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eastern screech owl

Otus asio

What do they look like?

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 colors. They are either gray or reddish, with darker streaking on the body. Both color variations make these owls blend in with the color of 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. These feather tufts really have nothing to do with the owl's ears, but they location on the side of the head makes them look like large, erect ears. (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

Where do they live?

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)

What kind of habitat do they need?

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 do well near humans, 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

How do they reproduce?

Most eastern screech-owls form pair bonds for life with individuals of the same age, although some males have more than one mate. 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 do not begin full-time incubation until the last egg is laid. Because of this, eggs laid first also develop and hatch first. With larger broods, where newly hatched owlets may be 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)

  • How often does reproduction occur?
    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.

How long do they live?

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)

How do they behave?

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)

How do they communicate with each other?

Eastern screech-owls have keen senses of hearing and vision which help them to locate prey in dim light. They use a variety of calls to communicate with others. 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 females use it to ask nestlings to come out of the nest and try flying. Other calls are hoots, rasps, chuckle-rattles, barks, and screeches. These calls generally indicate some degree of alarm or anxiety. (Gehlbach, 1995)

What do they eat?

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 mainly by using their vision. (Ears that are not symmetrical give owls a better ability to pinpoint the location of prey using only hearing.) 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 store prey in their nests to eat later or for their young to eat later. (Gehlbach, 1995; Gehlbach, 1995)

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

What eats them and how do they avoid being eaten?

Eastern screech-owls watch animal movements near their nest holes very carefully, they are always on the lookout for predators. 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. The colors of eastern screech-owls make them very difficult to see against a bark background, which protects them from predators as well. (Gehlbach, 1995)

  • These animal colors help protect them
  • cryptic

What roles do they have in the ecosystem?

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)

Species (or larger taxonomic groups) that are mutualists with this species

Do they cause problems?

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

How do they interact with us?

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

  • Ways that people benefit from these animals:
  • controls pest population

Are they endangered?

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.

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.

 
University of Michigan Museum of ZoologyNational Science Foundation

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McDonald, S. 1999. "Otus asio" (On-line), Animal Diversity Web. Accessed July 23, 2014 at http://www.biokids.umich.edu/accounts/Otus_asio/

BioKIDS is sponsored in part by the Interagency Education Research Initiative. It is a partnership of the University of Michigan School of Education, University of Michigan Museum of Zoology, and the Detroit Public Schools. This material is based upon work supported by the National Science Foundation under Grant DRL-0628151.
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