These are medium-sized owls, 30–46 cm (12–18 in) in length with 80–103 cm (31.5–40 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.
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.
These owls hunt over open fields or grasslands, taking mainly rodents, other small mammals and some birds.
Read more about Asio: Species