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Barn-owl

About: Barn-owl is a research topic. Over the lifetime, 286 publications have been published within this topic receiving 7614 citations. The topic is also known as: Barn Owls & Bay Owls.


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Journal ArticleDOI
TL;DR: A theory is presented to explain how a barn owl might locate the position of a sound source by moving its head until the intensity of all frequencies comprising a complex sound is brought to a maximum in both ears.
Abstract: 1. Barn owls ( Tyto alba ) can locate prey in total darkness using only the sense of hearing, with an error of less than I° in both the vertical and horizontal planes. 2. Differences between the behaviour of barn owls flying at prey in complete darkness (analysed from films taken under infra-red illumination) and their behaviour in the light are correlated with the problems they must face in acoustic orientation. 3. Experiments with owls trained to strike a concealed loudspeaker show that they depend on frequencies of sound above 5 kHz. 4. Measurements of sound pressure in the region of the owl9s eardrum, made with a probe-tube microphone while moving a loudspeaker around the owl9s head, reveal that for frequencies above 8-5 kHz the ear is highly directional. At such frequencies, regions of high sensitivity (tightly isolated by peripheral regions of low sensitivity) are directed along different paths for the two ears. 5. These regions of good sensitivity are correlated with the asymmetry of the barn owl9s external ears. Movements of a flap of skin in front of the ear opening changes the overall directional sensitivity patterns by redirecting the regions of maximum sensitivity. 6. A theory is presented to explain how a barn owl might locate the position of a sound source by moving its head until the intensity of all frequencies comprising a complex sound is brought to a maximum in both ears (aided perhaps by differences in inter-aural time delay that are enhanced by intensity disparities).

361 citations

Book
27 May 1994
TL;DR: This study highlights the importance of understanding the ecology and behaviour of the prey to understand the population size and regulation of the population and its role in conservation.
Abstract: Preface 1. Introduction 2. Distribution and variation 3. Diet 4. Foraging behaviour 5. The ecology and behaviour of the prey 6. Prey selection and energetics 7. Ranging and roosting behaviour 8. Moult 9. Breeding seasons 10. Nest sites 11. Courtship and eggs 12. Production of young 13. Dispersal 14. Mortality 15. Population size and regulation 16. Conservation 17. Conclusions Appendices References Index.

329 citations

Journal ArticleDOI
TL;DR: A baseline for the recognition of owls as agents of accumulation of small bones in the fossil record is provided and the actions of ancient predators may be revealed by species-specific patterns of bone destruction of an assemblage of fossil prey species are suggested.
Abstract: Owls are important consumers of small vertebrates, and because they regurgitate pellets rich in bone, they may be important potential contributors of the concentrated remains of small vertebrates to the fossil record. Owls of three sizes, the large great horned owl (Bubo virginianus), the medium-sized barn owl (Tyto alba), and the small screech owl (Otus asio), were fed a common diet of mice. The bony contents of the pellets were analyzed to determine the amount of bone loss by digestion, bone completeness, and sites of bone breakage. For all three species, only about half the number of bones ingested were recovered in the pellets. Mandibles and femora were most abundant, and pelves and scapulae were the least abundant. Screech owls broke 80% of the cranial and limb elements, barn owls only 30%. Skulls fared poorly in great horned and screech owl pellets, while barn owls returned 80% of the skulls intact, with only the caudal portion of the cranium damaged; barn owls also returned articulated strings of vertebrae and complete paws. These results provide a baseline for the recognition of owls as agents of accumulation of small bones in the fossil record and suggest that the actions of ancient predators may be revealed by species-specific patterns of bone destruction of an assemblage of fossil prey species.

