Tyto alba - (Scopoli, 1769)
Barn Owl
Other Common Names: Suindara
Taxonomic Status: Accepted
Related ITIS Name(s): Tyto alba (Scopoli, 1769) (TSN 177851)
French Common Names: effraie des clochers
Spanish Common Names: Lechuza de Campanario, Buho
Unique Identifier: ELEMENT_GLOBAL.2.100734
Element Code: ABNSA01010
Informal Taxonomy: Animals, Vertebrates - Birds - Other Birds
 
Kingdom Phylum Class Order Family Genus
Animalia Craniata Aves Strigiformes Tytonidae Tyto
Genus Size: C - Small genus (6-20 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: Tyto alba
Taxonomic Comments: Formerly known as Common Barn-Owl. Closely related to and sympatric with T. glaucops (Ashy-faced Owl) of Hispaniola (AOU 1998). Some authors suggest that populations in the Australian region may constitue a separate species, T. delicatula (AOU 1983).
Conservation Status
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NatureServe Status

Global Status: G5
Global Status Last Reviewed: 10Apr2016
Global Status Last Changed: 27Nov1996
Ranking Methodology Used: Ranked by inspection
Rounded Global Status: G5 - Secure
Nation: United States
National Status: N5 (05Jan1997)
Nation: Canada
National Status: N2B,N1N,NUM (14Dec2017)

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 (S3), Arizona (S5), Arkansas (S3), California (SNR), Colorado (S4B), Connecticut (S1), Delaware (S3), District of Columbia (S1), Florida (SNR), Georgia (S3S4), Idaho (S4), Illinois (S1S2), Indiana (S2), Iowa (S1B), Kansas (S3), Kentucky (S3), Louisiana (S5), Maryland (S2), Massachusetts (S2B,S2N), Michigan (S1), Mississippi (S3), Missouri (S3), Montana (S4), Navajo Nation (S3?B), Nebraska (S3), Nevada (S4), New Jersey (S3B,S3N), New Mexico (S4B,S4N), New York (S1S2), North Carolina (S2S3B,S3N), Ohio (S2), Oklahoma (S3), Oregon (S4?), Pennsylvania (S3B,S3N), Rhode Island (S1B,S1N), South Carolina (S4), South Dakota (S2B), Tennessee (S3), Texas (S5B), Utah (S3), Vermont (S1B), Virginia (S3B,S3N), Washington (S4), West Virginia (S2B,S2N), Wyoming (S2)
Canada British Columbia (S2?), Ontario (S1), Quebec (S1B)

Other Statuses

Implied Status under the Committee on the Status of Endangered Wildlife in Canada (COSEWIC):E,T
Comments on COSEWIC: The species was considered a single unit and designated Special Concern in April 1984. In April 1999, the Western and Eastern populations (Tyto alba pop. 1 and Tyto alba pop. 2, respectively) were assessed separately. The original designation for the Canadian range of the Barn Owl was de-activated.
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: RESIDENT: In the Americas from southern Canada and the northern U.S. south to southern South America, Greater Antilles (except Puerto Rico), and Lesser Antilles (AOU 1983, Marti 1992). Variable occurrence within this range, with low densities at northern periphery (Marti 1992). In Old World from British Isles, southern Russia, and southern Siberia south through Eurasia and Africa to southern Africa, Madagascar, East Indies, and Australia. Populations in northern North America are partially migratory. Introduced (1958 and later) in Hawaii; now on all main islands (AOU 1983).

Population Size Comments: In Canada, breeding population consists of about 250-275 pairs in British Columbia and 25-30 pairs in Ontario (Campbell and Campbell, 1984 COSEWIC report). Kirk et al. (1995) reported the estimated number of breeding pairs in Canada as 250-750.

