ANIMAL ESTATE client 1.02: BARN OWL
FROM ANIMAL ESTATES 1.0: NEW YORK
SCIENTIFIC NAME: Tyto Alba
ANIMAL PROFILE: The Barn Owl is a stunningly beautiful bird with golden/buff colored upper parts laced with silver grey and white under-parts. It has a distinctive white heart shaped face and when seen in flight the overall impression is of a large white bird. The flight is buoyant and wonderfully graceful. The wings (spanning 85cm) are much bigger than the body. A Barn Owl is fully grown from only ten weeks old, it stands 25cm tall (from head to feet) and is 33-35cm from the top of its head to the tip of its tail. Barn Owls shriek and hiss, they don't hoot (that's the Tawny Owl). Barn Owls hunt mainly from the air (rather than from a perch) and have some amazing adaptations enabling them to find and catch small mammals hidden in deep vegetation in the dark. They don't generally venture into dense woodland but will forage over any open habitat that supports a population of small mammals.
RANGE: Barn owls are the most widespread of all owl species, and are found on every continent except Antarctica. In the Americas, barn owls occur in suitable habitat throughout South and Central America, and in North America as far north as the northern United States and southwestern British Columbia. In Europe, barn owls range from southern Spain to southern Sweden and east to Russia. They are also found throughout Africa, across central and southern Asia, and throughout Australia. Barn owls have been introduced to some oceanic islands to control rodent pests.
HABITAT: Barn owls occupy a vast range of habitats from rural to urban. They are generally found at low elevations in open habitats, such as grasslands, deserts, marshes and agricultural fields. They require cavities for nesting, such as hollow trees, cavities in cliffs and riverbanks, nest boxes, caves, church steeples, barn lofts, and hay stacks. The availability of appropriate nesting cavities often limits use of suitable foraging habitat. ( Marti, 1992 )
BUILDING MATERIALS: Barn owl pairs often use an old nest that has been occupied for decades rather than building a new one. The female usually lines the nest with shredded pellets. ( "The Owl Pages", 2003 ; Marti, 1992 )
BUILDING MOTIVATION: Barn owls breed once per year. They can breed almost any time of the year, depending upon food supply. Most individuals begin breeding at 1 year old. Due to the short life span of barn owls (2 years on average), most individuals breed only once or twice. Barn owls usually raise one brood per year, though some pairs have been observed raising up to three broods in one year Barn owl pairs often use an old nest that has been occupied for decades rather than building a new one. The female usually lines the nest with shredded pellets. She lays 2 to 18 eggs (usually 4 to 7) at a rate of one egg every 2 to 3 days. The female incubates the eggs for 29 to 34 days. The altricial chicks are brooded and fed by the female for about 25 days after hatching. They leave the nest on their first flight 50 to 70 days after hatching, but return to the nest to roost for 7 to 8 weeks. The chicks usually become independent from the parents 3 to 5 weeks after they begin flying. ( "The Owl Pages", 2003 ; Marti, 1992 ) Female barn owls leave the nest during incubation only briefly and at long intervals. During this time, the male feeds the incubating female. All brooding is done by the female, beginning immediately after hatching and lasting until the oldest young is about 25 days old. Males bring food to the nest for the female and chicks, but only the female feeds the young, initially tearing the food into small pieces. The female also eats the feces of the chicks for the first few weeks after hatching in order to sanitize the nest. The parents continue to feed the chicks for up to 5 weeks after fledging. ( Marti, 1992 )
THREATS: Barn owls have few predators. Nestlings are occasionally taken by stoats and snakes. There is also some evidence that great horned owls occasionally prey upon adult barn owls. Barn owl subspecies in the western Palearctic are much smaller than those in North America. These subspecies are sometimes preyed upon by golden eagles , red kites , goshawks , buzzards , peregrine falcons , lanners , eagle owls and tawny owls . Threats to barn owl population include climatic changes, pesticides, and changing agricultural techniques. A change of the climate in northern regions is causing snow to last for longer periods, making winter survival difficult for the species. Unlike other birds, barn owls do not store extra fat in their body as a reserve for harsh winter weather. As a result, many owls die during freezing weather or are too weak to breed in the following spring. Pesticides have also contributed to declines in this species. For unknown reasons, barn owls suffer more severe effects from consuming pesticides than other species of owls. These pesticides are often responsible for eggshell thinning in females. Another major factor limiting population growth is modern agricultural methods. Traditional farms with many small structures favored barn owl populations. In modern farms, there is no longer an adequate amount of farm structures for nesting, and farm land can no longer support a sufficient population of rodents to feed a barn owl pair. The barn owl population, however, is declining only in some localities, not throughout the range. ( Marti, 1992 )
INTERESTING FACTS: Most barn owls have a relatively short life span. Many only survive one breeding season and the mortality rate may be as high as 75% in the first year of life. in one study, the mean age at death for 572 banded birds was 20.9 months. However, the longest recorded lifespan of a wild barn owl is 34 years. ( Marti, 1992 ) The ability of barn owls to locate prey by sound is the most accurate of any animal tested. This very acute sense of hearing allows barn owls to capture prey hidden by vegetation or snow. Their amazing ability to locate prey using sound is aided by their asymmetrically placed ears. This asymmetry allows these owls to better localize sounds generated by prey. Their ears are extremely sensitive and can be closed by small feathered flaps if the noise level is too disturbing. Barn owls also have excellent low-light vision.
MAKING A BARN OWL HOUSE: Barn Owls may roost or nest in any structure or tree that meets their requirements. There are three main types of nestbox, those for use in buildings, those for use on vertical tree trunks and those that are only suitable for use within the branches of very large trees. There are a variety of designs on the market, but the ones described here are the ones recommended by the Barn Owl Trust because of the benefits that they have over other designs. from Barn Owl Trust / link 01 / link 02 / link 03 / link 04
REFERENCES:
Bachynski, K. and M. Harris. 2002. "Tyto alba" (On-line), Animal Diversity Web. Accessed November 09, 2007 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Tyto_alba.html .
Perrins, Christopher, M.. et. al., The Encyclopedia of Birds. Facts on File Publications, 1985.
2003. "The Owl Pages" (On-line). Accessed January 26, 2004 at http://www.owlpages.com/species/tyto/alba/Default.htm .
Marti, C. 1992. Barn Owl. Pp. 1-15 in A. Poole, P. Stettenheim, F. Gill, eds. The Birds of North America , Vol. 1. Philadelphia: The Academy of Natural Sciences; Washington DC: The American Ornithologists' Union.