Owls | Strigiformes

Uilen | Rapaces nocturnas

Owls are chiefly night-hunting birds with large, forward-facing eyes for sharp vision in dim light, and a facial disc of stiff feathers that channels sound to asymmetrically placed ears, letting them pinpoint prey by hearing alone in total darkness. The outer edge of the flight feathers is comb-like and frayed, making the flight almost silent so prey does not hear the attack coming. The feet are powerful, with sharp talons and a reversible outer toe; prey is swallowed whole or in large pieces, and indigestible remains such as bones and fur are coughed up as pellets. Owls build no nest of their own, breeding instead in a tree cavity, an old raptor nest or on the ground; the female is usually larger than the male, and the downy chicks stay in the nest.

Families in this order

Bay owls and barn owls | Tytonidae1 speciesThe facial disc is heart-shaped and sharply bounded by a stiff ruff of short feathers; the asymmetry that allows the height of a sound to be judged lies here not in the skull but in movable flaps of skin in front of the ears. The eyes are small and dark, the head narrow, the legs long and thinly feathered, and the claw of the middle toe has a comb-like serrated edge with which the disc is combed and kept clean. These birds do not hoot but scream: a long, hoarse, piercing shriek, matched from the nest by a snoring, hissing wheeze from the young; when threatened the bird sways from side to side with its wings spread and snaps its bill. Hunting is done low and searching over open grassland, in a slow, wavering flight with the legs dangling, or by listening from a post. The diet consists almost entirely of mice and voles, and clutch size follows the vole cycle: in good years large clutches and sometimes two broods are raised. Below a regular roost a heap of pellets builds up.
Owls | Strigidae18 speciesIn most species the female starts incubating as soon as the first egg is laid, so the chicks hatch days apart in sequence; in lean years it is mainly the oldest chicks that survive. The Burrowing Owl breaks from most of its relatives by nesting not in a tree cavity but underground, in tunnels dug by prairie dogs or badgers. In most species the ear tufts on the head serve not to improve hearing but to break up the body's outline, signalling mood to both rivals and potential mates. Ahead of mating, the male repeatedly brings the female prey as a gift, a habit that strengthens the pair bond and helps bring her into good condition for the breeding season.