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Overview

Brief Summary

Biology

The barn owl feeds on small rodents, especially voles and mice (11), and on frogs and insects (2), which it locates using its excellent sense of hearing (9). It is usually active in the evening, early morning or at night (11), but in times of hard frost or snowfall, individuals may be forced to hunt for longer periods, and may be seen in the day (6). The unlined nest is made in hollow trees or in old buildings. In April or May, between 4 and 6 white eggs are laid. These are incubated solely by the female, who is fed by the male during this time (5). Incubation starts after the first egg is laid, so they hatch at intervals (11), 32-34 days after being laid (5). The young therefore vary widely in age and size (11), and spend a very long time in the nest, between 64-86 days (5).
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Tyto alba

A medium-sized (14-20 inches) owl, the Barn Owl is most easily identified by its tan head and body, pale breast, triangular facial disk (most owl species have round faces) and brown eyes. Part of a small group of owls mostly found in Australasia, this species is unlikely to be confused with owl species outside of its own family. Male and female Barn Owls are similar to one another in all seasons. Barn Owls occur across much of the globe. In the New World, this species occurs from extreme southern Canada and the northern United States south to the southern tip of South America, including the islands in the Caribbean. In the Old World, this species occurs in most of Europe, Africa, South Asia, and Australia. Barn Owls inhabit an enormous variety of open and semi-open habitats across this species’ wide range. These habitats include forest edges, grassland, scrub, meadows, agricultural fields, and even urban and suburban areas. Barn Owls eat a variety of small animals, primarily rodents (including mice, voles, and shrews). Like most owls, Barn Owls hunt at night, listening for movement in the undergrowth with their superb hearing and swooping down to capture prey. Birdwatchers may watch for this species at dawn or dusk, and may listen for this species’ grating “kschh” call. Barn Owls are primarily active at night.

Threat Status: Least concern

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Description

This ethereal, ghost-like owl has golden-grey coloured upperparts, and pure white underparts (5). The heart-shaped facial disc is pale, and the large eyes are black (2). It flies silently and slowly, often with the feet dangling (2). A number of vocalisations are produced, including an eerie drawn-out shriek (5).
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Comprehensive Description

Longueur : environ 34 cm (mâles et femelles identiques), envergure moyenne : 90 à 98 cm, poids : 290 à 340 g pour les mâles et 310 à 370 g pour les femelles.

La Chouette effraie possède un plumage assez clair. Le dessus est gris ponctué de fines tâches noires et blanches et le dessous est brun-jaune constellé de petites tâches brun-foncé ou blanc. Les longues pattes sont emplumées mais le plumage se raréfie à proximité des doigts. La Chouette effraie se caractérise par un masque facial pâle en forme de cœur qui permet de la différencier facilement des autres chouettes.

La Chouette effraie est essentiellement nocturne. L'activité de chasse semble intense surtout en début de nuit (dès 1h après le coucher du soleil), s'interrompant par une période de repos au cœur de la nuit, pour reprendre avant l'aube. En période de nourrissage des jeunes, cet oiseau peut commencer à chasser de jour.

La Chouette effraie est un oiseau sédentaire et les adultes sont fidèles à leur domaine vital. Cependant, certains individus pratiquent une migration sur plusieurs centaines voire plusieurs milliers de kilomètres. C’est un oiseau essentiellement solitaire : chaque individu possède des reposoirs attitrés et évite en général tout contact avec ses congénères sauf en période d’appariement et de ponte. En période de reproduction, la territorialité est particulièrement importante.

La Chouette effraie est marquée par une forte fécondité : un couple peut produire jusqu’à 6 jeunes par an notamment lorsqu’il effectue deux nichées ce qui est assez fréquent. Par ailleurs, la polygamie est possible, notamment la polygynie. A l’âge de 40 à 45 jours, les jeunes quittent le nid. Bien que non volants, ils peuvent réaliser de grands bonds et les parents continuent de les nourrir. A trois mois, à l’automne, ils dispersent à environ à 10 km (distances sensiblement identiques entre mâles et femelles).

C’est une espèce très agile. Elle chasse surtout en vol, par vol battu entrecoupé de vol plané, à environ 1 m à 4 m du sol. La Chouette effraie se nourrit principalement de rongeurs et plus précisément de Campagnol des champs. De manière anecdotique elle peut aussi prélever des oiseaux et des batraciens. Ses pelotes de réjection sont ventrues aux extrémités et mesurent en moyenne 41 mm de long et 26 mm de diamètre. Elles se distinguent de celles des autres rapaces par leur aspect laqué, lisse et noirâtre.

La Chouette effraie est fortement influencée par le climat. Elle ne peut constituer de fortes réserves de graisses et est donc très sensible aux rigueurs de l’hiver et aux forts enneigements. Par conséquent, l’espèce est présente essentiellement en plaine. Ses effectifs peuvent diminuer très fortement en hiver et son succès de reproduction connaît des fluctuations de 1 à 10.

La Chouette effraie occupe les bocages, les zones de cultures avec bosquets friches et vergers, les petits villages. Elle niche dans des cavités rocheuses, trous d’arbres ou bâtiments (notamment clochers d’église, combles, granges) et nécessite la présence de zones ouvertes pour sa chasse. La taille du domaine vital varie au cours d’une année et dépend aussi de la quantité de proies et de sites de nidification. On compte entre 90 ha et 136 ha pendant la période de reproduction et entre 363 ha et 465 ha après l’élevage des jeunes jusqu’à la fin novembre.

Manifestation vocale : Voix très différente des autres rapaces nocturnes allant de cri déchirant à des chuintements ronflants. Chant territorial composé d’appels stridents, déchirants et traînants, chruuuhiii, qui vont en s’amplifiant.

Pour en savoir plus : MEBS T. & SCHERZINGER W. (2006). Rapaces nocturnes de France et d’Europe. Les encyclopédies du naturaliste. Éditions Delachaux & Niestlé. 398 pages.
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Distribution

Barn owls are the most widespread of all owl species, and are found on every continent except Antarctica. In the Americas, barn owls occur in suitable habitat throughout South and Central America, and in North America as far north as the northern United States and southwestern British Columbia. In Europe, barn owls range from southern Spain to southern Sweden and east to Russia. They are also found throughout Africa, across central and southern Asia, and throughout Australia. Barn owls have been introduced to some oceanic islands to control rodent pests.

Biogeographic Regions: nearctic (Native ); palearctic (Native ); oriental (Native ); ethiopian (Native ); neotropical (Native ); australian (Native ); oceanic islands (Introduced )

Other Geographic Terms: holarctic ; cosmopolitan

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National Distribution

Canada

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

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Range

The barn owl is widespread throughout Britain, but is scarce or absent from the Highlands and the islands of Scotland (5). It is one of the most wide-ranging birds in the world, known from most of Europe, Africa, Asia, the Americas and Australasia (7).
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occurs (regularly, as a native taxon) in multiple nations

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Global Range: (>2,500,000 square km (greater than 1,000,000 square miles)) RESIDENT: In the Americas from southern Canada and the northern U.S. south to southern South America, Greater Antilles (except Puerto Rico), and Lesser Antilles (AOU 1983, Marti 1992). Variable occurrence within this range, with low densities at northern periphery (Marti 1992). In Old World from British Isles, southern Russia, and southern Siberia south through Eurasia and Africa to southern Africa, Madagascar, East Indies, and Australia. Populations in northern North America are partially migratory. Introduced (1958 and later) in Hawaii; now on all main islands (AOU 1983).

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Geographic Range

Barn owls are the most widespread of all owl species, and are found on every continent except Antarctica. In the Americas, barn owls occur in suitable habitat throughout South and Central America, and in North America as far north as the northern United States and southwestern British Columbia. In Europe, barn owls range from southern Spain to southern Sweden and east to Russia. They are also found throughout Africa, across central and southern Asia, and throughout Australia. Barn owls have been introduced to some oceanic islands to control rodent pests.

Biogeographic Regions: nearctic (Native ); palearctic (Native ); oriental (Native ); ethiopian (Native ); neotropical (Native ); australian (Native ); oceanic islands (Introduced )

Other Geographic Terms: holarctic ; cosmopolitan

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Physical Description

Morphology

Barn owls are medium-sized owls with long legs that are sparsely feathered down to their grey toes. The head is large and rounded without ear tufts. Barn owls have rounded wings and a short tail that is covered with white or light brown, downy feathers. The back and head of the bird are a light brown with variable black and white spots, while the underside is a grayish white. Barn owls are very striking in appearance. Females tend to be larger, weighing around 570 grams, while males weigh around 470 grams. Females also have a slightly longer body length (34 to 40 cm for females, 32 to 38 cm for males) and wingspan. Wingspan of males and females ranges from 107 to 110 cm.

Up to 35 subspecies of Tyto alba are recognized based on differences in body size and coloration.

Range mass: 430 to 620 g.

Range length: 32 to 40 cm.

Range wingspan: 107 to 110 cm.

Other Physical Features: endothermic ; homoiothermic; bilateral symmetry ; polymorphic

Sexual Dimorphism: female larger

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Physical Description

Barn owls are medium-sized owls with long legs that have feathers all the way down to their grey toes. They have large, round heads without ear tufts. Barn owls have rounded wings and a short tail that is covered with white or light-brown, downy feathers. They have a light brown spotted head and back, and a light grayish belly. Females are larger than males. They weigh 570 grams, while males weigh around 470 grams. Females also have a slightly longer body length (34 to 40 cm for females, 32 to 38 cm for males) and wingspan than males. The wingspan of barn owls ranges from 107 to 110 cm.

There are up to 35 subspecies of barn owls. These subspecies are different from each other in size and color.

Range mass: 430 to 620 g.

Range length: 32 to 40 cm.

Range wingspan: 107 to 110 cm.

Other Physical Features: endothermic ; homoiothermic; bilateral symmetry ; polymorphic

Sexual Dimorphism: female larger

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Size

Length: 16 cm

Weight: 490 grams

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Ecology

Habitat

Barn owls occupy a vast range of habitats from rural to urban. They are generally found at low elevations in open habitats, such as grasslands, deserts, marshes and agricultural fields. They require cavities for nesting, such as hollow trees, cavities in cliffs and riverbanks, nest boxes, caves, church steeples, barn lofts, and hay stacks. The availability of appropriate nesting cavities often limits use of suitable foraging habitat.

Habitat Regions: temperate ; tropical ; terrestrial

Terrestrial Biomes: desert or dune ; savanna or grassland ; forest ; scrub forest

Wetlands: marsh ; bog

Other Habitat Features: urban ; suburban ; agricultural ; riparian ; caves

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Habitat and Ecology

Systems
  • Terrestrial
  • Freshwater
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Comments: BREEDING: Fields of dense grass. Open and partly open country (grassland, marsh, lightly grazed pasture, hayfields) in a wide variety of situations, often around human habitation (AOU 1983). Nests in buildings (church steeples, attics, platforms in silos and barns, wooden water tanks, duckblinds), caves, crevices on cliffs, burrows, and hollow trees, rarely in trees with dense foliage (AOU 1983). Caves, cliff crevices, and cut bank burrows are commonly used in the western U.S., rarely in the east. Uses nest boxes (Marti and Wagner 1985). Reproductive success generally is higher in a properly placed and maintained nest box than in a natural nest cavity.

FORAGING HABITAT: Dense grass fields are the chief foraging habitat, including saltmarsh, wet meadows, lightly grazed pastures, grass hayfields, and recently abandoned agricultural fields (Colvin 1980, 1984, 1985; Rosenburg 1986; Gubanyi 1989). Radiotelemetry studies indicate that these habitats are actively selected (Colvin 1984, Rosenburg 1986, Gubanyi 1989). Furthermore, the quantity and quality of dense grass habitats are significantly correlated with nest activity (Colvin and Hegdal 1988).

Other habitats occasionally used include alfalfa/grass (Colvin 1984), small grain (Ault 1971, Rosenburg 1986), fencelines, and roadsides (Ault 1971, Byrd 1982). In an intensively farmed area in eastern Virginia where grass availability was very low, foraged in small grain, a five-year-old clearcut, barnyards, and a pine (PINUS spp.) plantation used as a blackbird roost (Rosenburg 1986). Cultivated habitats in general are of little importance because of low prey populations and/or dense protective cover (Colvin 1984, Rosenburg 1986).

