Barn Owls: Tytonidae
BARN OWLS: TytonidaeCOMMON BARN OWL (Tyto alba): SPECIES ACCOUNT
Like "typical" owls in the family Strigidae, barn owls have forward-facing eyes, excellent vision in dim light, and very sensitive ears. (Research shows that the common barn owl can locate prey by sound alone in complete darkness.) Tytonids differ from "typical" owls in having long, compressed bills, rather short tails, and rather long legs. The facial disk is heart-shaped instead of round. They lack the feather structures called ear tufts that many typical owls display. Their dark eyes are comparatively small and oval-shaped. The inner edge of the middle claw is serrated, like a comb. Barn owls use this claw to preen their feathers.
Most species in this group have a pale belly contrasting with a darker gray or brown back. The feathers show a beautiful allover speckling. Females tend to be larger, heavier, and darker in color than males.
The smallest member of this family is the Oriental bay owl, just 9 inches (23 centimeters) long. Common barn owls vary widely in size, and some members of this species are also very small. They may weigh as little as 6.6 ounces (187 grams). The longest and heaviest barn owls are female Australian masked owls at
2.8 pounds (1.3 kilograms) and 22.4 inches (57 centimeters).
Barn owls are widely distributed. The species for which the family is named, the barn owl, is the world's most widespread species of land bird. Barn owls are found on every continent except Antarctica and on many islands. No members of the family are found in Earth's coldest regions, however. No barn owls live in the Arctic or in the northernmost parts of Europe, Asia, or North America. Barn owls are also absent from the driest desert regions such as the Sahara and the Middle East.
Barn owls need a mix of wooded areas and open space. They also require tree cavities, caves, or other protected areas for nest sites.
Barn owls eat mostly small mammals such as voles and mice. They will also take birds, reptiles, amphibians, and large insects, however. In Australia, where there are no native mammals, barn owls prey on small marsupials. Barn owl pellets have a distinctive dark coating of mucus.
BEHAVIOR AND REPRODUCTION
Most barn owls are solitary in their habits, but some of the smallest species will gather in groups to hunt and roost when prey is plentiful. Usually they hunt from perches, but some of the smallest species hunt on the wing. Barn owls are almost exclusively nocturnal. They return to their roosts at dawn, often calling as they do so. They sleep by day, usually balancing on one leg with the wings closed and hunched forward to hide the pale belly.
LIFE ON THE FARM
Barn owls seem to be declining in numbers in the United States, Britain, and Canada. The likely reason for these declines is the loss of farmland, which makes very good habitat for barn owls. Barns and silos provide nest sites, and the owls can hunt for rodents in nearby fields. In the last few decades, however, many farms have been converted to housing developments or industrial parks. To help owl populations, conservationists are putting up nest boxes for owls in some areas. The boxes look like jumbo birdhouses. One reason to help owls is that they provide free pest control. One study by the Connecticut Department of Environmental Protection reports a barn owl family will eat more than 1,000 rats and mice in one nesting season.
Large species defend large home ranges. Small species are less territorial and defend only a small area around the nest site. When confronted with an intruder, barn owls perform distinctive defensive displays. A disturbed owl will make bowing movements, tilting forward with the tail raised, wings spread to the sides, and head lowered and swinging from side to side. At the same time it hisses and snaps its bill. If the intruder doesn't back off, the owl may strike with one foot or even spray feces.
Many typical owls make hooting calls, but no barn owls hoot. Their calls sound like screams, screeches, twitters, and whistles. A courting pair will engage in a trilling duet.
Most barn owls nest in sheltered locations such as tree holes and abandoned buildings. Grass owls are the exception—they tunnel into tall grass. The female incubates the eggs and broods the hatchlings while the male brings food to her and her young. Barn owls in temperate climates typically raise one brood per year. Species in warmer climates may raise two to three broods per year. Clutch size varies from one or two in sooty owls to seven or eight in barn owls and grass owls. Females lay more eggs when prey is abundant. After leaving the nest, the owlets may depend on their parents for food for several more weeks to months.
