Western screech-owls (Otus kennicotti) inhabit western North America, northwestern Mexico and coastal regions of the Pacific Northwest (Cannings and Angell, 2001). Ranging as far north as southeast Alaska and southern Canada to the Baja penninsula and into Mexico, western screech-owls make their homes within the diverse communities of the riparian deciduous woodlands of North America (Cornell Lab of Ornithology, 1999). Within the last 40 years, the range of western screech-owls has expanded as far east as Texas (perhaps due to increased tree-planting) and as a result they are now found sympatrically with their very close relative, eastern screech-owls (Otus asio). (Cannings and Angell, 2001; Cornell Lab of Ornithology, 1999)
Western screech-owls usually inhabit low elevation riparian and deciduous oak woodland commmunities (Campbell et al., 1990; Cannings, 1997; Cannings and Angell, 2001). They will often inhabit streamside groves, deserts, suburban parks and gardens (Cornell Lab of Ornithology, 1999). The abundance of O. kennicotti is positively associated with overstory cover of mesquite (prosopis) and understory cover of native perennial vegetation (Hardy et al., 1999).
Within the United Statesoccurs in high densities in the following regions:
Arizona: mesquite-riparian zones of the Sonoran Desert. In particular, western screech-owls are strongly associated with structurally diverse uplands of the Sonoran Desert, containing saguaros (Carnegiea gigantea), mesquite woodlands and cottonwood (Populus)-willow (Salix) riparian areas (Hardy et al., 1999).
Texas: lower elevations in riparian zones dominated by Arizona sycamore (Plantanus wrightii) as well as pure oak habitats (Gelbach and Leverett, 1995; Cannings and Angell, 2001).
California: western screech-owls are strongly associated with areas with fan palms (Washingtonia filifera) and oak woodlands (Feusier, 1989; Noble, 1990; Lehman, 1994; Cannings and Angell, 2001).
Washington and Alaska: western screech-owls are found in riparian habitats and the mixed forests of coastal regions consisting of big-leaf maple (Acer macrophyllum), red alder (Alnus rubra), Douglas fir (Psudotsuga menziesii), western hemlock (Tsuga heterophylla)and western red cedar (Thyja plicata) (Kitchin, 1949; Cannings and Angell, 2001).
Colorado: western screech-owls are primarily found in rural developed areas and areas with broad-leaved cottonwoods along river basins. They are also associated with farmyards containing mature, unpruned cottonwood trees and shrubbery. Throughout their range they are found in urban and suburban parks as well as residential areas (Levad, 1998; Cannings and Angell, 2001). (Campbell, et al., 1990; Cannings and Angell, 2001; Cornell Lab of Ornithology, 1999; Feusier, 1989; Gehlbach and Leverett, 1995; Hardy, et al., 1999; Kitchin, 1949; Lehman, 1994; Levad, 1998; Noble, 1990)
- Aquatic Biomes
is a small owl with feathered "ear tufts". Adults are 19 to 25.5 cm in length; and weigh 170.1 g on average. Male wingspans are 168.4 mm, female wingspans are 174.5 mm. Sexes are alike in plumage characteristics. Plumage of western screech-owls is generally monomorphhic in a given area; brown or gray-brown in the northwest and gray in southern deserts. Some populations in the coastal regions of the Pacific Northwest are more variable in color, often displaying reddish-brown morphs (Cannings and Angell, 2001).
The face of western screech-owls is pale with a dark lateral border, their underparts are streaked and barred. They have yellow eyes and dark bills. Their feet and toes are feathered in northern populations but bristled in southern deserts (Cannings and Angell, 2001). (Cannings and Angell, 2001)
- Sexual Dimorphism
- sexes alike
- female larger
- Range mass
- 163.5 to 183 g
- 5.76 to 6.45 oz
- Average mass
- 170.1 g
- 5.99 oz
- Range length
- 19 to 25.5 cm
- 7.48 to 10.04 in
- Range wingspan
- 168.4 to 174.5 mm
- 6.63 to 6.87 in
Development of young at age-
1 week: eyes open and egg tooth absent.
1-2 weeks: young bill snap in response to disturbance.
3 weeks: more aggressive, hissing and swaying with wings outstreched.