NESTING HABITAT: This is a cavity-nesting bird which uses natural as well as human-created cavities. Tree cavities are the principal nest site used in most areas of the Northeast (Colvin et al. 1984); those most frequently used are silver maple (ACER SACCHARINUM), American sycamore (PLATANUS OCCIDENTALIS), and white oak (QUERCUS ALBA) (Colvin et al. 1984, Byrd and Rosenburg 1986). Although cut bank burrows and cliff recesses are frequently used in the western U.S. (Otteni et al. 1972, Martin 1973, Rudolph 1978, Millsap and Millsap 1987, Gubanyi 1989), only a few cases of the use of such sites have been reported in the Northeast. R. Ferren (pers. comm.) described nest holes in the steep bluffs on the north and south ends of Block Island, Rhode Island. Recesses in a clay embankment along the Patuxent River in Maryland supported a breeding pair during the late 1980s (S. Smith, pers. comm.). Exposed barrels in a cut bank along the Rappahannock River of eastern Virginia supported approximately 15 nesting pairs in the late 1970s (S. Doggett, pers. comm.). A wide variety of human-made "cavities" are used as nest sites. Large platforms within barns and silos, tunnels dug into silage in roofed or topless silos, cavities among hay bales stored inside barns, barn cupola shelves, wooden water tanks, and offshore duckblinds are frequently used; feed bins, church steeples and belfries, platforms within commercial and industrial buildings (e.g., warehouses, grain elevators, mills, factories), attics of abandoned or occupied houses, ledges within chimneys, platforms beneath bridges, and World War II cement watch towers are occasionally used (Stotts 1958, Scott 1959, Reese 1972, Klaas et al. 1978, Soucy 1979, Bunn et al. 1982, Hegdal and Blaskiewicz 1984, Colvin 1984, Byrd and Rosenburg 1986, Matteson and Petersen 1988, Parker and Castrale 1990). In addition, nest boxes are readily used (Otteni et al. 1972, Marti et al. 1979, Soucy 1980, Ziesemer 1980, Colvin et al. 1984, Cook 1985, Schulz 1986, Byrd and Rosenburg 1986, Bendel and Therres 1988, Parker and Castrale 1990).

NON-BREEDING: In winter often roosts in dense conifers; also roosts in nest boxes if available (Marti and Wagner 1985).

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Barn owls are found in a variety of habitats from cities to rural areas. They are usually found at low elevations in open habitats, such as grasslands, deserts, marshes and agricultural fields. They need cavities for nesting, such as hollow trees, cavities in cliffs and riverbanks, nest boxes, caves, church steeples, barn lofts, and hay stacks.

Habitat Regions: temperate ; tropical ; terrestrial

Terrestrial Biomes: desert or dune ; savanna or grassland ; forest ; scrub forest

Wetlands: marsh ; bog

Other Habitat Features: urban ; suburban ; agricultural ; riparian ; caves

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Occurs in farmland with hedgerows and copses, uncultivated areas such as heaths and marshes, sometimes large gardens, and occasionally in villages close to fields (11). It typically nests in tree holes, ruined buildings and farm buildings, hence the association with barns reflected by the common name (2).
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Migration

Non-Migrant: Yes. At least some populations of this species do not make significant seasonal migrations. Juvenile dispersal is not considered a migration.

Locally Migrant: Yes. At least some populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).

Locally Migrant: Yes. At least some populations of this species make annual migrations of over 200 km.

Populations in northern North America are partially migratory; may winter up to several hundred km southward from breeding area, as far as southern Mexico and the West Indies. Long-distance movements (to Mexico) have been recorded also for a nonbreeding adult and nestling banded in Texas; movement of young may represent dispersal rather than migration. There is no evidence of migration in the northern range in Europe, nor in northern Utah (Marti 1989). At Cape May Point, New Jersey, 90% of fall migration was completed between late September and early November (Duffy and Kerlinger 1992). See also Russell et al. (1991) for an account of fall migration at Cape May Point, New Jersey (peak migration was mid- to late October).

Stewart (1952) described it as partly migratory in the Northeast and presents extensive evidence of individuals banded in northern latitudes that were later recovered in southern latitudes. Duffy (1985) reported that large numbers of migrants are captured during fall night trapping at Cape May, New Jersey. Although most captured owls were juveniles, 20% of 171 captures at Cape May were adults (P. Kerlinger, pers. comm.). Most adults migrate past Cape May early in October while hatching-year birds migrate throughout October and early November (Duffy 1985). Recoveries of barn owls banded in the northeastern U.S. indicate that migrant individuals winter chiefly in the southeastern U.S. and Texas (Stewart 1952, Soucy 1980).

Northeastern U.S. Christmas Bird Count data (Stewart 1980, Butcher and Lowe 1990) demonstrate that not all individuals near the northern edge of the range leave for the winter; numerous counts from all northeastern states except Maine, New Hampshire, and Vermont reported barn owls every year. During the winter of 1989- 90, 74% of 35 active Virginia sites visited supported wintering owls (C. Rosenburg, unpubl. data). Although there is an observed migration of both juveniles and adults, many individuals winter within the northeastern U.S. There seem to be no obvious migration patterns (e.g., coastal vs. inland populations, mild winters vs. severe winters) within the northeastern U.S.. However, no investigations have been made into the possible influence of microtine rodent abundance on the percentage of the population which apparently migrates.

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Trophic Strategy

Barn owls are nocturnal predators that prefer small mammals such as mice, voles, shrews, rats, muskrats, hares and rabbits. They may also prey on small birds. Barn owls begin hunting alone after sunset. As an aid for detecting movement in grassland, they have developed highly sensitive low-light vision. When hunting in complete darkness, however, the owl relies on its acute hearing to capture prey. Barn owls are the most accurate birds at locating prey by sound. Another trait that adds to their hunting success is their downy feathers, which help to muffle the sound of their movement. An owl can approach its prey virtually undetected. Barn owls attack their prey in low flights (1.5m-4.5 meters above the ground), capture the prey with their feet, and nip through the back of the skull with the bill. They then swallow the prey whole. Barn owls do cache extra food, especially during the breeding season.

Animal Foods: birds; mammals

Foraging Behavior: stores or caches food

Primary Diet: carnivore (Eats terrestrial vertebrates)

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Comments: Eats mainly small mammals, especially voles (MICROTUS spp.). BLARINA, THOMOMYS, SPERMOPHILUS, PEROGNATHUS, DIPODOMYS, and PEROMYSCUS can be locally important. Birds can be taken when small mammals are scarce; introduced rodents are important in some urban areas and (with bats and birds) in the West Indies. In northern and eastern North America, the shrew (Soricidae) component of diet has declined over the past several decades; in the northern and central range, percentage of exotic rats and mice has increased (Clark and Bunck 1991).

Numerous pellet analyses throughout north temperate North America and Europe have identified voles as the primary prey (Ticehurst 1935; Wilson 1938; Pearson and Pearson 1947; Wallace 1948; Phillips 1951; Boyd and Shriner 1954; Glue 1967, 1974; Smith et al. 1972; Marti 1973; Webster 1973; Jackson et al. 1976; Lovari et al. 1976; Dexter 1978; Bethge and Hayo 1979; Colvin 1980, 1984; Hegdal and Blaskiewicz 1984; Cook 1985; Colvin and McLean 1986; Rosenburg 1986; Campbell et al. 1987; Feldhamer et al. 1987; Parker 1987; Hammerson 1988; Marti 1988). The meadow vole (MICROTUS PENNSYLVANICUS) is the most important prey animal in the northeastern U.S. and the short-tailed shrew (BLARINA BREVICAUDA) is an important secondary prey. By frequency, meadow voles typically comprise 60-90% of the diet (Boyd and Shriner 1954, Jackson et al. 1976, Colvin 1984, Cook 1985, Rosenburg 1986, Hammerson 1988). The marsh rice rat (ORYZOMYS PALUSTRIS) can be an important prey animal in coastal areas of southeastern North America (Jemison 1962, Blem and Pagels 1973, Jackson et al. 1976, Colvin 1984, Feldhamer et al. 1987). In the southern U.S., the cotton rat (SIGMODON HISPIDUS) is the primary prey (Baumgartner and Baumgartner 1944, Parmalee 1954, Otteni et al. 1972, Hamilton and Neill 1981, Byrd 1982, Baker 1986, Marra et al. 1989). Colvin (1984) concluded that barn owls seek prey of a particular size (approximately 40-60 g), which provides the most energy efficient diet.

Shows greater diet diversity: 1) in areas with relatively low microtine or cotton rat availability (Ticehurst 1935; Hawbecker 1945; Pearson and Pearson 1947; Glue 1967, 1974; Blem and Pagels 1973; Marti 1974; Bauer 1983; Colvin 1984; Lenton 1984; Colvin and McLean 1986; Rosenburg 1986; Parker 1987; Campbell et al. 1987); 2) during times of poor microtine availability (Fitch 1947, Wallace 1948, Glue 1967, Otteni et al. 1972, Webster 1973, Marti 1974, Jackson et al. 1976, Bethge and Hayo 1979, Baker 1986); and 3) when nonmicrotine prey are readily available (Evans and Emlen 1947, Sage 1962, Carpenter and Fall 1967, Smith et al. 1972, Klaas et al. 1978, Byrd 1982, Fritzell and Thorne 1984, Rosenburg 1986, Jentzsch 1988). These studies identified birds (mostly blackbirds and sparrows), short-tailed shrews, least shrews (CRYPTOTIS PARVA), house mice (MUS MUSCULUS), and Norway rats as relatively important prey in such situations.

The foraging behavior has been well studied (Colvin 1980, 1984).

Typical foraging is done with a relatively low quartering flight which includes frequent hovering intervals (Honer 1963, Haverschmidt 1970, Burton 1973, Karalus and Eckert 1974, Marti 1974, 1989, Rudolph 1978, Bunn et al. 1982, Mikkola 1983, Rosenburg 1986). Some individuals also hunt rather frequently from a perch, especially along field edges (Byrd 1982, Rosenburg 1986).

In North America this owl is highly nocturnal (Colvin 1984, Rosenburg 1986); it has extremely keen hearing (Payne 1971, Konishi 1973) and night vision (Dice 1945, Marti 1974). Its ability to capture prey by hearing alone (Payne 1971) is especially advantageous for hunting animals such as voles and shrews which are often concealed from view as they travel in runways beneath grass cover.

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Food Habits

Barn owls hunt small mammals such as mice, Microtus, shrews, rats, Ondatra zibethicus, Lepus and Sylvilagus. They may also prey on small birds.

Barn owls begin hunting alone after sunset. They have excellent eyesight in near-darkness. When it is completely dark, owls use their excellent hearing to find prey. Owls have special feathers the make them very quiet fliers. They can attack an animal without being heard, which helps them hunt successfully. Barn owls attack their prey by flying low above the ground (1.5m-4.5 meters above the ground) and grabbing the prey with their feet. They use their bill to nip the prey through the back of the head to kill it, and then they swallow it whole. Barn owls save extra food to eat later, especially during the breeding season.

Animal Foods: birds; mammals

Foraging Behavior: stores or caches food

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Associations

Barn owls limit populations of the mammal and bird species that they prey upon. They also serve as food for those species that prey upon them. Barn owls are host to several parasites. Nestlings are commonly infested with the dipteran Carnus hemapterus. They also host several protozoan blood and intestinal parasites and two species of lice (Kirodaia subpachygaster and Strigiphilus aitkeir).

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Barn owls have few predators. Nestlings are occasionally taken by stoats and snakes. There is also some evidence that great horned owls occasionally prey upon adult barn owls. Barn owl subspecies in the western Palearctic are much smaller than those in North America. These subspecies are sometimes preyed upon by golden eagles, red kites, goshawks, buzzards, peregrine falcons, lanners, eagle owls and tawny owls.

When facing an intruder, barn owls spread their wings and tilt them so that their dorsal surface is towards the intruder. They then sway their head back and forth. This threat display is accompanied with hissing and billsnaps that are given with the eyes squinted. If the intruder persists, the owl falls on its back and strikes with its feet.

Known Predators:

  • stoats (Mustela)
  • snakes (Serpentes)
  • golden eagles (Aquila chrysaetos)
  • red kites (Milvus milvus)
  • northern goshawks (Accipiter gentilis)
  • common buzzards (Buteo buteo)
  • peregrine falcons (Falco peregrinus)
  • lanners (Falco biarmicus)
  • Eurasian eagle-owls (Bubo bubo)
  • tawny owls (Strix aluco)
  • great horned owls (Bubo virginianus)

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Ecosystem Roles

Barn owls affect the populations of the mammal and bird species that they prey upon. They also provide food for those species that prey upon them. Barn owls are also host to several parasites.

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Predation

Barn owls do not have many predators. Nestlings are sometimes taken by Mustela and snakes. Adults may be killed by Bubo virginianus occasionally. Barn owls in western Europe are much smaller than those in North America. These owls are sometimes killed by Aquila chrysaetos, Milvus milvus, Accipiter gentiles, Buteo buteo, Falco peregrinus, Falco biarmicus, Bubo bubo and Strix aluco.

