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Otus asioeastern screech owl(Also: eastern screech-owl)

By Tanya Dewey and Stephen McDonald

Ge­o­graphic Range

East­ern screech-owls are found through­out much of east­ern North Amer­ica, from the Rocky Moun­tains in the West to the At­lantic coast and from Florida and south­ern Texas in the south as far north as south­ern Canada. (Gehlbach, 1995)

Habi­tat

East­ern screech-owls have the broad­est eco­log­i­cal niche of any North Amer­i­can owl. They are found in vir­tu­ally all kinds of habi­tats below about 1500 me­ters el­e­va­tion, from ur­ban­ized sur­round­ings to bo­real forests. They are gen­er­ally found in wooded areas but do well in urban and sub­ur­ban areas and ac­cli­ma­tize read­ily to human pres­ence, often using bird boxes for nest­ing. These birds are cav­ity nesters and use nat­ural cav­i­ties or those cre­ated by other an­i­mals. (Gehlbach, 1995)

  • Range elevation
    1500 (high) m
    4921.26 (high) ft

Phys­i­cal De­scrip­tion

East­ern screech-owls are small owls, from 16 to 25 cm in length. Fe­males are gen­er­ally larger than males, which is com­mon in owls. East­ern screech-owls are dichro­matic, they come in two dis­tinct color morphs. They are ei­ther uni­formly gray or uni­formly ru­fous, with darker streak­ing on the body. Both color morphs make them very dif­fi­cult to dis­tin­guish from sur­round­ing tree bark. They have bold streak­ing on their breasts, yel­low beaks and eyes, rel­a­tively large feet with feath­ered toes, and large "ear" tufts on ei­ther side of their head. East­ern screech-owls are dis­tin­guished from their close rel­a­tive west­ern screech-owls, by their yel­low bill, de­scend­ing trill call, and by the ru­fous col­oration of some in­di­vid­u­als. (Gehlbach, 1995)

  • Sexual Dimorphism
  • female larger
  • Average mass
    164.1 g
    5.78 oz
    AnAge
  • Range length
    16 to 25 cm
    6.30 to 9.84 in
  • Average basal metabolic rate
    0.586 W
    AnAge

Re­pro­duc­tion

Most east­ern screech-owls form pair bonds for life with in­di­vid­u­als of the same age. Some mate switch­ing oc­curs after un­suc­cess­ful nest­ing at­tempts and some males have been ob­served nest­ing si­mul­ta­ne­ously and se­quen­tially with more than one fe­male. Both males and fe­males crouch and trill when their mate ap­proaches. (Gehlbach, 1995)

East­ern screech-owl fe­males lay eggs over a pe­riod of days to more than a week and gen­er­ally do not begin full-time in­cu­ba­tion until the last egg is laid. As a re­sult, eggs laid first also de­velop and hatch first. With larger broods, where newly hatched young may be de­vel­op­men­tally up to 8 days be­hind their nest­mates, younger nestlings tend to be killed ac­ci­den­tally or by their sib­lings. From 2 to 7 eggs, usu­ally 3 or 4, are laid in a large nest cav­ity. They are in­cu­bated for 26 (eggs laid last) to 34 days (ear­lier eggs), with an av­er­age of 30 days of in­cu­ba­tion. (Gehlbach, 1995)

  • Breeding interval
    Breeding occurs once a year, usually, but a second clutch may be attempted in areas with dense resources.
  • Breeding season
    Breeding occurs from February through March and perhaps later.
  • Range eggs per season
    2 to 7
  • Average eggs per season
    3.5
  • Average eggs per season
    4
    AnAge
  • Range time to hatching
    26 to 34 days
  • Range time to independence
    8 to 10 weeks
  • Average age at sexual or reproductive maturity (female)
    1 years
  • Average age at sexual or reproductive maturity (female)
    Sex: female
    365 days
    AnAge
  • Average age at sexual or reproductive maturity (male)
    1 years
  • Average age at sexual or reproductive maturity (male)
    Sex: male
    365 days
    AnAge

East­ern screech-owl fe­males in­cu­bate the eggs and brood the young. Males feed fe­males and guard nest cav­i­ties dur­ing in­cu­ba­tion and brood­ing. The young leave the nest at about 28 days old and re­main with the par­ents until they are 8 to 10 weeks old. Both par­ents feed the young dur­ing this pe­riod.

Lifes­pan/Longevity

An east­ern screech-owl lived in the wild for 14 years and 2 months, though most prob­a­bly live for much less than this. It is es­ti­mated that only 30 to 50% of young from one year sur­vive into the next year. (Gehlbach, 1995)

Be­hav­ior

East­ern screech-owls are not mi­gra­tory and often times a pair may keep the same nest, in win­ter and sum­mer. Fe­males re-use suc­cess­ful nest sites. These owls are soli­tary, ex­cept dur­ing the mat­ing sea­son and dur­ing win­ters when mates share a win­ter nest. Males de­fend ter­ri­to­ries in which they main­tain sev­eral nest­ing sites. These owls mainly fly but also hop and walk on the ground when chas­ing prey. (Gehlbach, 1995)

Home Range

Es­ti­mates of home range size vary with re­gion and sea­son, from 6 to 16 hectares in size. (Gehlbach, 1995)

Com­mu­ni­ca­tion and Per­cep­tion

East­ern screech-owls have acute senses of hear­ing and vi­sion which help them to lo­cate prey in dim light. They use a va­ri­ety of vo­cal­iza­tions. Nestlings and fe­males call softly from within the nest cav­ity. Both males and fe­males give the "trill" song, which may be used to ad­ver­tise nest sites, in court­ing, when ar­riv­ing at the nest with food, and to call nestlings out of the nest for fledg­ing. Other calls are hoots, rasps, chuckle-rat­tles, barks, and screeches. These calls gen­er­ally in­di­cate some de­gree of alarm or anx­i­ety. (Gehlbach, 1995)

