; female does not readily flush from nest; diligent search or dragging rope across area may reveal nest site; precautions should be taken against leading ground predators to nests (Tate 1992). Apparently, no data exist on the use of broadcasting tape-recorded vocalizations for detection or monitoring purposes.

Combs and Griffin (1990) reported that birds are most visible in June on Nantucket Island. Abundance was estimated by driving standard survey routes within territories and counting birds seen during early mornings and late afternoons. The owls are often active in early mornings, at dawn and just after, and late afternoons, two to three hours before sunset. Therefore, counts at these times of day are most beneficial for accurately censusing populations. On Nantucket most young have left the nest in June and are either dispersed nearby or have recently fledged (Holt and Melvin 1986; Tate and Melvin 1987, 1988; Combs and Melvin 1989). Therefore, population counts at this time would presumably include both adult males and females since the female is no longer on the nest. Seasonal timing of monitoring is important in obtaining an accurate count of total number of breeding pairs in an area. Fledged young may also be distinguished at this time by their darker overall coloration.

The general area of a nesting can be ascertained by diligent observation. If one is fortunate enough to observe courtship there is a very good likelihood that the pair will nest in the immediate vicinity (D. Holt, pers. comm.). Nests can be found by walking the area in question on foot in an attempt to flush the female. Repeated, systematic coverage is often needed due to the tenacity of the sitting female. During nest visits precautions should be taken against leading ground predators to nests.

Many short-eared owl nests have been found incidental to an ongoing study of waterfowl nesting at Grizzly Island Wildlife Area in California. Surveys of nesting waterfowl were made using a drag rope. It was concluded that this method was also efficient for surveying areas for nesting owls (Larsen 1987).

Management Research Needs: Adequate monitoring procedures are needed. Many of the present monitoring techniques, such as walking large areas in an attempt to flush sitting females, are labor and time intensive. Furthermore some procedures, such as counting birds seen from roadsides, may underestimate the number of individuals present. Short-eared owls are relatively inconspicuous and easily missed. Development and implementation of a standardized population monitoring procedure throughout the Northeast should be a high research priority.

Expanded efforts are needed to locate and study local breeding and wintering populations to (1) accurately determine number of breeding or wintering birds, (2) locate regularly occurring populations which would facilitate long-term ecological studies, and (3) determine more precisely the limiting factors and management needs of these populations. The location of regularly breeding and wintering populations would provide the data necessary for land protection efforts. The mapping of territories on Nantucket and Tuckernuck Islands, for example, has allowed the protection of known breeding sites by conservation organizations (Tate and Melvin 1987).

Mapping of breeding territories through the observation of territorial displays during the breeding season allows for good estimation of territory size (Lockie 1955, Tate 1991). More data is needed concerning relationships between territory size and the abundance of small mammals to determine the amount of open habitat and the prey base necessary to support a breeding pair. Such information would enhance the efficacy of land preservation efforts.

Research on the management of open habitat and its effect on prey populations is needed. The effect of such practices as burning, mowing, or plowing on small mammal populations must be taken into account. Any management for the restoration or maintenance of open grassland habitat must also manage for a sufficient prey base.

The question of habitat fragmentation, or isolation, may be important. Continuous expanses of open habitat are rare in the Northeast. The high mobility of the owl may allow it to utilize disjunct areas of habitat, but whether it will occupy an isolated patch of appropriately-sized habitat and breed successfully is not known. Wildlife managers seeking to design preserves would need to know to what degree utilization of fragmented habitat is detrimental to the owl's territorial integrity and breeding success.

Other research needs include (1) the investigation of nocturnal movements, (2) the study of movement in and out of isolated populations, e.g., Nantucket Island and Monomoy National Wildlife Refuge, and (3) estimates of adult and juvenile annual mortality.

Despite important research needs, there is presently enough information to effectively guide conservation efforts in the Northeast. Attention to conservation needs is needed soon if the short-eared owl is to persist as a breeding bird in the Northeast (Tate 1992).

Biological Research Needs: A critical research priority is to establish a long-term population monitoring program. This would best be carried out by annually monitoring breeding and wintering abundance at sites where owls are known to occur on a frequent basis. Satellite monitors (once available) could be used to track movement of individual owls and provide valuable data on seasonal and annual movements, including fidelity to breeding and wintering areas. Changing land-use practices on the Great Plains may be benefiting Short-eared Owls, but assessments are needed on how land set-aside programs (e.g., CRP, GRP) may be benefiting breeding and wintering owls.(Wiggins, Holt, and Leasure, 2006).
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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NatureServe Conservation Status Factors Edition Date: 10Nov2014
NatureServe Conservation Status Factors Author: Gotthardt, T. A., J. G. McClory, and G. Hammerson. Reviewed by Jack Whitman, Alaska Dept of Fish and Game, Fairbanks, AK. Further review by Dean and Sally Jue of the Florida Natural Areas Inventory
Management Information Edition Date: 13Nov1997
Management Information Edition Author: TATE, G. R.; REVISIONS BY D. W. MEHLMAN
Management Information Acknowledgments: Parts of this abstract were originally published by the U.S. Fish and Wildlife Service in Schneider and Pence (1992). Funding for the preparation of the original document was made possible by the U.S. Fish and Wildlife Service, Newton Corner, MA. Over the course of compiling the report the following people from across the country were contacted for state-specific or regional information, or for leads to appropriate literature or sources: J. Bazuin, D. Brauning, B. Busby, K. Combs, B. Dalzell, L. Davidson, D. Figg, C. Hedge, D. Holt, B. Jacobs, D. Paul, W. R. Peterson, D. Rice, J. Sheppard, T. Simmons, and G. A. Smith. G. A. Smith also reviewed and provided helpful suggestions on an early draft of the report. The author would like to especially thank J. E. Ebersole, J. J. Hatch, and R. Nickerson for reading and commenting on subsequent drafts. S. Melvin was helpful during many stages of this work in reviewing drafts, adding suggestions, and providing support. All of it is appreciated.
Element Ecology & Life History Edition Date: 30Mar1995
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).

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