Asio

These are medium-sized owls, 30–46 cm (12–18 in) in length with 80–103 cm (31–41 in) wingspans. They are long-winged and have the characteristic facial disc. The two northern species are partially migratory, moving south in winter from the northern parts of their range, or wandering nomadically in poor vole years in search of better food supplies. Tropical Asio owls are largely sedentary. These owls hunt over open fields or grasslands, taking mainly rodents, other small mammals and some birds.

Asio owls are mainly nocturnal, but short-eared owls are also crepuscular. Most species nest on the ground, but the long-eared owl (Asio otus) nests in the old stick nests of crows, ravens and magpies (family Corvidae) and various hawks.

Taxonomy

The genus Asio was introduced by the French zoologist Mathurin Jacques Brisson in 1760 with the long-eared owl (Asio otus) as the type species. The genus name is from asiō, the Latin name used by Pliny the Younger for a type of horned owl, the feather tufts on the head of these owls give the appearance of "ears" which is a defining characteristic.