Barred owl

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Barred owl
Strix-varia-005.jpg
Scientific classification
Kingdom:
Animalia
Phylum:
Chordata
Class:
Aves
Order:
Strigiformes
Family:
Strigidae
Genus:
Strix
Species:
S. varia
Binomial name
Strix varia
Barton, 1799
Subspecies
  • S. v. georgica
  • S. v. helveola
  • S. v. sartorii
  • S. v. varia
Synonyms

Syrnium varium

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The barred owl (Strix varia) is a large typical owl native to North America. Best known as the hoot owl for its distinctive call, it goes by many other names, including eight hooter, rain owl, wood owl, and striped owl.

Description

File:Barred Owl.jpg
Close-up, Richmond, Virginia

The adult is 40–63 cm (16–25 in) long with a 96–125 cm (38–49 in) wingspan. Weight in this species is 500 to 1,050 g (1.10 to 2.31 lb).[2] It has a pale face with dark rings around the eyes, a yellow beak and brown eyes. It is the only typical owl of the eastern United States which has brown eyes; all others have yellow eyes. The upper parts are mottled gray-brown. The underparts are light with markings; the chest is barred horizontally while the belly is streaked vertically (hence its name "barred owl"). The legs and feet are covered in feathers up to the talons.[3] The head is round and lacks ear tufts.

Outside of the closely related spotted owl, this streaky, dark-eyed, chunky-looking owl is unlikely to be confused over most of the range. The spotted owl is similar in appearance, but is slightly smaller and has spots rather than streaks down the underside. The great horned owl is much larger, has ear tufts, and has yellow eyes.

Distribution and habitat

During the past century, barred owls expanded their range from forests east of the Great Plains to forests throughout most of central and western North America.[4] Evidently, barred owls originally traveled across the northern Great Plains via the forested riparian corridors of the Missouri, Yellowstone and Musselshell rivers into east-central Montana by 1873.[4] From there, they accessed western forests in southwestern Montana (1909), moved to northwestern Montana (1922) and then expanded their range in two general directions.[4] They moved north and east to northern Alberta (1934) and Saskatchewan (1948) where they apparently encountered other barred owls coming westward from Manitoba.[4] They also moved north to northern British Columbia (1943), southeastern Alaska (1967) and Northwest Territories (1977), and west and south to Washington (1965), Idaho (1968), Oregon (1972), and California (1976).[4]

The historical lack of trees in the Great Plains evidently acted as a barrier to the range expansion and recent increases in forests broke down this barrier.[5] Increases in forest distribution along the Missouri River and its tributaries apparently provided barred owls with sufficient foraging habitat, protection from the weather, and, possibly, concealment from avian predators to allow barred owls to move westward; decades later, increases in forests in the northern Great Plains allowed them to connect their eastern and western distributions across southern Canada.[5] These increases in forests evidently were caused by European settlers (American settlers) excluding fires historically set by Native Americans, suppressing fires and planting trees; they apparently were caused, to lesser degrees, by European settlers extirpating bison (Bison bison), overhunting elk (Cervus elaphus) and deer (Odocoileus spp.) and, in some areas, extirpating beaver (Castor canadensis) and replacing native ungulates with livestock.[5] So it appears the range expansion was prohibited for millennia by actions of Native Americans and recently facilitated by actions of European settlers.[5][6] Increase in trees in the Great Plains from fire suppression or tree planting is considered a main cause of the range expansions of many other species of birds[7] including western kingbird (Tyrannus verticalis),[8][9] eastern phoebe (Sayornis phoebe),[10] eastern bluebird (Sialia sialis),[11] blue jay (Cyanocitta cristata),[12][13] brown thrasher (Toxostoma rufum),[14] red-tailed hawk (Buteo jamaicensis),[15] and American crow (Corvus brachyrhynchus).[16]

Breeding habitats are dense woods across Canada, the United States, and south to Mexico.[1][17] The species is particularly numerous in a variety of wooded habitats in the southeastern United States. Recent studies show suburban neighborhoods can be ideal habitat for barred owls. Using transmitters, scientists found that populations increased faster in the suburban settings than in old growth forest. A factor of this suburban success may be easily accessible rodent prey in such settings. However, for breeding and roosting needs, this species needs at least some large trees and can be locally absent in some urban areas for this reason. The main danger to owls in suburban settings is from cars. The increased offspring offset the death rate due to impacts from cars and disease.[18]

