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short-eared owl

Asio flammeus

What do they look like?

Short-eared owls are 340 to 423 mm long and have a wing length of 279 to 314 mm. Males and females are not easy to tell apart just by looking at them, but females are usually slightly larger. Their feathers are yellow-white and dark brown; parts of the head and especially the legs and flanks are white. Individuals vary considerably in colors. The right and left ears are positioned differently on the sides of their head, but the size and shape of the two ears are the same. (Holt and Leasure, 1993; Martin, 1990; Pearson, 1936)

  • Sexual Dimorphism
  • female larger
  • Range mass
    206 to 475 g
    7.26 to 16.74 oz
  • Average mass
    347 g
    12.23 oz
  • Range length
    340 to 423 mm
    13.39 to 16.65 in
  • Range wingspan
    950 to 1100 mm
    37.40 to 43.31 in
  • Average basal metabolic rate
    313.375 cm3.O2/g/hr

Where do they live?

Short-eared owls are one of the world's most widely distributed owls. They inhabit all of North and South America; this area includes the coast of the Arctic Ocean to Pantagonia. Short-eared owls can also be found on every continent except Australia and Antarctica. (Granlund et al., 1994; Welty, 1975; Pearson, 1936)

What kind of habitat do they need?

One of the world's most widely distributed owls, short eared owls can be found throughout much of North America and Eurasia. These owls prefer to live in marshes and bogs; they inhabit open, treeless areas. Their hunting and nesting habits make them well suited to relatively flat land. This species is migratory but uses relatively similar habitats during summer and winter. Short-eared owls have specialized eating habits and tend to stay where they can find ample food. They will leave an area to find preferred prey rather than eat other animals. Nests are usually located on dry sites and in open country supporting small mammals such as voles and lemmings.

(Martin, 1990; Sparks and Soper, 1989; Pearson, 1936)

How do they reproduce?

Owls usually live on their own so they have to learn to recognize each other as mating partners rather than prey or predator. They have some difficulty identifying the gender of prospective mates from a distance. Male short-eared owls use an aerial display that includes wing clapping to alert the female of his presence and sex. Males also may offer food to females; this prevents females from considering the male as food.

Males and females begin to form pairs in mid-February, continuing through June. Breeding usually begins in April. Short-eared owls are reported to also raise a second brood during the warm season, although this is not confirmed. To attract females, males perform sky dancing displays, day or night. The sky dance consists of a song accompanied by aerial acrobatics. Short-eared owls are generally thought to be monogamous; however, the pair bond probably does not last beyond the breeding season. (Holt and Leasure, 1993)

Breeding usually takes place in the summer habitat of short-eared owls, but they may breed in their wintering area if food is plentiful. They nest on the ground in protection provided by tall grasses, often returning to the same nests. Each nest contains 4 to 7 white, unspotted eggs. The eggs have an average incubation of 21 days. Nestlings have been known to prey on their smaller nest mates. The young usually disperse from the nest when they are about 14 to 17 days old. They are independent 1 to 2 weeks after fledging. (Holt and Leasure, 1993; Sparks and Soper, 1989; Pearson, 1936; Welty, 1975)

  • How often does reproduction occur?
    Short-eared owls typically breed once yearly in the spring. Second broods have been reported but data is still needed to confirm this.
  • Breeding season
    Short-eared owls typically breed late March to June, but mostly in April. In the southern hemisphere, breeding begins in September.
  • Range eggs per season
    1 to 11
  • Average eggs per season
    5.6
  • Average eggs per season
    6
    AnAge
  • Range time to hatching
    21 to 37 days
  • Range fledging age
    24 to 36 days
  • Range time to independence
    31 to 43 minutes
  • 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

Only females brood and feed nestlings, while male provide food and defend the nest with distraction displays and vocalizations. Females protect nestlings from some weather conditions by brooding when young, and mantling when larger. When they are born young are semi-altricial, which means that they are relatively immobile and helpless when they hatch, but are down-covered rather than naked. (Holt and Leasure, 1993)

How long do they live?

Records are limited, but the longevity record for a wild short-eared owl is 4 yrs, 2 months. Causes of mortality include occasionally being hit by cars and airplanes, or being shot or trapped.

How do they behave?

In contrast with many other owls, short-eared owls begin foraging during daylight or early evening. These owls may continue to be active into the night, but usually cease activity after nightfall. They have a tendency to form communal roosts during the winter months. In different times of the year, they may live alone or together, but they always hunt alone.

