|At British Wildlife Centre, Surrey, England|
many, see text
|Global range in green|
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 the barn owl family Tytonidae. These form one of two main lineages of living owls, the other being the typical owls (Strigidae). T. alba is found almost everywhere in the world except polar and desert regions, Asia north of the Alpide belt, most of Indonesia and some Pacific islands.
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 back is some shade of grey or brown, the underparts vary from white to brown, sometimes with some dark speckling. 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 known by many common names which mostly refer to its pale colouring or silent flight. It 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. Breeding takes place at varying times of year according to locality with a clutch averaging about four eggs, but occasionally more than double this number, laid in a nest in a hollow tree, old building or fissure in a cliff. When 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. However, some subspecies with restricted ranges are more threatened.
The barn owl is a pale, long-winged, long-legged owl with a short squarish tail. Generally a medium-sized owl, there is considerable size variation across the subspecies. The barn owl measures 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, ranging from 187 to 800 g (6.6 to 28.2 oz), with the owls living closer to the tropics being generally smaller. Tail shape is a way of distinguishing the barn owl from true owls when seen in the air, as are the undulating flight and the open dangling feathered legs. The light face with its heart shape and the black eyes give the flying bird an odd and startling appearance, like a flat mask with oversized oblique black eyeslits, the ridge of feathers above the bill somewhat resembling a nose.
Its head and upper body typically vary between a light brown and a light-coloured and dark grey (especially on the forehead and back) feathers in most subspecies. Some are purer, richer brown instead, and all have fine black-and-white speckles except on the remiges and rectrices, which are light brown with darker bands. The heart-shaped face is usually bright white, but in some subspecies it is browner. The underparts (including the tarsometatarsus feathers) vary from white to reddish buff among the subspecies, and are either mostly unpatterned or bear a varying amount of tiny blackish-brown speckles. It was found that at least in the continental European populations, females with more spotting are healthier on average. 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. The iris is blackish brown. The toes, as the bill, vary in colour; their colour ranges from pinkish to dark pinkish-grey. The talons are black.
On average, within any one population males tend to be less spotted on the underside and lighter coloured than females. The latter are also larger, as is common for owls. A strong female T. alba of a large subspecies may weigh over 550 g (19.4 oz), while males are typically about 10% lighter. Nestlings are covered in white down all over, but the heart-shaped facial disk is visible soon after hatching.
Contrary to popular belief, the barn owl does not hoot (such calls are made by typical owls, like the tawny owl or other 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, it throws itself on its back and flails with sharp-taloned feet, making for an effective defence. Also given in such situations is a rasp and a clicking snap, produced by the bill or possibly the tongue.
Taxonomy and etymology
The barn owl is known by many other names, which may 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. "Golden owl" might also refer to the related golden masked owl (T. aurantia). "Hissing owl" and, particularly in the USA and in India, "screech owl", referring to the piercing calls of these birds. The latter name, however, more correctly applies to a different group of birds, the screech-owls in the genus Megascops. The barn owl's scientific name, established by G.A. Scopoli in 1769, literally means "white owl", from the onomatopoetic Ancient Greek tyto (τυτώ) for an owl – compare English "hooter" – and Latin alba, "white".
The ashy-faced owl (T. glaucops) was for some time included in T. alba, and by some authors its Lesser Antilles populations insularis and nigrescens still are. The barn owls from the Indopacific region are sometimes separated as eastern barn-owl, Australian barn-owl, or delicate barn-owl (T. delicatula). While this may be warranted, it is not clear between which races to draw the line between the two species. Also, some island subspecies are occasionally treated as distinct species. While all this may be warranted, such a move is generally eschewed pending further information on barn owl phylogeography.