Food Habits

East­ern screech-owls eat the most var­ied diet of any North Amer­i­can owl. Their diet in­cludes large evening ac­tive in­sects, like moths and katy­dids, cray­fish, earth­worms, am­phib­ians, rep­tiles, small mam­mals, like mice and bats, and small birds. These owls have sym­met­ri­cal ears, which sug­gests that they hunt pri­mar­ily using their vi­sion. They do, how­ever, have ex­cel­lent hear­ing as they often cap­ture prey hid­den by leaf lit­ter. They hunt by sit­ting on a tree branch and wait­ing to see or hear prey. East­ern screech-owls cache prey in their nests for later con­sump­tion by adults or nestlings. (Gehlbach, 1995; Gehlbach, 1995)

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

Pre­da­tion

East­ern screech-owls are ex­tremely vig­i­lant near their nest holes, per­haps in order to as­sess preda­tor move­ments. They are preyed on as adults and fledg­lings by larger owls, hawks, and other east­ern screech-owls. Eggs and nestlings may be taken by black rat­snakes, Vir­ginia opos­sums, rac­coons, and ring­tails. East­ern screech-owls use alarm calls and will phys­i­cally at­tack po­ten­tial preda­tors that ap­proach their nestlings and fledg­lings. Their col­oration also makes them cryp­tic. (Gehlbach, 1995)

  • Anti-predator Adaptations
  • cryptic

Ecosys­tem Roles

East­ern screech-owls are some­times the most abun­dant and im­por­tant small preda­tor in urban and sub­ur­ban forested areas. They also de­lib­er­ately bring live an­i­mals, such as blind snakes into their nests. These an­i­mals feed on the ants, flies, and other in­sects that in­fest the nest cav­ity. Ac­ro­bat ants may in­habit the nest cav­ity of these owls and will repel in­trud­ers by spray­ing ir­ri­tat­ing se­cre­tions and bit­ing. (Gehlbach, 1995)

Mu­tu­al­ist Species

Eco­nomic Im­por­tance for Hu­mans: Pos­i­tive

East­ern screech-owls may help to con­trol the pop­u­la­tions of po­ten­tial pests such as mice and some in­sects.

  • Positive Impacts
  • controls pest population

Eco­nomic Im­por­tance for Hu­mans: Neg­a­tive

There are no neg­a­tive ef­fects of east­ern screech-owls on hu­mans.

Con­ser­va­tion Sta­tus

East­ern screech-owls may suf­fer as a re­sult of de­for­esta­tion and the loss of ap­pro­pri­ate nest­ing cav­i­ties and prey pop­u­la­tions. They are rel­a­tively com­mon through­out their range, though, and are not cur­rently threat­ened. (Gehlbach, 1995)

Con­trib­u­tors

Tanya Dewey (au­thor), An­i­mal Di­ver­sity Web, Kari Kirschbaum (ed­i­tor), An­i­mal Di­ver­sity Web.

Stephen Mc­Don­ald (au­thor), Uni­ver­sity of Michi­gan-Ann Arbor.

Glossary

Nearctic

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.

World Map

acoustic

uses sound to communicate

altricial

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.

carnivore

an animal that mainly eats meat

chaparral

Found in coastal areas between 30 and 40 degrees latitude, in areas with a Mediterranean climate. Vegetation is dominated by stands of dense, spiny shrubs with tough (hard or waxy) evergreen leaves. May be maintained by periodic fire. In South America it includes the scrub ecotone between forest and paramo.

chemical

uses smells or other chemicals to communicate

cryptic

having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.

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.

endothermic

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.

female parental care

parental care is carried out by females

fertilization

union of egg and spermatozoan

forest

forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.

insectivore

An animal that eats mainly insects or spiders.

internal fertilization

fertilization takes place within the female's body

iteroparous

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).

male parental care

parental care is carried out by males

monogamous

Having one mate at a time.

motile

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.

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

polygynous

having more than one female as a mate at one time

scrub forest

scrub forests develop in areas that experience dry seasons.

seasonal breeding

breeding is confined to a particular season

sedentary

remains in the same area

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

solitary

lives alone

stores or caches food

places a food item in a special place to be eaten later. Also called "hoarding"

suburban

living in residential areas on the outskirts of large cities or towns.

tactile

uses touch to communicate

temperate

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).

terrestrial

Living on the ground.

tropical savanna and grassland

A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.

savanna

A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.

temperate grassland

A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.

urban

living in cities and large towns, landscapes dominated by human structures and activity.

visual

uses sight to communicate

Ref­er­ences

Pear­son, T.G. 1940. Birds of Amer­ica. Third Edi­tion. Gar­den City Pub­lish­ing Com­pany, New York.

http://​www.​eecs.​tufts.​edu/​~cabotsch/bul­loughs/ver­te­brates/birds/eastern-screech-owl.​html

http://​www.​ai-design.​com/​stargig/​raptor/​global/​content/​report/​Eastern Screech owl.​html

Gehlbach, F. 1995. East­ern Screech Owl (Otus asio). The Birds of North Amer­ica, 165: 1-24.

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Classification

Classification

  • Kingdom Animalia animals
  • Phylum Chordata chordates
  • Subphylum Vertebrata vertebrates
  • Class Aves birds
  • Order Strigiformes owls
  • Family Strigidae typical owls
  • Genus Otus scops-owls and screech-owls
  • Species Otus asio eastern screech owl