Overall Threat Impact Comments: Population declines have been attributed mainly to commercial development of farmland, reduction in dairy and sheep industry, conversion to intensive row-crop farming, and decline in the number of farms and old farm structures, resulting in a loss of nest sites and important high-quality foraging habitat. Foraging habitat availability appears to limit numbers most significantly (Colvin et al. 1984, Colvin 1985, Rosenburg 1986, Ehresman et al. 1989, Gubanyi 1989). Loss of farmland to development and the intensification of agricultural practices on remaining farmlands have substantially reduced the quantity and quality of dense grass habitats in agricultural areas (Honer 1963, Shrub 1970, Colvin 1985, Rosenburg 1986). The availability of pasture and grass hayfield has been reduced substantially. Colvin (1985) reported an approximately 53% decline in hayfield acreage in Ohio between 1921-80 and identified a significant correlation between a population decline in Ohio and the replacement of grass-associated agriculture by row crops. In Virginia, the acreage of pasture, grass hayfield, and idle areas was reduced 55% between 1945-78 and the quality of pasture declined because of increased grazing pressure (Rosenburg 1986). In many intensively-farmed areas, dense grass habitats are present only in small fields that are patchily distributed; such fields would apparently provide a limited foraging resource (Rosenburg 1986). The reduced quality and quantity of dense grass habitats has substantially reduced prey availability in some areas. Prey availability has been shown to be closely associated with owl productivity (Ault 1971, Otteni et al. 1972, Colvin 1984, Gubanyi 1989). This association is so close that one year of poor meadow vole abundance can result in a rapid population decline while one year of substantial meadow vole abundance can result in rapid population recovery (B. Colvin, pers. comm.). NEST SITE AVAILABILITY: The availability of secure nest sites is an important limiting factor in some areas (Marti et al. 1979, Schulz and Yasuda 1985, Byrd and Rosenburg 1986, Gubanyi 1989). Tree cavity sites may be limited in availability (Rosenburg 1986), they are ephemeral (Colvin et al. 1984, Byrd and Rosenburg 1986), and relatively insecure (Colvin et al. 1984). Competition for this resource may also be a factor; Colvin (1984) documented usurpation of nest cavities by wood ducks (AIX SPONSA) and raccoons (PROCYON LOTOR). Secure nest sites within human-made structures are limited in availability (Schulz 1986; C. Rosenburg, unpubl. data). In addition, the gradual deterioration and disappearance of old-style barns, silos, and water tanks plus the screening of entrances to prevent rock dove (COLUMBA LIVIA) access has eliminated many previously productive nest sites (Honer 1963, Heintzelman 1966, Schulz and Yasuda 1985, Byrd and Rosenburg 1986, Parker and Castrale 1990). Areas that support abundant foraging habitat may lack an adequate supply of secure and stable nest sites in close proximity to foraging habitat. Kirkpatrick and Colvin (1986) suggested that salmonellosis may limit survival and reproduction at times when stresses, such as severe weather and poor prey availability, are acting. This stress dependent impact may be true for other diseases and parasites as well (Honer 1963, Kirkpatrick and Colvin 1989). Weather is the most important factor influencing annual productivity in southwestern New Jersey (B. Colvin, pers. comm.). Moist weather conditions enhance dense grass habitats and thereby enhance vole populations, which results in higher productivity. Exceedingly dry conditions have a negative impact on vole populations and result in poor productivity (Colvin and Hegdal 1986, 1987, 1988, 1989). Starvation of chicks, the single most important mortality factor (B. Colvin, pers. comm.), is widespread during exceedingly dry conditions. Throughout the Northeast, the owl is susceptible to starvation and exposure during extended periods of extreme cold and deep snow cover. Winter weather mortality has been documented in Wisconsin (Errington 1931), Illinois (Speirs 1940), Ohio (Stewart 1952), Massachusetts (Keith 1964), Utah (Marti and Wagner 1985), and Virginia (C. Rosenburg, unpubl. data). Marti and Wagner (1985) reported that some winter weather mortality appears to occur every winter in northern Utah and that such mortality is widespread and consequential in some years. They found 77 dead owls after severe weather during the winter of 1981-82, and a 40% decline in breeding attempts occurred the following summer. Keith (1964) documented winter weather mortality of more than ten owls during the winter of 1960-61 and the subsequent lack of nesting during the following three breeding seasons at Martha's Vineyard, Massachusetts. Barn owls did not nest at Martha's Vineyard again until 1973 (Brett 1987). PESTICIDES: Secondary poisoning from rodenticides has been considered to be a potential hazard because of the importance of rodents in the diet and the fairly widespread use of rodenticides in agricultural areas. Laboratory studies have demonstrated that the consumption of rats or mice poisoned with bromadiolone or brodifacoum rodenticides can cause lethal hemorrhaging and that consumption of rats poisoned with difencoum rodenticide can cause sublethal hemorrhaging (Mendenhall and Pank 1980; Newton et al., in press). These studies demonstrated that the owl is especially sensitive to the anticoagulant brodifacoum. Secondary poisoning from rodenticides has been documented in the U.S. (Schulz 1986; L. Soucy, pers. comm.) and Great Britain (Newton et al., in press). The potential for poisoning appears to be greatest in marginal habitat areas such as intensively farmed sites (Rosenburg 1986). However, there appears to be no appreciable impact to populations from rodenticide poisoning (Colvin 1984; Hegdal and Blaskiewicz 1984; Newton et al., in press). Organophosphate insecticides have been shown to be potentially hazardous. Laboratory experiments conducted by Hill and Mendenhall (1980) demonstrated that owls which consumed famphur-poisoned prey exhibit secondary poisoning in the form of significant cholinesterase inhibition. Mass mortality of wild raptors, including 22 barn owls, occurred after azodrin was improperly used to kill voles in Israel (Mendelssohn and Paz 1977). Rodents contaminated with organophosphate and carbamate insecticides are present in agricultural fields (Montz 1988). These rodents are potentially hazardous to raptors because birds in general are extremely sensitive to anti-cholinesterase compounds (Brealey et al. 1980). It is unlikely that organophosphate or carbamate insecticides have impacted populations since these pesticides are not targeted for foraging habitats or prey species (B. Colvin, pers. comm.). However, no field studies have examined cholinesterase levels of owls in agricultural areas where these pesticides are widely used. Further investigation may be warranted (L. Brewer, pers. comm.). The owl is sensitive to contamination from organochlorine insecticides. Laboratory studies by Mendenhall et al. (1983) found that it is very sensitive to eggshell thinning by DDE and that dieldrin can cause adult mortality. These insecticides were found in concentrations that may have been detrimental to reproduction in 15% of the barn owls in the lower Potomac River, Maryland in the early 1970s (Klaas et al. 1978). Extensive feeding on passerine birds by this portion of the population is believed to have caused the elevated organochlorine levels; the majority of the population preyed chiefly on mammals and remained relatively uncontaminated. In Great Britain, poisoning from organochlorine pesticides was an important cause of mortality during the years 1963-77 when these chemicals were used extensively (Newton and Wyllie, in press). Organochlorine insecticide residues have been found in barn owls and their eggs collected in Florida (Johnston 1978), Oregon (Henny et al. 1984), and Virginia (Gwynn 1987). Acute effects from organochlorine insecticides are unlikely, though, since raptors which feed chiefly upon small mammals are not highly susceptible to organochlorine insecticide poisoning (Henny 1972) and since few potentially harmful organochlorine insecticides are in use in the U.S. today (Newton 1979; S. Wiemeyer, pers. comm.). OTHER FACTORS: A number of other mortality factors have been identified. Collision with vehicles has been reported as an important mortality factor (Glue 1971; Smith and Marti 1976; Keran 1981; Schulz 1986; Newton and Wyllie, in press). Drowning of young as they attempt to fledge from offshore duck blinds appears to be acting as a population sink in coastal Maryland and possibly other areas where substantial numbers nest in these structures (G. Therres, pers. comm.). Other mortality factors include electrocution, entrapment in buildings, shootings, and entanglement in farm or industrial machinery (Glue 1971; Smith et al. 1974; Smith and Marti 1976; Keran 1981; Colvin 1984; Hegdal and Blaskiewicz 1984; Lerg 1984; Schulz and Yasuda 1985; Schulz 1986; Ehresman et al. 1989; Newton and Wyllie, in press; C. Rosenburg, unpubl. data). The degree to which these latter four factors limit numbers appears to be low. PREDATION: May limit numbers in some areas. Raccoons and black rat snakes (ELAPHE OBSOLETA) prey on eggs and nestlings (Ehresman 1984; B. Colvin, pers. comm.; C. Rosenburg, unpubl. data), and great horned owls (BUBO VIRGINIANUS) prey on juveniles and adults (Rudolph 1978, Knight and Jackman 1984, Lerg 1984, Rosenburg 1986, Millsap and Millsap 1987, Ehresman et al. 1989) and may inhibit barn owl activity because of their dominance (Rudolph 1978). Information concerning predation rates on eggs, nestlings, juveniles, and adults is limited and further investigation is warranted (Hands et al. 1989).

Short-term Trend Comments: Population declines have been evident in the Midwest and Northeast U.S. and have been reported in several other areas. Western U.S. populations appear to be mostly stable (Marti and Marks 1987). See Rosenburg (1992) for information on status in particular states in the northeastern U.S. See Hands et al. (1989) for information on status in the north-central U.S. Trend in Canada was reported as "stable" by Kirk et al. (1995), probably slowly declining by Campbell and Campbell (1984).

Other NatureServe Conservation Status Information

Protection Needs: In the northeastern U.S., large tracts of foraging habitat need to be protected.

Distribution
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Global Range: (>2,500,000 square km (greater than 1,000,000 square miles)) RESIDENT: In the Americas from southern Canada and the northern U.S. south to southern South America, Greater Antilles (except Puerto Rico), and Lesser Antilles (AOU 1983, Marti 1992). Variable occurrence within this range, with low densities at northern periphery (Marti 1992). In Old World from British Isles, southern Russia, and southern Siberia south through Eurasia and Africa to southern Africa, Madagascar, East Indies, and Australia. Populations in northern North America are partially migratory. Introduced (1958 and later) in Hawaii; now on all main islands (AOU 1983).

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 AL, AR, AZ, CA, CO, CT, DC, DE, FL, GA, IA, ID, IL, IN, KS, KY, LA, MA, MD, MI, MO, MS, MT, NC, NE, NJ, NM, NN, NV, NY, OH, OK, OR, PA, RI, SC, SD, TN, TX, UT, VA, VT, WA, WV, WY
Canada BC, ON, QC

