Montana Field Guide

Barn Owl - Tyto alba

A medium-sized owl, the Barn Owl is approximately 38 cm (16 inches) in length with a wingspan of 106 cm. They have broad, rounded wings and long legs. The features of dark eyes and a white disk-shaped face rimmed in dark cinnamon are unique to the species. Their head, back, and wings are a pale, tawny, buff color, finely marked with black and white. The tail, which is also tawny and matches the coloration of the wings, is short. The breast is white as are the sparsely feathered legs. The bill is light colored and the lower legs, feet and toes are a light gray, with dark gray claws (Marti 1992). True to most owls, the female is larger than the male (females average 34 to 40 cm, males are 32 to 38 cm) (Marti 1992). The breast of the female is slightly darker in coloration than that of the male and is sometimes heavily spotted (Marti 1992).

Juveniles resemble adults. Males younger than one year may have buff coloration on the breast (whereas adult males almost always lack such coloration) but are not as heavily speckled as females (Bloom 1978).

Vocalizations of the Barn Owl include a long hissing shriek "csssssshhH" (Sibley 2000) or an advertising call, identified as a drawn-out gargling scream "karr-r-r-r-r-ick" (Marti 1992).

The white, heart-shaped face with dark eyes, light breast, and tawny-buff back distinguish this species from other owls. The Barn Owl lacks ear tuffs, yellow eyes, and breast barring found in other owl species (Marti 1992, Sibley 2000). Barn Owls may be confused with Short-eared Owls in Montana but Barn Owls are much paler in color and have dark eyes.

Montana Range

Barn Owls have been recorded in Montana from January to October (Montana Bird Distribution 2003). These observations, however, arise from different locations across different years, and do not necessarily indicate near year-round presence. These occasional reports may represent migrations into the state only during seasons or years that are favorable, suggesting presence may be a year-dependent dispersal or migration phenomenon. Indeed, little information is available on the migratory habits of this species, particularly in the western portion of its range (Marti 1992). Until the Barn Owl is more commonly reported, it will be considered a rare visitor to the state. In nearby Wyoming, the Barn Owl breeds regularly in the southern portion of the state (Johnsgard 1986).

One report for the southeast corner of the state indicates the bird observed was foraging over shrub-steppe habitat (Montana Bird Distribution 2003). Other specific information on habitat use in Montana is not documented, although it is likely the Barn Owl uses habitat similar to that which is used where the species is more common: open grassland, marsh, pasture lands, croplands, and hayfields.

No food habit information on Barn Owls is available in Montana. Information from other regions of the species' range state the main prey of the Barn Owl is small mammals (Microtus is principal prey in many areas); Blarina, Thomomys, Spermophilus, Perognathus, Dipodomys, and Peromyscus are locally important and sometimes birds are taken when small mammals are scarce. Introduced rodents provide a majority of the food source in some urban areas and (with bats and birds) in the West Indies. This owl hunts mainly by quartering flights 1.5 to 4.5 meters above the ground (Marti 1989). In northern and eastern North America, the shrew component of the diet has declined over the past several decades; in the northern and central range, the percentage of exotic rats and mice has increased, probably due to human-induced changes in habitats (Clark and Bunck 1991). As much as 5.6 kilometers may be traveled between a nest site and foraging areas, although distances within 1.6 kilometers are more usual (Colvin 1984, Hegdal and Blaskiewicz 1984, Rosenburg 1986).

Typical foraging is done with a relatively low quartering flight that includes frequent hovering intervals (Honer 1963, Burton 1973, Karalus and Eckert 1974, Marti 1974, Rudolph 1978, Bunn et al. 1982, Mikkola 1983, Rosenburg 1986). Some individuals also hunt frequently from a perch, especially along field edges (Byrd 1982, Rosenburg 1986). Highly nocturnal, this owl has extremely keen hearing (Payne 1971, Konishi 1973) and night vision (Dice 1945, Marti 1974). Its ability to capture prey by hearing alone (Payne 1971) is especially advantageous when hunting animals such as voles (Microtus spp.) and shrews (Soricidae), species that are often concealed from view as they travel in runways beneath grass cover.

Numerous pellet analyses throughout north temperate North America and Europe have identified microtines as the primary prey (Ticehurst 1935, Wilson 1938, Pearson and Pearson 1947, Wallace 1948, Campbell et al. 1987, Marti 1988). The meadow vole (Microtus pennsylvanicus) is the most important prey animal in the northeastern U.S. and the short-tailed shrew (Blarina brevicauda) is an important secondary prey. By frequency, meadow voles typically comprise 60 to 90% of the diet (Boyd and Shriner 1954, Rosenburg 1986). The marsh rice rat (Oryzomys palustris) is occasionally an important prey animal in coastal areas (Blem and Pagels 1973, Colvin 1984). In the southern U.S., the cotton rat (Sigmodon hispidus) is the primary prey (Baumgartner and Baumgartner 1944, Otteni et al. 1972, Byrd 1982). The foraging behavior of the Barn Owl, which has been closely studied (Colvin 1980, 1984), indicates that prey of a particular size (approximately 40 to 60 grams), provides the most energy efficient diet. The average weights of the meadow vole, marsh rice rat, cotton rat, and Norway rat (Rattus norvegicus) juveniles fall into this size range.

The Barn Owl shows greater diet diversity 1) in areas with relatively low microtine or cotton rat availability (Ticehurst 1935, Hawbecker 1945, Pearson and Pearson 1947, Glue 1967, Blem and Pagels 1973); 2) during times of poor microtine availability (Fitch 1947, Wallace 1948, Glue 1967, Bethge and Hayo 1979); and 3) when non-microtine prey are readily available (Evans and Emlen 1947, Klaas et al. 1978, Rosenburg 1986). These studies identified birds (mostly blackbirds and sparrows), short-tailed shrews, least shrews (Cryptotis parva), house mice (Mus musculus), and Norway rats as relatively important prey in such situations.

