Barn owl

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Barn Owl
Barn Owl.jpg
European barn owl
Tyto alba alba
Scientific classification
Kingdom Information
Domain Eukaryota
Kingdom Animalia
Subkingdom Bilateria
Branch Deuterostomia
Phylum Information
Phylum Chordata
Sub-phylum Vertebrata
Infraphylum Gnathostomata
Class Information
Superclass Tetrapoda
Class Aves
Sub-class Neornithes
Infra-class Neoaves
Order Information
Order Strigiformes
Family Information
Family Tytonidae
Sub-family Tytoninae
Genus Information
Genus Tyto
Species Information
Species T. alba
Population statistics

Barn owls are medium-sized owls found world-wide, the most-widespread of the owls. Due to similarities, the name "barn owl" is used in reference to thirteen species of the genus Tyto, but generally restricted to Tyto alba, the species found throughout much of the northern hemisphere.

Etymology

Barn owls are the familiar owls on farms, hence the name. Other names given by farmers include "straw owl", "barnyard owl", and "night owl". It has also been called the "monkey-faced owl" due to a slight resemblance to monkeys. "Ghost owl", "church owl", "death owl", "hissing owl", "hobgoblin or hobby owl" have also been used, due to the superstitious nature the owl represents.

Description

Barn owls are, depending on subspecies, between 9-20 inches in length and have a wingspan of 30-43 inches. Females are slightly-larger. The fluff of the feathers - which enable these birds to be completely silent in flight - gives the bird a much larger appearance.

Barn owls are immediately identifiable by their heart-shaped facial disk, which is light in color and ringed by a dark-colored line. A brownish wash lies between the lower edge of the eyes and the base of the bill, which is a light pinkish color. A pair of dark eyes completes the look of the face, which is mask-like and startling.

The crown and top portion of the body, wings, and tail are yellowish-brown to and orange-buff, with a grey "sheet" stretching from the back of the head to the base of the tail; scattered throughout are white spots surrounded by black rings. The primaries, secondaries, and tail feathers are barred in a slightly-darker brown, with white dots near the feather tips. The chest and belly are whitish to pure white with a scattering of small, dark spots; females have a larger number of belly spots than males. The legs are feathered to the toes.

Habitat

Barn owls are an "open country" bird; they prefer open areas where they can exploit their prey animals, from sea level upwards to 13,000 feet elevation. These areas include grasslands, marshes, plowed fields, deserts, small forested strips and woodlots, open ranch lands, brushy fields, and the relatively open areas of suburbs and cities. Tree cavities, caves, and buildings are their nesting sites.

Aware of their impact on the rodent population, farmers have allowed barn owls to nest in their buildings, sometimes even altering the building's appearance by creating an access point of entry.

Feeding

Barn owls use a combination of eyesight and hearing when hunting, and are very successful at catching prey animals in extreme low-light conditions.

Barn owls hunt small mammals, such as mice, rats, shrews, voles, and lemmings. In addition, rabbits, bats, small reptiles and amphibians, birds, and insects are also taken. Prey is swallowed whole, with bones, hair and feathers later regurgitated as a pellet; these pellets, littering the area under a nesting site, are invaluable to researchers studying the bird's habits and effects on prey population.

Barn owls are on the hunt at night; they are able to see their prey in extremely low-light conditions. They further supplement their hunting with an acute sense of hearing (the basilar papilla of the cochlea in the inner ear is large relative to the size of the head, at 9.5–11.5 mm long[1]), which is so powerful they can detect the movement of a mouse and accurately make a kill while the mouse is not visible at all, such as under a snowbank or leaf litter. Experiments on barn owl hearing in the early 1970's show they can successfully kill a mouse in one pass while in a room under total darkness[2]. This hearing ability was also the subject of a study to find and correct problems in human hearing[3].

Breeding

Barn owls prefer an enclosed space in which to make a nest, one that is not visible to others. Generally this would take place within a hole in an embankment or a tree cavity; sheltered spaces on buildings are also used, in addition to spaces within buildings and barns.

Eggs are laid within a three-day period, with as many as eleven eggs laid in a clutch; they take between 29-34 days to hatch. The young take about eight weeks to fledge.

Distribution

Barn owls are probably the most successful wild bird of any kind; they are found on all continents (except Antarctica) and many islands throughout the world.

Subspecies

Twenty-seven subspecies are recognized; some authorities consider upwards of forty-six. Tropical birds are generally smaller than their counterparts in more temperate climates; where different subspecies meet there is a possibility of crossbreeding. Coloration and plumage patterns differ among the subspecies.

  • T. a. alba. Western Europe and British Isles, western Turkey; coastal north Africa south to Sudan near Nile Valley.
  • T. a. javanica. Malay Peninsula to western islands of Indonesia and southern Borneo.
  • T. a. guttata. Central and eastern Europe.
  • T. a. guatemalae. Central America and the Pearl Islands.
  • T. a. bargei. Found on the islands of Curaçao and Bonaire, West Indies.
  • T. a. sumbaensis. Found on the island of Sumba, Indonesia.
  • T. a. delicatula. Australian continent and surrounding islands, as well as eastern Indonesia.
  • T. a. pratincola. North America, from Canada south to Mexico.
  • T. a. furcata. Cuba, Jamaica, Cayman Islands.
  • T. a. tuidara. Subtropical and temperate areas of South America, to Tierra del Fuego and the Falkland Islands.
  • T. a. punctatissima. Galápagos Islands; some authorities consider it a distinct species.
  • T. a. poensis. Found on Bioko, an island off the west African coast.
  • T. a. thomensis. Found on São Tomé Island, an island off the west African coast; some authorities consider it a distinct species.
  • T. a. affinis. East Africa south of the Sahara Desert; islands of Seychelles, Comoros, and Madagascar.
 
  • T. a. gracilirostris. Found on the Canary Islands, eastern Atlantic Ocean.
  • T. a. hellmayri. South America, from eastern Venezuela south to the Amazon River.
  • T. a. bondi. Endemic to small islands north of Honduras.
  • T. a. niveicauda. Found on Isla de la Juventud, Cuba.
  • T. a. contempta. South America: northeastern Andes to Colombia and Venezuela.
  • T. a. schmitzi. Found on Madeira and Porto Santo islands, eastern Atlantic Ocean.
  • T. a. ernesti. Found on the islands of Corsica and Sardinia, Mediterranean Sea.
  • T. a. erlangeri. Southern Aegean islands to Crete and Cyprus, and countries and coastal areas of the Middle East to Iran.
  • T. a. stertens. Southern to southeast Asia and Sri Lanka.
  • T. a. crassirostris. Found on the Tanga Islands, northeast of Papua New Guinea.
  • T. a. interposita. Found on the south Pacific islands of Santa Cruz, Banks, and Efate.
  • T. a. meeki. Eastern New Guinea, Manam, and Karkar islands.
  • T. a. detorta. Found on the Cape Verde Islands, eastern Atlantic Ocean. Some authorities consider it a distinct species.


References

  1. http://www.sciencedirect.com/science/article/pii/0378595585900681
  2. http://www.americanscientist.org/issues/num2/how-the-owl-tracks-its-prey/1
  3. http://www.sciencedaily.com/releases/2007/08/070801091509.htm
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