When facing an intruder, barn owls squint their eyes, spread their wings and sway their head back and forth while hissing. If the intruder is not scared away by this display, the owl falls on its back and strikes at the intruder with its feet.

Known Predators:

  • stoats (Mustela)
  • snakes (Serpentes)
  • golden eagles (Aquila_chrysaetos)
  • red kites (Milvus_milvus)
  • northern goshawks (Accipiter_gentilis)
  • common buzzards (Buteo_buteo)
  • peregrine falcons (Falco_peregrinus)
  • lanners (Falco_biarmicus)
  • Eurasian eagle-owls (Bubo_bubo)
  • tawny owls (Strix_aluco)
  • great horned owls (Bubo_virginianus)

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Known predators

Tyto alba is prey of:
Serpentes
Mustela
Accipiter gentilis
Buteo buteo
Aquila chrysaetos
Milvus milvus
Falco peregrinus
Falco biarmicus
Bubo virginianus
Bubo bubo
Strix aluco

This list may not be complete but is based on published studies.
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Known prey organisms

Tyto alba preys on:
Geomyidae
Dipodomys
Sylvilagus
Microtus ochrogaster
Microtus pennsylvanicus
Chaetodipus hispidus
Aves
Sturnella neglecta
Peromyscus maniculatus
Orthoptera
Mammalia
Corvus caurinus
Parascalops breweri
Microtus longicaudus
Microtus californicus
Ondatra zibethicus
Rattus exulans
Pteropus tonganus
Chaetodipus nelsoni
Muscardinus avellanarius
Peromyscus aztecus
Sorex araneus
Plecotus auritus
Nyctinomops laticaudatus

Based on studies in:
USA: California, Cabrillo Point (Grassland)

This list may not be complete but is based on published studies.
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General Ecology

Individuals range over large areas; mean home range size (based on the minimum home range method (Mohr and Stumpf 1966)) has been reported as 355 ha in southern Texas (Byrd 1982), 757 ha and 921 ha in southwestern New Jersey (Colvin 1984, Hegdal and Blaskiewicz 1984), 414 ha in eastern Virginia (Rosenburg 1986), 850 ha in Virginia (Byrd and Johnston 1991), and 198 ha in western Nebraska (Gubanyi 1989). As much as 5.6 km may be traveled between a nest site and foraging areas, although distances within 1.6 km are more usual (Colvin 1984, Hegdal and Blaskiewicz 1984, Rosenburg 1986). Overlap of individual home ranges is common, particularly where nest sites and prey are abundant. (Smith et al. 1974, Colvin 1984, Rosenburg 1986).

Young disperse widely from natal area, commonly more than 80 km, up to hundreds or 1900 km documented; wide dispersal facilitates colonization of new areas. Hatching-year barn owls have been recovered great distances from natal areas (commonly > 80 km and as much as 1800 km) (Stewart 1952; Soucy 1980, 1985). Although juveniles have been recovered from essentially every compass direction from their natal area, most had traveled in a southerly direction (Stewart 1952). Juveniles in the northern U.S. migrate south but return to nest somewhere within 320 km of their natal sites (Stewart 1952). Most individuals banded as nestlings and later found breeding did so at distances of about 50 km from their natal areas (Marti 1990). Cases of dispersal > 320 km have also been documented. An individual banded as a nestling in southwestern Iowa was recovered as a breeding adult 419 km to the east (Ehresman et al. 1989). A nestling banded in central New Jersey was found nesting in Ohio (B. Colvin, pers. comm.). Extensive banding of nestlings and capture of adults in southwest New Jersey reveals that only a small percentage of nestlings banded within the study area enter the adult population there: 5% of 181 nestlings banded in 1988 were found in the adult population in 1989 (Colvin and Hegdal 1989). Although they may return to breed relatively close to their natal area, individuals frequently become established great distances away. Very successful at colonizing new areas because of this broad dispersal behavior.

Susceptible to starvation during prolonged low temperatures and snow cover (Marti and Wagner 1985). In Utah, most adults survived only 1 breeding season (Marti 1989). Disease, parasites, and predation are natural factors that may in part limit populations. Appears to be resistant to many diseases that infect other raptors (Schulz 1986). In California, diseases documented include tuberculosis, aspergillosis, and trichomoniasis (Schulz 1986). Toxoplasmosis and eastern equine encephalitis have been detected in New Jersey, although no impact to the birds was apparent (Colvin and Hegdal 1986, 1987). Salmonellosis has been recorded in Pennsylvania (Locke and Newman 1970) and New Jersey (Kirkpatrick and Colvin 1986). Kirkpatrick and Colvin (1986) found SALMONELLA-positive nestlings at five of the 25 New Jersey nest sites examined, and reported that all infected young apparently fledged.

Dipteran ectoparasites and lice have been found on owls (Schulz 1986, Kirkpatrick and Colvin 1989). The endoparasites TRYPANOSOMA, CAPILLARIA, and PORROCAECUM have been identified from the feces of New Jersey owls (Colvin and Hegdal 1986).

NON-BREEDING: solitary or in pairs.

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Life History and Behavior

Behavior

Barn owls communicate with vocalizations and physical displays. Owlets still in the nest utter several distinct vocalizations, including a twitter used to express discomfort, attention-seeking, and when quarreling with nestmates. Young also give a raspy snoring food call. Adults use a variety of vocalizations, including the advertising call, a drawn-out gargling scream that is probably the best known call. The distress call is a series of drawn-out screams. Other vocalizations include a defensive hissing sound, a fast, often prolonged, twitter for feeding, and an explosive yell that is usually directed at a mammalian predator. Also, greeting and conversational twitters seem to convey recognition of mate and accompany various courtship activities. Barn owls are much less vocal when not breeding.

The ability of barn owls to locate prey by sound is the most accurate of any animal tested. This very acute sense of hearing allows barn owls to capture prey hidden by vegetation or snow. Their amazing ability to locate prey using sound is aided by their asymmetrically placed ears. This asymmetry allows these owls to better localize sounds generated by prey. Their ears are extremely sensitive and can be closed by small feathered flaps if the noise level is too disturbing. Barn owls also have excellent low-light vision.

Communication Channels: visual ; acoustic

Perception Channels: visual ; tactile ; acoustic ; chemical

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Communication and Perception

Barn owls communicate with vocalizations and physical displays. Owl chicks in the nest make several different calls. Chicks use a “twitter” call to express discomfort, to seek attention, and when quarreling with other chicks in the nest. They also give a raspy snoring food call.

Adults use a variety of vocalizations. Their common drawn-out gargling scream is an advertising call. They also use twitters to greet their mate and during courtship activities. Barn owls are vocal while breeding, but quiet during the rest of the year.

Barn owls have an amazing ability to locate prey by sound. They are better at this than any other animal that has been tested. Barn owls are so good at finding prey by hearing, that they capture prey that is hidden under vegetation or snow. Their ears are extremely sensitive and can be closed by small feathered flaps if the noise level is too loud. Barn owls also have excellent vision for seeing at night.

Communication Channels: visual ; acoustic

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Cyclicity

Comments: Hunts mostly at night, from about 1 hour after sunset to about one hour before sunrise (Marti 1989).

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Life Expectancy

Most barn owls have a relatively short life span. Many only survive one breeding season and the mortality rate may be as high as 75% in the first year of life. in one study, the mean age at death for 572 banded birds was 20.9 months. However, the longest recorded lifespan of a wild barn owl is 34 years.

Range lifespan

Status: wild:
34 (high) years.

Average lifespan

Status: wild:
20.9 months.

Average lifespan

Status: wild:
185 months.

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Lifespan/Longevity

Most barn owls do not live very long. Many only survive one breeding season. However, some individuals do live for many years. The oldest wild barn owl lived 34 years.

Range lifespan

Status: wild:
34 (high) years.

Average lifespan

Status: wild:
20.9 months.

Average lifespan

Status: wild:
185 months.

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Lifespan, longevity, and ageing

Maximum longevity: 34 years (wild) Observations: These animals have a relatively short lifespan in the wild with one study estimating an average lifespan of 1.7 years. Nonetheless, it has been reported that they can live up to 34 years in the wild (http://bna.birds.cornell.edu/). This is not impossible but questionable considering that the oldest individual in banding studies involving thousands of recoveries was 21.3 years of age (Moller 2006).
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Reproduction

Barn owls are most commonly monogamous, although several reports of polygyny exist. Pairs typically remain together as long as both individuals live.

Courtship begins with display flights by males which are accompanied by advertising calls and chasing the female. During the chase, both the male and the female screech. The male will also hover with feet dangling in front of the perched female for several seconds; these are known as moth flights.

Copulation occurs every few minutes during the nest site search. Both sexes crouch down in front of each other to solicit copulation. The male mounts the female, grasps her neck, and balances with spread wings. Copulation continues with decreasing frequency throughout incubation and chick rearing.

Mating System: monogamous

Barn owls breed once per year. They can breed almost any time of the year, depending upon food supply. Most individuals begin breeding at 1 year old. Due to the short life span of barn owls (2 years on average), most individuals breed only once or twice. Barn owls usually raise one brood per year, though some pairs have been observed raising up to three broods in one year

Barn owl pairs often use an old nest that has been occupied for decades rather than building a new one. The female usually lines the nest with shredded pellets. She lays 2 to 18 eggs (usually 4 to 7) at a rate of one egg every 2 to 3 days. The female incubates the eggs for 29 to 34 days. The altricial chicks are brooded and fed by the female for about 25 days after hatching. They leave the nest on their first flight 50 to 70 days after hatching, but return to the nest to roost for 7 to 8 weeks. The chicks usually become independent from the parents 3 to 5 weeks after they begin flying.

Breeding interval: Barn owls breed once yearly; somtimes two or even three broods per year are produced.

Breeding season: Barn owls breed essentially any time of the year, depending upon food supply.

Range eggs per season: 2 to 18.

Average eggs per season: 5.5.

Range time to hatching: 29 to 34 days.

Range fledging age: 50 to 70 days.

Average fledging age: 64.3 days.

Range time to independence: 3 to 5 weeks.

Average age at sexual or reproductive maturity (female): 1 years.

Average age at sexual or reproductive maturity (male): 1 years.

Key Reproductive Features: iteroparous ; year-round breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; oviparous

Average eggs per season: 6.

Female barn owls leave the nest during incubation only briefly and at long intervals. During this time, the male feeds the incubating female. All brooding is done by the female, beginning immediately after hatching and lasting until the oldest young is about 25 days old. Males bring food to the nest for the female and chicks, but only the female feeds the young, initially tearing the food into small pieces. The female also eats the feces of the chicks for the first few weeks after hatching in order to sanitize the nest. The parents continue to feed the chicks for up to 5 weeks after fledging.

Parental Investment: no parental involvement; altricial ; pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth (Protecting: Female); pre-weaning/fledging (Provisioning: Male, Female, Protecting: Female); pre-independence (Provisioning: Male, Female, Protecting: Male, Female)

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Nests in late winter, spring, and/or early summer in most of North America. Breeds throughout year in Texas. Nests with eggs or young have been found in the northeastern U.S. during every month of the year (Poole 1930; Bent 1938; Scott 1950; Stewart 1952; C. Rosenburg, unpubl. data), but peak egg laying occurs during mid-April (Colvin 1984, Byrd and Rosenburg 1986). Second clutches are typically laid between June and September (Wallace 1948, Keith 1964, Reese 1972, Soucy 1979). As many three broods per year; some California birds attempt two broods per year; one brood per year in most of the range. Clutch size ranges between one to 13 eggs (Bent 1938, Parker and Castrale 1990) with the mean clutch size ranging between four to six eggs (Otteni et al. 1972, Reese 1972, Smith et al. 1974). Clutch size depends on condition; increases with food supply and after mild winters in some areas. Eggs are usually laid two days apart and hatch asynchronously since incubation starts after the laying of the first egg (Wallace 1948, Smith et al. 1974). Incubation by female, 21-24 days for single egg, 29-34 days for full clutch (Smith et al. 1974, Marshall et al. 1986). The peak of hatching in the Northeast occurs in mid-May (Colvin 1984; Byrd and Rosenburg 1986; S. Smith, pers. comm.). Female broods and feeds young, male brings food. Young reportedly fly at 50-55 days in England; young fledge at 8-10 weeks in U.S. (Pickwell 1948, Reese 1972, Smith et al. 1974). Peak fledging occurs in mid to late July (Colvin 1984, Byrd and Rosenburg 1986). Juveniles may remain in the vicinity of the nest site for several weeks before dispersing (Otteni et al. 1972, Smith et al. 1974, Marti 1990). Male may care for fledged young as female begins second clutch. In northern Utah, 71% of all nesting attempts yielded at least one fledgling; reproductive success and productivity were reduced following winters with particularly low temperatures and long periods of deep snow cover (Marti 1994). Breeding density depends on availability of nest sites and on food supply. See Marti (1989) for information on breeding phenology in different areas.

