Short-eared Owls are a small to medium-sized owl. Published lengths range from 37 to 39 centimeters (Cramp 1985) to 34 to 42 centimeters (Mikkola 1983), with females slightly larger than males and considerably heavier, averaging 411 grams compared to 350 grams for males (Mikkola 1983). They are excellent flyers with long wings (95 to 110 centimeters) (Cramp 1985), and light wing-loading (0.333 gram per centimeter squared) (Clark 1975). There is little difference in wing length between the sexes (Clark and Ward 1974). The back and upper wing surfaces are tawny-brown to buff-colored with heavy but indistinct streaking. The ventral surfaces are much lighter, with bold, vertical brown streaking on the breast, and a pair of barely visible ear tufts close together at the top of the facial disk. The belly is pale, lightly streaked; the wings are long and have a buffy patch beyond the wrist above and a dark patch at the base of the primaries below; the dark facial disk contrasts with yellow eyes; and the legs and feet are feathered. Mature males are bright white on the underwing, while mature females show somewhat more buff coloration (Bent 1938, Village 1987). It is, nonetheless, difficult to sex or age these birds in the field. Females are generally darker than males but young birds are also darker than older ones (Mikkola 1983), thus a young male may be darker than an old female. Both sexes have a distinct, black carpal bar and dark wingtips. Juveniles possess full adult plumage by October of the first year (Bent 1938, Cramp 1985). The facial disc is circular and whitish with dark areas around the bright, yellow eyes, black bill. Recently fledged and juvenile Short-eared Owls show much darker coloration overall and a much darker facial disc which whitens with age. The Short-eared Owl gets its common name from the small ear tufts over the eyes. These inconspicuous tufts are part of the facial disc and are generally not seen except when female is in camouflage position on nest or erected when the bird is annoyed or alert. They may possibly aid in making birds more cryptic when in vegetation by breaking the line of the circular facial disc.
The bird is generally silent but does vocalize in courtship (a low, repeated, hooting "voo, hoo, hoo, hoo
", or in conjunction with defensive behavior or annoyance, yaps or barks). The call is given approximately 15 times during courtship flight and is also accompanied by an audible wing-clap and dive between calls. Young give a food-begging call ("pssssip
") that apparently aids adults in locating them from the time they leave the nest until after fledging. Adults may squeal while feigning injury during broken-wing acts to distract intruders from nests or young. Both young and adults will clack their bills when annoyed or in defense. Apparently, no data exist on the use of broadcasting tape-recorded vocalizations for detection or monitoring purposes.
For a comprehensive review of the conservation status, habitat use, and ecology of this and other Montana bird species, please see Marks et al. 2016, Birds of Montana.
Short-eared Owls can be distinguished by large "wrist" patches and moth-like flight. Long-eared Owl (Asio otis) has a smaller "wrist" patch, buffy underwings, and a darker belly. Although Long-eared Owls hunt similarly to Short-eared Owls, they are rarely seen hunting during the day. Short-eared Owls are probably the most diurnal of owls (Lockie 1955, Clark 1975) and may often be observed from late afternoon until nightfall, or at dawn. A crow-sized owl seen abroad during daylight in open country will most likely be a Short-eared Owl. However, they also hunt at night. They are easily recognized by their blunt-headed profile and the fact that they glide with their wings held horizontally. This contrasts with the shallow v-shape of the Northern Harrier (Circus cyaneus) with which the Short-eared Owl often shares habitat and may be confused. Northern Harriers may also be distinguished by their white rump patch. Habitat is useful in separating Short-eared Owls from Long-eared Owls, the latter being predominantly a woodland dweller. The Long-eared Owl is also more slender with much longer ear tufts. Burrowing Owl also inhabits open country but is smaller (24 centimeters vs. 38 centimeters), has relatively longer legs, a yellow to whitish bill, and (in adults) has at least some horizontal barring on the breast. The Short-eared Owl's style of flight is unique and has at times been called mechanical, moth-like, or even slovenly (Peterson 1934).
Western Hemisphere Range
Migratory; however, some individuals may not migrate. Migratory in northern parts of range (Johnsgard 1988). Some suggestion of migration in MT: late February to early March (Davis 1961).
Open grasslands, plains, and agricultural areas with suitable vegetation and food.
A vole or field mouse specialist; almost the entire diet made up of these small rodents. A study of Short-eared Owl pellets in Ninepipes NWR yielded a 3.7:1 ratio of female:male Microtus (montanus and pennsylvanicus) eaten; snap-trap data yielded a 2.4:1 ratio (Holt and Williams 1995); it is impossible, however, to conclude from this data that Short-eared Owls were preferentially selecting females over males, as there could be more females in the prey population.
Reproduction and population dynamics are closely linked to fluctuating prey density (Wiggins et al. 2006).
Begins nesting in late February to March. Nests on the ground in a small depression, often with grasses placed around the depression; nest resembles a small bowl. Clutch size four to ten. Incubation approximately 26 days. Young fledge at 30 to 40 days. Egg records are from April 3 to June 13 (Davis 1961).
Short-eared owls require relatively large areas of grassland and are ground nesters, and thus are susceptible to the increased predation pressure often associated with fragmented habitats and nearby rural developments. As a result, they seem to be especially sensitive to loss and fragmentation of habitat. (Wiggins et al. 2006)