Asio otuslong-eared owl

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Geographic Range

Long-eared owls are found throughout the northern hemisphere. Their range extends throughout temperate North America, through Europe and the former Soviet Union as far east as Japan. Isolated populations are also found North and East Africa, the Azores, and the Canary Islands.

Habitat

Long-eared owls inhabit dense vegetation close to grasslands, as well as open forests shrub lands from sea level up to 2000 m elevation. They are common in tree belts along streams of plains and even desert oases. They can also be found in shelterbelts, small tree groves, thickets surrounded by wetlands, grasslands, marshes and farmlands.

  • Range elevation
    0 to 2000 m
    0.00 to 6561.68 ft

Physical Description

Long-eared owls are medium-sized owls. Females are generally much larger than males, (260 to 435 g and 27 to 40 cm in length versus 220-305 g and 35 to 37.5 cm in length for males). Long-eared owls are the most slender of all North American owls, an attribute that they use as a defense against predators. When perched, long-eared owls elongate their body and ear tufts, and compresses its feathers, making them resembles a tree limb. Long-eared owls have long, rounded wings and a long tail. The wings are so long that they cross each other in the back when the bird is perched. The wingspan of adults ranges from 90 to 100 cm. The head of long-eared owls is large and round, topped with long blackish ear tufts that are close together and are not visible in flight.

Long-eared owls are brownish gray, with vertical streaks that distinguishing them from great horned owls, which have horizontal streaks. Long-eared owls have pale patches on the face that give the appearance of white eyebrows, and a white patch below the bill. They have a black bill, orange or yellow eyes, and their legs and toes are completely feathered.

Females are generally darker and more richly colored than males. Juveniles look similar to adults, but have softer, looser feathers.

  • Sexual Dimorphism
  • female larger
  • sexes colored or patterned differently
  • Range mass
    220 to 435 g
    7.75 to 15.33 oz
  • Range length
    35 to 40 cm
    13.78 to 15.75 in
  • Range wingspan
    90 to 100 cm
    35.43 to 39.37 in
  • Average basal metabolic rate
    0.954 W
    AnAge

Reproduction

Long-eared owls are monogamous, though polygyny is occasionally observed in this species. Pairs begin to form in winter, and breeding takes place from February to mid-July. Males advertise for a mate using songs and aerial displays, such as zig-zag flights through trees in the breeding habitat.

Long-eared owls breed between February and July, and raise one brood per season. Males begin advertising for a mate as early as January. They use songs and aerial displays to attract a female.

Long-eared owls nest in trees, usually in stick nests built by other species. They may occasionally build a nest of their own, or use a nest located in an old tree stump or on the ground, but this is uncommon. Once a nest is selected, the female lays 2 to 10 (usually 5 to 6) eggs at 2-day intervals. The eggs are white, smooth and glossy. The female incubates the eggs for 25 to 30 (usually 26-28) days. She never leaves the eggs uncovered during the day, though she takes short breaks at night. The chicks are semi-altricial, and are brooded by the female for at least 2 weeks. The young leave the nest at about 21 days, though they are still flightless (called branching), and reside in nearby vegetation. They begin making short flights at about 35 days old and become independent at 10 to 11 weeks old. The male provides food for the female and owlets throughout incubation and brood-rearing. Long-eared owls usually begin breeding at 1 year.

Long-eared owls breed between February and July. They raise one brood per season. Long-eared owls nest in trees in nests built by other species. Once they choose a nest, the female lays 2 to 10 (usually 5 to 6) eggs. She lays one egg every other day. The eggs are white, smooth and glossy. The female incubates the eggs for 25 to 30 (usually 26-28) days. She never leaves the eggs uncovered during the day, but she takes short breaks at night. The chicks are semi-altricial. The female broods them for at least 2 weeks. The young leave the nest when they are about 21 days old, but they cannot fly yet. They leave the nest by walking, and live on branches near the nest. They begin flying when they are about 35 days old. The male brings food for the female and chicks until the chicks become independent. This happens when they are 10 to 11 weeks old. Long-eared owls usually begin breeding at 1 year.

  • Breeding interval
    Long-eared owls breed once yearly.
  • Breeding season
    Long-eared owls breed between February and July.
  • Range eggs per season
    2 to 10
  • Average eggs per season
    5-6
  • Average eggs per season
    4
    AnAge
  • Range time to hatching
    25 to 30 days
  • Average time to hatching
    26-28 days
  • Average fledging age
    21 days
  • Average time to independence
    8-9 weeks
  • Average age at sexual or reproductive maturity (female)
    1 years
  • Average age at sexual or reproductive maturity (male)
    1 years

Female long-eared owls incubate the eggs and brood the semi-altricial chicks for at least two weeks. During incubation and brood rearing, the male provides food for the female and chicks. The male continues to feed the chicks until they become independent at 10 to 11 weeks old.

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

Lifespan/Longevity

The oldest known wild long-eared owl lived 27 years and 9 months. Adult annual survivorship in Germany and Switzerland was estimated to be 69%.

Behavior

Long-eared owls are strictly nocturnal. They live in pairs during the breeding season, but are tolerant of other long-eared owls, and often roost in groups of 2 to 20 during the non-breeding season. During the breeding season, long-eared owls defend only the area immediately surrounding the nest. Nests may be found in a loose colony, with closest nests only 14 m apart.

Some long-eared owls are migratory, while others spend the winter in the breeding range. Other long-eared owls appear to be nomadic, moving in response to fluctuations in food availability.

Home Range

The home range size of long-eared owls appears to vary considerably between pairs, seasons and localities. Studies have estimated home range sizes between 0.7 and 20.25 square kilometers.