Matures and breeds within its first year (Stewart 1952, Maestrelli 1973, Marti 1990) and sometimes as early as seven months of age (B. Colvin, pers. comm.). It is typically monogamous, but Colvin and Hegdal (1989) reported that as many as 10% of the adult males in their New Jersey study area may be polygynous.

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Barn owls are monogamous. Mated pairs usually stay together as long as both owls are alive.

Courtship begins with display flights by males which are accompanied by advertising calls and chasing the female. During the chase, both the male and the female screech. The male will also hover with feet dangling in front of the perched female for several seconds; these are known as moth flights.

Mating System: monogamous

Barn owls breed once per year. They can breed almost any time of the year, depending upon the food supply. Most barn owls first breed when they are 1 year old. Most barn owls raise one brood per year, but some pairs have raised up to three broods in one year

Barn owl pairs often use an old nest instead of building a new one. The female lines the nest with shredded pellets to make a soft surface for the eggs. She lays 2 to 18 eggs (usually 4 to 7). The female incubates the eggs for 29 to 34 days. The chicks are altricial, and must be brooded by the female for about 25 days after hatching. They leave the nest on their first flight 50 to 70 days after hatching, but they return to the nest to roost for 7 to 8 weeks. The chicks usually become independent from the parents 3 to 5 weeks after they begin flying.

Breeding interval: Barn owls breed once yearly; somtimes two or even three broods per year are produced.

Breeding season: Barn owls breed essentially any time of the year, depending upon food supply.

Range eggs per season: 2 to 18.

Average eggs per season: 5.5.

Range time to hatching: 29 to 34 days.

Range fledging age: 50 to 70 days.

Average fledging age: 64.3 days.

Range time to independence: 3 to 5 weeks.

Average age at sexual or reproductive maturity (female): 1 years.

Average age at sexual or reproductive maturity (male): 1 years.

Key Reproductive Features: year-round breeding ; gonochoric/gonochoristic/dioecious (sexes separate)

Average eggs per season: 6.

Female barn owls incubate the eggs and brood the chicks until the oldest chick is about 25 days old. The male brings food to the female and the chicks. The female tears up the food to feed it to the chicks. The female also keeps the nest clean by eats the feces of the chicks for the first few weeks after they hatch. The parents feed the chicks for up to 5 weeks after they fledge.

Parental Investment: no parental involvement; altricial ; pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth (Protecting: Female); pre-weaning/fledging (Provisioning: Male, Female, Protecting: Female); pre-independence (Provisioning: Male, Female, Protecting: Male, Female)

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Molecular Biology and Genetics

Molecular Biology

Barcode data: Tyto alba

The following is a representative barcode sequence, the centroid of all available sequences for this species.


There are 21 barcode sequences available from BOLD and GenBank.

Below is a sequence of the barcode region Cytochrome oxidase subunit 1 (COI or COX1) from a member of the species.

See the BOLD taxonomy browser for more complete information about this specimen and other sequences.

CGATGATTATTCTCAACAAACCACAAAGACATTGGCACCCTGTACCTAGTCTTCGGCGCATGAGCCGGCATAGTAGGAACAGCCCTCAGCCTCCTAATCCGGGCAGAACTAGGACAACCAGGAACCCTCCTGGGAGAC---GACCAAATCTACAATGTAATTGTCACTGCCCACGCCTTTGTAATAATTTTCTTCATAGTAATACCCATTATGATCGGCGGATTTGGAAACTGACTAGTCCCTCTCATAATCGGAGCCCCGGACATAGCATTTCCCCGTATAAATAATATAAGTTTCTGACTACTTCCCCCCTCCTTCCTATTACTGCTAGCATCCTCCACAGTAGAAGCAGGAGCAGGCACGGGTNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNCCAAACACCCCTGTTTGTGTGGCCAGCCNNNATCACCGCGATCCAACTACTACTATCACTCCCAGTACTAGCCGCTGGCATTACCATGCTCTTAACCGACCGAAACCTAAACACCACATTCTTTGACCCCGCCGGAGGGGGCGACCCTATCCTGTACCAACACCTTTTCTGATTCTTTGGTCATCCCGAGGTGTACATCCTGATCCTCCCGGGATTTGGAATTATCTCGCACGTAGTAGCGTACTATGCGGGCAAAAAAGAACCATTGGGCTACATAGGGATAGTCTGAGCAATACTCTCTATTGGATTCCTAGGATTTATTGTCTGAGCCCATCATATATTCACCGTAGGAATAGATGTTGACACACGAG
-- end --

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Statistics of barcoding coverage: Tyto alba

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 24
Specimens with Barcodes: 43
Species With Barcodes: 1
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Conservation

Conservation Status

Barn owls are protected under the U.S. Migratory Bird Treaty Act and under CITES Appendix II. They are not federally threatened or endangered in the United States, but they are protected in some individual U.S. states--including Michigan, where they are considered endangered.

Threats to barn owl population include climatic changes, pesticides, and changing agricultural techniques. A change of the climate in northern regions is causing snow to last for longer periods, making winter survival difficult for the species. Unlike other birds, barn owls do not store extra fat in their body as a reserve for harsh winter weather. As a result, many owls die during freezing weather or are too weak to breed in the following spring. Pesticides have also contributed to declines in this species. For unknown reasons, barn owls suffer more severe effects from consuming pesticides than other species of owls. These pesticides are often responsible for eggshell thinning in females. Another major factor limiting population growth is modern agricultural methods. Traditional farms with many small structures favored barn owl populations. In modern farms, there is no longer an adequate amount of farm structures for nesting, and farm land can no longer support a sufficient population of rodents to feed a barn owl pair. The barn owl population, however, is declining only in some localities, not throughout the range.

US Migratory Bird Act: protected

US Federal List: no special status

CITES: appendix ii

State of Michigan List: endangered

IUCN Red List of Threatened Species: least concern

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IUCN Red List Assessment


Red List Category
LC
Least Concern

Red List Criteria

Version
3.1

Year Assessed
2012

Assessor/s
BirdLife International

Reviewer/s
Butchart, S. & Symes, A.

Contributor/s

Justification
This species has an extremely large range, and hence does not approach the thresholds for Vulnerable under the range size criterion (Extent of Occurrence <20,000 km2 combined with a declining or fluctuating range size, habitat extent/quality, or population size and a small number of locations or severe fragmentation). The population trend appears to be stable, and hence the species does not approach the thresholds for Vulnerable under the population trend criterion (>30% decline over ten years or three generations). The population size is extremely large, and hence does not approach the thresholds for Vulnerable under the population size criterion (<10,000 mature individuals with a continuing decline estimated to be >10% in ten years or three generations, or with a specified population structure). For these reasons the species is evaluated as Least Concern.
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National NatureServe Conservation Status

Canada

Rounded National Status Rank: N3 - Vulnerable

United States

Rounded National Status Rank: N5 - Secure

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NatureServe Conservation Status

Rounded Global Status Rank: G5 - Secure

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Barn owl populations are decreasing in some areas. In some northern regions, snow is staying on the ground longer. This makes it difficult for barn owl to find food and survive the winter. Barn owls are also poisoned by pesticides that are used to kill weeds or crop pests. Finally, barn owls used to be able to nest successfully on many farms. However, newer farms have fewer buildings for nesting and fewer rodents for food, so they are not very good habitat for barn owls.

Barn owls are protected under the U.S. Migratory Bird Treaty Act and under CITES Appendix II. They are not federally threatened or endangered in the United States, but they are protected in some U.S. states--including Michigan, where they are considered endangered.

IUCN Red List of Threatened Species: least concern

US Migratory Bird Act: protected

US Federal List: no special status

CITES: appendix ii

State of Michigan List: endangered

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Status in Egypt

Resident breeder.

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Status

Specially protected under Schedules 1 and 9 of the Wildlife and Countryside Act 1981 (3). Listed as a Species of Conservation Concern by the UK Biodiversity Action Plan, but not a priority species (8). Included in the Birds of Conservation Concern Amber List (medium conservation concern) (10).
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Population

Population Trend
Stable
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Threats

