Owls have large forward-facing eyes and ears, a hawk-like beak, 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.Owls are far-sighted, and are unable to clearly see anything within a few inches of their eyes. Their far vision, particularly in low light, is exceptionally good, and they can turn their head 135 degrees in either direction; they can thus look behind their own shoulders. It is not correct, however, that they can turn the head so far as to face completely backwards.Different species of owls make different sounds; the wide range of calls aids owl species in finding mates or announcing their presence to potential competitors, and 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 (Norberg, 1977).