Barred owl and northern spotted owl

File:Barred owl.jpg
Gatineau Park, Gatineau, Quebec

Barred owls evidently are partly responsible for the recent decline of the northern spotted owl, native to British Columbia, Washington, Oregon, and California.[19][20][21][22] The 2011 Revised Recovery Plan for the Northern Spotted Owl (p. vi) states “Based on the best available scientific information, competition from the barred owl (S. varia) poses a significant and complex threat to the spotted owl.”[23] Since the 1960s, barred owls have been expanding their range westward from the eastern US and Canada (see “Distribution and habitat” section above).[24] When spotted owls and barred owls share the same area, the barred owls generally are more aggressive and out-compete the spotted owls, leading to decreased populations of the native owls.[25] Barred owls may even kill spotted owls.[26] Barred owls and spotted owls occasionally interbreed, creating hybrids ("sparred owl" or "botted owl").[27] Only 47 hybrids with barred owls were found in an analysis of more than 9000 banded spotted owls; consequently, hybridization between these two species is considered by the authors of that analysis to be “an interesting biological phenomenon that is probably inconsequential compared with the real threat—direct competition between the 2 species for food and space” (p. 808).[28]

On 5 April 2007, White House officials announced a U.S. Fish and Wildlife Service proposal to shoot barred owls to reduce the threat they pose to the spotted owl.[29] It called for delineating 18 sites within the range of the spotted owl where 12–32 barred owls would be taken per site for 5 to 10 years.[29] Approximately 2150 to 2850 barred owls would be killed for a 3- to 5-year study, and 4650 Barred Owls would be killed for a 10-year study[30] If the precedent-setting removal study[31] is implemented, it would, during its first year, result in the death of 36 times more raptors than in all other conservation-based projects combined in the United States and its territories, and 84 times more raptors than in the largest ongoing effort worldwide, at a cost of $1 million annually; simplifying the cost to dollars per barred owl killed approximates $700 per barred owl for the first year and $2800 per barred owl for each subsequent year.[30] Many environmentalists fear increased blame on barred owls for declining spotted owl numbers will result in less attention being paid to territorial protection and resumption of logging in protected spotted owl habitat.

Behavior

Barred owl near Blue Spring State Park, Florida

Reproduction

The barred owl's nest is often in a tree cavity, often ones created by pileated woodpeckers; it may also take over an old nesting site made previously by a red-shouldered hawk, Cooper's hawk, crow, or squirrel.[32] It is a permanent resident, but may wander after the nesting season. If a nest site has proved suitable in the past they will often reuse it as the birds are non-migratory. In the United States, eggs are laid from early-January in southern Florida to mid-April in northern Maine, and consist of 2 to 4 eggs per clutch. Eggs are brooded by the female with hatching taking place approximately 4 weeks later. Young owls fledge four to five weeks after hatching.[33] These owls have few predators, but young, unwary owls may be taken by cats. The most significant predator of barred owls is the great horned owl.[34] The barred owl has been known to live up to 10 years in the wild and 23 years in captivity.[2]

Food and feeding

The barred owl is a generalist predator. The principal prey of this owl are meadow voles, followed by mice and shrews of various species; other mammals preyed upon include rats, squirrels, rabbits, bats, moles, opossums, mink, and weasels.[17][35] A barred owl was photographed in Minnesota in 2012 grabbing and flying off with a full-grown domestic cat, a semi-regular prey item for the great horned owl but previously unknown to be taken by this species.[36] Birds are taken occasionally and commonly include woodpeckers, grouse, quails, jays, icterids, doves, pigeons[17][35] and even domestic ducks, and chickens, where they will swoop through small openings in enclosed and covered runs. Less commonly, other raptors are predated, including smaller owls.[34] Avian prey are typically taken as they settle into nocturnal roosts, because these owls are not generally nimble enough to catch birds on the wing. It occasionally wades into water to capture fish, turtles, frogs and crayfish.[3][17][37][38] Additional prey include snakes, lizards, salamanders, slugs, scorpions, beetles, crickets, grasshoppers, and earthworms.[17][39] Barred owls have been known to be attracted to campfires and lights where they forage for large insects. Prey is usually devoured on the spot. Larger prey is carried to a feeding perch and torn apart before eating.

