American Barn Owl

Description

The barn owl is a medium-sized, pale-coloured owl with long wings and a short, squarish tail. There is some size variation across the subspecies, with a typical specimen measuring about 33 to 35 cm (13 to 14 in) in overall length, with a wingspan of 80 to 95 cm (31 to 37 in). Adult weight is also variable, with nominate T. a. alba from Italy weighing 240–310 g (8.5–10.9 oz), T. a. guttata in Germany weighing 290–480 g (10–17 oz), while T. a. poensis from South Africa weighs 295–380 g (10.4–13.4 oz); the sexes are broadly similar in weight, with females on average slightly heavier than males (typically about 10% heavier), but with considerable overlap. 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. Birds found dead or dying from starvation weighed 190–240 g (6.7–8.5 oz). 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 gives 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. 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. Both leucistic and melanistic barn owls have been recorded in the wild and in captivity, with melanistic individuals estimated to occur with odds of 1 out of every 100,000 birds. On average within any one population, males tend to have fewer spots on the underside and are paler in colour than females. Nestlings are covered in white down, but the heart-shaped facial disk becomes 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 members of the genus Strix). It instead produces a characteristic piercing shree scream, 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.

Range & habitat

Its range includes all of Europe (except Fennoscandia and Malta), most of Africa apart from the Sahara, and southwest Asia east to western Iran. 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. 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. Ten geographical subspecies are currently accepted:

Behaviour

Like most owls, the barn owl is crepuscular to nocturnal, relying on its acute sense of hearing when hunting in complete darkness. It often becomes active shortly before dusk and can be seen during the day when relocating from one roosting site to another. In Britain, it sometimes hunts by day. This practice may depend on whether the owl is mobbed by other birds if it emerges in daylight. However, in Britain, some barn owls continue to hunt by day even when mobbed by birds like magpies, rooks and black-headed gulls, such diurnal activity possibly occurring when the previous night has been wet or windy 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. 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 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. 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.

Adapted from Western barn owl on Wikipedia, used under CC BY-SA 4.0.