Reach fledgling state within approximately 35 days. For the first 5 weeks following fledging, juvenilles will remain in close association with thier parents and most probably begin breeding when 1 year old (Sumner 1929, Cannings and Angell 2001).
is usually monogomous, although polygamy occurs occasionally.
Before the breeding season, male (Cornell Lab of Ornithology, 1999)defend an area containing several nest cavities. Pair formation begins during the months of January and February throughout the range. Allopreening is an important part of continuous pair-bonding behavior and occurs at all times of the year. Courtship-feeding is common. The male will present food to the female and perform elaborate courtship displays involving bowing, bill snapping, and hopping.
- Mating System
Throughout its range,will nest in tree cavities, most commonly those excavated by other species. Examples include: fox squirrels, northern flickers, gilded flickers, pileated woodpeckers and European starlings (Campbell et al., 1990; Cannings and Angell, 2001; Cornell Lab of Ornithology, 1999). They also inhabit natural tree cavites and nest boxes.
Eggs are laid during March and April. They are white and oval to broadly eliptical. Females lay 2 to 7 eggs per clutch (3 to 5 on average). Incubation lasts 26 to 34 days and the chicks fledge in 27 to 35 days.
Western screech-owls probably begin breeding when they are 1 year old, adults attempt to nest every year (Cannings and Angell, 2001). (Campbell, et al., 1990; Cannings and Angell, 2001; Cornell Lab of Ornithology, 1999)
- Key Reproductive Features
- seasonal breeding
- gonochoric/gonochoristic/dioecious (sexes separate)
- Breeding interval
- Western screech owls breed once yearly.
- Breeding season
- Eggs are laid in March or April.
- Range eggs per season
- 2 to 7
- Average eggs per season
- Range time to hatching
- 26 to 34 days
- Range fledging age
- 29 to 35 days
- Average age at sexual or reproductive maturity (female)
- 1 years
- Average age at sexual or reproductive maturity (male)
- 1 years
Western screech-owls add no new material to the nest site, rather they use whatever substrate is already present. They prefer to nest in tree cavities or nest boxes. Cottonwood seems to be favored wherever available, most likely because of its tendency to form large natural cavities (Cannings and Angell, 2001).
Altricial nestlings are covered in white down when they hatch. Their eyes are closed and they have an egg tooth. Males will feed females throughout egg-laying, incubation and brooding periods until the young are about 3 weeks old (Cannings and Angell, 2001). Both males and females provide food for the nestlings (Cornell Lab of Ornithology, 1999; Ehrlich et al., 1988). (Cannings and Angell, 2001; Cornell Lab of Ornithology, 1999; Ehrlich, et al., 1988)
- Parental Investment
- no parental involvement
Western screech-owls usually live from 1 to 8 years in the wild. The longest recorded lifespan for a western screech-owl in the wild is 13 years, in captivity the longest recorded lifespan is 19 years.
- Range lifespan
- 13 (high) years
- Range lifespan
- Range lifespan
- 19 (high) years
- Range lifespan
- Typical lifespan
- 1 to 8 years
- Typical lifespan
The wings ofhave a low aspect ratio, which is typical of sit-and-wait predators that do not fly long distances (Johnson, 1997; Cannings and Angell, 2001). Young are very capable climbers and adults are able to effectively walk into thickets for roosting (Cannings and Angell, 2001).
has been observed to bathe occasionally. Males roost in close proximity to the nest during breeding season, this reduces the flying distance to the nest throughout the nestling period. Males are joined by the females during the last weeks of the nestling period and they systematically position their roosts opposite the nest cavity entrance to provide increased protection from crows, jays, and other diurnal predators (Cannings and Angell; 2001).
Territories are defended year-round, however, responses to calls by conspecifics decline during the incubation and nestling periods. Western screech-owls react agressively to calls of spotted owls (Strix occidentalis) and great horned owls (Bubo virginianus) (Cannings and Angell; 2001).
Throughout the year, western screech-owls live in pairs. However, they can be found in small family groups before the juvenilles disperse (Cannings and Angell; 2001). (Cannings and Angell, 2001; Johnson, 1997)
We do not have in formation on home range for this species at this time.
Communication and Perception
The song of (Cannings and Angell, 2001)consists of 5 to 15 hollow whistle hoots of a single pitch that accelerate towards the end in a "bouncing ball" sequence (Cannings and Angell, 2001).
