OWL

any member of the order Strigiformes, nocturnal birds of prey. According to some classifications, there are three extant families in the order: Strigidae (typical owls), Tytonidae (barn owls and grass owls), and Phodilidae (bay owls). Unlike other birds of prey, owls have virtually noiseless flight, the butterfly-like flapping of wings being muffled by the velvety surface of the flight feathers. Owls are protectively coloured, generally in shades of brown. Many species, such as the scops and screech owls, show two phases of coloration, one in which the brown tends toward red and one in which it tends toward gray. The females are usually larger than the males. Owls often go unnoticed because of their nocturnal habit. They nest in buildings, holes in trees, or nests abandoned by other birds. Some, such as the burrowing owl, nest on the ground or in holes abandoned by other animals. The white eggs are usually nearly round. With their round, forward-looking eyes, large heads, and sharply hooked beaks, owls are easily recognized. Their hearing and vision are acute. The disk framing the face on most nocturnal species helps reflect sound to the ears, thus aiding the bird in locating its prey. In many species the ear openings are asymmetrical, further increasing the ability to localize sounds. Some species can turn their heads as much as 270 in one direction. Most owls are nocturnal and prey on insects, birds, or small mammals. The fish owl, with bristly foot pads that help hold fish, and the hawk owl, which often hunts by day, are less typical. All these birds produce owl pellets, composed of the regurgitated, indigestible portions of their prey, such as bone, fur, and chitin. Barn owls have heart-shaped facial disks, weakly forked tails, long legs, relatively small eyes, and no ear tufts; bay owls are similar, but the facial disk does not cross the forehead. The approximately 120 species of typical owls (Strigidae) have larger, more prominent eyes and rounded tails. Many species have ear tufts. They range in size from the tiny 1315-centimetre (56-inch) elf owl to the 70-centimetre (2.3-foot) eagle owl. Found worldwide except for Antarctica, owls occur in habitats ranging from tundra to scrubby desert, although most species, such as the horned and wood owls, prefer wooded areas. any member of the homogeneous order Strigiformes of primarily nocturnal birds of prey. They have nearly worldwide distribution. Their secretive habits, quiet flight, and weird calls have made them the objects of superstition and even fear in many parts of the world. The same characteristics have made the scientific study of them more difficult, with the result that the ecology, behaviour, and taxonomy of many species remain poorly understood. Additional reading Mary Louise Grossman and John Hamlet, Birds of Prey of the World (1964, reprinted 1988), a heavily illustrated work dealing with both owls and falconiforms, provides range maps for each species, good photographs, and a reading list by geographic region and by genus. John J. Craighead and Frank C. Craighead, Jr., Hawks, Owls, and Wildlife (1956, reprinted 1969), is a detailed study of the ecology of raptorial birds and their impact on prey populations. Broad coverage of owls can be found in Leslie Brown, African Birds of Prey (1970), an ecological study of owls and falconiforms on the African continent; Michael Everett, A Natural History of Owls (1977); John A. Burton (ed.), Owls of the World: Their Evolution, Structure, and Ecology, rev. ed. (1984); John Sparks and Tony Soper, Owls: Their Natural and Unnatural History (1989); and Rob Hume and Trevor Boyer, Owls of the World (1991). Of a more specialized nature are R.S. Payne and W.H. Drury, Jr., Tyto alba, II: Marksman of the Darkness, Natural History, 67:316323 (June 1958), describing the discovery of the hearing ability of the barn owl; D.S. Bunn, A.B. Warburton, and R.D.S. Wilson, The Barn Owl (1982); J. David Ligon, The Biology of the Elf Owl, Micrathene Whitneyi (1968), a detailed study of the life history of the smallest owl, compared with other owls; Anthony Ross, Ecological Aspects of the Food Habits of Insectivorous Screech-owls, Proceedings of the Western Foundation of Vertebrate Zoology, 1(6):301344 (1969), showing a definitive correlation between body size and prey size, one of the few such papers in which stomach contents are correctly identified; L.W. Walker, Nocturnal Observations of Elf Owls, Condor, 45(5):165167 (SeptemberOctober 1943), with excellent photography and concise scientific writing; and G. Ronald Austing and John B. Holt, Jr., The World of the Great Horned Owl (1966). Joe T. Marshall The Editors of the Encyclopdia Britannica