Animal Diversity Web

Ge­o­graphic Range

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)

• Biogeographic Regions
• nearctic
  • native

Habi­tat

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 States O. ken­ni­cot­tii oc­curs 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)

• Habitat Regions
• temperate
• terrestrial

• Terrestrial Biomes
• desert or dune
• forest

• Aquatic Biomes
• coastal

• Other Habitat Features
• suburban
• agricultural
• riparian

Phys­i­cal De­scrip­tion

Otus ken­ni­cot­tii 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)

• Other Physical Features
• endothermic
• bilateral symmetry

• 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

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).

Re­pro­duc­tion

Otus ken­ni­cot­tii is usu­ally mono­go­mous, al­though polygamy oc­curs oc­ca­sion­ally.

Be­fore the breed­ing sea­son, male O. ken­ni­cot­tii 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. (Cor­nell Lab of Or­nithol­ogy, 1999)

• Mating System
• monogamous

Through­out its range, O. ken­ni­cot­tii 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
• iteroparous
• seasonal breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual
• fertilization
  • internal
• oviparous

• 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

  3

• 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
• altricial
• pre-fertilization
• pre-hatching/birth
  • protecting
    • female
• pre-weaning/fledging
  • provisioning
    • male
    • female
  • protecting
    • female

Lifes­pan/Longevity

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
  Status: wild

  13 (high) years

• Range lifespan
  Status: captivity

  19 (high) years

• Typical lifespan
  Status: wild

  1 to 8 years

Be­hav­ior

The wings of Otus ken­ni­cot­tii have 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).

Otus ken­ni­cot­tii 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)

• Key Behaviors
• flies
• nocturnal
• motile
• territorial

Home Range

We do not have in for­ma­tion on home range for this species at this time.

Com­mu­ni­ca­tion and Per­cep­tion

The song of Otus ken­ni­cot­tii 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). (Can­nings and An­gell, 2001)

• Communication Channels
• acoustic

• Perception Channels
• visual
• tactile
• acoustic
• chemical

Food Habits

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, O. ken­ni­cot­tii 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 for O. ken­ni­cot­tii and 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).

West­ern screech-owls com­monly eat: small mam­mals, birds, an­nelid worms, in­sects, cray­fish and fish. (Can­nings and An­gell, 2001; Gehlbach and Lev­erett, 1995; Hay­ward and Gar­ton, 1988)

• Primary Diet
• carnivore
  • eats terrestrial vertebrates
  • piscivore
  • insectivore
  • eats non-insect arthropods

• Animal Foods
• birds
• mammals
• fish
• insects
• terrestrial non-insect arthropods
• terrestrial worms

Pre­da­tion

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)

• Known Predators

  • spotted owls (Strix occidentalis)
  • great horned owls (Bubo virginianus)
  • barred owls (Strix varia)
  • raccoons (Procyon lotor)
  • gopher snakes (Pituophis melanoleucus)
  • crows and jays (Corvidae)

Ecosys­tem Roles

Colonies of tree ants (genus Cre­mato­gaster) will often oc­cupy the nest sites of Otus ken­ni­cot­tii 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)

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 ken­ni­cot­tii (pre­vi­ously thought to be con­spe­cific with 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)

• Positive Impacts
• ecotourism
• research and education

Eco­nomic Im­por­tance for Hu­mans: Neg­a­tive

There are no known ad­verse af­fects of west­ern screech-owls on hu­mans.

Con­ser­va­tion Sta­tus

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)

• IUCN Red List

  Least Concern
  More information

• IUCN Red List

  Least Concern
  More information

• US Migratory Bird Act

  Protected

• US Federal List

  No special status

• CITES

  Appendix II

Other Com­ments

West­ern screech-owls (Otus ken­ni­cot­tii), long con­sid­ered con­spe­cific with east­ern 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).

De­spite its abun­dance, lit­tle is known about Otus ken­ni­cot­tii, 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). (Can­nings and An­gell, 2001)

Con­trib­u­tors

Alaine Cam­field (ed­i­tor), An­i­mal Di­ver­sity Web.

Erin Quist (au­thor), Uni­ver­sity of Ari­zona, Todd McWhorter (ed­i­tor), Uni­ver­sity of Ari­zona.

Ref­er­ences

Camp­bell, R., N. Dawe, I. Mc­Tag­gert-Cowan, J. Cooper, G. Kaiser. 1990. The birds of British Co­lum­bia. Vol 2: di­ur­nal birds of prey through wood­peck­ers. Co­lum­bia Mu­seum, Vic­to­ria: R. Br.

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.

Can­nings, R., T. An­gell. 2001. West­ern Screech-Owl (Otus Ken­ni­cot­tii). In the Birds of North Amer­ica, No. 597. Philadel­phia, PA: (A. Poole and F. Gill, eds.). The Birds of North Amer­ica, Inc.

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.