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.
The genusAsio was introduced by the French zoologist Mathurin Jacques Brisson in 1760 with the long-eared owl (Asio otus) as the type species.[1][2] The genus name is from asiō, the Latin name used by Pliny the Younger for a type of horned owl,[3] the feather tufts on the head of these owls give the appearance of "ears" which is a defining characteristic.[4]
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.[9]
^Gill, Frank; Donsker, David; Rasmussen, Pamela, eds. (January 2021). "Owls". IOC World Bird List Version 11.1. International Ornithologists' Union. Retrieved 27 May 2021.
^Collins, P. W., D. A. Guthrie, E. L. Whistler, R. L. Vellanoweth, and J. M. Erlandson. 2018. Terminal Pleistocene–Holocene avifauna of San Miguel and Santa Rosa islands: identifications of previously unidentified avian remains recovered from fossil sites and prehistoric cave deposits. Western North American Naturalist 78(3):370–404.
