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Strix virgatamottled owl

By Jess Fetter

Geographic Range

Strix virgata is widely distributed throughout the Nearctic and Neotropics, from northern Mexico to Brazil and Argentina. ("Handbook of the Birds of the World. Vol. 5. Barn-owls to Hummingbirds", 1999)

Habitat

Inhabiting elevations between sea level and 2500 meters, mottled owls are often quite abundant within their range. Their habitats are extensive and diverse; they can live in a wide variety of forest and thicket edge, tropical rainforest, dry thorn forest, tropical lowland forest, pine-oak woodland, and humid evergreen jungle. They can also live in areas with scattered trees, often close to towns and villages. ("Handbook of the Birds of the World. Vol. 5. Barn-owls to Hummingbirds", 1999)

  • Range elevation
    0 to 2500 m
    0.00 to 8202.10 ft

Physical Description

Strix virgata individuals are medium-sized owls with brown eyes. They are mostly dark except for light brown facial markings. Mottled owls have yellow-grey to blue-grey bills and their toes are greyish-yellow. Their dorsal markings are much less noticeable than the vertical streaks on their chest and throat. They look larger than they are because of their thick feathers. ("Handbook of the Birds of the World. Vol. 5. Barn-owls to Hummingbirds", 1999; "A Dictionary of Birds", 1985)

In owls, females are generally larger than the males. This evolution of a reversed size dimorphism has been explained in many different ways. Researchers measure body mass during the breeding season, wing length, tail length, bill length, tarsal length, and foot span. Female mottled owls weighed significantly more than males and have significantly longer wing chords. Strix virgata has the most noticable dimorphism yet documented among owls. (; Gerhardt and Gerhardt, 1987)

  • Sexual Dimorphism
  • female larger
  • Range mass
    175 to 320 g
    6.17 to 11.28 oz
  • Range length
    355 to 280 mm
    13.98 to 11.02 in

Reproduction

Mottled owls are monogamous, neither female nor male have any involvement with other nesting birds besides their mate. (Gerhardt, et al., 1994; "A Dictionary of Birds", 1985)

Strix virgata have smaller clutches than ecologically similar or closely related species. This species usually lays 1 to 2 eggs between February and May. Mottled owls usually nest in holes of trees, tops of broken off palm and occasionally in empty nests of other birds. (; Gerhardt and Gerhardt, 1987)

  • Breeding interval
    Mottled owls breed once yearly.
  • Breeding season
    The breeding season occurs between February and May.
  • Range eggs per season
    1 to 2

Females incubate eggs while males find food and bring it back to the nest. Both males and females care for the young. (Gerhardt, et al., 1994; "A Dictionary of Birds", 1985)

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

Lifespan/Longevity

There is no information available regarding the lifespan of this species.

Behavior

Mottled owls are solitary and strictly nocturnal. They roost in dense foliage by day and may be mobbed by small birds if detected. These owls spend their waking hours hunting, preening, yawning, stretching, and combing their heads with their claws. ("Handbook of the Birds of the World. Vol. 5. Barn-owls to Hummingbirds", 1999)

Home Range

The home range of male S. virgata is 2.8 hectares. (Gerhardt, et al., 1994)

Communication and Perception

This species uses an array of vocalizations, such as hoots, whistles, screeches, screams, purrs, snorts, chitters, and hisses. When a mottled owl hoots, it is often territorial and associated with courting. The males have a lower pitched hoot than females. When faced with a threat, owls produce clicking noises with their tongues. As part of a mating display, owls have the ability to clap their wings in flight. (Gerhardt, 1991)

Mottled owls produce an array of calls. Their territorial call consists of a series of deep hoots, sounding like "bru bru" and "bu bu bu" or cowooawoo or keeooweeyo. They also have a whistled screech. Mottled owls have been observed to have an enlarged voice box which allows them to produce low-pitched notes for their size. (Gerhardt, 1991)

Owls have keen hearing and vision in low-light situations. They lack color vision.