- Communication Channels
Western screech-owls are "sit-and-wait" predators. They leave their roosts to forage just before sunset. Their hunting technique may predispose the northern populations to primarily hunt mice. When foraging near bodies of water,will perch and wait until crayfish emerge in the shallows, then it will fly down and grab one by dipping only its legs into the water. It will also hawk for flying insects and glean arthropods from folage, but it prefers to catch small, terrestrial mammals (Hayward and Garton, 1988; Cannings and Angell, 2001).
Songbirds are a frequent meal forand as a result the owls are often mobbed in response to their threats. Frequent mobbers are those songbirds that are most often preyed upon (for example, northern cardinals and white-throated sparrows). Mobbing by songbirds occurs most frequently during the spring and early summer nesting period. Most mobbers are permanent residents that are always part of the avian prey community. Birds use seasonal song, age-realted plumage and nest-area cues of western screech-owls to help assess the danger of predation (Gehlbach and Leverett, 1995).
- Primary Diet
- Animal Foods
- terrestrial non-insect arthropods
- terrestrial worms
Western screech-owls typically react to the presence of predators with bill snaps and bark calls.
Known predators include: spotted owls (Strix occidentalis), great horned owls (Bubo virginianus), barred owls (Strix varia), raccoons (Procyon lotor), gopher snakes (Pituophis melanoleucus) and crows and jays (family Corvidae). (Cannings and Angell, 2001)
Colonies of tree ants (genus Crematogaster) will often occupy the nest sites of and apparantly protect the nest from disturbance by biting or stinging potential predators. This relationship seems to be a unique symbiosis in the genus Otus, however, it is infrequent (McCallum et al., 1995).
The abundance of western screech-owls is positively associated with the abundance of elf owls (Micrathene whitneyi) in the Sonoran Desert (Hardy et al., 1999). (Hardy, et al., 1999; McCallum, et al., 1995)
- tree ants (genus Crematogaster)
Economic Importance for Humans: Positive
Western screech-owls can live in suburban habitats where nest and root sites are available. Pairs nesting in these suburban habitats are often tolerant of humans close to their nests , this allows birders to visit their nest sites (Cannings and Angell, 2001). In addition, Otus asio), challenges researchers to discover more about this magnificent bird and hopefully urge conservationists to adopt an active role in habitat preservation. (Cannings and Angell, 2001)(previously thought to be conspecific with
- Positive Impacts
- research and education
Economic Importance for Humans: Negative
There are no known adverse affects of western screech-owls on humans.
Western screech-owls are closely linked to the riparian habitats of its range; these areas are often the first habitat in any given area to suffer the effects of urban development. Although pairs nesting in suburban areas are generally tolerant of humans close to their nests, they may be sensitive to local disturbance at nest sites from frequent visits by birders (Hardy et al., 1999; Cannings and Angell, 2001). Breeding populations are continually threatend by rapid urbanization and degradation of habitat, and face possible competition from exotic species such as European starlings (Sturnus vulgaris) (Hardy et al., 1999).
Currently there are no official data on the trends of population densities for western screech-owls. However, their populations are probably declining slowly as habitat is lost (Cannings and Angell, 2001).
Western screech-owls are protected by the US MBTA and are listed under Appendix II by CITES, but are not listed on the US Federal List or the IUCN Red List. (Cannings and Angell, 2001; Hardy, et al., 1999)
Western screech-owls (Otus asio), were finally recognized as a seperate species in 1983. Their re-classification was based on signifigant differences in vocalization and behavior between the two species (Cannings and Angell, 2001).), long considered conspecific with eastern screech-owls (
Despite its abundance, little is known about (Cannings and Angell, 2001), including basic parameters such as survival rates and breeding success. Priorities for future research include vocalization studies that could focus on the geographic variation in calls, and genetic analysis of various subspecies for taxonomic purposes (Cannings and Angell, 2001).
Alaine Camfield (editor), Animal Diversity Web.
Erin Quist (author), University of Arizona, Todd McWhorter (editor), University of Arizona.
living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.
uses sound to communicate
living in landscapes dominated by human agriculture.
young are born in a relatively underdeveloped state; they are unable to feed or care for themselves or locomote independently for a period of time after birth/hatching. In birds, naked and helpless after hatching.