Across its vast range, the barn owl has formed many subspecies, but several are considered to be intergrades between more distinct populations today. Still, some 20–30 seem to be worthy of recognition as long as the species is not split up. They vary mainly in size and colour, sometimes according to Bergmann's and Gloger's Rules, sometimes more unpredictably. This species ranges in colour from the almost beige-and-white nominate subspecies, erlangeri and niveicauda to the nearly black-and-brown contempta:
|T. a. alba (Scopoli, 1769)||Upperparts grey and light buff. Underparts white, with few if any black spots; males often appear entirely unspotted.||W Europe from the British Isles south to the Maghreb and west along Mediterranean coastal regions to NW Turkey in the north and the Nile in the south, where it reaches upstream to NE Sudan. Also Aïr Mountains in the Sahara of Niger, Balearic Islands and Sicily in the Mediterranean, and the W Canary Islands (El Hierro, La Gomera, La Palma Gran Canaria and Tenerife). Intergrades with guttata from the Balkans through Hungary and along the Rhine and lower Meuse rivers, and with affinis around the Egypt-Sudan border.||Includes hostilis, kirchhoffi, kleinschmidti, pusillus.
African populations might belong to erlangeri.
|T. a. javanica (J.F.Gmelin, 1788)||Large. Similar to alba but darker above, and with conspicuous speckling overall.||Pacific barn owl — Malay Peninsula through the southern Greater Sunda Islands including Kangean Islands, Krakatoa and the Thousand Islands; also Alor Archipelago, Kalao and Tanahjampea in the Selayar Islands, Kalaotoa, and possibly S Borneo.||Southeast Asian birds are sometimes placed here but seem closer to stertens.|
|T. a. furcata (Temminck, 1827)||Large. Upperparts pale orange-buff and brownish-grey, underparts whitish with few speckles. Face white.||Cuba, Jamaica, Cayman Islands (rare or extinct on Grand Cayman).||Might include niveicauda.|
|T. a. tuidara (J.E.Grey, 1829)||Upperparts grey and orange-buff. Underparts whitish to light buff with little speckling. Face white. Resembles pale Old World guttata.||South American lowlands east of the Andes and south of the Amazon River all the way south to Tierra del Fuego; also on the Falkland Islands.||Includes hauchecornei and possibly hellmayri.|
|T. a. guttata (C.L.Brehm, 1831)||More grey on upperparts than alba. Underparts buff to rufous with some dark speckles (more than in alba). Face whitish. Females are on average redder below than males.||C Europe north of the Alps from the Rhine to Latvia, Lithuania and Ukraine, and south to Romania, NE Greece and the S Balkans. Intergrades with alba at the western border of its range.||Includes rhenana.|
|T. a. delicatula (Gould, 1837)||Similar to alba; slightly darker above, more speckles below. Tail with 4 bark brown bars.||Australia and offshore islets (not on Tasmania), Lesser Sunda Islands (Savu, Timor, Jaco, Wetar, Kisar, Tanimbar, possibly Rote), Melanesia (New Caledonia and Loyalty Islands; Aneityum, Erromango and Tanna in S Vanuatu; Solomon Islands including Bougainville; Long Island, Nissan, Buka and perhaps New Ireland and N New Britain), W Polynesia (Fiji and Rotuma, Niue, Samoan Islands, Tonga, Wallis and Futuna); introduced to Lord Howe Island but became extinct again.||Includes bellonae, everetti, kuehni, lifuensis and lulu.
Reports of blackish barn-owls on Fiji require investigation.
