Temporal range: Late Pliocene to present
7, see text.
Asio is a genus of typical owls, or true owls, in the family Strigidae. The genus Asio contains the eared owls, which are characterised by feather tufts on the head which give the appearance of "ears". This group has representatives over most of the planet, and the short-eared owl is one of the most widespread of all bird species, breeding in Europe, Asia, North and South America, the Caribbean, Hawaii and the Galápagos Islands. Its geographic range extends to all continents except Antarctica and Australia.
These are medium-sized owls, 30–46 centimetres (12–18 in) in length with 80–103 centimetres (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.
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.
- Stygian owl, Asio stygius
- Long-eared owl, Asio otus
- Abyssinian owl, Asio abyssinicus
- Madagascar owl, Asio madagascariensis
- Short-eared owl, Asio flammeus
- Marsh owl, Asio capensis
- Striped owl, Asio clamator - often placed in Pseudoscops or Rhinoptynx
Two fossil species are recognized nowadays:
- Asio brevipes (Glenns Ferry Late Pliocene of Hagerman, USA)
- Asio priscus (Late Pliocene of Santa Rosa Island, USA)
The supposed Late Eocene/Early Oligocene eared owl "Asio" henrici has been recognized as a member of the fossil barn-owl genus Selenornis. "Asio" pygmaeus (often misspelt pigmaeus) cannot be assigned to a genus without restudy of the material. "Asio" collongensis (Middle Miocene of Vieux-Collonges, France) is now placed in the genus Alasio.(Mlíkovský 2002)