Tyto alba

Written by on November 19, 2010 in Indonesia Bird with 0 Comments

Tyto alba, Barn Owl, Serak Jawa

Tyto-alba-01-800

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 Common Barn Owl, to distinguish it from other species in the barn-owl family Tytonidae. These form one of the two living main lineages groups of owls, the other being the typical owls (Strigidae). T. alba is found almost anywhere in the world outside polar and desert regions, as well as all of Asia north of the Alpide belt, most of Indonesia and the Pacific islands.

It is known by many other, some of them rather ambiguous. They often refer to the appearance, habitat or the eerie, silent flight: White Owl, Silver Owl, Demon Owl, Ghost Owl, Death Owl, Night Owl, Rat Owl, Monkey-faced Owl, Church Owl, Cave Owl or Stone Owl. Golden Owl might also refer to the related Golden Masked-owl (T. aurantia). Hissing Owl and – particularly in the USA – “screech owl” refer to the piercing calls of these birds, but the latter term usually refers to typical owls of the genus Megascops.

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.

The Barn Owl is a pale, long-winged, long-legged owl with a short squarish tail. Depending on subspecies, it measures c.25-45 cm in overall length, with a wingspan of about 75-100 cm. Tail shape is a way of distinguishing the Barn Owl from true owls when seen in flight, as are the wavering motions and the open dangling feathered legs. The light face with its peculiar 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 upperparts are a mixture of buff and 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 color; their color ranges from pinkish to dark pinkish-grey. The talons are black.

Barn Owl nestlings are covered in off-white down all over, but the heart-shaped facial disk is visible soon after hatching.

Contrary to popular belief, it 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. It can hiss like a snake, and when captured or cornered, it throws itself on its back and flails with sharp-taloned feet, making for an effective defense.

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 color, sometimes according to Bergmann’s and Gloger’s Rules, sometimes more unpredictably. This species ranges in color from the almost beige-and-white nominate subspecies, erlangeri and niveicauda to the nearly black-and-brown contempta:

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