Food Habits

Strix virgata individuals feed on a diverse diet including large insects such as beetles, grasshoppers, and cockroaches. They also feed on small mammals, birds, snakes, lizards, salamanders, and frogs. They are considered opportunistic feeders as they may be attracted to artificial lights. Mottled owls primarily hunt from perches which can be found along a forest edge. ("Handbook of the Birds of the World. Vol. 5. Barn-owls to Hummingbirds", 1999)

Mottled owls have keen vision, hearing, and maneuverable flight, contributing to their success as predators. Although they lack color vision, these owls can rotate their heads to see in different directions. These owls also have sensitive ears that allow them to pinpoint sound sources in total darkness. Still, their ranges of hearing are not wide and contain deaf spots. Their wing feathers have adapted to dampen sound during flight, so they can approach their prey without being heard.

  • Animal Foods
  • birds
  • mammals
  • amphibians
  • reptiles
  • insects

Predation

Owls are at the top of the food web. They have no major predators. ("The Owl Pages: Information about Owls", 2005; "Owl Facts", 2004)

Ecosystem Roles

This species is a generalist predator, and potentially impacts many prey populations. ("Handbook of the Birds of the World. Vol. 5. Barn-owls to Hummingbirds", 1999)

Economic Importance for Humans: Positive

Mottled owls have been studied by scientists and research has been published on their breeding behavior. They also help control some rodent and insect pest populations. ("The Food Habits of Sympatric Ciccaba Owls in Northern Guatemala.", 1994; Buchanan, 1971; Gerhardt, 1991; Gerhardt, et al., 1994; Wylie , 1976)

  • Positive Impacts
  • research and education
  • controls pest population

Economic Importance for Humans: Negative

There are no known adverse affects of Strix virgata on humans.

Conservation Status

This widespread species is not globally threatened. Strix virgata are considered common in many habitats and can be seen largely in protected areas. ("Handbook of the Birds of the World. Vol. 5. Barn-owls to Hummingbirds", 1999)

Contributors

Matthew Wund (editor), University of Michigan-Ann Arbor.

Jess Fetter (author), University of Michigan-Ann Arbor, Phil Myers (editor), Museum of Zoology, 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

Neotropical

living in the southern part of the New World. In other words, Central and South America.

World Map

acoustic

uses sound to communicate

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

chemical

uses smells or other chemicals to communicate

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.

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.

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).

monogamous

Having one mate at a time.

motile

having the capacity to move from one place to another.

nocturnal

active during the night

oviparous

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

rainforest

rainforests, both temperate and tropical, are dominated by trees often forming a closed canopy with little light reaching the ground. Epiphytes and climbing plants are also abundant. Precipitation is typically not limiting, but may be somewhat seasonal.

seasonal breeding

breeding is confined to a particular season

sexual

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

solitary

lives alone

tactile

uses touch to communicate

terrestrial

Living on the ground.

territorial

defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement

visual

uses sight to communicate

References

The British Ornithologists' Union. 1985. A Dictionary of Birds. South Dakota: Buteo Books.

1999. Handbook of the Birds of the World. Vol. 5. Barn-owls to Hummingbirds. Barcelona: Lynx Edicions.

Birds of Prey Foundation. 2004. "Owl Facts" (On-line). Accessed March 28, 2003 at http://www.birds-of-prey.org/educate/owls.htm.

1994. The Food Habits of Sympatric Ciccaba Owls in Northern Guatemala.. Journal of Field Ornithology, 65: 258-264.

Owl Pages. 2005. "The Owl Pages: Information about Owls" (On-line). Accessed September 22, 2004 at http://www.owlpages.com/species/strix/virgata/Default.htm.

Buchanan, M. 1971. The Mottled Owl Ciccaba Virgata in Trinidad.. Ibis, 113: 105-106.

Gerhardt, , D. Gerhardt. 1987. Size, Dimorspism, and Related Characteristics of Ciccaba Owls From Guatemala. 2nd Owl Symposium: 190-196. Accessed September 22, 2004 at http://www.ncrs.fs.fed.us/pubs/gtr/other/gtr-nc190/GERHARD.PDF#xml.

Gerhardt, R. 1991. Response of Mottled Owls to Broadcast of Conspecific Call.. Journal of Field Ornithology, 62: 239-244.

Gerhardt, R., D. Gerhardt, C. Flatten. 1994. Breeding Biology and Home Range of Two Ciccaba Owls. Wilson Bulletin, 106: 629-639.

Wylie , S. 1976. Breeding the Mottled Owl at the St. Louis Zoo. The Avicultural Magazine, 82: 64-65.

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