Owl Birds

Owls have 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 for sharply focusing sounds that come from varying distances and those made by prospective prey, on the owls' asymmetrically placed ear cavities. Most birds of prey sport 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 other birds — so they must turn their entire head to change views. Owls can rotate their heads and necks as much as 270 degrees in either direction. As owls are farsighted, they are unable to see clearly anything within a few centimeters of their eyes. Caught prey can be felt by owls with the use of filoplumes — small hair-like feathers on the beak and feet that act as "feelers". Their far vision, particularly in low light, is exceptionally good.
The smallest owl — weighing as little as 31 g (1.1 oz) and measuring some 13.5 cm (5.3 inches) — is the Elf Owl (Micrathene whitneyi). 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, and have a wingspan of almost 2 m (6.6 ft), and an average weight of nearly 4.5 kg (10 lb).
Different species of owls make different sounds; this 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 owls to funnel the sound of prey to their ears. In many species, these discs are placed asymmetrically, for better directional location.
The plumage of owls is generally cryptic, but many species have facial and head markings, including face masks, ear tufts and brightly coloured irises. These markings are generally more common in species inhabiting open habitats, and are thought to be used in signaling with other owls in low light conditions.