BARN OWLS AND PEOPLE
With their pale feathers and eerie calls, barn owls are sometimes called "ghost owls" or "spirit owls." In many cultures, they are regarded as associates of witches. They have a long history of living in association with humans. Evidence from Pleistocene cave dwellings shows that owls and humans shared the same caves.
Three species are listed as Endangered, facing a very high risk of extinction, on the IUCN Red List, the Madagascar red owl, Africa bay owl, and the Taliabu masked owl. One barn owl species, the Minahassa masked owl, is listed as Vulnerable, facing a high risk of extinction.
Physical characteristics: Sometimes called simply the barn owl, this species is widely distributed. Populations in different locations can be quite different in size and appearance. They range in length from 11 to 17 inches (29 to 44 centimeters) and vary in weight from
0.4 to 1.5 pounds (0.2 to 0.7 kilograms). The North American subspecies is the largest. The feathers are subtly colored but quite beautiful seen up close. They are mottled gray and buff-brown on the back and pale on the belly, with fine spots overall. Members of island populations tend to be darker in color than mainland populations. Males and females look alike.
Geographic range: This is the most widely distributed owl species. Barn owls occur on every continent except Antarctica.
Habitat: Barn owls prefer areas of open woods, grasslands, and brushy areas. Areas near cliffs offer nest sites. They will live near humans on farms or in urban areas as long as there are nest sites (for example, barns, silos, or church steeples) and open space for hunting.
Diet: Barn owls take whatever prey is available, the right size, and active at night. They seem to choose the slowest and fattest species among all the possible prey, usually specializing in small rodents such as voles, mice, and shrews. Small birds, amphibians, reptiles, and fish are occasionally taken, and invertebrates such as insects are rarely eaten.
Though most owls are "sit and wait" predators, barn owls often hunt by flying low and slow over open ground. They use their sense of hearing more than sight to locate prey. They usually hunt alone, but if prey is plentiful, they may hunt in groups.
Barn owls are monogamous (muh-NAH-guh-mus). At the beginning of the breeding season, males make courtship flights, patrolling their territories while calling loudly. Sometimes a male and female will fly together, or the male will chase the female while both scream loudly. One courtship display is the moth flight. The male hovers in mid air in front of a female. Another is the in-and-out flight. The male flies into and out of the nest sight as if showing it off. The female shows her interest with a snoring call, and the male responds with a gift of food.
Barn owls adjust their nesting efforts to the amount of prey that is available. If food is plentiful, the female lays a large number of eggs and may even nest a second time in the same year. She lays one egg every two or three days till the clutch is complete but starts incubating the eggs right away. This means the first owlet may hatch two to three weeks before the last. Young owls leave the nest when they are fifty-six to sixty-two days old. A female may start to lay more eggs before the last owlet from her first clutch has fledged.
Barn owls and people: One nickname for the common barn owl is monkey-faced owl. Some people actually believed they were flying monkeys. Barn owls have been introduced to some islands as a form of natural pest control. Grape growers in California are among the farmers that now welcome barn owls to their properties by hanging up nesting boxes. The owls help to control rodent pests.
Conservation status: Barn owls in North America have been declining slightly in numbers for the past four decades. Similar small declines are documented in Canada, Britain and Europe. So far, wildlife experts are not concerned that the species is threatened. ∎
FOR MORE INFORMATION
BirdLife International. Threatened Birds of the World. Barcelona and Cambridge, U.K.: Lynx Edicions and BirdLife International, 2000.
Duncan, James R. Owls of the World: Their Lives, Behavior and Survival. Buffalo, NY: Firefly Books, 2003
Johnsgard, Paul A. North American Owls: Biology and Natural History. Washington, DC: Smithsonian Institution Press, 2002.
BirdLife International. http://www.birdlife.net (accessed on June 28, 2004).
Lewis, Deane P. The Owl Pages. http://www.owlpages.com (accessed on June 28, 2004).