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Owls - Strigiformes

Owls - StrigiformesView owl pictures

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Owls (Strigiformes) are medium to large birds with strong talons, a downward-curved bill, acute hearing and keen eyesight. In this article, we'll explore basic facts about owls including how they are classified, what they eat, where they live and the characteristics that make them different from other bird groups.

Most owls are nocturnal hunters that locate their prey using a combination of sight and sound. Their eyes are large, enabling them to gather ample light under dim conditions. Owls' eyes face forward, giving them binocular vision, a characteristic that helps them sight their prey with great accuracy. Owls have cylindrical-shaped eyes and because of this shape, owls cannot rotate their eyes within their sockets to change their point of focus. Instead an owl must rotate its head to redirect their gaze. To compensate, an owl can rotate its head about 270 degrees, offering it a wide range of sight.

Owls also have sharp hearing. Their ear openings are located asymmetrically on either side of their head, a configuration that gives them three-dimensional sound perception and enables them to pinpoint the slightest scuffle or rustle made by potential prey.

Owls have a distinct profile—their posture is upright and they have a large, round head. They have a short tail and broad wings. Their plumage is soft and dense and their flight feathers are specialized for silent flight.

The elf owl is the world's smallest owl (about 5 inches long and 1.4 ounces). Other small owls include long-whiskered owlets, Tamaulipas pygmy owls and least pygmy owls. The Eurasian eagle owl is the world's largest owl (measuring as much as 30 inches long, 79 inches wingspan and 10 pounds). Other large owls include Blakiston's fish-owls and Verreaux's eagle-owls.

Owls hunt prey that includes mammals, other birds, reptiles, and insects. They do not have teeth to chew their food and consequently swallow their prey whole. About 6 hours after feeding, owls regurgitate the indigestible parts of their meal as a pellet of bones, feathers or fur. Owl pellets often accumulate in the debris beneath their nesting and roosting sites.

Owls live on every continent except Antarctica. They inhabit a variety of terrestrial habitats around the world from the thick forest to the wide-open grasslands. Snowy owls inhabit tundra habitat throughout a circumpolar range in the Arctic. Common barn owls, the most widespread of all owl species, live on every continent around the globe and inhabit temperate forests, tropical forests, coniferous forests and various types of grasslands and savannas. The great horned owl occupies a wide range that stretches throughout most parts of North, Central and South America.

Owls undergo sexual reproduction. Females lay hard-shelled amniotic eggs. Owls, unlike many birds, do not build nests. Instead, they use nests built by other species in previous seasons or make their homes in the hollows of trees, in crevices or in depressions on the ground. Owl eggs are nearly spherical in shape. Most owls lay between 2 and 7 eggs that hatch at 2-day intervals. This means that the young are of various sizes and if food is scarce, the older, larger chicks commandeer the bulk of the food causing the smaller, younger chicks to starve.

Fossil owls have been discovered in deposits dating as far back as the Paleocene. There are 41 species of extinct owls. It appears that the oldest know owls belonged to the barn owls group while true owls appear to be more recently differentiated. It is unclear whether early owls first appeared in the eastern or western hemisphere.

Classification

Owls are a group of birds that includes 205 species. Owls are divided into two groups, true owls and barn owls. There are close to 190 species of true owls and about 16 species of barn owls. Some better-known owl species include common barn owls, spectacled owls, great horned owls, spotted owls, snowy owls, tawny owls and short-eared owls.

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