The Eastern barn owl (Tyto javanica) is usually considered a subspecies group and together with the American barn owl group, the western barn owl group, and sometimes the Andaman masked owl make up the genus Tyto. The cosmopolitan barn owl is recognized by most taxonomic authorities. A few (including the International Ornithologists' Union) separate them into distinct species, as is done here. The eastern barn owl is native to southeastern Asia, New Zealand, and Australasia.
The eastern barn owl is nocturnal over most of its range, but in some Pacific islands, it also hunts by day. They 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 is killed, after which 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 tree hollow, 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.
König proposed that Tyto alba 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.
Taxonomy The eastern barn owl was formally described in 1788 by the German naturalist Johann Friedrich Gmelin in his revised and expanded edition of Carl Linnaeus's Systema Naturae. He placed it with the other owls in the genus Strix and coined the binomial name Strix javanica. Gmelin based his description on the "Nachteule von Java" that had been described in 1787 by the German botanist Friedrich von Wurmb. The eastern barn owl is now placed with 16 other owls in the genus Tyto that was introduced in 1828 by the Swedish naturalist Gustaf Johan Billberg.
The barn owl (Tyto alba) was formerly considered to have a global distribution with around 28 subspecies. In the list of birds maintained by Frank Gill, Pamela Rasmussen and David Donsker on behalf of the International Ornithological Committee (IOC) the barn owl is now split into four species: the western barn owl (Tyto alba) (10 subspecies), the American barn owl (Tyto furcata) (12 subspecies), the eastern barn owl (Tyto javanica) (7 subspecies) and the Andaman masked owl (Tyto deroepstorffi). This arrangement is followed here. Some support for this split was provided by a molecular phylogenetic study by Vera Uva and collaborators published in 2018 that compared the DNA sequences of three mitochondrial and one nuclear loci. This split has not been adopted by other taxonomic authorities such as the Clements Checklist of Birds of the World maintained by members of Cornell University or by the list maintained by BirdLife International that is used by the International Union for Conservation of Nature.
Seven subspecies are recognised: In Handbook of Birds of the World, Volume 5: Barn-owls to Hummingbirds, the following subspecies are listed:Bruce (1999) pp. 34–75
Subspecies Description Range Synonyms T. j. javanica (J. F. Gmelin, 1788) Large. Similar to the western barn owl (Tyto alba), but darker above and with conspicuous speckling overall. The Malay Peninsula through to the southern Greater Sunda Islands (including the Kangean Islands, Krakatoa and the Thousand Islands); the Alor Archipelago; Kalao Island and Tanahjampea Island in the Selayar Islands; Kalaotoa Island and possibly southern Borneo. Pacific barn owl - Southeast Asian birds are sometimes placed here, but seem closer to stertens. T. j. delicatula (Gould, 1837) Similar to T. alba; slightly darker above, more speckling below. Tail with four dark brown bars. Australia and offshore islets (not on Tasmania); New Zealand (colonised from 2008); the Lesser Sunda Islands (Savu, Timor, Jaco, Wetar, Kisar, Tanimbar, possibly Rote); Melanesia (New Caledonia and the Loyalty Islands, Aneityum, Erromango and Tanna in southern Vanuatu, the Solomon Islands including Bougainville, Long Island, Nissan, Buka and perhaps New Ireland and northern New Britain); western Polynesia (Fiji, Rotuma, Niue, the Samoan Islands, Tonga and Wallis and Futuna); introduced to Lord Howe Island, but now extirpated there. Australian barn owl – includes bellonae, everetti, kuehni, lifuensis and lulu.Reports of blackish barn owls on Fiji require investigation. T. j. sumbaensis (Hartert, 1897) Large, particularly the bill. Similar to javanica; tail whitish with black bars. Endemic to Sumba. T. j. meeki (Rothschild & Hartert, 1907) Large. Similar to javanica; tail whitish with grey bars, underparts silvery-white with arrowhead-shaped speckles (which are larger than in javanica). Eastern New Guinea, Manam and Karkar Island. T. j. stertens (Hartert, 1929) Similar to T. alba, but noticeably speckled below. Western Pakistan through India east to Yunnan and Vietnam; southern Thailand; northern Sri Lanka. Southeast Asian birds sometimes included in javanica. T. j. crassirostris (Mayr, 1935) Similar to delicatula; darker, with stronger bill and feet. Endemic to the Tanga Islands. Boang barn owl T. j. interposita (Mayr, 1935) Similar to delicatula; darker, with orange hue. The Santa Cruz Islands and the Banks Islands south to Efate Island (Vanuatu).
Distribution The eastern barn owl occurs on the Indian subcontinent, Southeast Asia, Australia, and many Pacific Islands.Shawyer (1994) p. 10 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 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. In 2008, eastern barn owls were recorded for the first time breeding in New Zealand.
Behaviour and ecology
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. 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.
The barn owl is a bird of open country such as farmland or grassland with some interspersed woodland, usually at altitudes below but occasionally as high as 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.Taylor (2004) pp. 47–61
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 (mainly small rodents, such as mice, small rats and voles, and small marsupials), but bats and birds are also taken, as well as lizards, amphibians, insects and spiders.C. König , F. Weick , and J.-H. Becking . 1999. Owls: A Guide to the Owls of the World. Yale University Press, New Haven, Connecticut. Even when they are plentiful and other prey scarce, earthworms do not seem to be consumed.Taylor (2004) pp. 29–46
Mice and rats form the main foodstuffs in the tropics, subtropics and Australia. Barn owls are usually more specialist feeders in productive areas and generalists in drier areas. Locally superabundant rodent species in the weight class of several grams per individual usually make up the single largest proportion of prey. 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 twenty-three percent of the bird's bodyweight. Excess food is often cached at roosting sites and can be used when food is scarce.Taylor (2004) pp. 91–95
On bird-rich islands, a barn owl might include some fifteen to twenty percent of birds in its diet.
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. 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.
Breeding 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.
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.Shawyer (1994) pp. 67–87