Owls are solitary predators with soft plumage, sharp hooked bills and sharp talons. Large forward-looking eyes and feathered facial disks are distinctive to this avian order. They communicate by hooting, screeching or whistling. Their main foraging strategy is to perch and wait, then pounce on prey. Unlike most other birds, females are usually larger than males. Smaller owl species are insectivorous, while larger species consume rodents and other small mammals and birds. Owls regurgitate pellets of indigestible parts of prey. Most owl species nest in cavities (natural or man-made) or usurp tree nests of species such as crows.
There are just over 200 owl species in the world, divided into two families (Tytonidae and Strigidae); nineteen owl species occur in North America, and twelve of these are resident in Saskatchewan. The only member of the Tytonidae, the cosmopolitan barn owl (Tyto alba), measures between 36 and 51 cm, and has a distinctive heart-shaped face; it is an irregular breeder in southeast Saskatchewan, nesting in abandoned buildings. The eastern screech owl (Otus asio) measures between 20 and 25 cm, and is uncommon in the riparian woodland of the river valleys of the southeast. The owl that most people will see is the great horned owl (Bubo virginianus), which measures between 46 and 64 cm. This large, powerful owl can take prey larger than itself and is found throughout the province in open areas with trees, abandoned buildings, or ledges. The Arctic-breeding, mostly white snowy owl (Nyctea scandiaca), which measures between 51 and 69 cm, can winter in the grasslands and farmlands of Saskatchewan. The diurnal northern hawk owl (Surnia ulula) measures between 36 and 43 cm and is usually found in open areas in the boreal forest, nesting in large tree cavities or abandoned tree nests. The other owl commonly seen in daylight is the declining and endangered long-legged burrowing owl (Athene cunicularia); measuring between 23 and 28 cm, it nests in burrows of rodents and badgers, in grasslands and pastures. The dark-eyed barred owl (Strix varia), measuring between 43 and 61 cm, has expanded its range in the boreal forest: increased numbers have been found in old-growth forest since the 1950s, nesting in abandoned nests. The great grey owl (Strix nebulosa), from 61 to 84 cm tall, is the biggest owl, with huge facial disks of dark grey concentric circles. It nests in tree snags in old-growth forest and bogs. The slender long-eared owl (Asio otus) measures between 33 and 41 cm and has distinctive closely-set ear tufts; it nests in abandoned tree nests in aspen groves, wooded coulees, and abandoned farmsteads. The threatened short-eared owl (Asio flammeus), from 33 to 43 cm tall, nests on the ground in the grasslands, farmlands and marshes of southern Saskatchewan, where there are large vole populations. The flat-headed boreal owl (Aegolius funerus) measures between 20 and 30 cm; it nests in tree cavities, in mature coniferous and mixedwood stands of the boreal forest. The northern saw-whet owl (Aegolius acadicus) is the smallest owl in Saskatchewan (18-20 cm) and nests in tree cavities in the southern Boreal forest, Aspen Parkland and Cypress Hills.