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)
AL Elmore (01051), Franklin (01059), Greene (01063)*, Hale (01065), Madison (01089)
AZ Coconino (04005), Navajo (04017)
CT Fairfield (09001), Hartford (09003)*, Litchfield (09005)*, Middlesex (09007), New Haven (09009)*, New London (09011)*
GA Baker (13007), Banks (13011), Bartow (13015), Chatham (13051), Clarke (13059), Coffee (13069), Decatur (13087), Early (13099), Emanuel (13107), Floyd (13115), Franklin (13119), Glynn (13127), Gordon (13129), Hall (13139), Harris (13145), Hart (13147), Henry (13151), Houston (13153), Jackson (13157), Johnson (13167), Lamar (13171), Madison (13195), Mcintosh (13191), Mitchell (13205), Morgan (13211), Newton (13217), Oconee (13219), Oglethorpe (13221), Peach (13225), Rockdale (13247), Terrell (13273), Thomas (13275), Walton (13297), Washington (13303), White (13311), Wilkinson (13319)
IA Adair (19001), Adams (19003), Audubon (19009), Boone (19015), Carroll (19027), Clarke (19039), Clinton (19045), Crawford (19047), Fremont (19071), Greene (19073), Guthrie (19077), Humboldt (19091), Johnson (19103), Jones (19105), Lee (19111), Lucas (19117), Madison (19121), Mahaska (19123), Marion (19125), Mills (19129), Montgomery (19137), Muscatine (19139), Page (19145), Polk (19153), Ringgold (19159), Sac (19161), Tama (19171), Taylor (19173), Van Buren (19177), Washington (19183), Wayne (19185), Woodbury (19193)
ID Idaho (16049), Jefferson (16051), Washington (16087)
IL Bond (17005), Carroll (17015)*, Champaign (17019)*, Christian (17021), Clark (17023), Clay (17025), Clinton (17027), Coles (17029), DuPage (17043), Edwards (17047), Effingham (17049), Fayette (17051), Ford (17053)*, Franklin (17055), Fulton (17057), Gallatin (17059), Hamilton (17065), Iroquois (17075), Jackson (17077), Jasper (17079), Jefferson (17081), Johnson (17087), Lawrence (17101), Marion (17121), Massac (17127), Menard (17129)*, Montgomery (17135), Perry (17145), Pike (17149)*, Pope (17151), Pulaski (17153), Putnam (17155), Randolph (17157), Saline (17165), Sangamon (17167), Shelby (17173), St. Clair (17163), Union (17181), Washington (17189), Wayne (17191), White (17193)*, Whiteside (17195)*, Will (17197), Williamson (17199)
IN Allen (18003), Bartholomew (18005), Benton (18007)*, Boone (18011), Cass (18017), Clark (18019), Daviess (18027), Dearborn (18029), Dubois (18037), Floyd (18043), Fulton (18049)*, Gibson (18051), Greene (18055), Henry (18065), Huntington (18069), Jackson (18071), Jay (18075), Jefferson (18077), Jennings (18079), Johnson (18081), Knox (18083), Lagrange (18087)*, Lake (18089), Lawrence (18093), Morgan (18109), Noble (18113), Ohio (18115), Orange (18117), Perry (18123), Pike (18125), Randolph (18135), Ripley (18137), Rush (18139), Spencer (18147), Sullivan (18153), Switzerland (18155), Tippecanoe (18157)*, Vigo (18167), Wabash (18169), Warren (18171), Warrick (18173), Washington (18175), Wayne (18177)*
KY Allen (21003), Bath (21011), Bell (21013), Boone (21015), Boyle (21021), Bracken (21023)*, Breckinridge (21027), Butler (21031), Carlisle (21039), Carroll (21041)*, Christian (21047), Daviess (21059), Fayette (21067), Fleming (21069), Garrard (21079), Grant (21081), Graves (21083), Harrison (21097), Hart (21099), Henry (21103), Hickman (21105), Jefferson (21111), Jessamine (21113), Kenton (21117), Letcher (21133), Lewis (21135), Livingston (21139), Logan (21141), Madison (21151), Marion (21155), Marshall (21157), McCracken (21145), McLean (21149), Menifee (21165)*, Montgomery (21173)*, Muhlenberg (21177), Nelson (21179), Nicholas (21181)*, Owen (21187), Pulaski (21199), Rowan (21205)*, Scott (21209), Shelby (21211), Simpson (21213), Trigg (21221)*, Warren (21227), Whitley (21235)
MA Barnstable (25001), Berkshire (25003)*, Bristol (25005)*, Dukes (25007), Essex (25009), Hampden (25013)*, Hampshire (25015), Middlesex (25017)*, Nantucket (25019), Plymouth (25023)*, Suffolk (25025)
MI Lapeer (26087)*, Monroe (26115)*
MO Adair (29001), Barry (29009), Barton (29011), Bates (29013), Butler (29023), Callaway (29027), Cape Girardeau (29031), Cass (29037), Dade (29057), DeKalb (29063), Dunklin (29069), Greene (29077), Grundy (29079), Harrison (29081), Henry (29083), Holt (29087), Jackson (29095), Jasper (29097), Johnson (29101), Lawrence (29109), Lewis (29111)*, Lincoln (29113), Livingston (29117), New Madrid (29143), Pemiscot (29155), Perry (29157), Pettis (29159), Platte (29165), Ralls (29173), Saline (29195), Scott (29201), St. Charles (29183), St. Louis (29189), Stoddard (29207), Vernon (29217), Webster (29225), Wright (29229)
MS Grenada (28043), Hancock (28045), Hinds (28049), Jackson (28059), Lee (28081)*, Madison (28089), Oktibbeha (28105)*, Quitman (28119), Rankin (28121), Tallahatchie (28135)
NE Banner (31007), Butler (31023), Chase (31029), Dawes (31045), Deuel (31049), Frontier (31063), Garden (31069), Hayes (31085), Keith (31101), Lincoln (31111), Morrill (31123), Red Willow (31145), Sioux (31165)
NJ Bergen (34003), Cape May (34009), Hudson (34017), Hunterdon (34019), Monmouth (34025), Ocean (34029)
NM Dona Ana (35013), Mckinley (35031), San Juan (35045)
NY Bronx (36005), Clinton (36019), Columbia (36021), Delaware (36025), Kings (36047), Nassau (36059), Orange (36071), Queens (36081), Richmond (36085), Suffolk (36103), Sullivan (36105), Ulster (36111)
OK Craig (40035), Delaware (40041), Johnston (40069), Oklahoma (40109), Ottawa (40115), Woodward (40153)
PA Adams (42001), Bedford (42009), Berks (42011), Blair (42013), Bucks (42017)*, Centre (42027), Clarion (42031), Clinton (42035), Crawford (42039), Cumberland (42041), Dauphin (42043), Delaware (42045), Franklin (42055), Fulton (42057), Greene (42059), Huntingdon (42061), Juniata (42067), Lancaster (42071), Lebanon (42075), Lehigh (42077)*, Lycoming (42081), Mifflin (42087), Montour (42093), Northumberland (42097), Perry (42099), Philadelphia (42101), Schuylkill (42107), Snyder (42109), Union (42119), Venango (42121), Washington (42125), York (42133)
RI Newport (44005), Washington (44009)
SC Anderson (45007), Charleston (45019), Georgetown (45043)*, Greenville (45045), Laurens (45059), Oconee (45073), Pickens (45077), Richland (45079)*
SD Bon Homme (46009), Brookings (46011), Brule (46015), Buffalo (46017), Campbell (46021), Charles Mix (46023), Clay (46027), Corson (46031), Dewey (46041), Fall River (46047), Haakon (46055), Harding (46063), Hughes (46065), Jackson (46071), Lyman (46085), Potter (46107), Shannon (46113), Stanley (46117), Sully (46119), Todd (46121), Walworth (46129)
TN Anderson (47001), Blount (47009)*, Carroll (47017), Carter (47019)*, Claiborne (47025), Coffee (47031), Davidson (47037), Gibson (47053), Giles (47055)*, Greene (47059), Hamilton (47065)*, Hawkins (47073)*, Johnson (47091)*, Knox (47093), Maury (47119), Meigs (47121), Obion (47131)*, Rutherford (47149)*, Sevier (47155), Shelby (47157), Sullivan (47163)*, Sumner (47165)*, Warren (47177), Washington (47179), Wayne (47181)*, Weakley (47183)*, Wilson (47189)
VT Addison (50001), Chittenden (50007)*
WV Brooke (54009), Grant (54023), Greenbrier (54025), Hampshire (54027), Hardy (54031), Monroe (54063), Preston (54077)*, Wood (54107)
WY Big Horn (56003), Campbell (56005), Converse (56009), Crook (56011), Goshen (56015), Johnson (56019), Lincoln (56023), Platte (56031), Sweetwater (56037)
* Extirpated/possibly extirpated
U.S. Distribution by Watershed Help
Watershed Region Help Watershed Name (Watershed Code)
01 Middle Connecticut (01080201)+, Lower Connecticut (01080205)+, Farmington (01080207)+*, Charles (01090001)+, Cape Cod (01090002)+, Narragansett (01090004)+, Pawcatuck-Wood (01090005)+, Thames (01100003)+*, Quinnipiac (01100004)+*, Housatonic (01100005)+*, Saugatuck (01100006)+