Ecological information is currently unavailable for Barn Owls in the state. Generally, individuals range over large areas; mean home range size, based on the minimum home range method (Mohr and Stumpf 1966) has been reported as 355 hectares in southern Texas (Byrd 1982), 757 hectares and 921 hectares in southwestern New Jersey (Colvin 1984, Hegdal and Blaskiewicz 1984), 414 hectares in eastern Virginia (Rosenburg 1986), 850 hectares in Virginia (Byrd and Johnston 1991), and 198 hectares in western Nebraska (Gubanyi 1989). Overlap of individual home ranges is common, particularly where nest sites and prey are abundant (Smith et al. 1974, Colvin 1984, Rosenburg 1986).

Young disperse widely from natal areas, commonly more than 80 kilometers, with distances of up to 1900 kilometers documented, facilitating colonization of new areas. Juveniles in the northern U.S. migrated south but generally returned to nest somewhere within 50 to 320 kilometers of their natal sites (Stewart 1952, Marti 1990). Cases of dispersal greater than 320 kilometers from natal sites have also been documented (Ehresman et al. 1989). Although Barn Owls may return to breed relatively close to their natal areas, they do exhibit broad dispersal behavior, are very successful at colonizing new areas, and individuals frequently become established great distances away.

During prolonged low temperatures and snow cover Barn Owls are susceptible to starvation (Marti and Wagner 1985). In Utah, most adults survived only one breeding season (Marti 1989). Disease, parasites, and predation are natural factors that may, in part, limit populations. This species of owl appears to be resistant to many diseases that infect other raptors (Schulz 1986). In California, diseases documented include tuberculosis, aspergillosis, and trichomoniasis (Schulz 1986). Toxoplasmosis and eastern equine encephalitis have been detected in New Jersey, although no impact to the birds was apparent (Colvin and Hegdal 1986, 1987). Salmonellosis has been recorded in Pennsylvania (Locke and Newman 1970) and New Jersey (Kirkpatrick and Colvin 1986). Kirkpatrick and Colvin (1986) found Salmonella-positive nestlings at five of the 25 New Jersey nest sites examined, and reported that all infected young apparently fledged.

Dipteran ectoparasites and lice have been found on Barn Owls (Schulz 1986, Kirkpatrick and Colvin 1989). The endoparasites Trypanosoma, Capillaria, and Porrocaecum have been identified from the feces of New Jersey owls (Colvin and Hegdal 1986).

During the non-breeding season, Barn Owls may be found solitary or in pairs.

Two breeding occurrences are known in Montana, one in the Bitterroot Valley and one in Carbon County (Montana Bird Distribution 2003). The Bitterroot Valley observation indicated that four young were observed in July, but no further details on the nesting event are recorded. No details are available on the breeding record for Carbon County, and no other information or evidence on specific nesting locations or habitat utilized is documented for the state (Montana Bird Distribution 2003).

Reproductive information provided is from studies and sources in other areas of the speices' range. These studies indicate nesting takes place in cavities without any nesting material or occasionally lined with a scattering of owl pellets (Baicich and Harrison 1997). The Barn Owl usually lays four to seven (Otteni et al. 1972, Reese 1972, Smith et al. 1974) long, subelliptical to elliptical smooth, glossy white eggs (42 x 33 mm); a clutch can sometimes consist of one to 13 eggs (Bent 1938, Parker and Castrale 1990, Baicich and Harrison 1997). The size of the clutch usually depends on local conditions and increases with food supply and after mild winters in some areas.

Barn Owls nest in late winter, spring, and/or early summer in most of North America, and throughout the year in Texas. Nests with eggs and/or young have been found in the northeastern U.S. during every month of the year (Poole 1930, Bent 1938, Scott 1950, Stewart 1952, C. Rosenburg, unpubl. data), with peak egg production occurring during mid-April (Colvin 1984, Byrd and Rosenburg 1986). Second clutches are typically laid between June and September (Wallace 1948, Keith 1964, Reese 1972, Soucy 1979). Across most of their range, Barn Owls usually produce one brood per year, but have been recorded with as many three broods in one year. Eggs are usually laid two days apart and hatch asynchronously since incubation starts after the laying of the first egg (Wallace 1948, Smith et al. 1974). Incubation is by the female, and lasts 21 to 24 days for a single egg, 29 to 34 days for a full clutch (Smith et al. 1974, Marshall et al. 1986). The peak of hatching in the Northeast occurs in mid-May (Colvin 1984, Byrd and Rosenburg 1986).

The female broods and feeds the young, while the male brings food. Young can fly at 50 to 55 days. The juveniles may return to roost at the nest for several (seven to eight) weeks before dispersing (Otteni et al. 1972, Smith et al. 1974, Marti 1990, Marti 1992). Peak fledging occurs in mid- to late July (Colvin 1984, Byrd and Rosenburg 1986). The male may care for fledged young as the female begins a second clutch. In northern Utah, 71% of all nesting attempts yielded at least one fledgling; reproductive success and productivity were reduced following winters with particularly low temperatures and long periods of deep snow cover (Marti 1994). Breeding density depends on availability of nest sites and on food supply. See Marti (1989) for information on breeding phenology in different areas.

The Barn Owl matures and breeds within its first year (Stewart 1952, Maestrelli 1973, Marti 1990). The species is typically monogamous, but Colvin and Hegdal (1989) reported that as many as 10% of the adult males in their New Jersey study area may be polygynous.

No management activities in Montana specific to Barn Owl are documented. Barn Owls are a Species of Management Cocern in Region 6 (U.S. Fish and Wildlife Service (1995).