Owls

Owls comprise two closely related families in the avian order Strigiformes: the barn owls (Tytonidae) and the typical owls (Strigidae). Owls are relatively large birds, with a big head and short neck, a hooked beak, talons adapted to seizing prey, and soft, dense plumage adapted for swift yet almost silent flight. Owls have large eyes located on the front of their face but almost fixed in their socket, so that the entire head must be rotated or bobbed for the gaze to be shifted and for distance to be visually gauged.

Owls have excellent hearing and extremely large ears, although these are covered by feathers and not readily seen. The ears are placed asymmetrically on the head to aid in detecting the location of distant, weakly noisy prey. The sense of hearing is probably also aided by the facial disk of many owls, which helps to focus sound waves onto the ears. The sense of hearing of owls is so acute that the nocturnally hunting species can accurately strike their prey in total darkness, following the squeaks and rustling noises created by a small mammal.

The sex of an owl is not easy to distinguish, although typically females are larger than males. Owls begin to incubate their eggs as they are laid, which means that hatching is sequential and different-sized young are in the nest at the same time. During years in which prey is relatively abundant, all of the young will have enough to eat and may survive. In leaner years, however, only the largest young will be fed adequately.

Most owls are nocturnal predators, feeding on small mammals and birds, but sometimes also on small reptiles, frogs, larger insects, and earthworms. A few specialized owls feed on fish. Owls are known to change their food preference, depending on local or seasonal availability of prey. Most owls do not digest the fur, feathers, or bones of their prey. They regurgitate these items as pellets, which can be collected at roosts and examined to learn about the feeding habits of the owl.