Communication and Perception

Long-eared owls use a wide repertoire of calls to communicate primarily during the breeding season. They are mostly silent at other times of the year. The most common vocalizations are soft musical hoots and single quavering hoots. When excited, long-eared owls may also shriek or whistle. Alarm calls are demonstrated by both sexes. Parents strongly defend their young, with vocalizations as well as a "crippled wing act" used as a lure. Threat displays are also used, generally directed at human intruders or predators rather than toward one another.

Long-eared owls have excellent hearing and vision that aids them in perceiving their environment and in catching prey.

Food Habits

Long-eared owls hunt almost exclusively at night and in open habitats. During brood-rearing, they may begin hunting before sunset. Long-eared owls are active search-hunters. They most likely capture prey using their excellent low-light eyesight and their superb hearing. Most prey are captured on the ground or from low vegetation.

Long-eared owls probably prey opportunistically on small mammals under 100 g. Their principal prey are voles and deer mice. Other small mammals taken include pocket mice, kangaroo rats, pocket gophers, shrews (genera Glarina, Cryptotis and Sorex), juvenile rabbits (genera Sylvilagus and Lepus) and juvenile rats. Long-eared owls also occasionally eat small birds, small snakes, and insects. After capturing prey, long-eared owls kill it by biting the back of the skull and then swallow it whole. Excess prey is stored at the nest during incubation and during the nestling stage.

There is no information available regarding how long-eared owls drink or obtain sufficient water.

  • Primary Diet
  • carnivore
    • eats terrestrial vertebrates
  • Animal Foods
  • birds
  • mammals
  • reptiles
  • insects

Predation

Adult long-eared owls are preyed upon by many other raptors. Raptors that have been observed taking long-eared owls include great-horned owls, barred owls, golden eagles, red-tailed hawks, red-shouldered hawks, northern goshawks, eagle owls, common buzzards, and peregrine falcons. Incubating female long-eared owls have been killed by raccoons.

Long-eared owl nestlings are vulnerable to predation by porcupines, bull snakes, American crows, black-billed magpies, and several hawk species.

Roosting adults are difficult to see because their coloration, slender body and ear tufts help them to look like a branch of the tree that they are roosting in. When a predator approaches a nest, adult long-eared owls defend the eggs or young by circling the nest and snapping their bill at the predator, or dive-bombing the predator while making alarm calls. They may also pretend to be injured in order to draw the predator away from the nest. In some cases, adults from several nearby nests may all perform defense displays when a single nest is threatened.

  • Anti-predator Adaptations
  • cryptic

Ecosystem Roles

Long-eared owls impact the local populations of their prey. They also host several external and internal parasites.

Economic Importance for Humans: Positive

Long-eared owls help to control populations of rodents that are considered to be agricultural pests.

  • Positive Impacts
  • controls pest population

Economic Importance for Humans: Negative

Long-eared owls have no known negative effect on humans.

Conservation Status

Populations of long-eared owls are difficult to track. However, within the U.S., populations appear to be largely stable, with declines locally in some states, including New Jersey, Minnesota and California. Most deaths are probably due to starvation or predation, though destruction of vegetation and alteration of habitat are also potential causes of population declines. Adults are occasionally killed by cars or shot by hunters in the U.S., but this is not common.

Long-eared owls are protected under CITES Appendix II and the U.S. Migratory Bird Act. They are not federally endangered or threatened in the United States, but they are considered threatened in the state of Michigan.

Other Comments

Six subspecies of Asio otus are recognized. The population endemic to Madagascar is usually treated as a full species (Asio madagascariensis).

Contributors

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

Alicia Ivory (author), University of Michigan-Ann Arbor.

Glossary

Ethiopian

living in sub-Saharan Africa (south of 30 degrees north) and Madagascar.

World Map

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

Palearctic

living in the northern part of the Old World. In otherwords, Europe and Asia and northern Africa.

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acoustic

uses sound to communicate

agricultural

living in landscapes dominated by human agriculture.

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.

arboreal

Referring to an animal that lives in trees; tree-climbing.

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

colonial

used loosely to describe any group of organisms living together or in close proximity to each other - for example nesting shorebirds that live in large colonies. More specifically refers to a group of organisms in which members act as specialized subunits (a continuous, modular society) - as in clonal organisms.

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.

forest

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

holarctic

a distribution that more or less circles the Arctic, so occurring in both the Nearctic and Palearctic biogeographic regions.

World Map

Found in northern North America and northern Europe or Asia.

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).

marsh

marshes are wetland areas often dominated by grasses and reeds.

migratory

makes seasonal movements between breeding and wintering grounds

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.

nocturnal

active during the night

nomadic

generally wanders from place to place, usually within a well-defined range.

oviparous

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

riparian

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

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"

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.

visual

uses sight to communicate

References

Marks, J.S., D.L. Evans, and D.W. Holt. 1994. Long-eared owl (Asio otus). In The Birds of North America, No. 133 (A. Poole and F. Gill, Eds.). Philadelphia: The Academy of Natural Sciences; Washington, D.C.: The American Ornithologists' Union.

Terres, J. The Audubon Society Encyclopedia of North American Birds. Alfred A. Knopf, New York, 1980.

"The Raptor Center; University of Minnesota College of Veterinary Medicine" (On-line). Accessed (Date Unknown) at http://www.ahc.umn.edu/ahc_content/colleges/vetmed/Depts_and_Centers/Raptor_Center/index2.cfm/nav/9773/parent/9748/type/F/content_path/colleges@vetmed@Depts_and_Centers@Raptor_Center@Information_about_Raptors/content_name/Long-eared_Owl.htm/pic/none/bold/Information_about_Raptors.