Great Horned Owl


ORDER: Strigiformes

FAMILY: Strigidae

GENUS: Bubo

SPECIES: virginianus

DESCRIPTION:
A large powerful owl ranging in length from 20 to 23.5 inches. Females are larger than males, weighing 2.2 to 5.5 pounds as compared to 1.5 to 3.2 pounds in the male. This bird has a rust-colored facial disc, large erect ear tufts, yellow eyes, and a white chin and throat. Upper parts are mottled and barred gray to gray-brown and under parts are mottled brown with a reddish tinge. Legs and feet are covered with buff to tawny feathers. Talons and mandibles are black. Size and color may vary from region to region, e.g. they are larger in Alaska than in tropical lowland forest and desert regions, and Alaskan owls have white breasts rather than orange.

GEOGRAPHICAL RANGE AND HABITAT:
Alaska through North America (except for tundra regions), Central America and South America (with the exception of the West Indies, most islands and most of Amazonia). Forest, swamps, woodland, farmlands, towns, mangroves, and deserts with scrub.

DIET:
Small mammals (up to 90 per cent of their diet and especially rodents) birds, fish, snakes and insects. Hunts from a perch, using a shallow gliding drop to prey. Owls usually swallow their prey whole. Strong stomach fluids dissolve the flesh while bones, teeth and fur are regurgitated in pellets after about 8-12 hours.

LIFE CYCLE/SOCIAL STRUCTURE:
Nocturnal. Hunts mostly at dusk or during the night, but occasionally during the day when food is scarce or nights are short. They usually do not migrate except for those in the far north or far south. They are solitary except during the breeding season (varies from December to July depending on the bird's range). Males call females to their territory and offer food and suitable nest sites such as tree hollows, old nests of other birds, caves, abandoned buildings, or among tree roots. One to 3 white eggs are laid and incubated for 28 to 30 days by the female. The male provides all food for his mate during incubation and for the young for the first two weeks. The female then joins in searching for the vast amount of food needed. Young owls wander from the nest before they can fly, using their talons and beaks to scramble up and down. They remain in the nest for 35 to 45 days, but are cared for by parents up to five months. Owls first breed at two years of age. Life span in the wild is 15 to 20 years.

SPECIAL ADAPTATIONS:
Modified hearing and specialized feathers allow successful hunting after sunset. Ears are set asymmetrically in a wide skull (one set higher and one sometimes larger) which allows the owl to pinpoint sound very accurately. The facial disc helps in directing sound waves to the ears located below. The edges of the discs are fringed by short, stiff feathers carried upon flaps which can move to control the size of the ear opening (a long vertical slit) which lets it scan different parts of their environment, much as some mammals move their ears to scan. Feathers have evolved to facilitate silent flying; the surfaces of all feathers are covered in very fine down and the trailing edges of flight feathers are softer and less defined. The birds are light in relation to wing area and thus have effortless flight with no noisy flapping. Owls cannot see well when it is extremely dark but have huge pupils and a retina with many rods which provide good vision in low levels of light. Large forward-facing eyes give them a good degree of binocular vision which also helps in catching prey. Eyeballs, shaped like tapering cylinders to provide the largest possible retina, lack the ability to rotate in any direction, but an exceptionally long and flexible neck enables the owl to turn its head at least 180 degrees. Long sharp claws and a hooked bill are also suited to a predatory life style. The bill is sharply deflected downward to reduce obstruction of vision. Feathered feet give extra protection from biting prey animals and provide insulation against cold temperatures.

INTERPRETIVE INFORMATION:
Owls of the genus Bubo are known as eagle owls, nocturnal counterparts of such large birds of prey as eagles and buzzards. B. virginianus is the only New World species; the other thirteen Bubo species are in the Old World. Owls are prominent in myth, superstition and legend. Athena, the Greek Goddess of Wisdom is associated with the owl as is Merlin, King Arthur's mentor. Owls are no more intelligent than any other predatory bird, but perhaps their daytime silence has been equated with deepthinking and wisdom. Owls also have figured as a prophet of doom and death in many cultures and often in literature, probably because oftheir low, mournful hoots. The call of the Great Horned Owl is "ho-hohoo ho ho". Three to eight hoots are given with both individualand geographical variation in number, arrangement and accent. Youngbirds make a high screeching call. As predators, owls are hated and feared by most other birds and if spotted in the daytime, they are instinctively mobbed furiously by many different species. This behavior has been exploited in the past by using a tethered owl to entice birds within the range of guns, nets or snares. This method is still used to capture birds for banding.

OUR ANIMALS:
Our owl is used in our Zoomobile and Education programs and may not be viewable by the public.

STATUS IN WILD:
Very common. Not globally threatened. Loss of habitat can be a problem.

BIBLIOGRAPHY:

  1. Burton, John. Owls of the World. 1984. Peter Lowe Publishers, UK, pp. 32-37, 198.
  2. Internet: www.torontozoo.com
  3. Olendorf, Donna Ed. Grzimek's Animal Life Encyclopedia: Volume 9. 2003. The Gale group, Farmington Hills, MI, pp.349, 356-7.
  4. Sibley, Charles and Burt Monroe, Jr. Sibley's Distribution and Taxonomy of Birds of the World. 1990. Yale University Press, New Haven, CT, p. 174.

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