02 Middle Hudson (02020006)+, Rondout (02020007)+, Bronx (02030102)+, Hackensack-Passaic (02030103)+, Sandy Hook-Staten Island (02030104)+, Raritan (02030105)+, Northern Long Island (02030201)+, Southern Long Island (02030202)+, Long Island Sound (02030203)+*, Upper Delaware (02040101)+, Crosswicks-Neshaminy (02040201)+*, Lower Delaware (02040202)+, Schuylkill (02040203)+, Cohansey-Maurice (02040206)+, Mullica-Toms (02040301)+, Upper Susquehanna-Lackawanna (02050107)+, Bald Eagle (02050204)+, Lower West Branch Susquehanna (02050206)+, Lower Susquehanna-Penns (02050301)+, Upper Juniata (02050302)+, Raystown (02050303)+, Lower Juniata (02050304)+, Lower Susquehanna-Swatara (02050305)+, Lower Susquehanna (02050306)+, South Branch Potomac (02070001)+, Cacapon-Town (02070003)+, Conococheague-Opequon (02070004)+, Monocacy (02070009)+
03 Coastal Carolina (03040208)+*, Enoree (03050108)+, Saluda (03050109)+, Congaree (03050110)+*, Santee (03050112)+*, Cooper (03050201)+, Bulls Bay (03050209)+, Seneca (03060101)+, Tugaloo (03060102)+, Upper Savannah (03060103)+, Broad (03060104)+, Lower Savannah (03060109)+, Upper Ogeechee (03060201)+, Ogeechee Coastal (03060204)+, Upper Oconee (03070101)+, Lower Oconee (03070102)+, Upper Ocmulgee (03070103)+, Lower Ocmulgee (03070104)+, Ohoopee (03070107)+, Satilla (03070201)+, Cumberland-St. Simons (03070203)+, Aucilla (03110103)+, Apalachee Bay-St. Marks (03120001)+, Upper Chattahoochee (03130001)+, Middle Chattahoochee-Lake Harding (03130002)+, Kinchafoonee-Muckalee (03130007)+, Lower Flint (03130008)+, Ichawaynochaway (03130009)+, Spring (03130010)+, Oostanaula (03150103)+, Etowah (03150104)+, Lower Tallapoosa (03150110)+, Upper Tombigbee (03160101)+*, Town (03160102)+*, Tibbee (03160104)+*, Middle Tombigbee-Lubbub (03160106)+*, Noxubee (03160108)+*, Lower Black Warrior (03160113)+, Mississippi Coastal (03170009)+, Middle Pearl-Strong (03180002)+, Lower Pearl. Mississippi (03180004)+
04 St. Joseph (04050001)+, Flint (04080204)+*, Ottawa-Stony (04100001)+*, St. Marys (04100004)+, Lake Champlain (04150408)+
05 Middle Allegheny-Tionesta (05010003)+, French (05010004)+, Clarion (05010005)+, Upper Monongahela (05020003)+*, Lower Monongahela (05020005)+, Upper Ohio (05030101)+, Upper Ohio-Wheeling (05030106)+, Upper Ohio-Shade (05030202)+, Greenbrier (05050003)+, Whitewater (05080003)+, Ohio Brush-Whiteoak (05090201)+, Middle Ohio-Laughery (05090203)+, Licking (05100101)+, South Fork Licking (05100102)+, North Fork Kentucky (05100201)+, Lower Kentucky (05100205)+, Upper Green (05110001)+, Barren (05110002)+, Lower Green (05110005)+, Pond (05110006)+, Upper Wabash (05120101)+, Salamonie (05120102)+, Mississinewa (05120103)+, Eel (05120104)+, Tippecanoe (05120106)+*, Middle Wabash-Little Vermilion (05120108)+, Vermilion (05120109)+*, Middle Wabash-Busseron (05120111)+, Embarras (05120112)+, Lower Wabash (05120113)+, Little Wabash (05120114)+, Skillet (05120115)+, Upper White (05120201)+, Lower White (05120202)+, Driftwood (05120204)+, Flatrock-Haw (05120205)+, Upper East Fork White (05120206)+, Muscatatuck (05120207)+, Lower East Fork White (05120208)+, Patoka (05120209)+, Upper Cumberland (05130101)+, Upper Cumberland-Lake Cumberland (05130103)+, Collins (05130107)+, Lower Cumberland-Old Hickory Lake (05130201)+*, Lower Cumberland-Sycamore (05130202)+, Stones (05130203)+, Lower Cumberland (05130205)+, Red (05130206)+, Silver-Little Kentucky (05140101)+, Salt (05140102)+, Rolling Fork (05140103)+, Blue-Sinking (05140104)+, Lower Ohio-Little Pigeon (05140201)+, Highland-Pigeon (05140202)+, Lower Ohio-Bay (05140203)+, Saline (05140204)+, Lower Ohio (05140206)+
06 North Fork Holston (06010101)+*, South Fork Holston (06010102)+*, Watauga (06010103)+, Holston (06010104)+*, Lower French Broad (06010107)+, Nolichucky (06010108)+, Watts Bar Lake (06010201)+*, Powell (06010206)+, Lower Clinch (06010207)+, Middle Tennessee-Chickamauga (06020001)+, Wheeler Lake (06030002)+, Upper Elk (06030003)+, Lower Elk (06030004)+*, Bear (06030006)+, Lower Tennessee-Beech (06040001)+*, Upper Duck (06040002)+, Lower Duck (06040003)+, Lower Tennessee (06040006)+
07 Apple-Plum (07060005)+, Copperas-Duck (07080101)+, Lower Wapsipinicon (07080103)+, Flint-Henderson (07080104)+, South Skunk (07080105)+, Skunk (07080107)+, Lower Cedar (07080206)+, Middle Iowa (07080208)+, Lower Iowa (07080209)+, Lower Rock (07090005)+*, East Fork Des Moines (07100003)+, Middle Des Moines (07100004)+, North Raccoon (07100006)+, South Raccoon (07100007)+, Lake Red Rock (07100008)+, Lower Des Moines (07100009)+, Bear-Wyaconda (07110001)+*, North Fabius (07110002)+, The Sny (07110004)+*, Salt (07110007)+, Cuivre (07110008)+, Peruque-Piasa (07110009)+, Kankakee (07120001)+, Iroquois (07120002)+, Des Plaines (07120004)+, Lower Illinois-Senachwine Lake (07130001)+, Lower Illinois-Lake Chautauqua (07130003)+, Upper Sangamon (07130006)+*, South Fork Sangamon (07130007)+, Lower Sangamon (07130008)+*, Cahokia-Joachim (07140101)+, Upper Mississippi-Cape Girardeau (07140105)+, Big Muddy (07140106)+, Whitewater (07140107)+, Cache (07140108)+, Upper Kaskaskia (07140201)+, Middle Kaskaskia (07140202)+, Shoal (07140203)+, Lower Kaskaskia (07140204)+
08 Bayou De Chien-Mayfield (08010201)+, Obion (08010202)+*, South Fork Obion (08010203)+, Wolf (08010210)+, New Madrid-St. Johns (08020201)+, Little River Ditches (08020204)+, Tallahatchie (08030202)+, Yalobusha (08030205)+, Lower Big Black (08060202)+*
10 Big Horn Lake (10080010)+, Middle Fork Powder (10090201)+, Middle Cheyenne-Spring (10120109)+, Upper Belle Fourche (10120201)+, Upper Lake Oahe (10130102)+, Lower Lake Oahe (10130105)+, South Fork Grand (10130302)+, Fort Randall Reservoir (10140101)+, Bad (10140102)+, Upper White (10140201)+, Little White (10140203)+, Lewis and Clark Lake (10170101)+, Upper Big Sioux (10170202)+, Glendo Reservoir (10180008)+, Middle North Platte-Scotts Bluff (10180009)+, Lower Laramie (10180011)+, Horse (10180012)+, Pumpkin (10180013)+, Lower North Platte (10180014)+, Lower South Platte (10190018)+, Middle Platte-Buffalo (10200101)+, Monona-Harrison Ditch (10230004)+, Boyer (10230007)+, West Nishnabotna (10240002)+, East Nishnabotna (10240003)+, West Nodaway (10240009)+, Nodaway (10240010)+, Platte (10240012)+, One Hundred and Two (10240013)+, Upper Republican (10250004)+, Frenchman (10250005)+, Red Willow (10250007)+, Medicine (10250008)+, Upper Big Blue (10270201)+, Upper Grand (10280101)+, Thompson (10280102)+, Lower Grand (10280103)+, Upper Chariton (10280201)+, Lower Marais Des Cygnes (10290102)+, Little Osage (10290103)+, Marmaton (10290104)+, Harry S. Missouri (10290105)+, Sac (10290106)+, South Grand (10290108)+, Upper Gasconade (10290201)+, Lower Missouri-Crooked (10300101)+, Lower Missouri-Moreau (10300102)+, Lamine (10300103)+, Blackwater (10300104)+
11 James (11010002)+, Upper Black (11010007)+, Lower Cimarron-Skeleton (11050002)+, Middle Neosho (11070205)+, Lake O' the Cherokees (11070206)+, Spring (11070207)+, Elk (11070208)+, Lower Neosho (11070209)+, Lower Beaver (11100201)+, Lower Wolf (11100203)+, Middle North Canadian (11100301)+, Deep Fork (11100303)+, Blue (11140102)+
13 Tularosa Valley (13050003)+
14 Upper Green-Slate (14040103)+, Muddy (14040108)+, Chaco (14080106)+
15 Upper Puerco (15020006)+, Polacca Wash (15020013)+, Moenkopi Wash (15020018)+
17 Beaver-Camas (17040214)+, Brownlee Reservoir (17050201)+, South Fork Clearwater (17060305)+
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 bird (owl).
General Description: ADULTS: body length 30-37 cm, wingspread 104-120 cm (Colvin 1984, Marti 1990). Upper plumage golden-brown with varying amounts of gray. Breast and belly color ranges from white to buff and is sparsely to heavily speckled with small black spots. Head lacks ear tufts and has relatively small dark eyes and a distinctive heart-shaped facial disk which ranges in color from white to buff.