Comments: Population declines have been attributed mainly to commercial development of farmland, reduction in dairy and sheep industry, conversion to intensive row-crop farming, and decline in the number of farms and old farm structures, resulting in a loss of nest sites and important high-quality foraging habitat. Foraging habitat availability appears to limit numbers most significantly (Colvin et al. 1984, Colvin 1985, Rosenburg 1986, Ehresman et al. 1989, Gubanyi 1989). Loss of farmland to development and the intensification of agricultural practices on remaining farmlands have substantially reduced the quantity and quality of dense grass habitats in agricultural areas (Honer 1963, Shrub 1970, Colvin 1985, Rosenburg 1986). The availability of pasture and grass hayfield has been reduced substantially. Colvin (1985) reported an approximately 53% decline in hayfield acreage in Ohio between 1921-80 and identified a significant correlation between a population decline in Ohio and the replacement of grass-associated agriculture by row crops. In Virginia, the acreage of pasture, grass hayfield, and idle areas was reduced 55% between 1945-78 and the quality of pasture declined because of increased grazing pressure (Rosenburg 1986). In many intensively-farmed areas, dense grass habitats are present only in small fields that are patchily distributed; such fields would apparently provide a limited foraging resource (Rosenburg 1986). The reduced quality and quantity of dense grass habitats has substantially reduced prey availability in some areas. Prey availability has been shown to be closely associated with owl productivity (Ault 1971, Otteni et al. 1972, Colvin 1984, Gubanyi 1989). This association is so close that one year of poor meadow vole abundance can result in a rapid population decline while one year of substantial meadow vole abundance can result in rapid population recovery (B. Colvin, pers. comm.). NEST SITE AVAILABILITY: The availability of secure nest sites is an important limiting factor in some areas (Marti et al. 1979, Schulz and Yasuda 1985, Byrd and Rosenburg 1986, Gubanyi 1989). Tree cavity sites may be limited in availability (Rosenburg 1986), they are ephemeral (Colvin et al. 1984, Byrd and Rosenburg 1986), and relatively insecure (Colvin et al. 1984). Competition for this resource may also be a factor; Colvin (1984) documented usurpation of nest cavities by wood ducks (AIX SPONSA) and raccoons (PROCYON LOTOR). Secure nest sites within human-made structures are limited in availability (Schulz 1986; C. Rosenburg, unpubl. data). In addition, the gradual deterioration and disappearance of old-style barns, silos, and water tanks plus the screening of entrances to prevent rock dove (COLUMBA LIVIA) access has eliminated many previously productive nest sites (Honer 1963, Heintzelman 1966, Schulz and Yasuda 1985, Byrd and Rosenburg 1986, Parker and Castrale 1990). Areas that support abundant foraging habitat may lack an adequate supply of secure and stable nest sites in close proximity to foraging habitat. Kirkpatrick and Colvin (1986) suggested that salmonellosis may limit survival and reproduction at times when stresses, such as severe weather and poor prey availability, are acting. This stress dependent impact may be true for other diseases and parasites as well (Honer 1963, Kirkpatrick and Colvin 1989). Weather is the most important factor influencing annual productivity in southwestern New Jersey (B. Colvin, pers. comm.). Moist weather conditions enhance dense grass habitats and thereby enhance vole populations, which results in higher productivity. Exceedingly dry conditions have a negative impact on vole populations and result in poor productivity (Colvin and Hegdal 1986, 1987, 1988, 1989). Starvation of chicks, the single most important mortality factor (B. Colvin, pers. comm.), is widespread during exceedingly dry conditions. Throughout the Northeast, the owl is susceptible to starvation and exposure during extended periods of extreme cold and deep snow cover. Winter weather mortality has been documented in Wisconsin (Errington 1931), Illinois (Speirs 1940), Ohio (Stewart 1952), Massachusetts (Keith 1964), Utah (Marti and Wagner 1985), and Virginia (C. Rosenburg, unpubl. data). Marti and Wagner (1985) reported that some winter weather mortality appears to occur every winter in northern Utah and that such mortality is widespread and consequential in some years. They found 77 dead owls after severe weather during the winter of 1981-82, and a 40% decline in breeding attempts occurred the following summer. Keith (1964) documented winter weather mortality of more than ten owls during the winter of 1960-61 and the subsequent lack of nesting during the following three breeding seasons at Martha's Vineyard, Massachusetts. Barn owls did not nest at Martha's Vineyard again until 1973 (Brett 1987). PESTICIDES: Secondary poisoning from rodenticides has been considered to be a potential hazard because of the importance of rodents in the diet and the fairly widespread use of rodenticides in agricultural areas. Laboratory studies have demonstrated that the consumption of rats or mice poisoned with bromadiolone or brodifacoum rodenticides can cause lethal hemorrhaging and that consumption of rats poisoned with difencoum rodenticide can cause sublethal hemorrhaging (Mendenhall and Pank 1980; Newton et al., in press). These studies demonstrated that the owl is especially sensitive to the anticoagulant brodifacoum. Secondary poisoning from rodenticides has been documented in the U.S. (Schulz 1986; L. Soucy, pers. comm.) and Great Britain (Newton et al., in press). The potential for poisoning appears to be greatest in marginal habitat areas such as intensively farmed sites (Rosenburg 1986). However, there appears to be no appreciable impact to populations from rodenticide poisoning (Colvin 1984; Hegdal and Blaskiewicz 1984; Newton et al., in press). Organophosphate insecticides have been shown to be potentially hazardous. Laboratory experiments conducted by Hill and Mendenhall (1980) demonstrated that owls which consumed famphur-poisoned prey exhibit secondary poisoning in the form of significant cholinesterase inhibition. Mass mortality of wild raptors, including 22 barn owls, occurred after azodrin was improperly used to kill voles in Israel (Mendelssohn and Paz 1977). Rodents contaminated with organophosphate and carbamate insecticides are present in agricultural fields (Montz 1988). These rodents are potentially hazardous to raptors because birds in general are extremely sensitive to anti-cholinesterase compounds (Brealey et al. 1980). It is unlikely that organophosphate or carbamate insecticides have impacted populations since these pesticides are not targeted for foraging habitats or prey species (B. Colvin, pers. comm.). However, no field studies have examined cholinesterase levels of owls in agricultural areas where these pesticides are widely used. Further investigation may be warranted (L. Brewer, pers. comm.). The owl is sensitive to contamination from organochlorine insecticides. Laboratory studies by Mendenhall et al. (1983) found that it is very sensitive to eggshell thinning by DDE and that dieldrin can cause adult mortality. These insecticides were found in concentrations that may have been detrimental to reproduction in 15% of the barn owls in the lower Potomac River, Maryland in the early 1970s (Klaas et al. 1978). Extensive feeding on passerine birds by this portion of the population is believed to have caused the elevated organochlorine levels; the majority of the population preyed chiefly on mammals and remained relatively uncontaminated. In Great Britain, poisoning from organochlorine pesticides was an important cause of mortality during the years 1963-77 when these chemicals were used extensively (Newton and Wyllie, in press). Organochlorine insecticide residues have been found in barn owls and their eggs collected in Florida (Johnston 1978), Oregon (Henny et al. 1984), and Virginia (Gwynn 1987). Acute effects from organochlorine insecticides are unlikely, though, since raptors which feed chiefly upon small mammals are not highly susceptible to organochlorine insecticide poisoning (Henny 1972) and since few potentially harmful organochlorine insecticides are in use in the U.S. today (Newton 1979; S. Wiemeyer, pers. comm.). OTHER FACTORS: A number of other mortality factors have been identified. Collision with vehicles has been reported as an important mortality factor (Glue 1971; Smith and Marti 1976; Keran 1981; Schulz 1986; Newton and Wyllie, in press). Drowning of young as they attempt to fledge from offshore duck blinds appears to be acting as a population sink in coastal Maryland and possibly other areas where substantial numbers nest in these structures (G. Therres, pers. comm.). Other mortality factors include electrocution, entrapment in buildings, shootings, and entanglement in farm or industrial machinery (Glue 1971; Smith et al. 1974; Smith and Marti 1976; Keran 1981; Colvin 1984; Hegdal and Blaskiewicz 1984; Lerg 1984; Schulz and Yasuda 1985; Schulz 1986; Ehresman et al. 1989; Newton and Wyllie, in press; C. Rosenburg, unpubl. data). The degree to which these latter four factors limit numbers appears to be low. PREDATION: May limit numbers in some areas. Raccoons and black rat snakes (ELAPHE OBSOLETA) prey on eggs and nestlings (Ehresman 1984; B. Colvin, pers. comm.; C. Rosenburg, unpubl. data), and great horned owls (BUBO VIRGINIANUS) prey on juveniles and adults (Rudolph 1978, Knight and Jackman 1984, Lerg 1984, Rosenburg 1986, Millsap and Millsap 1987, Ehresman et al. 1989) and may inhibit barn owl activity because of their dominance (Rudolph 1978). Information concerning predation rates on eggs, nestlings, juveniles, and adults is limited and further investigation is warranted (Hands et al. 1989).

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From the middle of the 19th century, this beautiful owl began to decline in Britain. The original decline is thought to have been the result of an increase in persecution. The decline continued as a result of agricultural intensification, poor winter weather, traffic deaths, pesticide use and a loss of hunting and nesting sites (4).
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Management

Restoration Potential: High recovery and management potential (Rosenburg 1992). They have a potentially high reproductive output because of 1) large clutch size, 2) occasional second broods, 3) sexual maturity at one year, 4) lack of strict territoriality, and 5) occasional polygyny. These characteristics provide mechanisms for rapid population expansion during times of prey availability (Wallace 1948, Stewart 1952, Henny 1969, Colvin 1984). This potentially high reproductive output, coupled with the owl's colonizing abilities, indicates an ability to establish or expand populations in areas where stable habitats exist. This ability was demonstrated during the first part of this century when the owl rapidly expanded its range into the Midwest in response to the clearing of forests and the establishment of agriculture which supported an abundance of dense grass habitats (B. Colvin, pers. comm.). In addition, the major biological and ecological limiting factors are fairly well understood and management techniques have been developed.

Preserve Selection and Design Considerations: The most important land protection tool for maintaining or expanding populations is the preservation of dense grass foraging habitats (Lerg 1984; Rosenburg 1986; Gubanyi 1989; B. Colvin, pers. comm.). Acquisition of fee title or the use of conservation easements, management agreements, property registration, or tax incentives (Millsap et al. 1987) are means of preserving existing grasslands or acquiring additional land, such as cropland, which can be converted to grassland. Large-scale habitat acquisition programs are very costly. Programs which utilize other preservation strategies, such as conservation easements and tax incentives, and which focus on all of the grassland dependent species of management concern may be cost effective.

EDUCATION: Efforts towards educating farmers and other landowners about the owl's unique characteristics, rodent-catching abilities, and reliance upon dense grass habitats should be made. Educational efforts will generate a stronger interest in the barn owl and may stimulate beneficial conservation efforts. Educational efforts are also a good public relations tool that may result in a better acceptance of state and regional conservation efforts. They often lead to reports of owls and may help identify individuals who are willing to conduct local nest box programs (A. Parker, pers. comm.). Potential educational efforts include natural history and nest box pamphlets, articles in conservation and agricultural magazines, and slide presentations to ornithological groups. The Indiana Department of Natural Resources produced a barn owl slide program which has been very popular and has stimulated local nest box programs (A. Parker, pers. comm.).

Management Requirements: Habitat manipulation should focus on maintaining the grass sere without removing dense ground cover essential for meadow voles (Rosenburg 1992). Grass fields should be lightly grazed or mowed once a year. Litter from mowing should be left in the field to maintain high vole populations. However, one annual hay cutting appears to have little long-term impact on vole carrying capacity and should therefore be considered compatible with grassland management objectives. Prescribed burning may be a potential management practice in some areas. Tidewater marshes of Maryland are burned extensively during winter months resulting in rapid vegetation growth without removing litter (S. Smith, pers. comm.).

Other factors which affect meadow vole abundance and which may therefore deserve management attention are vegetational nitrogen content (Huntly and Inouye 1987) and the availability of preferred forage (Zimmerman 1965). Important forage plants for the meadow vole include AGROPYRON, AMBROSIA, BROMUS, CAREX, FRAGARIA, MEDICAGO, MUHLENBERGIA, PANICUM, POA, TARAXACUM, and TRIFOLIUM spp. (Zimmerman 1965, Lindroth and Batzli 1984, Marquis and Batzli 1989, Bucyanayandi and Bergeron 1990).

Provision of nest boxes may result in increased populations if prey populations are adequate. Nests should not be disturbed during incubation or near fledging time (to avoid nest abandonment and premature fledging). To avoid having raccoons follow human scent to vulnerable nest sites, sprinkle naphthalene or paradichlorobenzene flakes on the ground at nest site entrances.

Management Research Needs: Recommended research objectives that warrant attention include: 1) Identify important habitat variables associated with successful nest sites in the Northeast. Compare habitat variables (e.g., percentage of open vs. wooded vegetation, acreage of grass habitats supporting MICROTUS spp., and kilometers of edge) within 1.6 km of successful nest sites versus random points. Separate comparisons should be made for agricultural and coastal marsh sites. 2) Determine the results of habitat manipulation upon meadow vole populations in order to evaluate the effects of existing land use practices and potential management practices upon this important prey species. 3) Identify the levels of anticoagulant rodenticide and organophosphate insecticide residues present in free-ranging owls. Liver, blood, and brain tissue samples should be collected from owls euthanized in wildlife rehabilitation centers or those found shortly after death (S. Porter, pers. comm.). Liver samples can also be taken from owls which were not found shortly after death. Liver tissue samples should be analyzed for residues of difencoum and brodifacoum (Newton et al. 1990). Blood and brain tissue samples should be analyzed for significant cholinesterase inhibition (Hill and Fleming 1982; Hill 1988; L. Brewer, pers. comm.). Fresh pellet and fecal samples should be collected at various intensively farmed areas of the Northeast. Analyses of these pellet and fecal samples can identify organophosphate insecticide groups that may be present (L. Brewer, pers. comm.).

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Needs: In the northeastern U.S., large tracts of foraging habitat need to be protected.

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Conservation

Under the Wildlife and Countryside Act, 1981, it is illegal to kill, injure or take a barn owl or to remove or damage eggs. The Barn Owl Conservation Network (BOCN), a project of the Hawk and Owl Trust, is promoting a habitat creation scheme, with the provision of nest boxes to help this species (9).
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Relevance to Humans and Ecosystems

Benefits

There are no negative impacts of barn owls on humans.

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Barn owls limit rodent pest populations, benefiting farmers and others.

Positive Impacts: controls pest population

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Economic Importance for Humans: Negative

There are no negative impacts of barn owls on humans.

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Economic Importance for Humans: Positive

Barn owls limit rodent pest populations, benefiting farmers and others.

Positive Impacts: controls pest population

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Risks

Stewardship Overview: In the Northeast, inhabits agricultural grasslands and tidewater marshlands where it typically nests in tree cavities or in barns, silos, church steeples, warehouses, and other structures. Although little reliable historical data demonstrates that populations have changed significantly since 1900, limited data suggests a general decline throughout the Northeast and several states consider it as rare and declining. The loss of dense grass habitats for foraging appears to be the most significant limiting factor, but this could be overcome by grassland management programs aimed at preserving large fields near to nesting sites. Long-term monitoring of grassland availability and small mammal abundance, as well as nest sites, should be implemented regionally to track population trends. Nest boxes can be placed in areas of good foraging habitat to supplement natural nest sites. Grass habitats can also be managed by light grazing or mowing to maintain the grass sere without altering dense ground cover used by small mammals (Rosenburg 1992).

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Wikipedia

Barn owl

This article is about the common barn owl species. For the entire barn owl family, see Tytonidae.

The barn owl (Tyto alba) is the most widely distributed species of owl, and one of the most widespread of all birds. It is also referred to as the common barn owl, to distinguish it from other species in its family, Tytonidae, which forms one of the two main lineages of living owls, the other being the typical owls (Strigidae). The barn owl is found almost everywhere in the world except polar and desert regions, Asia north of the Himalayas, most of Indonesia and some Pacific islands.[2]

Phylogenetic evidence shows that there are at least three major lineages of barn owl, one in Eurasia and Africa, one in Australasia and one in the New World, and some highly divergent taxa on islands. Some authorities further split the group, recognising up to five species, and further research needs to be done to clarify the position. There is considerable variation between the sizes and colouring of the approximately 28 subspecies but most are between 33 and 39 cm (13 and 15 in) in length with wingspans ranging from 80 to 95 cm (31 to 37 in). The plumage on head and back is a mottled shade of grey or brown, the underparts vary from white to brown and are sometimes speckled with dark markings. The face is characteristically heart-shaped and is white in most species. This owl does not hoot, but utters an eerie, drawn-out shriek.