|T. a. pratincola (Bonaparte, 1838)||Large. Upperparts grey and orange-buff. Underparts whitish to light buff with much speckling. Face white. Resembles pale Old World guttata, but usually more speckles below.||North America from S Canada south to C Mexico; Bermuda, Bahamas, Hispaniola; introduced to Lord Howe Island (where it became extinct again) and in 1958 to Hawaii (where it persists).||Includes lucayana and might include bondi, guatemalae, subandeana.|
|T. a. punctatissima (G.R.Grey, 1838)||Small. Dark greyish brown above, with white part of spots prominent. Underparts white to golden buff, with distinct pattern of brown vermiculations or fine dense spots.||Galápagos barn owl — Endemic to the Galápagos islands.||Sometimes considered a distinct species.|
|T. a. poensis (Fraser, 1842)||Upperparts golden-brown and grey with very bold pattern. Underparts light buff with extensive speckles. Face white.||Endemic to Bioko, if not the same as affinis.|
|T. a. thomensis (Hartlaub, 1852)||Smallish. Upperparts dark brownish grey with bold pattern, including lighter brown bands on remiges and rectrices. Underparts golden brown with extensive speckles. Face buff.||Endemic to São Tomé Island. A record from Príncipe is in error.||Sometimes considered a distinct species.|
|T. a. affinis (Blyth, 1862)||Similar to poensis, but supposedly lighter on average. Upperparts very grey. Underparts light buff with extensive speckles. Face white.||Sub-Saharan Africa, including the Comoros, Madagascar, Pemba and Unguja islands; introduced to the Seychelles. Intergrades with alba around the Egypt-Sudan border.||Includes hypermetra; doubtfully distinct from poensis.|
|T. a. guatemalae (Ridgway, 1874)||Similar to dark pratincola; less grey above, coarser speckles below.||Guatemala or S Mexico through Central America to Panama or N Colombia; Pearl Islands.||Includes subandeana; doubtfully distinct from pratincola.|
|T. a. bargei (Hartert, 1892)||Similar to alba; smaller and noticeably short-winged.||Endemic to Curaçao and maybe Bonaire in the West Indies.|
|T. a. sumbaensis (Hartert, 1897)||Large, particularly the bill. Similar to javanica; tail whitish with black bars.||Endemic to Sumba.|
|T. a. contempta (Hartert, 1898)||Almost black with some dark grey above, the white part of the spotting showing prominently. Reddish brown below.||NE Andes from W Venezuela through E Colombia (rare in the Cordillera Central and Cordillera Occidental) south to Peru.||Includes stictica.|
|T. a. schmitzi (Hartert, 1900)||Small. Similar to guttata, but breast region light buff.||Endemic to Madeira and Porto Santo islands in the E Atlantic.|
|T. a. ernesti (Kleinschmidt, 1901)||Similar to alba; breast region always pure unspotted white.||Endemic to Corsica and Sardinia in the Mediterranean.|
|T. a. gracilirostris (Hartert, 1905)||Small. Similar to schmitzi but breast darker, approaching guttata. Face light buff.||Canary barn owl — Endemic to the E Canary Islands (Chinijo Archipelago, Fuerteventura, Lanzarote; perhaps formerly also on Lobos).|
|T. a. meeki (Rothschild & Hartert, 1907)||Large. Similar to javanica; tail whitish with grey bars, underparts silvery-white with arrowhead-shaped speckles (larger than in javanica).||E New Guinea and Manam and Karkar islands.|
|T. a. detorta Hartert, 1913||Similar to guttata, but less reddish. Face buff.||Endemic to the Cape Verde Islands.||Sometimes considered a distinct species.|
|T. a. erlangeri W.L.Sclater, 1921||Similar to ernesti; upperparts lighter and yellower.||Crete and southern Aegean islands to Cyprus; Near and Middle East including Arabian Peninsula coastlands, south to Sinai and east to SW Iran.||Might include African populations assigned to alba.|
|T. a. stertens Hartert, 1929||Similar to alba, but noticeably speckled below.||W Pakistan through India east to Yunnan and Vietnam, south S Thailand; N Sri Lanka.||Southeast Asian birds sometimes included in javanica.|
|T. a. crassirostris Mayr, 1935||Similar to delicatula; darker, with stronger bill and feet.||Endemic to the Tanga Islands.|
|T. a. interposita Mayr, 1935||Similar to delicatula; darker, with orange hue.||Santa Cruz Islands and Banks Islands south to Efate Island (Vanuatu).|
|T. a. hellmayri Griscom & Greenway, 1937||Similar to tuidara but larger.||NE South American lowlands from E Venezuela south to the Amazon River.||Doubtfully distinct from tuidara.|
|T. a. bondi Parks & Phillips, 1978||Similar to pratincola; smaller and paler on average.||Endemic to Roatán and Guanaja in the Bay Islands.||Doubtfully distinct from pratincola.|
|T. a. niveicauda Parks & Phillips, 1978||Large. Similar to furcata; paler in general. Resembles Old World alba.||Endemic to Isla de la Juventud.||Doubtfully distinct from furcata.|
The barn owl is considered to be the most widespread landbird species in the world, occurring in every continent except Antarctica. Its range includes all of Europe (except Fennoscandia and Malta), most of Africa apart from the Sahara, the Indian subcontinent, Southeast Asia, Australia, the Pacific Islands, North, Central and South America. 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 are vacant. In the British Isles, the young seem to largely disperse along river corridors and the distance travelled from their natal site averages about 9 km (5.6 mi). 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 departure. 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. The barn owl has been introduced into the Hawaiian island of Kauai in an attempt to control rodents.
