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Barn Owls
The barn owl (Tyto alba) is the most widespread of all species of birds

They are found almost everywhere in the world except for the polar and desert regions. Globally they are considered to be of least conservation concern.

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. As more species of owl were described, the genus Strix came to refer solely to the wood owls in the typical-owl family Strigidae; and the barn owl became Tyto alba in the barn-owl family Tytonidae. Tyto alba literally means 'white owl', from the onomatopoeic Ancient Greek τυτώ tyto, 'owl'. The bird is known by many common names that 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, screech owl, straw owl, barnyard owl, and delicate owl.

The barn owl is a medium-sized, pale-coloured owl with long wings and a short, squarish tail. They measure around 29cm to 44 cm (11 to 17 in). Barn owls have a wingspan from 68 cm to 105 cm (27 to 41 in). Adults weigh between 224g to 710 g (7.9 to 25.0 oz). Female barn owls are larger than males.

The barn owl mostly hunts in twilight and the dark but it has also been known to hunt by day. Barn owls specialise in hunting animals on the ground and their food consists of rodents and other small mammals as their main diet, but also eat lizards, amphibians, insects and small birds too. They locate their food by sound as their hearing is very acute. Barn owls have a high metabolic rate so require more food than other owl species.

Barn owls are not particularly territorial but have a home range inside which they forage. For males in Scotland this home range has a radius of about 1 km (0.6 mi) from the nest site and an average area of about 300 hectares (740 acres).

Owls usually mate for life unless one of the pair is killed, then a new pair bond may be formed. Breeding takes place to match the region’s dry spell. A clutch of eggs averages four, in a nest in a hollow tree, old building, or fissure in a cliff, farm sheds and church towers. Buildings are preferred to trees in wetter climates as it provides better protection from the weather for the fledgling. 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. The female does all of the incubation, and she and the young chicks are reliant on the male for food. The female tears up the food brought by the male and distributes it to the chicks. Initially, the chicks make a "chittering" sound but this soon changes into a food-demanding "snore". When food is readily available, barn owl populations can expand rapidly.

The chicks are first covered with greyish-white down and develop rapidly. Within a week they can hold their heads up and shuffle around in the nest. By two weeks old they are already half their adult weight. By three weeks old, quills are starting to push through the skin and the chicks can stand. By four weeks old the female leaves the nest and roosts elsewhere. By the sixth week the chicks are fully grown. By the ninth week they are fully fledged and start leaving the nest briefly themselves. They are still dependent on both parents until thirteen weeks and receive training from the female in finding and catching prey.

Feathers need to be replaced at intervals. Barn owls are particularly dependent on their ability to fly quietly and manoeuvre efficiently. 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. It takes several years for a barn owl to moult and replace all of its feathers, as only a few each year are moulted so that the owls can still fly and hunt.

The male owl moults later in the year than the female, at a time when there is an abundance of food, and the female has recommenced hunting, and the demands of the chicks are lessening. Their moult follows a pattern similarly prolonged as that of the female. 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.

Predators of the barn owl include large opossums, the common raccoon, and similar carnivorous mammals, as well as eagles, larger hawks, and other owls. Among the latter, the great horned owl, and the Eurasian eagle-owl are noted predators of barn owls. In Europe, although less dangerous than the eagle-owls, the chief diurnal predators are the northern goshawk and the common buzzard. About 12 other large diurnal raptors and owls have also been reported as predators of barn owls, ranging from the similar-sized Cooper's hawk and scarcely larger tawny owl to huge bald and golden eagles. The goshawk and the eagle-owls are on the increase because of the greater protection these birds now receive.

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 outstretched and drooped while the bird emits hisses and makes snapping noises with its beak. Another defensive attitude involves lying flat on the ground or crouching with wings spread out.

Unusually for a medium-sized carnivorous animal, the barn owl produces a large number of offspring with a high growth rate, which have a low probability of surviving to adulthood. While wild barn owls are usually short-lived, usually around fours years, their potential lifespan is much higher. Captive individuals may reach 20 years of age or more. A captive barn owl, in England, lived to be over 25 years old.

The most significant cause of death in temperate areas is likely to be starvation, particularly during the autumn and winter, when first-year birds are still perfecting their hunting skills. Collision with road vehicles is another cause of death, 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. 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 being shot accounts for others.

In some conservation projects, the use of poison for pest control was replaced by adding nest boxes for barn owls, which has been shown to be a less costly method of rodent control. Which not only help barn owls, it reduces the need for toxic chemicals that could accidentally be consumed by other wildlife.