322 citations

Journal ArticleDOI
TL;DR: The dynamics and accuracy of sound localization by the barn owl were studied by exploiting the natural head-orienting response of the owl to novel sound stimuli using an adaptation of the search coil technique which provided continous high resolution azimuthal and elevational information during the behavior.
Abstract: The dynamics and accuracy of sound localization by the barn owl (Tyto alba) were studied by exploiting the natural head-orienting response of the owl to novel sound stimuli. Head orientation and movement were measured using an adaptation of the search coil technique which provided continuous high resolution azimuthal and elevational information during the behavior. The owls responded to sound sources with a quick, stereotyped head saccade; the median latency of the response was 100 ms, and its maximum angular velocity was 790°/s. The head saccade terminated at a fixation point which was used to quantify the owl's sound localization accuracy. When the sound target was located frontally, the owl's localization error was less than 2° in azimuth and elevation. This accuracy is superior to that of all terrestrial animals tested to date, including man. When the owls were performing open-loop localization (stimulus off before response begins), their localization errors increased as the angular distance to the target increased. Under closed-loop conditions (stimulus on throughout response), the owls again committed their smallest errors when localizing frontal targets, but their errors increased only out to target angles of 30°. At target angles greater than 30°, the owl's localization errors were independent of target location. The owl possesses a frontal region wherein its auditory system has maximum angular acuity. This region is coincident with the owl's visual axis.

234 citations

Journal ArticleDOI
TL;DR: In this paper, four species of owls, Great Horned (Bubo virginianus), Long-eared (Asio otus), Burrowing (Speotyto cunicularia), and Barn (Tyto alba), which occur together on the short-grass prairie and farmland of north-central Colorado, were selected for a study of feeding ecology.
Abstract: Four species of owls, Great Horned (Bubo virginianus), Long-eared ( Asio otus), Burrowing (Speotyto cunicularia), and Barn (Tyto alba), which occur together on the short-grass prairie and farmland of north-central Colorado, were selected for a study of feeding ecology. The purpose of this study was to assess the overlap in foods of the four owls and to examine feeding mechanisms which allow them to coexist. Primary objectives were (1) to analyze and compare the food habits of each owl species considering frequency of occurrence of prey species and biomass contributed by each prey species, and (2) to describe and evaluate the primary factors involved in capture of prey by the four owl species. Few studies have been attempted in relation to the feeding of owls in this geographic area and none was a long-term study. Reed (1957) examined Barn Owl pellets from Larimer County, and Kelso (1938) and Hamilton (1941) noted Burrowing Owl foods in the Denver area. Catlett et al. (1958) studied foods of Long-eared Owls near Boulder, and Long and Kerfoot (1963) listed Great Horned Owl foods from east-central Wyoming. Most abundant of these owls is the Great Horned. This species, a permanent resident of the area, is extremely versatile in both its nesting and feeding, allowing it to utilize a wide variety of habitats. The Burrowing Owl is abundant during summer. Burrowing Owls are restricted to open lands with available nesting and roosting sites in abandoned mammal burrows, chiefly those of black-tailed prairie dogs (Cynomys ludovicianus). Arriving by mid-April, they spend about 6 months in the area before returning south in midto late October. Barn Owls are less common. Northcentral Colorado is close to the northern limits of this species' range and some may move south in winter. However, some remain through the year. Rock cliffs or ditch banks are sought for nesting and roosting by Barn Owls. Long-eared Owls are also uncommon. They appear to be nomadic-there one year and gone the next. Low, dense coniferous or deciduous trees attract them for nesting and roosting. A number of other vertebrate predators are present in this area whose diets may overlap with those of the four owl species. Other avian predators are the Golden Eagle (Aquila chrysaetos), Marsh Hawk (Circus cyaneus), Red-tailed Hawk (Buteo jamaicensis), Swainson's Hawk (B. swainsoni), Rough-legged Hawk (B. lagopus), Ferruginous Hawk (B. regalis), American Kestrel (Falco sparverius), Prairie Falcon (F. mexicanus), and Loggerhead Shrike (Lanius ludovicianus). Mammalian predators include red fox (Vulpes fulva), coyote (Canis latrans), raccoon (Procyon lotor), American badger (Taxidea taxus), striped skunk (Mephitis mephitis), and longtailed weasel (Mustela frenata). The more abundant reptilian predators are the gopher snake (Pituophus melanoleucus) and prairie rattlesnake (Crotalus viridis). The research was carried out from Decem-

195 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202323
202243
202110
20206
201911
201812