Most owls are nocturnal, and the barn owl is no exception, 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 when it emerges in daylight. However, in Britain, some birds are mobbed by rooks, magpies and black-headed gulls and continue to hunt by day, the practice possibly occurring when the previous night has been wet making hunting difficult. Strangely, in southern Europe and the tropics, the birds are strictly nocturnal.
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.
The barn owl is a bird of open country such as farmland or grassland with some interspersed woodland, usually below 2,000 metres (6,600 ft) ASL 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. The behaviour and ecological preferences may differ slightly even among neighboring 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.
Diet and feeding
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 eaten.
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 part of the diet 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. On the Cape Verde Islands, geckos are the mainstay of the diet, supplemented with birds such as plovers, godwits, turnstones, weavers and pratincoles, and on a rocky island off the coast of California, a clutch of four young was successfully reared on a diet of Leach's storm petrel. 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. Locally superabundant rodent species in the weight class of several grams per individual usually make up the single largest proportion of prey. Such animals probably make up at least three-quarters of the biomass eaten by each and every barn owl, except in some island populations.
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. Studies have shown that an individual barn owl may eat one or more voles (or their equivalent) per night, equivalent to about 23% of their bodyweight. Excess food is often cached at roosting sites and can be utilised when food is scarce.
Small prey is usually torn into chunks and eaten completely including bones and fur, while prey larger than about 100 g (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, different foods outside of rodents are utilized as per availability. On bird-rich islands, a barn owl might contain some 15–20% 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 toads and squamates may as well make up a minor but conspicuous part of the prey; small Soricomorpha like Suncus shrews (which to a hunting barn owl probably look much like mice) may be secondary prey of major importance.
The barn owl has acute hearing, with ears placed asymmetrically for improved detection of sound position and distance, and it does not require sight to hunt. The facial disc plays a part in this process, and with the ruff feathers removed, the bird can still locate the source in azimuth but fails to do so in elevation. Hunting nocturnally or crepuscularly, it can target and dive down, penetrating its talons through snow, grass or brush to seize rodents with deadly accuracy. Compared to other owls of similar size, the barn owl has a much higher metabolic rate, requiring relatively more food. Pound for pound, 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 to farmers. 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.
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 areas around the nest site and often with the phase of the rodent abundance cycle. An increase in rodent populations will usually soon cause the local barn owls to begin nesting; thus, even in the cooler parts of its range two broods are often raised each year.
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 is killed. 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 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.
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. She apparently detects his imminent arrival in some way indiscernible to a human observer. 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.
Barn owls are cavity nesters. They choose holes in trees, fissures in cliff faces, the nests of other birds such as the hamerkop 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. 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 nest in the same hollow tree or building and seem to live harmoniously with the owls.
Before starting to lay eggs, the female spends her 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 clutch size averages about five, varying from about two to nine. The eggs are chalky white, somewhat elliptical and about the size of bantams' 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.
