Asio is a genus o typical houlets, or true houlets, in the Strigidae faimily. The genus Asio contains the eared houlets, which are characterised bi feather tufts on the heid which gie the appearance o "ears". This group haes representatives ower maist o the planet, an the Short-eared Houlet is ane o the maist widespread o aw bird species, breedin in Europe, Asie, North an Sooth Americae, the Caribbean, Hawaii an the Galápagos Islands. Its geografic range extends tae aw continents except Antarctica an Australie.
These are medium-sized houlets, 30–46 cm (12–18 in) in length wi 80–103 cm (31.5–40 in) wingspans. Thay are lang winged an hae the characteristic facial disc.
The twa northren species are pairtially migratory, movin sooth in winter frae the northren pairts o thair range, or wanderin nomadically in puir vole years in search o better fuid supplies. Tropical Asio houlets are lairgely sedentary.
Asio houlets are mainly nocturnal, but Short-eared Houlets are an aa crepuscular. Maist species nest on the grund, but the Lang-eared Houlet, Asio otus, nests in the auld stick nests o craws, ravens an magpies (faimily Corvidae) an various hawks.
- Stygian Houlet, Asio stygius
- Lang-eared Houlet, Asio otus
- Abyssinian Houlet, Asio abyssinicus
- Madagascar Houlet, Asio madagascariensis
- Short-eared Houlet, Asio flammeus
- Marsh Houlet, Asio capensis
- Striped Houlet, Asio clamator - eften placed in Pseudoscops or Rhinoptynx
Twa fossil species are recognized nouadays:
- Asio brevipes (Glenns Ferry Late Pliocene o Hagerman, USA)
- Asio priscus (Late Pliocene o Santa Rosa Island, USA)
The supposed Late Eocene/Early Oligocene eared houlet "Asio" henrici haes been recognized as a member o the fossil barn-houlet genus Selenornis. "Asio" pygmaeus (often misspelt pigmaeus) cannae be assigned tae a genus wioot restudy o the material. "Asio" collongensis (Middle Miocene o Vieux-Collonges, Fraunce) is nou placed in the genus Alasio.(Mlíkovský 2002)