The Owls are an order of birds of prey. Most are solitary, and nocturnal, with some exceptions (e.g. the Burrowing Owl). They are classified in the order Strigiformes, in which there are over 200 extant species. Owls mostly hunt small mammals, insects, and other birds, though a few species specialize in hunting fish. They are found in all regions of the Earth except Antarctica, most of Greenland, and some remote islands. Though owls are typically solitary, the literary collective noun for a group of owls is a parliament.

The living owls are divided into two families, the typical owls, Strigidae, and the barn-owls, Tytonidae.

Description

Owls have large forward-facing eyes and ear-holes, a hawk-like beak, a flat face, and usually a conspicuous circle of feathers around each eye called a facial disc. Although owls have binocular vision, their large eyes are fixed in their sockets, as with other birds, and they must turn their entire head to change views.

The smallest owl is the Elf Owl (Micrathene whitneyi), at as little as 31 g (1.1 oz) and 13.5 cm (5.3 inches). Some of the pygmy owls are scarcely larger. The largest owls are two of the eagle owls, the Eurasian Eagle Owl (Bubo bubo) and Blakiston's Fish Owl (Bubo blakistoni), which may reach a size of 60-71 cm (28.4 in) long, have a wingspan of almost 2 m (6.6 ft), and weight of nearly 4.5 kg (10 lb).

Owls are far-sighted, and are unable to see anything clearly within a few inches of their eyes. Caught prey can be felt by owls with the use of filoplumes, which are small hair-like feathers on the beak and feet that act as "feelers". Their far vision, particularly in low light, is exceptionally good. They can turn their head 135 degrees in either direction; they can thus look behind their own shoulders.

Different species of owls make different sounds; the wide range of calls aids owls in finding mates or announcing their presence to potential competitors, and also aids ornithologists and birders in locating these birds and recognizing species. The facial disc helps to funnel the sound of prey to their ears. In many species, these are placed asymmetrically, for better directional location (Cotty, 2008).

Owl eggs are usually white and almost spherical, and range in number from a few to a dozen, depending on species. The eggs are laid in intervals of 1–3 days and do not hatch at the same time. This accounts for the wide variation in the size of sibling nestlings. Owls do not construct nests but rather look for a sheltered nesting site or an abandoned nest, in trees, underground burrows, or in buildings, barns and caves.

Behavior

Most owls are nocturnal, actively hunting for prey only under the cover of darkness. Several types of owl, however, are crepuscular, or active during the twilight hours of dawn and dusk; one example is the pygmy owl (Glaucidium). A few owls are also active during the day; examples are the Burrowing Owl (Speotyto cunicularia) and the Short-eared Owl (Asio flammeus). The time at which an owl hunts can be determined by the colour of its eyes. Dark brown or black eyes indicate nocturnal activity, orange indicates dawn or dusk, and owls with yellow eyes are diurnal and hunt during the day.Fact: date=October 2008 There are exceptions to this general rule, however, so the colour of an owl's eyes is not the only indicator of its active hours.