Owls | Strigiformes

Uilen | Rapaces nocturnas

Hunters with a large, broad head in which both eyes face forward, so that the fields of view overlap and the bird sees depth; the eyes are tubular and fixed in their sockets, which is why an owl turns its whole head — fourteen neck vertebrae allow well over half a turn. A disc of short, stiff feathers around each eye guides sound to the ear openings, and in a number of species those openings sit at unequal heights, so a sound can be placed in the vertical as well and a strike made in complete darkness. The plumage is soft and downy and the outer primary carries a comb-like leading edge, so the wingbeat is all but silent; the outer toe is reversible and the claws are long and strongly curved. Prey goes down whole and what will not digest — bone, fur, feathers — comes back up as a pellet; the white, almost round eggs are laid in a cavity or a disused nest with nothing built by the bird itself, and because incubation begins with the first egg the young of one brood differ greatly in size.

Families in this order

Barn owls | Tytonidae1 speciesThe facial disc is heart-shaped and drawn down into a narrow point; the eyes are small and dark for an owl, the head is narrow and the legs are long and feathered to the toes. The inner toe is as long as the middle toe, and the claw of that middle toe carries a row of fine teeth used to comb the disc clean; the breastbone is fused with the wishbone. Hooting is absent: these birds hiss, snore and shriek. They hunt low and quartering over open rough ground, almost entirely on mice, voles and shrews, and breed in a dark cavity in a building, cliff or tree; clutch size follows the rodent supply, so a good year can bring two broods and a poor one none at all.
Typical owls | Strigidae16 speciesThe facial disc is round and the eyes are large, with an iris ranging from yellow to almost black; many species carry two erectile feather tufts on the head, which have nothing to do with hearing but do break up the head's outline. The inner toe is shorter than the middle toe and the middle claw is smooth; within this one family size runs from a bird of sixty grams to one of three kilos, with densely feathered toes in the northern species and bare or bristled toes in the southern ones. The voice consists of low, far-carrying notes or clear whistles that hold the territory outside the breeding season as well — usually the first thing by which the species is known. Nesting is in a tree hole, an old crow or raptor nest, on a cliff ledge or simply on the ground; the female incubates and broods, the male brings in all the food.