The barn owl is nocturnal over most of its range but in Britain and some Pacific islands, it also hunts by day. Barn owls specialise in hunting animals on the ground and nearly all of their food consists of small mammals which they locate by sound, their hearing being very acute. They mate for life unless one of the pair gets killed, when a new pair bond may be formed. Breeding takes place at varying times of year according to locality, with a clutch, averaging about four eggs, being laid in a nest in a hollow tree, old building or fissure in a cliff. The female does all the incubation, and she and the young chicks are reliant on the male for food. When large numbers of small prey are readily available, barn owl populations can expand rapidly, and globally the bird is considered to be of least conservation concern. Some subspecies with restricted ranges are more threatened.

Taxonomy and etymology[edit]

In silent flight
Male Tyto alba alba (left) and female T. a. guttata barn owl in the Netherlands, where these subspecies intergrade

The barn owl was one of several species of bird first described in 1769 by the Tyrolean physician and naturalist Giovanni Antonio Scopoli in his Anni Historico-Naturales. He gave it the scientific name Strix alba.[3][4] As more species of owl were described, the genus name Strix came to be used solely for the wood owls in the typical owl family Strigidae, and the barn owl became Tyto alba in the barn owl family Tytonidae. The name literally means "white owl", from the onomatopoeic Ancient Greek tyto (τυτώ) for an owl – compare English "hooter" – and Latin alba, "white".[2] The bird is known by many common names which refer to its appearance, call, habitat or its eerie, silent flight: white owl, silver owl, demon owl, ghost owl, death owl, night owl, rat owl, church owl, cave owl, stone owl, monkey-faced owl, hissing owl, hobgoblin or hobby owl, dobby owl, white-breasted owl, golden owl, scritch owl, screech owl, straw owl, barnyard owl, and delicate owl.[2][5] "Golden owl" might also refer to the related golden masked owl (T. aurantia). "Hissing owl" and, particularly in the US and in India, "screech owl", refers to the piercing calls of these birds.[6] The latter name is more correctly applied to a different group of birds, the screech-owls in the genus Megascops.[2]

The ashy-faced owl (T. glaucops) was for some time included in T. alba, and by some authors its populations from the Lesser Antilles still are. Based on DNA evidence, König, Weick & Becking (2009) recognised the American Barn Owl (T. furcata) and the Curaçao Barn Owl (T. bargei) as separate species.[7] They also proposed that T. a. delicatula should be split off as a separate species, to be known as the eastern barn owl, which would include the subspecies T. d. sumbaensis, T. d. meeki, T. d. crassirostris and T. d. interposita.[8] However the International Ornithological Committee has doubts about this and states that the split of Tyto delicatula from T. alba "may need to be revisited".[9] Some island subspecies are occasionally treated as distinct species, a move which should await further research into barn owl phylogeography. According to Bruce in the Handbook of Birds of the World, Volume 5: Barn-owls to Hummingbirds, "a review of the whole group [is] long overdue".[2] Molecular analysis of mitochondrial DNA shows a separation of the species into two clades, an Old World alba and a New World furcata, but this study did not include T. a. delicatula which the authors seem to have accepted as a separate species. A high amount of genetic variation was also found between the Indonesian T. a. stertens and other members of the alba clade.[10]

The barn owl has a wider distribution than any other species of owl. Many subspecies have been proposed over the years but several are generally considered to be intergrades between more distinct populations. Twenty to thirty are usually recognised, varying mainly in body proportions, size and colour. Island forms are mostly smaller than mainland ones, and those inhabiting forests have darker plumage and shorter wings than those occurring in open grasslands.[11] Barn owls range in colour from the almost beige-and-white nominate subspecies, erlangeri and niveicauda, to the nearly black-and-brown contempta.[2]

In the Handbook of Birds of the World, Volume 5: Barn-owls to Hummingbirds, the following subspecies are listed:[2]

Description[edit]

The barn owl is a medium-sized, pale-coloured owl with long wings and a short, squarish tail. There is considerable size variation across the subspecies with a typical specimen measuring about 33 to 39 cm (13 to 15 in) in overall length, with a wingspan of some 80 to 95 cm (31 to 37 in). Adult body mass is also variable with male owls from the Galapagos weighing 260 g (9.2 oz) while male Pacific barn owls average 555 g (19.6 oz). In general, owls living on small islands are smaller and lighter, perhaps because they have a higher dependence on insect prey and need to be more manoeuvrable.[16] The shape of the tail is a means of distinguishing the barn owl from typical owls when seen in the air. Other distinguishing features are the undulating flight pattern and the dangling, feathered legs. The pale face with its heart shape and black eyes give the flying bird a distinctive appearance, like a flat mask with oversized, oblique black eyeslits, the ridge of feathers above the bill somewhat resembling a nose.[17]

Showing intricate feather details

The bird's head and upper body typically vary between pale brown and some shade of grey (especially on the forehead and back) in most subspecies. Some are purer, richer brown instead, and all have fine black-and-white speckles except on the remiges and rectrices (main wing feathers), which are light brown with darker bands. The heart-shaped face is usually bright white, but in some subspecies it is brown. The underparts, including the tarsometatarsal (lower leg) feathers, vary from white to reddish buff among the subspecies, and are either mostly unpatterned or bear a varying number of tiny blackish-brown speckles. It has been found that at least in the continental European populations, females with more spotting are healthier than plainer birds. This does not hold true for European males by contrast, where the spotting varies according to subspecies. The bill varies from pale horn to dark buff, corresponding to the general plumage hue, and the iris is blackish brown. The toes, like the bill, vary in colour, ranging from pink to dark pinkish-grey and the talons are black.[2][12]

On average within any one population, males tend to have fewer spots on the underside and are paler in colour than females. The latter are also larger with a strong female T. alba of a large subspecies weighing over 550 g (19.4 oz), while males are typically about 10% lighter. Nestlings are covered in white down, but the heart-shaped facial disk becomes visible soon after hatching.[18]

Contrary to popular belief, the barn owl does not hoot (such calls are made by typical owls, like the tawny owl or other members of the genus Strix). It instead produces the characteristic shree scream, ear-shattering at close range, an eerie, long-drawn-out shriek. Males in courtship give a shrill twitter. Both young and old can hiss like a snake to scare away intruders. Other sounds produced include a purring chirrup denoting pleasure, and a "kee-yak", which resembles one of the vocalisations of the tawny owl. When captured or cornered, the barn owl throws itself on its back and flails with sharp-taloned feet, making for an effective defence. In such situations it may emit rasping sounds or clicking snaps, produced probably by the bill but possibly by the tongue.[17][19]

Distribution[edit]

The barn owl is the most widespread landbird species in the world, occurring in every continent except Antarctica.[20] Its range includes all of Europe (except Fennoscandia and Malta), most of Africa apart from the Sahara, the Indian subcontinent, Southeast Asia, Australia, many Pacific Islands, North, Central and South America.[20] In general it is considered to be sedentary, and indeed many individuals, having taken up residence in a particular location, remain there even when better foraging areas nearby become vacant. In the British Isles, the young seem largely to disperse along river corridors and the distance travelled from their natal site averages about 9 km (5.6 mi).[21]

In continental Europe the distance travelled is greater, commonly somewhere between 50 and 100 kilometres (31 and 62 mi) but exceptionally 1,500 km (932 mi), with ringed birds from the Netherlands ending up in Spain and in Ukraine. In the United States, dispersal is typically over distances of 80 and 320 km (50 and 199 mi), with the most travelled individuals ending up some 1,760 km (1,094 mi) from the point of origin. Movements in the African continent include 1,000 km (621 mi) from Senegambia to Sierra Leone and up to 579 km (360 mi) within South Africa. In Australia there is some migration as the birds move towards the northern coast in the dry season and southward in the wet, and also nomadic movements in association with rodent plagues. Occasionally, some of these birds turn up on Norfolk Island, Lord Howe Island or New Zealand, showing that crossing the ocean is not beyond their capabilities.[2] In 2008, barn owls were recorded for the first time breeding in New Zealand.[22] The barn owl has been successfully introduced into the Hawaiian island of Kauai in an attempt to control rodents, however it has been found to also feed on native birds.[23]

Behaviour and ecology[edit]

The talons are powerful

Like most owls, the barn owl is nocturnal, relying on its acute sense of hearing when hunting in complete darkness. It often becomes active shortly before dusk and can sometimes be seen during the day when relocating from one roosting site to another. In Britain, on various Pacific Islands and perhaps elsewhere, it sometimes hunts by day. This practice may depend on whether the owl is mobbed by other birds if it emerges in daylight.[2] However, in Britain, some birds continue to hunt by day even when mobbed by such birds as magpies, rooks and black-headed gulls, such diurnal activity possibly occurring when the previous night has been wet making hunting difficult. By contrast, in southern Europe and the tropics, the birds seem to be almost exclusively nocturnal, with the few birds that hunt by day being severely mobbed.[24]

Barn owls are not particularly territorial but have a home range inside which they forage. For males in Scotland this has a radius of about 1 km (0.6 mi) from the nest site and an average size of about 300 hectares. Female home ranges largely coincide with that of their mates. Outside the breeding season, males and females usually roost separately, each one having about three favoured sites in which to conceal themselves by day, and which are also visited for short periods during the night. Roosting sites include holes in trees, fissures in cliffs, disused buildings, chimneys and haysheds and are often small in comparison to nesting sites. As the breeding season approaches, the birds move back to the vicinity of the chosen nest to roost.[25]

Being mobbed by Brewer's blackbird in California

The barn owl is a bird of open country such as farmland or grassland with some interspersed woodland, usually at altitudes below 2,000 metres (6,600 ft) but occasionally as high as 3,000 metres (9,800 ft) in the tropics. This owl prefers to hunt along the edges of woods or in rough grass strips adjoining pasture. It has an effortless wavering flight as it quarters the ground, alert to the sounds made by potential prey. Like most owls, the barn owl flies silently; tiny serrations on the leading edges of its flight feathers and a hairlike fringe to the trailing edges help to break up the flow of air over the wings, thereby reducing turbulence and the noise that accompanies it. Hairlike extensions to the barbules of its feathers, which give the plumage a soft feel, also minimise noise produced during wingbeats.[26] The behaviour and ecological preferences may differ slightly even among neighbouring subspecies, as shown in the case of the European T. a. guttata and T. a. alba that probably evolved, respectively, in allopatric glacial refugia in southeastern Europe, and in Iberia or southern France.[12][27]

Diet and feeding[edit]

Skull, showing the rodent-killer beak

The diet of the barn owl has been much studied; the items consumed can be ascertained from identifying the prey fragments in the pellets of indigestible matter that the bird regurgitates. Studies of diet have been made in most parts of the bird's range, and in moist temperate areas over 90% of the prey tends to be small mammals, whereas in hot, dry, unproductive areas, the proportion is lower, and a great variety of other creatures are eaten depending on local abundance. Most prey is terrestrial but bats and birds are also taken, as well as lizards, amphibians and insects. Even when they are plentiful and other prey scarce, earthworms do not seem to be consumed.[28]

In North America and most of Europe, voles predominate in the diet and shrews are the second most common food choice. Mice and rats form the main foodstuffs in the Mediterranean region, the tropics, sub-tropics and Australia. Barn owls are usually more specialist feeders in productive areas and generalists in drier areas.[28] On the Cape Verde Islands, geckos are the mainstay of the diet, supplemented by birds such as plovers, godwits, turnstones, weavers and pratincoles,[29] and on a rocky islet off the coast of California, a clutch of four young were being reared on a diet of Leach's storm petrel (Oceanodroma leucorhoa).[30] In Ireland, the accidental introduction of the bank vole in the 1950s led to a major shift in the barn owl's diet: where their ranges overlap, the vole is now by far the largest prey item.[31] Locally superabundant rodent species in the weight class of several grams per individual usually make up the single largest proportion of prey.[32] In the United States, rodents and other small mammals usually make up ninety-five percent of the diet[33] and worldwide, over ninety percent of the prey caught.[34]

In silent flight

The barn owl hunts by flying slowly, quartering the ground and hovering over spots that may conceal prey. It may also use branches, fence posts or other lookouts to scan its surroundings, and this is the main means of prey location in the oil palm plantations of Malaysia. The bird has long, broad wings, enabling it to manoeuvre and turn abruptly. Its legs and toes are long and slender which improves its ability to forage among dense foliage or beneath the snow and gives it a wide spread of talons when attacking prey.[26] Studies have shown that an individual barn owl may eat one or more voles (or their equivalent) per night, equivalent to about twenty-three percent of the bird's bodyweight. Excess food is often cached at roosting sites and can be used when food is scarce.[35]