Sexes differ in size and plumage. Females are larger and heavier (569 g vs. 475 g), darker, and more heavily speckled than males (Bloom 1978, Colvin 1984). Variability of these characteristics makes it difficult to objectively determine the sex of some individuals. Linear discriminant functions which use weight and color measurements can be used for determining sex (Colvin 1984).

JUVENILES: resemble adults. Males younger than one year may have buff coloration on the breast (whereas adult males almost always lack such coloration) but are not as heavily speckled as females (Bloom 1978). Molt patterns provide a means of distinguishing adults from juveniles and for accurately aging individuals through 36 months (Bloom 1978).

VOCALIZATIONS: Fifteen vocal and two nonvocal sounds were described by Bunn et al. (1982). B. Colvin (pers. comm.) described the five most frequently heard vocalizations: 1) the "contact call" is a drawn-out screech frequently given in flight when approaching a nest site from a distance; 2) the "alarm call" is an intense screech made in response to human or other disturbance which is typically given at a nest site and only after chicks have hatched; 3) "squeaking/ticking calls" are rapid, high-pitched notes which are associated with pair bond maintenance or distress situations; these calls are commonly produced during courtship, incubation, and first evening flights after chicks have hatched; 4) "snoring" is a greatly varying hiss which is repeated persistently by juveniles in and out of the nest; this call is used for food begging and may be heard at nest sites from sunset to sunrise; and 5) the "defensive hiss" is a very loud and prolonged hiss typically produced by nestlings when disturbed.

Reproduction Comments: Nests in late winter, spring, and/or early summer in most of North America. Breeds throughout year in Texas. Nests with eggs or young have been found in the northeastern U.S. during every month of the year (Poole 1930; Bent 1938; Scott 1950; Stewart 1952; C. Rosenburg, unpubl. data), but peak egg laying occurs during mid-April (Colvin 1984, Byrd and Rosenburg 1986). Second clutches are typically laid between June and September (Wallace 1948, Keith 1964, Reese 1972, Soucy 1979). As many three broods per year; some California birds attempt two broods per year; one brood per year in most of the range. Clutch size ranges between one to 13 eggs (Bent 1938, Parker and Castrale 1990) with the mean clutch size ranging between four to six eggs (Otteni et al. 1972, Reese 1972, Smith et al. 1974). Clutch size depends on condition; increases with food supply and after mild winters in some areas. Eggs are usually laid two days apart and hatch asynchronously since incubation starts after the laying of the first egg (Wallace 1948, Smith et al. 1974). Incubation by female, 21-24 days for single egg, 29-34 days for full clutch (Smith et al. 1974, Marshall et al. 1986). The peak of hatching in the Northeast occurs in mid-May (Colvin 1984; Byrd and Rosenburg 1986; S. Smith, pers. comm.). Female broods and feeds young, male brings food. Young reportedly fly at 50-55 days in England; young fledge at 8-10 weeks in U.S. (Pickwell 1948, Reese 1972, Smith et al. 1974). Peak fledging occurs in mid to late July (Colvin 1984, Byrd and Rosenburg 1986). Juveniles may remain in the vicinity of the nest site for several weeks before dispersing (Otteni et al. 1972, Smith et al. 1974, Marti 1990). Male may care for fledged young as female begins second clutch. In northern Utah, 71% of all nesting attempts yielded at least one fledgling; reproductive success and productivity were reduced following winters with particularly low temperatures and long periods of deep snow cover (Marti 1994). Breeding density depends on availability of nest sites and on food supply. See Marti (1989) for information on breeding phenology in different areas.

Matures and breeds within its first year (Stewart 1952, Maestrelli 1973, Marti 1990) and sometimes as early as seven months of age (B. Colvin, pers. comm.). It is typically monogamous, but Colvin and Hegdal (1989) reported that as many as 10% of the adult males in their New Jersey study area may be polygynous.

Ecology Comments: Individuals range over large areas; mean home range size (based on the minimum home range method (Mohr and Stumpf 1966)) has been reported as 355 ha in southern Texas (Byrd 1982), 757 ha and 921 ha in southwestern New Jersey (Colvin 1984, Hegdal and Blaskiewicz 1984), 414 ha in eastern Virginia (Rosenburg 1986), 850 ha in Virginia (Byrd and Johnston 1991), and 198 ha in western Nebraska (Gubanyi 1989). As much as 5.6 km may be traveled between a nest site and foraging areas, although distances within 1.6 km are more usual (Colvin 1984, Hegdal and Blaskiewicz 1984, Rosenburg 1986). Overlap of individual home ranges is common, particularly where nest sites and prey are abundant. (Smith et al. 1974, Colvin 1984, Rosenburg 1986).

Young disperse widely from natal area, commonly more than 80 km, up to hundreds or 1900 km documented; wide dispersal facilitates colonization of new areas. Hatching-year barn owls have been recovered great distances from natal areas (commonly > 80 km and as much as 1800 km) (Stewart 1952; Soucy 1980, 1985). Although juveniles have been recovered from essentially every compass direction from their natal area, most had traveled in a southerly direction (Stewart 1952). Juveniles in the northern U.S. migrate south but return to nest somewhere within 320 km of their natal sites (Stewart 1952). Most individuals banded as nestlings and later found breeding did so at distances of about 50 km from their natal areas (Marti 1990). Cases of dispersal > 320 km have also been documented. An individual banded as a nestling in southwestern Iowa was recovered as a breeding adult 419 km to the east (Ehresman et al. 1989). A nestling banded in central New Jersey was found nesting in Ohio (B. Colvin, pers. comm.). Extensive banding of nestlings and capture of adults in southwest New Jersey reveals that only a small percentage of nestlings banded within the study area enter the adult population there: 5% of 181 nestlings banded in 1988 were found in the adult population in 1989 (Colvin and Hegdal 1989). Although they may return to breed relatively close to their natal area, individuals frequently become established great distances away. Very successful at colonizing new areas because of this broad dispersal behavior.