The barred owl hunts by waiting on a high perch at night, or flying through the woods and swooping down on prey. A barred owl can sometimes be seen hunting before dark. This typically occurs during the nesting season or on dark and cloudy days. Of the North American owls, the pygmy, hawk, snowy and burrowing owls are more likely to be active during the day. Daytime activity is often most prevalent when barred owls are raising chicks.[3][38] However, this species still generally hunts near dawn or dusk.

Vocalization

The usual call is a series of eight accented hoots ending in oo-aw, with a downward pitch at the end. The most common mnemonic device for remembering the call is "Who cooks for you, who cooks for you all." It is noisy in most seasons. When agitated, this species will make a buzzy, rasping hiss and click its beak together forcefully. While calls are most common at night, the birds do call during the day as well.[40]

In art

John James Audubon illustrated the barred owl in Birds of America (published, London 1827-38) as Plate 46 where it is shown threatening a grey squirrel. The image was engraved and colored by Robert Havell's, London workshops. The original aquatint by Audubon is owned by the Brooklyn Museum.[41]

References

  1. ↑ 1.0 1.1 * Lua error in package.lua at line 80: module 'strict' not found. .
  2. ↑ 2.0 2.1 http://www.owlpages.com/owls.php?genus=Strix&species=varia
  3. ↑ 3.0 3.1 3.2 Lua error in package.lua at line 80: module 'strict' not found.
  4. ↑ 4.0 4.1 4.2 4.3 4.4 Livezey KB. 2009a. Range expansion of Barred Owls, part I: chronology and distribution. American Midland Naturalist 161:49–56.
  5. ↑ 5.0 5.1 5.2 5.3 Livezey KB. 2009b. Range expansion of Barred Owls, part 2: facilitating ecological changes. American Midland Naturalist 161:323–349.
  6. ↑ Livezey KB, Root TL, Gremel SA, and Johnson C. 2008a. Natural range expansion of Barred Owls? A critique of Monahan and Hijmans (2007). Auk 125:230–232.
  7. ↑ Livezey KB. 2010b. Killing barred owls to help spotted owls II: implications for many other range-expanding species. Northwestern Naturalist 91:251–270.
  8. ↑ Houston S. 1979. The spread of the Western Kingbird across the prairies. Blue Jay 37:149–157.
  9. ↑ Gamble LR, Bergin TM. 1996. Western Kingbird (Tyrannus verticalis), no. 227. In: A. Poole (ed.). The Birds of North America Online. Cornell Lab of Ornithology, Ithaca, New York
  10. ↑ Weeks HP. 1994. Eastern Phoebe (Sayornis phoebe), no. 94. In: A. Poole (ed.). The Birds of North America Online. Cornell Lab of Ornithology, Ithaca, New York.
  11. ↑ Gowaty PA, Plissner GH. 1998. Eastern Bluebird (Sialia sialis), no. 381. In: A. Poole (ed.). The Birds of North America Online. Cornell Lab of Ornithology, Ithaca, New York.
  12. ↑ Smith GH. 1978. Range extension of the Blue Jay into western North America. Bird-Banding 49:208–214.
  13. ↑ Tarvin KA, Woolfenden GE. 1999. Blue Jay (Cyanocitta cristata), no. 469. In: A. Poole (ed.). The Birds of North America Online. Cornell Lab of Ornithology, Ithaca, New York.
  14. ↑ Cavitt JF, Haas CA. 2000. Brown Thrasher (Toxostoma rufum), no. 557. In: A. Poole (ed.). The Birds of North America Online. Cornell Lab of Ornithology, Ithaca, New York.
  15. ↑ Houston S. 1983. Trees and the Red-tailed Hawk in southern Saskatchewan. Blue Jay 41:99–109.
  16. ↑ Houston S. 1977. Changing patterns of Corvidae on the prairies. Blue Jay 35:149–155.