Small prey is usually torn into chunks and eaten completely including bones and fur, while prey larger than about 100 g (4 oz), such as baby rabbits, Cryptomys blesmols, or Otomys vlei rats, is usually dismembered and the inedible parts discarded. Contrary to what is sometimes assumed, the barn owl does not eat domestic animals on any sort of regular basis. Regionally, non-rodent foods are used as per availability. On bird-rich islands, a barn owl might include some fifteen to twenty percent of birds in its diet, while in grassland it will gorge itself on swarming termites, or on Orthoptera such as Copiphorinae katydids, Jerusalem crickets (Stenopelmatidae) or true crickets (Gryllidae). Bats and even frogs, lizards and snakes may make a minor but significant contribution to the diet; small Soricomorpha like Suncus shrews may be a secondary prey of major importance.[14][27][32]

The barn owl has acute hearing, with ears placed asymmetrically. This improves detection of sound position and distance and the bird does not require sight to hunt. The facial disc plays a part in this process, as is shown by the fact that with the ruff feathers removed, the bird can still locate the source in azimuth but fails to do so in elevation.[36] Hunting nocturnally or crepuscularly, this bird can target its prey and dive to the ground, penetrating its talons through snow, grass or brush to seize small creatures with deadly accuracy. Compared to other owls of similar size, the barn owl has a much higher metabolic rate, requiring relatively more food. Weight for weight, barn owls consume more rodents—often regarded as pests by humans—than possibly any other creature. This makes the barn owl one of the most economically valuable wildlife animals for agriculture. Farmers often find these owls more effective than poison in keeping down rodent pests, and they can encourage barn owl habitation by providing nest sites.[37]

Breeding[edit]

Egg, Collection Museum Wiesbaden, Germany

Barn owls living in tropical regions can breed at any time of year, but some seasonality in nesting is still evident. Where there are distinct wet and dry seasons, egg-laying usually takes place during the dry season, with increased rodent prey becoming available to the birds as the vegetation dies off. In arid regions, such as parts of Australia, breeding may be irregular and may happen in wet periods, triggered by temporary increases in the populations of small mammals. In temperate climates, nesting seasons become more distinct and there are some seasons of the year when no egg-laying takes place. In Europe and North America, most nesting takes place between March and June when temperatures are increasing. The actual dates of egg-laying vary by year and by location, being correlated with the amount of prey-rich foraging habitat around the nest site and often with the phase of the rodent abundance cycle.[38] An increase in rodent populations will usually stimulate the local barn owls to begin nesting; thus, even in the cooler parts of its range, two broods are often raised in a good year. [5]

Females are ready to breed at ten to eleven months of age although males sometimes wait till the following year. Barn owls are usually monogamous, sticking to one partner for life unless one of the pair dies. During the non-breeding season they may roost separately, but as the breeding season approaches they return to their established nesting site, showing considerable site fidelity. In colder climates, in harsh weather and where winter food supplies may be scarce, they may roost in farm buildings and in barns between hay bales, but they then run the risk that their selected nesting hole may be taken over by some other, earlier-nesting species. Single males may establish feeding territories, patrolling the hunting areas, occasionally stopping to hover, and perching on lofty eminences where they screech to attract a mate. Where a female has lost her mate but maintained her breeding site, she usually seems to manage to attract a new spouse.[39]

Once a pair-bond has been formed, the male will make short flights at dusk around the nesting and roosting sites and then longer circuits to establish a home range. When he is later joined by the female, there is much chasing, turning and twisting in flight, and frequent screeches, the male's being high-pitched and tremulous and the female's lower and harsher. At later stages of courtship, the male emerges at dusk, climbs high into the sky and then swoops back to the vicinity of the female at speed. He then sets off to forage. The female meanwhile sits in an eminent position and preens, returning to the nest a minute or two before the male arrives with food for her. Such feeding behaviour of the female by the male is common, helps build the pair-bond and increases the female's fitness before egg-laying commences.[39]

An Eulenloch ("owl-hole") in northern Germany lets barn owls access the attic for nesting
Clutch of eggs

Barn owls are cavity nesters. They choose holes in trees, fissures in cliff faces, the large nests of other birds such as the hamerkop (Scopus umbretta) and, particularly in Europe and North America, old buildings such as farm sheds and church towers. Buildings are preferred to trees in wetter climates in the British Isles and provide better protection for fledglings from inclement weather. Trees tend to be in open habitats rather than in the middle of woodland and nest holes tend to be higher in North America than in Europe because of possible predation by raccoons (Procyon lotor). No nesting material is used as such but, as the female sits incubating the eggs, she draws in the dry furry material of which her regurgitated pellets are composed, so that by the time the chicks are hatched, they are surrounded by a carpet of shredded pellets. Oftentimes other birds such as jackdaws (Corvus monedula) nest in the same hollow tree or building and seem to live harmoniously with the owls.[40]

Before commencing laying, the female spends much time near the nest and is entirely provisioned by the male. Meanwhile the male roosts nearby and may cache any prey that is surplus to their requirements. When the female has reached peak weight, the male provides a ritual presentation of food and copulation occurs at the nest. The female lays eggs on alternate days and the clutch size averages about five eggs (range two to nine). The eggs are chalky white, somewhat elliptical and about the size of bantam's eggs, and incubation begins as soon as the first egg is laid. While she is sitting on the nest, the male is constantly bringing more provisions and they may pile up beside the female. The incubation period is about thirty days, hatching takes place over a prolonged period and the youngest chick may be several weeks younger than its oldest sibling. In years with plentiful supplies of food, there may be a hatching success rate of about 75%. The male continues to copulate with the female when he brings food which makes the newly hatched chicks vulnerable to injury.[39]

Brood prior to fledging, beginning to shed their nestling down

The chicks are at first covered with greyish-white down and develop rapidly. Within a week they can hold their heads up and shuffle around in the nest. The female tears up the food brought by the male and distributes it to the chicks. Initially these make a "chittering" sound but this soon changes into a food-demanding "snore". By two weeks old they are already half their adult weight and look naked as the amount of down is insufficient to cover their growing bodies. By three weeks old, quills are starting to push through the skin and the chicks stand, making snoring noises with wings raised and tail stumps waggling, begging for food items which are now given whole. The male is the main provider of food until all the chicks are at least four weeks old at which time the female begins to leave the nest and starts to roost elsewhere. By the sixth week the chicks are as big as the adults but have slimmed down somewhat by the ninth week when they are fully fledged and start leaving the nest briefly themselves. They are still dependent on the parent birds until about thirteen weeks and receive training from the female in finding, and eventually catching, prey.[39]

Moulting[edit]

Feathers become abraded over time and all birds need to replace them at intervals. Barn owls are particularly dependent on their ability to fly quietly and manoeuvre efficiently, and in temperate areas their prolonged moult lasts through three phases over a period of two years. The female starts to moult while incubating the eggs and brooding the chicks, a time when the male feeds her so she does not need to fly much. The first primary feather to be shed is the central one, number 6, and it has regrown completely by the time the female resumes hunting. Feathers 4, 5, 7 and 8 are dropped at a similar time the following year and feathers 1, 2, 3, 9 and 10 in the bird's third year of adulthood. The secondary and tail feathers are lost and replaced over a similar timescale, again starting while incubation is taking place. In the case of the tail, the two outermost tail feathers are first shed followed by the two central ones, the other tail feathers being moulted the following year.[41]

In temperate areas, the male owl moults rather later in the year than the female, at a time when there is an abundance of food, the female has recommenced hunting and the demands of the chicks are lessening. Unmated males without family responsibilities often start losing feathers earlier in the year. The moult follows a similar prolonged pattern to that of the female and the first sign that the male is moulting is often when a tail feather has been dropped at the roost.[41] A consequence of moulting is the loss of thermal insulation. This is of little importance in the tropics and barn owls here usually moult a complete complement of flight feathers annually. The hot-climate moult may still take place over a long period but is usually concentrated at a particular time of year outside the breeding season.[42]

Predators and parasites[edit]

Predators of the barn owl include large American opossums (Didelphis), the common raccoon, and similar carnivorous mammals, as well as eagles, larger hawks and other owls. Among the latter, the great horned owl (Bubo virginianus) in the Americas and the Eurasian eagle-owl (B. bubo) are noted predators of barn owls (though there is little evidence for predation on wild birds by great horned owls).[43] In Europe, the chief diurnal predators are the northern goshawk (Accipiter gentilis) and the common buzzard (Buteo buteo). The goshawk and the eagle owl are on the increase because of the greater protection these birds now receive.[24]

Three barn owl chicks threatening an intruder

When disturbed at its roosting site, an angry barn owl lowers its head and sways it from side to side, or the head may be lowered and stretched forward and the wings drooped while the bird emits hisses and makes snapping noises with its bill. A defensive attitude involves lying flat on the ground or crouching with wings spread out.[19]

Barn owls are hosts to a wide range of parasites. Fleas are present at nesting sites and externally the birds are attacked by feather lice and feather mites which chew the barbules of the feathers and which are transferred from bird to bird by direct contact. Blood-sucking flies such as Ornithomyia avicularia are often present, moving about among the plumage. Internal parasites include the fluke Strigea strigis, the tape worm Paruternia candelabraria, several species of parasitic round worm and spiny-headed worms in the genus Centrorhynchus. These gut parasites are acquired when the birds feed on infected prey which provide intermediate hosts for the parasites.[44] There is some indication that female birds with more and larger spots have a greater resistance to external parasites. This is correlated with smaller bursae of Fabricius, glands associated with antibody production, and a lower fecundity of the blood-sucking fly Carnus hemapterus that attacks nestlings.[45]

Lifespan[edit]

Captive bird landing
Landing on a handler's gloved hand. Captive birds often live longer than wild ones

Unusually for such a medium-sized carnivorous animal, the barn owl exhibits r-selection, producing large number of offspring with a high growth rate, many of which have a relatively low probability of surviving to adulthood.[46] While wild barn owls are thus decidedly short-lived, the actual longevity of the species is much higher – captive individuals may reach twenty years of age or more. But occasionally, a wild bird reaches an advanced age. The American record age for a wild barn owl is eleven and a half years, while a Dutch bird was noted to have reached an age of seventeen years, ten months. Another captive barn owl, in England, lived to be over twenty-five years old. Taking into account such extremely long-lived individuals, the average lifespan of the barn owl is about four years, and statistically two-thirds to three-quarters of all adults survive from one year to the next. However, the mortality is not evenly distributed throughout the bird's life, and only one young in three manages to live to its first breeding attempt.[5]

The most significant cause of death in temperate areas is likely to be starvation, particularly over the autumn and winter period when first year birds are still perfecting their hunting skills. In northern and upland areas, there is some correlation between mortality in older birds and adverse weather, deep-lying snow and prolonged low temperatures. Collision with road vehicles is another cause of mortality, and may result when birds forage on mown verges. Some of these birds are in poor condition and may have been less able to evade oncoming vehicles than fit individuals would have been. Historically, many deaths were caused by the use of pesticides, and this may still be the case in some parts of the world. Collisions with power-lines kill some birds and shooting accounts for others, especially in Mediterranean regions.[47]

Status and conservation[edit]

Barn owls are relatively common throughout most of their range and not considered globally threatened. However, locally severe declines from organochlorine (e.g., DDT) poisoning in the mid-20th century and rodenticides in the late 20th century have affected some populations, particularly in Europe and North America. Intensification of agricultural practices often means that the rough grassland that provides the best foraging habitat is lost.[48] While barn owls are prolific breeders and able to recover from short-term population decreases, they are not as common in some areas as they used to be. A 1995–1997 survey put their British population at between 3,000 to 5,000 breeding pairs, out of an average of about 150,000 pairs in the whole of Europe. In the USA, barn owls are listed as endangered species in seven Midwestern states, and in the European Community they are considered a Species of European Concern.[2][5]

In some areas, it may be an insufficiency of suitable nesting sites that is the factor limiting barn owl numbers. The provision of nest boxes under the eaves of buildings and in other locations can be very successful in increasing the local population. In Malaysia, large areas of rainforest were felled to make way for oil palm plantations and with few tree cavities for breeding, the barn owl population, with its ability to control rodent pests, diminished. The provision of two hundred nest boxes in a trial saw almost one hundred percent occupancy and as the programme expanded, the plantations supported one of the densest barn owl populations in the world.[48] Similarly, providing nesting boxes has increased the number of barn owls in rice-growing areas of Malaysia where the rodents do much damage to the crop. However, although barn owl numbers have increased in both these instances, it is unclear as to how effective this biological control of the rats is as compared to the trapping and baiting that occurred previously.[49]

Barn owl on Lithuanian silver coin of 5 litas (2002)

