Owl

Athene cuniculariaa

Cross-eyed owl

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Great Horned Owl in a Rain Storm in the Mojave

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Great Horned Owl at twilight, Mojave Desert

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Owls are birds from the order Strigiformes, which includes over 200 species of mostly solitary and nocturnal birds of prey typified by an upright stance, a large, broad head, binocular vision, binaural hearing, sharp talons, and feathers adapted for silent flight. Exceptions include the diurnal northern hawk-owl and the gregarious burrowing owl.

Owls hunt mostly small mammals, insects, and other birds, although a few species specialize in hunting fish. They are found in all regions of the Earth except polar ice caps and some remote islands.

Anatomy and Morphology

Owls possess large, forward-facing eyes and ear-holes, a hawk-like beak, a flat face, and usually a conspicuous circle of feathers, a facial disc, around each eye. The feathers making up this disc can be adjusted to sharply focus sounds from varying distances onto the owls' asymmetrically placed ear cavities. Most birds of prey have eyes on the sides of their heads, but the stereoscopic nature of the owl's forward-facing eyes permits the greater sense of depth perception necessary for low-light hunting. Although owls have binocular vision, their large eyes are fixed in their sockets—as are those of most other birds—so they must turn their entire head to change views.

Owls can rotate their heads and necks as much as 270 degrees. Owls have 14 neck vertebrae compared to seven in humans, which makes their necks more flexible. They have adaptations in the cervical vertebrae, including ventral and dorsal vertebral artery passages, which allow for this extreme degree of rotation without cutting off blood flow to the brain.

The coloration of the owl's plumage plays a key role in its ability to sit still and blend into the environment, making it nearly invisible to prey. Some species have ear tufts, which are thought to be a form of camouflage; with the tufts raised, they break up the outline of the owl's head, helping the bird to appear less visible to its prey.

Behavior

Most owls are nocturnal, actively hunting their prey in darkness. Several types of owls, however, are crepuscular, active during the twilight hours of dawn and dusk; one example is the pygmy owl (Glaucidium). A few owls are active during the day, notably the burrowing owl (Speotyto cunicularia) and the short-eared owl (Asio flammeus).

Owls exhibit various behaviors that are characteristic of their nocturnal and solitary nature. This includes silent flight, which is achieved through specialized feather adaptations that reduce flight noise. Owls have a fringed edge to their flight feathers, allowing them to fly silently and surprise their prey without being heard.

Reproduction

Owls are known for their distinctive hooting, screeching, and whistling sounds, which are used during the breeding season. Owl communication can also include physical displays and territorial calls. Most owls are monogamous, often forming lifelong bonds with their mates. Nest sites vary widely among species, from tree holes and nest boxes to ground burrows and abandoned nests of other birds.

Eggs are typically white and almost spherical, with a variable number of eggs laid depending on species and environmental conditions. The female does most of the incubation, and both parents take care of the young. The owl chicks are called "owlets."

Conservation

Many owl species are considered endangered or at risk due to habitat loss, pesticides, and rodenticides. Conservation efforts for owls include habitat preservation, banning of harmful pesticides, and the use of owl nest boxes to encourage breeding in safe environments.