Susceptible to starvation during prolonged low temperatures and snow cover (Marti and Wagner 1985). In Utah, most adults survived only 1 breeding season (Marti 1989). Disease, parasites, and predation are natural factors that may in part limit populations. Appears to be resistant to many diseases that infect other raptors (Schulz 1986). In California, diseases documented include tuberculosis, aspergillosis, and trichomoniasis (Schulz 1986). Toxoplasmosis and eastern equine encephalitis have been detected in New Jersey, although no impact to the birds was apparent (Colvin and Hegdal 1986, 1987). Salmonellosis has been recorded in Pennsylvania (Locke and Newman 1970) and New Jersey (Kirkpatrick and Colvin 1986). Kirkpatrick and Colvin (1986) found SALMONELLA-positive nestlings at five of the 25 New Jersey nest sites examined, and reported that all infected young apparently fledged.

Dipteran ectoparasites and lice have been found on owls (Schulz 1986, Kirkpatrick and Colvin 1989). The endoparasites TRYPANOSOMA, CAPILLARIA, and PORROCAECUM have been identified from the feces of New Jersey owls (Colvin and Hegdal 1986).

NON-BREEDING: solitary or in pairs.

Non-Migrant: Y
Locally Migrant: Y
Long Distance Migrant: Y
Mobility and Migration Comments: Populations in northern North America are partially migratory; may winter up to several hundred km southward from breeding area, as far as southern Mexico and the West Indies. Long-distance movements (to Mexico) have been recorded also for a nonbreeding adult and nestling banded in Texas; movement of young may represent dispersal rather than migration. There is no evidence of migration in the northern range in Europe, nor in northern Utah (Marti 1989). At Cape May Point, New Jersey, 90% of fall migration was completed between late September and early November (Duffy and Kerlinger 1992). See also Russell et al. (1991) for an account of fall migration at Cape May Point, New Jersey (peak migration was mid- to late October).

Stewart (1952) described it as partly migratory in the Northeast and presents extensive evidence of individuals banded in northern latitudes that were later recovered in southern latitudes. Duffy (1985) reported that large numbers of migrants are captured during fall night trapping at Cape May, New Jersey. Although most captured owls were juveniles, 20% of 171 captures at Cape May were adults (P. Kerlinger, pers. comm.). Most adults migrate past Cape May early in October while hatching-year birds migrate throughout October and early November (Duffy 1985). Recoveries of barn owls banded in the northeastern U.S. indicate that migrant individuals winter chiefly in the southeastern U.S. and Texas (Stewart 1952, Soucy 1980).

Northeastern U.S. Christmas Bird Count data (Stewart 1980, Butcher and Lowe 1990) demonstrate that not all individuals near the northern edge of the range leave for the winter; numerous counts from all northeastern states except Maine, New Hampshire, and Vermont reported barn owls every year. During the winter of 1989- 90, 74% of 35 active Virginia sites visited supported wintering owls (C. Rosenburg, unpubl. data). Although there is an observed migration of both juveniles and adults, many individuals winter within the northeastern U.S. There seem to be no obvious migration patterns (e.g., coastal vs. inland populations, mild winters vs. severe winters) within the northeastern U.S.. However, no investigations have been made into the possible influence of microtine rodent abundance on the percentage of the population which apparently migrates.

Palustrine Habitat(s): HERBACEOUS WETLAND, Riparian
Terrestrial Habitat(s): Cliff, Cropland/hedgerow, Grassland/herbaceous, Savanna, Suburban/orchard, Urban/edificarian
Habitat Comments: BREEDING: Fields of dense grass. Open and partly open country (grassland, marsh, lightly grazed pasture, hayfields) in a wide variety of situations, often around human habitation (AOU 1983). Nests in buildings (church steeples, attics, platforms in silos and barns, wooden water tanks, duckblinds), caves, crevices on cliffs, burrows, and hollow trees, rarely in trees with dense foliage (AOU 1983). Caves, cliff crevices, and cut bank burrows are commonly used in the western U.S., rarely in the east. Uses nest boxes (Marti and Wagner 1985). Reproductive success generally is higher in a properly placed and maintained nest box than in a natural nest cavity.

FORAGING HABITAT: Dense grass fields are the chief foraging habitat, including saltmarsh, wet meadows, lightly grazed pastures, grass hayfields, and recently abandoned agricultural fields (Colvin 1980, 1984, 1985; Rosenburg 1986; Gubanyi 1989). Radiotelemetry studies indicate that these habitats are actively selected (Colvin 1984, Rosenburg 1986, Gubanyi 1989). Furthermore, the quantity and quality of dense grass habitats are significantly correlated with nest activity (Colvin and Hegdal 1988).

Other habitats occasionally used include alfalfa/grass (Colvin 1984), small grain (Ault 1971, Rosenburg 1986), fencelines, and roadsides (Ault 1971, Byrd 1982). In an intensively farmed area in eastern Virginia where grass availability was very low, foraged in small grain, a five-year-old clearcut, barnyards, and a pine (PINUS spp.) plantation used as a blackbird roost (Rosenburg 1986). Cultivated habitats in general are of little importance because of low prey populations and/or dense protective cover (Colvin 1984, Rosenburg 1986).

NESTING HABITAT: This is a cavity-nesting bird which uses natural as well as human-created cavities. Tree cavities are the principal nest site used in most areas of the Northeast (Colvin et al. 1984); those most frequently used are silver maple (ACER SACCHARINUM), American sycamore (PLATANUS OCCIDENTALIS), and white oak (QUERCUS ALBA) (Colvin et al. 1984, Byrd and Rosenburg 1986). Although cut bank burrows and cliff recesses are frequently used in the western U.S. (Otteni et al. 1972, Martin 1973, Rudolph 1978, Millsap and Millsap 1987, Gubanyi 1989), only a few cases of the use of such sites have been reported in the Northeast. R. Ferren (pers. comm.) described nest holes in the steep bluffs on the north and south ends of Block Island, Rhode Island. Recesses in a clay embankment along the Patuxent River in Maryland supported a breeding pair during the late 1980s (S. Smith, pers. comm.). Exposed barrels in a cut bank along the Rappahannock River of eastern Virginia supported approximately 15 nesting pairs in the late 1970s (S. Doggett, pers. comm.). A wide variety of human-made "cavities" are used as nest sites. Large platforms within barns and silos, tunnels dug into silage in roofed or topless silos, cavities among hay bales stored inside barns, barn cupola shelves, wooden water tanks, and offshore duckblinds are frequently used; feed bins, church steeples and belfries, platforms within commercial and industrial buildings (e.g., warehouses, grain elevators, mills, factories), attics of abandoned or occupied houses, ledges within chimneys, platforms beneath bridges, and World War II cement watch towers are occasionally used (Stotts 1958, Scott 1959, Reese 1972, Klaas et al. 1978, Soucy 1979, Bunn et al. 1982, Hegdal and Blaskiewicz 1984, Colvin 1984, Byrd and Rosenburg 1986, Matteson and Petersen 1988, Parker and Castrale 1990). In addition, nest boxes are readily used (Otteni et al. 1972, Marti et al. 1979, Soucy 1980, Ziesemer 1980, Colvin et al. 1984, Cook 1985, Schulz 1986, Byrd and Rosenburg 1986, Bendel and Therres 1988, Parker and Castrale 1990).

NON-BREEDING: In winter often roosts in dense conifers; also roosts in nest boxes if available (Marti and Wagner 1985).

Adult Food Habits: Carnivore
Immature Food Habits: Carnivore
Food Comments: Eats mainly small mammals, especially voles (MICROTUS spp.). BLARINA, THOMOMYS, SPERMOPHILUS, PEROGNATHUS, DIPODOMYS, and PEROMYSCUS can be locally important. Birds can be taken when small mammals are scarce; introduced rodents are important in some urban areas and (with bats and birds) in the West Indies. In northern and eastern North America, the shrew (Soricidae) component of diet has declined over the past several decades; in the northern and central range, percentage of exotic rats and mice has increased (Clark and Bunck 1991).