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" sound. By two weeks old they are half their adult weight and look naked as the down is insufficient to cover their growing bodies. By three weeks old, quills are starting to push through and the chicks stand, making snoring noises with wings raised and tail stumps waggling, to receive food items whole. The male is the main provider of food until all the chicks are at least four weeks old when the female begins to leave the nest and 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.
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 she flies little and the male feeds her and the young chicks. 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.
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 but 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. 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 place over a long period but is usually concentrated at a particular time of year outside the breeding season.
Lifespan and predators
An angry barn owl lowers its head and sways it from side to side near the ground, or the head may be lowered and stretched forward and the wings drooped while the bird emits hisses and snaps its bill. A defensive attitude involves lying flat on the ground or crouching with wings spread out.
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. 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. But as noted above, 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. Causes of death are variable but the most significant one 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.
Predators of the barn owl include large American opossums (Didelphis), the common raccoon (Procyon lotor), and similar carnivorous mammals, as well as large raptors such as hawks, eagles, 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). In Europe, the chief diurnal predators are the northern goshawk and the common buzzard. The goshawk and the eagle owl are on the increase because of the greater protection these birds now receive.
Status and conservation
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. While the barn owl is a prolific breeder and able to recover from short-term population decreases, they are not as common in some places as they used to be. The most recent survey (1995–1997) 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.
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 100% occupancy and as the programme expanded, the plantations supported one of the densest barn owl populations in the world. 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.
Common names such as "demon owl", "death owl", or "ghost owl" show that for long, rural populations in many places considered barn owls to be birds of evil omen. Consequently, they were often persecuted by farmers, unaware of the benefit these birds bring. As late as 1975, hunting by fearful locals was limiting the population of T. a. gracilirostris on Fuerteventura. In current times, rodenticide poisoning is the main threat for the Canary barn owl, which in the Chinijo Archipelago is on the verge of disappearance while on Fuerteventura only a few dozen pairs remain overall. There, the abandonment of much agricultural land and the subsequent decline of rodent pests seem to have decreased the owl's numbers even further. Only on Lanzarote does a somewhat larger number of these birds still seem to exist, but altogether this particular subspecies is precariously rare: Probably less than 300 and perhaps less than 200 birds still exist, and it is classified as insuficientemente conocida ("data deficient") by the Spanish Ministry of Environment. Similarly, the birds on the western Canary Islands which are usually assigned to the nominate subspecies (though this seems suspect on grounds of biogeography) have declined much, and here wanton destruction seems still to be significant. On Tenerife they seem to be not uncommon, while on the other islands, the situation looks about as bleak as on Fuerteventura. Due to the assignment to the nominate subspecies, which is common in mainland Spain, the western Canary Islands population is not classified as threatened.
In the United Kingdom, the "Barn Owl Nest Box Scheme" is promoted by the World Owl Trust 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. 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".
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|Wikimedia Commons has media related to Tyto alba.|
- Birdlife species factsheet
- BrainMaps: Tyto alba (barn owl) brain
- Barn Owl videos, photos & sounds on the Internet Bird Collection
- Barn Owl – Tyto alba – USGS Patuxent Bird Identification InfoCenter
- Barn Owl Species Account – Cornell Lab of Ornithology
- The Barn Owl Trust registered charity dedicated to conserving the Barn Owl and its environment. Main source of Barn Owl information in the UK
- BTO – BOMP – BTO Barn Owl Monitoring Project (BOMP)
- Suffolk Community Barn Owl Project – Suffolk Community Barn Owl Project
- Barn Owl Project in Austria – Barn Owl Project in Austria
- World Owl Trust Website
- Ageing and sexing (PDF; 5.3 MB) by Javier Blasco-Zumeta & Gerd-Michael Heinze
- Feathers of Barn Owl (Tyto alba)
- The Owl Channel
- Barn Owl – Species text in The Atlas of Southern African Birds.
- Barn Owl in New Zealand
- Nature Friendly Farming Owls Project - Conservation Grade & Barn Owl Conservation Network (BOCN),