Common names such as "demon owl", "death owl", or "ghost owl" show that traditionally, rural populations in many places considered barn owls to be birds of evil omen. Consequently, they were often persecuted by farmers who were unaware of the benefit these birds bring.[50] The Canary barn owl is particularly at risk, and as late as 1975, hunting by fearful locals was limiting the population on Fuerteventura where only a few dozen pairs remain. On Lanzarote a somewhat larger number of these birds still seem to exist, but altogether this particular subspecies is precariously rare: Probably less than three hundred and perhaps fewer than two hundred individuals still remain. Similarly, the birds on the western Canary Islands which are usually assigned to the nominate subspecies have declined much, and here wanton destruction seems still to be significant. On Tenerife they seem relatively numerous but on the other islands, the situation looks about as bleak as on Fuerteventura. Due to their assignment to the nominate subspecies, which is common in mainland Spain, the western Canary Islands population is not classified as threatened.[51][52][53]

In the United Kingdom, the "Barn Owl Nest Box Scheme" is promoted by the World Owl Trust[54] and has many participants in local areas such as Somerset where a webcam has been set up inside a nest box in which seven young were reared in 2014.[55] Another barn owl nest box live-streaming webcam located in California, United States has proved popular online.[56] In May 2012, it was revealed that farmers in Israel and Jordan had, over a period of ten years, replaced pesticides by barn owls in a joint conservation venture called "Project Barn Owl".[57]

References[edit]

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  2. ^ a b c d e f g h i j k l m n o p q r s t u v w x y z aa ab ac ad ae af ag ah ai aj ak al am an ao ap aq ar as at au av aw ax ay az ba bb bc bd be bf bg bh bi bj Bruce (1999) pp. 34–75
  3. ^ Peters, James Lee (1964). Check-list of Birds of the World. Volume IV. Harvard University Press. p. 77. 
  4. ^ Scopoli, Giovanni Antonio (1769). "Strix alba". Annus I Historico-Naturalis (in Latin). C. G. Hilscheri. pp. 21–22. 
  5. ^ a b c d "Barn Owl Tyto alba (Scopoli, 1769)". British Trust for Ornithology. 2009. Retrieved 2014-09-08. 
  6. ^ Ali, S. (1993). The Book of Indian Birds. Bombay: Bombay Natural History Society. ISBN 0-19-563731-3. 
  7. ^ König, Claus; Weick, Friedhelm; Becking, Jan-Hendrik (2009). Owls of the World. Bloomsbury Publishing. pp. 46–48. ISBN 978-1-4081-0884-0. 
  8. ^ König, Claus; Weick, Friedhelm; Becking, Jan-Hendrik (2009). Owls of the World. Bloomsbury Publishing. p. 209. ISBN 978-1-4081-0884-0. 
  9. ^ "Owls". IOC World Bird List: Version 4.3. IOC. Retrieved 2014-09-18. 
  10. ^ Alaie Kakhki, N.; Aliabadian, M. (2012). "Mitochondrial DNA (CYTB) divergences in two distinct, Old World and New World barn owls". Iranian Journal of Animal Biosystematics 8 (1): 47–55. ISSN 1735-434X. 
  11. ^ Taylor (2004) p. 24
  12. ^ a b c d Mátics, Róbert; Hoffmann, Gyula (2002). "Location of the transition zone of the barn owl subspecies Tyto alba alba and Tyto alba guttata (Strigiformes: Tytonidae)". Acta Zoologica Cracoviensia 45 (2): 245–250. 
  13. ^ Olson, Storrs L.; James, Helen F.; Meister, Charles A. (1981). "Winter field notes and specimen weights of Cayman Island Birds". Bulletin of the British Ornithologists' Club 101 (3): 339–346. 
  14. ^ a b c Traylor, Melvin A.; Parelius, Daniel (1967). "A collection of birds from the Ivory Coast". Fieldiana Zoology 51 (7): 91–117. 
  15. ^ Krabbe, Niels; Flórez, Pablo; Suárez, Gustavo; Castaño, José; Arango, Juan David; Duque, Arley (2006). "The birds of Páramo de Frontino, western Andes of Colombia". Ornitología Colombiana 4: 39–50. 
  16. ^ Taylor (2004) pp. 19–22
  17. ^ a b Bruce (1999) pp 34–75, Svensson et al. (1999) pp. 212–213
  18. ^ Taylor (2004) p. 169
  19. ^ a b Witherby (1943) pp. 343–347
  20. ^ a b Shawyer (1994) p. 10
  21. ^ Shawyer (1994) p. 91
  22. ^ Hyde, N. H. S.; Matthews, K.; Thompson, M.; Gale, R. (2009). "First record of barn owls (Tyto alba) breeding in the wild in New Zealand". Notornis 56 (4): 169–175. 
  23. ^ Denny, Jim (2006). "Introduced birds: Barn owl". Birds of Kaua'i. Retrieved 2014-07-24. 
  24. ^ a b Martin, Jeff (2013-07-08). "The daylight activity of barn owls". BritishBirds. BritishBirds Rarities Committee. Retrieved 2014-07-19. 
  25. ^ Taylor (2004) pp. 96–107
  26. ^ a b Taylor (2004) pp. 47–61
  27. ^ a b Ehrlich et al. (1994) pp. 250–254
  28. ^ a b Taylor (2004) pp. 29–46
  29. ^ Naurois, R. de (1982). "Le statut de la Chouette effraie de l'archipel du Cape Verte Tyto alba detorta". Rivista italiana di Ornitologia (in French) 52 (3-4): 154–166. 
  30. ^ Bonnot, Paul (1928). "An outlaw Barn Owl". Condor 30 (5): 320. JSTOR 1363231. 
  31. ^ Kelleher, K. M.; Oliver, G. A.; Sleeman, D. P. (2010). "The composition and sex of rodent prey taken by Barn Owls Tyto alba at a roost in County Cork". Irish Birds 9: 35–40. ISSN 0332-0111. 
  32. ^ a b Laudet, Frédéric; Denys, Christiane; Senegas, Frank (2002). "Owls, multirejection and completeness of prey remains: implications for small mammal taphonomy". Acta Zoologica Cracoviensia 45: 341–355. 
  33. ^ Ingles, Chuck (1995). "Summary of California studies analyzing the diet of barn owls". Sustainable Agriculture/Technical Reviews 2: 14–16. 
  34. ^ Taylor (2004) p. 29
  35. ^ Taylor (2004) pp. 91–95
  36. ^ Knudsen, Eric I.; Konishi, Masakazu (1979). "Mechanisms of sound localization in the barn owl (Tyto alba)". Journal of Comparative Physiology 133 (1): 13–21. doi:10.1007/BF00663106. 
  37. ^ Meyrom, Kobi; Motro, Yoav; Leshem, Yossi; Aviel, Shaul; Izhaki, Ido; Argyle, Francis; Charter, Motti (2009). "Nest-box use by the barn owl Tyto alba in a biological pest control program in the Beit She'an Valley, Israel". Ardea 97 (4): 463–467. doi:10.5253/078.097.0410. 
  38. ^ Taylor (2004) pp. 121–135
  39. ^ a b c d Shawyer (1994) pp. 67–87
  40. ^ Taylor (2004) pp. 136–148
  41. ^ a b Shawyer (1994) pp. 88–90
  42. ^ Taylor (2004) pp. 108–120
  43. ^ Marti, Carl D.; Poole, Alan F.; Bevier, L. R. (2005): Barn Owl (Tyto alba) The Birds of North America Online (A. Poole, Ed.). Ithaca: Cornell Lab of Ornithology; Barn owl
  44. ^ Bunn, D. S.; Warburton, A. B.; Wilson, R. D. S. (2010). The Barn Owl. Bloomsbury Publishing. p. 177. ISBN 978-1-4081-3961-5. 
  45. ^ Roulin, Alexandre; Riols, Christian; Dijkstra, Cor; Ducrest, Anne-Lyse (2001). "Female plumage spottiness signals parasite resistance in the barn owl (Tyto alba)". Behavioral Ecology 12 (1): 103–110. doi:10.1093/oxfordjournals.beheco.a000371. 
  46. ^ Altwegg, Res; Schaub, Michael; Roulin, Alexandre (2007). "Age‐specific fitness components and their temporal variation in the barn owl". The American Naturalist 169 (1): 47–61. doi:10.1086/510215. 
  47. ^ Taylor (2004) pp. 203–215
  48. ^ a b Taylor (2004) pp. 242–261
  49. ^ Wood, B. J.; Fee, Chung Gait (2003). "A critical review of the development of rat control in Malaysian agriculture since the 1960s". Crop Protection 22 (3): 445–461. doi:10.1016/S0261-2194(02)00207-7. 
  50. ^ Spence, Cindy (1999-10-28). "Spooky owl provides natural rodent control for farmers". UF News. University of Florida. Retrieved 2014-07-14. 
  51. ^ Álamo Tavío, Manuel (1975). "Aves de Fuerteventura en peligro de extinción". Aves y plantas de Fuerteventura en peligro de extinción (in Spanish). Asociación Canaria para Defensa de la Naturaleza. pp. 10–32. 
  52. ^ "Tyto alba gracilirostris Hartert, 1905" (in Spanish). El Ministerio de Medio Ambiente agradece sus comentarios, Spain. 2006. Retrieved 2014-09-19. 
  53. ^ Palacios, César-Javier (2004). "Current status and distribution of birds of prey in the Canary Islands". Bird Conservation International 14 (3): 203–213. doi:10.1017/S0959270904000255. 
  54. ^ "Nest-boxes for Barn Owls". World Owl Trust. Retrieved 2014-07-24. 
  55. ^ "Barn Owl Project". Somerset Wildlife Trust. Retrieved 2014-07-24. 
  56. ^ "Owl Cam a Hoot Online". CBS News. 2010-04-12. Retrieved 2014-10-02. 
  57. ^ Santorelli, Tom (2012-05-18). "The Israeli-Jordan barn owl love that knows no borders". BBC News: Middle East. Retrieved 2014-07-24. 

Bibliography[edit]

  • Bruce, M. D. (1999). "Family Tytonidae (Barn-owls)". In del Hoyo, J.; Elliott, A.; Sargatal, J. Handbook of Birds of the World, Volume 5: Barn-owls to Hummingbirds. Lynx Edicions. ISBN 84-87334-25-3. 
  • Ehrlich, Paul R.; Dobkin, David S.; Wheye, Darryl; Pimm, Stuart L. (1994). The Birdwatcher's Handbook: A Guide to the Natural History of the Birds of Britain and Europe. Oxford University Press. ISBN 0-19-858407-5. 
  • Shawyer, Colin (1994). The Barn Owl. Hamlyn. ISBN 0-600-57949-2. 
  • Svensson, Lars; Zetterström, Dan; Mullarney, Killian; Grant, Peter, J. (1999). Collins Bird Guide. Harper & Collins. ISBN 0-00-219728-6. 
  • Taylor, Iain (2004). Barn Owls: Predator-prey Relationships and Conservation. Cambridge University Press. ISBN 978-0-521-54587-7. 
  • Witherby, H. F. (1943). Handbook of British Birds, Volume 2: Warblers to Owls. H. F. and G. Witherby. 
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Notes

"Cool facts"

Ghostly pale and strictly nocturnal, Barn Owls are silent predators of the night world. Lanky, with a whitish face, chest, and belly, and buffy upperparts, this owl roosts in hidden, quiet places during the day. By night, they hunt on buoyant wingbeats in open fields and meadows. You can find them by listening for their eerie, raspy calls, quite unlike the hoots of other owls. Despite a worldwide distribution, Barn Owls are declining in parts of their range due to habitat loss.

Barn Owls swallow their prey whole—skin, bones, and all. About twice a day, they cough up pellets instead of passing all that material through their digestive tracts. The pellets make a great record of what the owls have eaten, and scientists study them to learn more about the owls and the ecosystems they live in.

Up to 46 different races of the Barn Owl have been described worldwide. The North American form is the largest, weighing more than twice as much as the smallest race from the Galapagos Islands.

Barn Owl females are somewhat showier than males. She has a more reddish and more heavily spotted chest. The spots may indicate the quality of the female. Heavily spotted females get fewer parasitic flies and may be more resistant to parasites and diseases. The spots may also stimulate the male to help more at the nest. In an experiment where some females’ spots were removed, their mates fed their nestlings less often than for females whose spots were left alone.

The Barn Owl has excellent low-light vision, and can easily find prey at night by sight. But its ability to locate prey by sound alone is the best of any animal that has ever been tested. It can catch mice in complete darkness in the lab, or hidden by vegetation or snow out in the real world.

The oldest known North American Barn Owl lived in Ohio and was at least 15 years, 5 months old.

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Names and Taxonomy

Taxonomy

Comments: Formerly known as Common Barn-Owl. Closely related to and sympatric with T. glaucops (Ashy-faced Owl) of Hispaniola (AOU 1998). Some authors suggest that populations in the Australian region may constitue a separate species, T. delicatula (AOU 1983).

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