Numerous pellet analyses throughout north temperate North America and Europe have identified voles as the primary prey (Ticehurst 1935; Wilson 1938; Pearson and Pearson 1947; Wallace 1948; Phillips 1951; Boyd and Shriner 1954; Glue 1967, 1974; Smith et al. 1972; Marti 1973; Webster 1973; Jackson et al. 1976; Lovari et al. 1976; Dexter 1978; Bethge and Hayo 1979; Colvin 1980, 1984; Hegdal and Blaskiewicz 1984; Cook 1985; Colvin and McLean 1986; Rosenburg 1986; Campbell et al. 1987; Feldhamer et al. 1987; Parker 1987; Hammerson 1988; Marti 1988). The meadow vole (MICROTUS PENNSYLVANICUS) is the most important prey animal in the northeastern U.S. and the short-tailed shrew (BLARINA BREVICAUDA) is an important secondary prey. By frequency, meadow voles typically comprise 60-90% of the diet (Boyd and Shriner 1954, Jackson et al. 1976, Colvin 1984, Cook 1985, Rosenburg 1986, Hammerson 1988). The marsh rice rat (ORYZOMYS PALUSTRIS) can be an important prey animal in coastal areas of southeastern North America (Jemison 1962, Blem and Pagels 1973, Jackson et al. 1976, Colvin 1984, Feldhamer et al. 1987). In the southern U.S., the cotton rat (SIGMODON HISPIDUS) is the primary prey (Baumgartner and Baumgartner 1944, Parmalee 1954, Otteni et al. 1972, Hamilton and Neill 1981, Byrd 1982, Baker 1986, Marra et al. 1989). Colvin (1984) concluded that barn owls seek prey of a particular size (approximately 40-60 g), which provides the most energy efficient diet.

Shows greater diet diversity: 1) in areas with relatively low microtine or cotton rat availability (Ticehurst 1935; Hawbecker 1945; Pearson and Pearson 1947; Glue 1967, 1974; Blem and Pagels 1973; Marti 1974; Bauer 1983; Colvin 1984; Lenton 1984; Colvin and McLean 1986; Rosenburg 1986; Parker 1987; Campbell et al. 1987); 2) during times of poor microtine availability (Fitch 1947, Wallace 1948, Glue 1967, Otteni et al. 1972, Webster 1973, Marti 1974, Jackson et al. 1976, Bethge and Hayo 1979, Baker 1986); and 3) when nonmicrotine prey are readily available (Evans and Emlen 1947, Sage 1962, Carpenter and Fall 1967, Smith et al. 1972, Klaas et al. 1978, Byrd 1982, Fritzell and Thorne 1984, Rosenburg 1986, Jentzsch 1988). These studies identified birds (mostly blackbirds and sparrows), short-tailed shrews, least shrews (CRYPTOTIS PARVA), house mice (MUS MUSCULUS), and Norway rats as relatively important prey in such situations.

The foraging behavior has been well studied (Colvin 1980, 1984).

Typical foraging is done with a relatively low quartering flight which includes frequent hovering intervals (Honer 1963, Haverschmidt 1970, Burton 1973, Karalus and Eckert 1974, Marti 1974, 1989, Rudolph 1978, Bunn et al. 1982, Mikkola 1983, Rosenburg 1986). Some individuals also hunt rather frequently from a perch, especially along field edges (Byrd 1982, Rosenburg 1986).

In North America this owl is highly nocturnal (Colvin 1984, Rosenburg 1986); it has extremely keen hearing (Payne 1971, Konishi 1973) and night vision (Dice 1945, Marti 1974). Its ability to capture prey by hearing alone (Payne 1971) is especially advantageous for hunting animals such as voles and shrews which are often concealed from view as they travel in runways beneath grass cover.

Adult Phenology: Crepuscular, Nocturnal
Immature Phenology: Crepuscular, Nocturnal
Phenology Comments: Hunts mostly at night, from about 1 hour after sunset to about one hour before sunrise (Marti 1989).
Length: 16 centimeters
Weight: 490 grams
Economic Attributes Not yet assessed
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Management Summary
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Stewardship Overview: In the Northeast, inhabits agricultural grasslands and tidewater marshlands where it typically nests in tree cavities or in barns, silos, church steeples, warehouses, and other structures. Although little reliable historical data demonstrates that populations have changed significantly since 1900, limited data suggests a general decline throughout the Northeast and several states consider it as rare and declining. The loss of dense grass habitats for foraging appears to be the most significant limiting factor, but this could be overcome by grassland management programs aimed at preserving large fields near to nesting sites. Long-term monitoring of grassland availability and small mammal abundance, as well as nest sites, should be implemented regionally to track population trends. Nest boxes can be placed in areas of good foraging habitat to supplement natural nest sites. Grass habitats can also be managed by light grazing or mowing to maintain the grass sere without altering dense ground cover used by small mammals (Rosenburg 1992).
Restoration Potential: High recovery and management potential (Rosenburg 1992). They have a potentially high reproductive output because of 1) large clutch size, 2) occasional second broods, 3) sexual maturity at one year, 4) lack of strict territoriality, and 5) occasional polygyny. These characteristics provide mechanisms for rapid population expansion during times of prey availability (Wallace 1948, Stewart 1952, Henny 1969, Colvin 1984). This potentially high reproductive output, coupled with the owl's colonizing abilities, indicates an ability to establish or expand populations in areas where stable habitats exist. This ability was demonstrated during the first part of this century when the owl rapidly expanded its range into the Midwest in response to the clearing of forests and the establishment of agriculture which supported an abundance of dense grass habitats (B. Colvin, pers. comm.). In addition, the major biological and ecological limiting factors are fairly well understood and management techniques have been developed.
Preserve Selection & Design Considerations: The most important land protection tool for maintaining or expanding populations is the preservation of dense grass foraging habitats (Lerg 1984; Rosenburg 1986; Gubanyi 1989; B. Colvin, pers. comm.). Acquisition of fee title or the use of conservation easements, management agreements, property registration, or tax incentives (Millsap et al. 1987) are means of preserving existing grasslands or acquiring additional land, such as cropland, which can be converted to grassland. Large-scale habitat acquisition programs are very costly. Programs which utilize other preservation strategies, such as conservation easements and tax incentives, and which focus on all of the grassland dependent species of management concern may be cost effective.

EDUCATION: Efforts towards educating farmers and other landowners about the owl's unique characteristics, rodent-catching abilities, and reliance upon dense grass habitats should be made. Educational efforts will generate a stronger interest in the barn owl and may stimulate beneficial conservation efforts. Educational efforts are also a good public relations tool that may result in a better acceptance of state and regional conservation efforts. They often lead to reports of owls and may help identify individuals who are willing to conduct local nest box programs (A. Parker, pers. comm.). Potential educational efforts include natural history and nest box pamphlets, articles in conservation and agricultural magazines, and slide presentations to ornithological groups. The Indiana Department of Natural Resources produced a barn owl slide program which has been very popular and has stimulated local nest box programs (A. Parker, pers. comm.).

Management Requirements: Habitat manipulation should focus on maintaining the grass sere without removing dense ground cover essential for meadow voles (Rosenburg 1992). Grass fields should be lightly grazed or mowed once a year. Litter from mowing should be left in the field to maintain high vole populations. However, one annual hay cutting appears to have little long-term impact on vole carrying capacity and should therefore be considered compatible with grassland management objectives. Prescribed burning may be a potential management practice in some areas. Tidewater marshes of Maryland are burned extensively during winter months resulting in rapid vegetation growth without removing litter (S. Smith, pers. comm.).

Other factors which affect meadow vole abundance and which may therefore deserve management attention are vegetational nitrogen content (Huntly and Inouye 1987) and the availability of preferred forage (Zimmerman 1965). Important forage plants for the meadow vole include AGROPYRON, AMBROSIA, BROMUS, CAREX, FRAGARIA, MEDICAGO, MUHLENBERGIA, PANICUM, POA, TARAXACUM, and TRIFOLIUM spp. (Zimmerman 1965, Lindroth and Batzli 1984, Marquis and Batzli 1989, Bucyanayandi and Bergeron 1990).