- bilateral symmetry
having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.
an animal that mainly eats meat
uses smells or other chemicals to communicate
the nearshore aquatic habitats near a coast, or shoreline.
- desert or dunes
in deserts low (less than 30 cm per year) and unpredictable rainfall results in landscapes dominated by plants and animals adapted to aridity. Vegetation is typically sparse, though spectacular blooms may occur following rain. Deserts can be cold or warm and daily temperates typically fluctuate. In dune areas vegetation is also sparse and conditions are dry. This is because sand does not hold water well so little is available to plants. In dunes near seas and oceans this is compounded by the influence of salt in the air and soil. Salt limits the ability of plants to take up water through their roots.
humans benefit economically by promoting tourism that focuses on the appreciation of natural areas or animals. Ecotourism implies that there are existing programs that profit from the appreciation of natural areas or animals.
animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.
union of egg and spermatozoan
forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.
An animal that eats mainly insects or spiders.
- internal fertilization
fertilization takes place within the female's body
offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).
Having one mate at a time.
having the capacity to move from one place to another.
- native range
the area in which the animal is naturally found, the region in which it is endemic.
active during the night
reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.
an animal that mainly eats fish
Referring to something living or located adjacent to a waterbody (usually, but not always, a river or stream).
- seasonal breeding
breeding is confined to a particular season
reproduction that includes combining the genetic contribution of two individuals, a male and a female
living in residential areas on the outskirts of large cities or towns.
uses touch to communicate
that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).
Living on the ground.
defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement
uses sight to communicate
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Cannings, R. 1997. A survey of the Western-Screech Owl (Otus kennicottii macfarleanei) in the interior of British Columbia. Lands and Parks, Victoria, British Columbia: Unpubl. rep., Ministry of Environment.
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Cornell Lab of Ornithology, 1999. "The Birdhouse Network-Eastern Screech-Owl" (On-line). Accessed 01/23/04 at http://birds.cornell.edu/birdhouse/speciesaccounts/EASTSCREECHOWL.htm.
Ehrlich, P., D. Dobkin, D. Wheye. 1988. The Birder's Handbook: A field guide to the natural history of North American birds. New York: Simon & Schuster Inc.
Feusier, S. 1989. Distribution and behavior of Western Screech-Owls (Otus kennicottii) of the Starr Ranch Audubon Sanctuary, Orange Co., California. Humboldt State University, CA: M.S. thesis.
Gehlbach, F., J. Leverett. 1995. Mobbing of eastern screech-owls: predatory cues, risk to mobbers and degree of threat. The Condor, 97(3): 831-834.
Hardy, P., M. Marrison, R. Barry. 1999. Abundance and habitat associations of Elf Owls and Western Screech-Owls in the Sonoran Desert. The Southwestern Naturalist, 44(3): 311-323.
Hayward, G., E. Garton. 1988. Resource partitioning among forest owls in the River of No Return Wilderness, Idaho. Oecologica, 75: 253-265.
Johnson, D. 1997. Wing loading in 15 species of North American owls. Pp. 553-561 in Biology and conservation of owls of the Northern Hemisphere: 2nd International Symposium; 1997 February 5-9; Winnipeg, MB. Stn. Gen. Tech. Rep. NC-190, St. Paul, MN: (J.R. duncan, D.H. Johnson and T.H. Nichols, eds.) USDA Forest Service, North Central Res.
Kitchin, E. 1949. Birds of the Olympic Peninsula. Port Angeles, WA: Olympic Stationers.
Lehman, P. 1994. The birds of Santa Barbara Co., California. University of California, Santa Barbara: Vertebrate Museum.
Levad, R. 1998. Western Screech-Owl. Pp 212-213 in Colorado breeding bird atlas (H.E. Kingery, ed.). , Denver: Colorado Bird Atlas Partnership and Colorado Division of Wildlife.
McCallum, D., F. Gehlbach, S. Webb. 1995. Life history and ecology of Flammulated Owls in a marginal New Mexico population. Wilson Bulletin, 107(3): 530-537.
Noble, P. 1990. Distribution and density of owls at Monte Bello Open Space Preserve, Santa Clara Co., California. Western Birds, 21: 11-16.
Sumner, E. 1929. Comparative studies on the growth of young raptors. The Condor, 31: 85-111.