  17. ↑ 17.0 17.1 17.2 17.3 17.4 Livezey KB. 2007. Barred Owl habitat and prey: a review and synthesis of the literature. Journal of Raptor Research 41:177–201.
  18. ↑ Owls Get Wise to Better Life in Cities, Jeanna Bryner, LiveScience Staff Writer, 2007
  19. ↑ Livezey KB. 2005. Iverson (2004) on Spotted Owls and Barred Owls: comments on methods and conclusion. Journal of Raptor Research 39:102–103.
  20. ↑ Pearson RR, Livezey KB. 2007. Spotted Owls, Barred Owls, and Late-Successional Reserves. Journal of Raptor Research 41:156–161.
  21. ↑ Pearson RR, Livezey KB. 2003. Distribution, numbers, and site characteristics of Spotted Owls and Barred Owls in the Cascade Mountains of Washington. Journal of Raptor Research 37:265–276.
  22. ↑ Kelly EG, Forsman ED, Anthony RG. 2003. Are Barred Owls displacing Spotted Owls? Condor 105:45–53.
  23. ↑ U.S. Fish and Wildlife Service. 2011. Revised Recovery Plan for the Northern Spotted Owl (Strix occidentalis caurina). U.S. Fish and Wildlife Service, Portland, Oregon. xvi + 258 pp.
  24. ↑ Barred Owl Displaces Northern Spotted Owl at Olympic, Scott Gremel, Natural Resources Year in Review, National Park System.
  25. ↑ Using Ecological-Niche Modeling to Predict Barred Owl Invasions with Implications for Spotted Owl Conservation, A. Townsend Peterson and C. Richard Robins, Conservation Biology, pages 1161-1165, Volume 17, No. 4, August 2003
  26. ↑ Leskiw T, Gutierrez RJ. 1998. Possible predation of a spotted owl by a barred owl. Western Birds 29:225–226.
  27. ↑ Interbreeding Threatens Rare Species, Experts Claim,Guynup, Sharon, National Geographic
  28. ↑ Kelly EG, Forsman ED. 2004. Recent records of hybridization between barred owls (Strix varia) and northern spotted owls (S. occidentalis caurina). Auk 121:806–810.
  29. ↑ 29.0 29.1 Durbin, Kathy. "White House Proposes Killing Spotted Owl Rival, Owls at Odds." The Columbian. 27 April 2007. NCCSP.org
  30. ↑ 30.0 30.1 Livezey KB. 2010a. Killing barred owls to help spotted owls I: a global perspective. Northwestern Naturalist 91:107–133.
  31. ↑ Johnson DH, White GC, Franklin AB, Diller LV, Blackburn I, Pierce DJ, Olson GS, Buchanan JB, Thrailkill J, Woodbridge B, Ostwald M. 2008. Study designs for Barred Owl removal experiments to evaluate potential effects on Northern Spotted Owls. Report prepared for the U.S. Fish and Wildlife Service, Lacey, WA and Yreka, CA. Olympia, WA: Washington Department of Fish and Wildlife. 32 p.
  32. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  33. ↑ Barred Owl Factsheet, Lee and Rose Warner Nature Center, 2008
  34. ↑ 34.0 34.1 http://www.fcps.edu/islandcreekes/ecology/barred_owl.htm
  35. ↑ 35.0 35.1 Hamer TE, Hays DL, Senger CM, Forsman ED. 2001. Diets of northern barred owls and northern spotted owls in an area of sympatry. Journal of Raptor Research 35:221–227.
  36. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  37. ↑ Barred Owl, Owling
  38. ↑ 38.0 38.1 Habitat Suitability Index Models:Barred Owl, US Fish and Wildlife Service
  39. ↑ Livezey KB, Elderkin MF, Cott PA, Hobbs J, Hudson JP. 2008b. Barred owls eating worms and slugs: the advantage in not being picky eaters. Northwestern Naturalist 89:185–190.
  40. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  41. ↑ Lua error in package.lua at line 80: module 'strict' not found.

External links

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