After breeding, a mated pair remains together for the current breeding season. These owls defend their territories during the breeding season through skirmishes and chases; the size of this area depends on food availabiltiy. (Holt and Leasure, 1993; Martin, 1990; Sparks and Soper, 1989)

Short-eared owls are thought to be highly migratory in the northern part of their range, above around 50 degrees north latitude. Some individuals in more southern parts of the range may make small migratory movements into warmer areas. Foraging movements, migration, and juvenile dispersal may sometimes be confused.

  • Range territory size
    .18 to 2.42 km^2

Home Range

Breeding territories vary widely in size, depending on the density of resources in the area.

How do they communicate with each other?

Short-eared owl nestlings give high pitched calls from within the egg, and from hatching until they are about 7 days old. These are probably begging calls or perhaps expressing discomfort. The vocal pitch changes at about 7 days and becomes lower. Adults sometimes direct calls at human territorial intruders. Both males and females bark, scream, whine, and give broken wing distraction displays to defend the nest and young from potential threats. In late February and March, territorial songs are sung. (Holt and Leasure, 1993)

Short-eared owls have keen vision, especially in low light. They also use their excellent sense of hearing to help locate and capture prey.

What do they eat?

Short-eared owls prey primarily on voles, mice, and other small mammals. Their strong talons and sharp beak make them well adapted to 'picking up' their food while in flight. These owls may utilize a 'perch-and-pounce' hunting method if there is an adequate perching point available. Otherwise, they hunt by flying two meters above the ground in a regular, slow manner. Short-eared owls rely mainly on auditory clues; using these alone, they can catch prey that is under continuous grass cover. (Martin, 1990 and Pearson, 1936)

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

What eats them and how do they avoid being eaten?

Short-eared owls are vulnerable primarily to mammalian predation due to the type of open habitat they occupy and their ground nesting habit. Short-eared owls fly fast and directly at an intruder, pulling up and presenting their talons at the last moment. They often use thermal updrafts during skirmishes and rise vertically, chasing and interacting with intruders. They may scream, whine, and distract predators on eggs or nestlings by pretending to have a broken wing.

What roles do they have in the ecosystem?

Short-eared owls are important predators on populations of many different types of small mammals and birds.

Do they cause problems?

There are no known negative effects of short-eared owls on humans.

How do they interact with us?

Short-eared owls help manage animals that humans consider to be pests; a large portion of their diet is small rodents, such as mice and voles. In areas where small mammals can reach plague numbers, short-eared owls capitalize on the opportunity and settle in large numbers. (Sparks and Soper, 1989 and Pearson, 1936)

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

Are they endangered?

Due to their wide distribution, short-eared owls are not a federally endangered species; however, in the Great Lakes region of the United States, conditions are worse. This species is threatened by the diminishing area of marshes, bogs, and open grasslands. Nesting habits and nomadism make this species particularly vulnerable to habitat loss during any season. Due to these factors, short-eared owls are endangered in Michigan, Illinois, and Pennsylvania. They are also threatened in Minnesota and of special concern in Indiana and Ohio. They are among the rarest nesting owls in Michigan. There are no major efforts to help them recover in these areas. (Granlund et al., 1994)

Contributors

Nathan Doan (author), University of Michigan-Ann Arbor, Kathleen Bachynski (editor), University of Michigan-Ann Arbor, Tanya Dewey (editor), Animal Diversity Web.

References

Granlund, J., G.A. McPeek, and R.J. Adams. 1994. The Birds of Michigan. Indiana University Press, Bloomington.

Holt, D.W. 1993. The Birds of North America. The American Ornithologists' Union and The Academy of Natural Sciences of Philadelphia, Philadelphia.

Martin, G. 1990. Birds by Night. T& AD Poyser, London.

Pearson, T. G., ed. 1936. Birds of America. Garden City Books, Garden City.

Sparks, J. and T. Soper. 1989. Owls:Their Natural and Unnatural History. Facts on File, New York.

Wety, J.C. 1975. The Life of Birds. Second Edition. W.B. Saunder Company, Philadelphia.

Wiggins, D., D. Holt, S. Leasure. 2006. Short-eared Owl (Asio flammeus). Pp. 1-19 in A Poole, ed. The Birds of North America Online, Vol. 62. Ithaca, NY: Cornell Laboratory of Ornithology. Accessed July 26, 2007 at http://bna.birds.cornell.edu/BNA/account/Short-eared_Owl/.

 
University of Michigan Museum of ZoologyNational Science Foundation

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Doan, N. 1999. "Asio flammeus" (On-line), Animal Diversity Web. Accessed November 27, 2014 at http://www.biokids.umich.edu/accounts/Asio_flammeus/

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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