Provision of nest boxes may result in increased populations if prey populations are adequate. Nests should not be disturbed during incubation or near fledging time (to avoid nest abandonment and premature fledging). To avoid having raccoons follow human scent to vulnerable nest sites, sprinkle naphthalene or paradichlorobenzene flakes on the ground at nest site entrances.

Monitoring Requirements: It is essential that baseline population data be gathered and that populations are thereafter monitored closely so that sound decisions can be made concerning status assignments and management objectives (Rosenburg 1992). Blodget (1988) suggests that Northeast states institute a long-term, systematic monitoring scheme using a fixed number of "sentinel nest box" monitoring stations (Colvin et al. 1984, Henry 1987). Blodget (1988) and Hands et al. (1989) emphasized the need for consistency and coordination of such efforts among state wildlife agencies. This may best be accomplished by a regional agency such as the U.S. Fish and Wildlife Service.

In each state, an extensive system for identifying nest sites should be initiated or expanded. Two years of diligent efforts should be made to gather specific site data. All states should identify (using remote sensing, U.S. Geological Survey Land Use and Land Cover, or state Geographic Information System (GIS) data) areas in which large amounts of dense grass habitats are found. Survey efforts should then be concentrated in these areas.

Effective methods of identifying sites include 1) advertising in farm magazines, state naturalist magazines, county newspapers, and agricultural and naturalist newsletters; 2) distributing "wanted posters" to feed stores, Soil Conservation Service (SCS), Agricultural Stabilization and Conservation Service (ASCS), Cooperative Extension Service (CES), and Farm Bureau offices; 3) using radio station public service message or advertising services; 4) contacting state wildlife biologists and game wardens as well as local bird club members, livestock veterinarians, SCS, ASCS, and CES representatives; 5) reviewing American Birds, state ornithological journals, and bird club records (where available) for Christmas Bird Count and other reports; 6) requesting site details from people who reported owls during state Breeding Bird Atlases; 7) searching appropriate structures and, as much as possible, tree cavities in areas supporting quality habitat; and 8) listening by ear or with bioacoustics equipment to locate food-begging nestlings or fledglings (Petersen 1980; Colvin 1984; Colvin et al. 1984; Hegdal and Blaskiewicz 1984; Lerg 1984; Byrd and Rosenburg 1986; A. Parker, pers. comm).

After the two-year site establishment phase, a long-term population monitoring program can be initiated. Long-term monitoring is essential for species which are highly dependent upon a cyclic prey base such as microtine mammals (Blodget 1988; Taylor et al. 1988; B. Colvin, pers. comm.). The number of active sites should be identified, the number of nests that are successful, and the number of young fledged for each state. To identify the number of young fledged, a minimum of two visits is necessary. At least one must be made during the nestling stage to count and band young and another made after young fledge to identify the number of banded young that died prior to fledging (Colvin et al. 1984).

It is important to avoid disturbing nests during incubation and when young near fledging age are present so that nest abandonment and premature fledging is avoided (Colvin et al. 1984, Grier and Fyfe 1987). Nests should not be disturbed until young are at least two weeks old (Colvin et al. 1984). It is best to band young between three to six weeks of age. The variability of egg-laying dates makes it difficult to totally avoid disturbing nests at critical times, but problems can be minimized by scheduling nest visits in June and early July. Since there is potential for raccoons to follow human scent into nest sites, naphthalene or paradichlorobenzene crystals should be scattered on the ground at entrances of vulnerable sites (e.g., silos) to discourage subsequent predation (Ray 1968).

PREY: Long-term meadow vole population monitoring should be conducted in each state in conjunction with owl population monitoring. Such surveys are needed to track the relative abundance of this cyclic prey species and to provide a means of testing for a correlation between the relative abundance of prey and barn owl productivity. Such data may reveal that short-term owl population fluctuations are caused by prey cycles as opposed to environmental degradation.

HABITAT: A long-term grassland monitoring system should be established throughout the Northeast in order to monitor trends in the availability of this essential resource. Productive grasslands are a declining resource and the availability of quality grass habitats is the single greatest factor limiting productivity. The use of remote sensing or state GIS data is the ideal means for monitoring this resource. The U.S. Department of Commerce, Census of Agriculture (e.g., U.S. Department of Commerce 1981) also provides grassland area data within its state land-use summaries which are conducted at approximately five-year intervals. These summaries can be used when more reliable sources are not available. Conscientious monitoring programs may identify a need for grassland acquisition programs or expanded conservation programs.

Management Research Needs: Recommended research objectives that warrant attention include: 1) Identify important habitat variables associated with successful nest sites in the Northeast. Compare habitat variables (e.g., percentage of open vs. wooded vegetation, acreage of grass habitats supporting MICROTUS spp., and kilometers of edge) within 1.6 km of successful nest sites versus random points. Separate comparisons should be made for agricultural and coastal marsh sites. 2) Determine the results of habitat manipulation upon meadow vole populations in order to evaluate the effects of existing land use practices and potential management practices upon this important prey species. 3) Identify the levels of anticoagulant rodenticide and organophosphate insecticide residues present in free-ranging owls. Liver, blood, and brain tissue samples should be collected from owls euthanized in wildlife rehabilitation centers or those found shortly after death (S. Porter, pers. comm.). Liver samples can also be taken from owls which were not found shortly after death. Liver tissue samples should be analyzed for residues of difencoum and brodifacoum (Newton et al. 1990). Blood and brain tissue samples should be analyzed for significant cholinesterase inhibition (Hill and Fleming 1982; Hill 1988; L. Brewer, pers. comm.). Fresh pellet and fecal samples should be collected at various intensively farmed areas of the Northeast. Analyses of these pellet and fecal samples can identify organophosphate insecticide groups that may be present (L. Brewer, pers. comm.).
Population/Occurrence Delineation
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Group Name: Large Owls

Use Class: Breeding
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: 10 km
Separation Distance for Suitable Habitat: 10 km
Separation Justification: Separation distance based conservatively on larger home ranges (greater than 800 hectares). Home ranges generally well over 100 hectares, often over 500 hectares. Northern Hawk-Owl: average 372 hectares (Baekken et al. 1987). Great Horned Owl: average 483 hectares in Yukon (Rohner 1997), average about 106 hectares in Utah (Smith 1969). Barred Owl: average 273-971 hectares (Elody and Sloan 1985, Nicholls and Fuller 1987, Mazur et al. 1998). Great Gray Owl, varied from 239-400 hectares (Craighead and Craighead 1956, Winter 1982). Barn Owl: averages range from 198-921 hectares (Byrd 1982, Colvin 1984, Hegdal and Blaskiewicz 1984, Rosenburg 1986, Byrd and Johnston 1991, Gubanyi 1989).
Inferred Minimum Extent of Habitat Use (when actual extent is unknown): 1.5 km
Inferred Minimum Extent Justification: Based on a conservatively small home range of just under 200 hectares (see Separation Justification).
Date: 02Nov2001
Author: Cannings, S.
Notes: Contains all North American owls larger than Screech-Owls, except Spotted, Long-eared, and Short-eared Owls.

Use Class: Nonbreeding
Minimum Criteria for an Occurrence: Evidence of recurring presence of wintering individuals outside their breeding area (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: 10 km
Separation Distance for Suitable Habitat: 10 km
Separation Justification: Separation distance based conservatively on larger home ranges (greater than 800 hectares; see Separation Justification in Breeding class).
Inferred Minimum Extent of Habitat Use (when actual extent is unknown): 1.5 km
Inferred Minimum Extent Justification: Based on a conservatively small home range of just under 200 hectares (see Separation Justification in Breeding Class).
Date: 16Oct2002
Author: Cannings, S.
Notes: Contains all North American owls larger than Screech-Owls, except Spotted, Long-eared, and Short-eared Owls.

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: 10 km
Separation Distance for Suitable Habitat: 10 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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Management Information Edition Date: 01Jun1992
Management Information Edition Author: ROSENBURG, C.; REVISIONS BY G. HAMMERSON, M. KOENEN, AND 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. Manuscript quality was improved through critical review by B. Blodget, B. Colvin, C. Marti, S. Smith, and G. Therres.
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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