SPECIES: A. flammeus
Common Name(s): Short-eared owl, Evening Owl, Marsh Owl, Bog Owl, Swamp Owl, Grass Owl, Meadow Owl, Mouse-hawk, Flat-faced Owl
Owls belonging to genus Asio are known as the eared owls, as they have tufts of feathers resembling mammalian ears. These "ear" tufts may or may not be visible. Asio flammeus will display its tufts when in a defensive pose. However, its very short tufts are usually not visible.
The word flammeus is Latin for "flaming, or the color of fire".
Currently, there are ten recognized subspecies of the Short-eared Owl
The Short-eared Owl is a medium-sized Owl. The plumage is buffy brown with dark streaks on the chest, belly, and back. Males tend to be lighter in color than females. This coloring provides good camouflage, but if this fails, a Short-eared Owl will feign death to avoid detection. The wings and tail are strongly barred.
The yellow eyes are circled with black and set in whitish or buffy-white facial disks, which are suffused with a ring of brown. The bill is black. The head appears round without ear tufts, but at very close range small ear tufts are visible. In flight, the dark "wrist" on the underwing is the key field mark.
Often easily identified by behavior alone, the Short-eared is most readily confused with the Long-eared Owl. In flight, both species share similar underwing coloration, and often a good view of a sitting bird is needed to discern the many obvious differences such as the Long-eared Owl's ear tufts, red facial disks, barred underparts, and lack of tawny coloration. This owl also is potentially confused with the Barred Owl, but easily distinguished by eye and bill color, face and underpart patterning. Barn Owl occupies similar habitat but is much paler and lacks streaking on the underparts.
Males and females are not easily distinguishable from each other externally, but females are usually slightly larger. Individuals vary considerably in colors. The right and left ears occupy different vertical positions on the sides of their head, but the size and shape of the two ears are the same.
Lengths average 33-43cm (13-17in).
Wingspan of the female averages 107cm (42in), and of the male 105cm (41in).
Weights average 206-475g (7-17oz) Females are slightly larger than Males.
The Short-eared Owl occurs on all continents except Antarctica and Australia; thus it has one of the largest distributions of any bird. A. flammeus breeds in Europe, Asia, North and South America, the Caribbean, Hawaii and the Galápagos Islands. It is partially migratory, moving south in winter from the northern parts of its range. The Short-eared Owl is known to relocate to areas of higher rodent populations. It will also wander nomadically in search of better food supplies during years when vole populations are low. In North America it breeds from Alaska to Labrador south across approximately the upper third of the U.S., though its is now a rare breeder in the northeast U.S. Wintering birds migrate as far south as Florida, central Mexico, and Baja California.
Short-eared Owls inhabit wide open spaces such as annual and perennial grasslands, prairie, agricultural fields, salt marshes, estuaries, mountain meadows, dunes, and alpine and Arctic tundra. Breeding habitat must have sufficient ground cover to conceal nests and nearby sources of small mammals for food. Communal roosts occur in oldgrowth fields, along thick hedgerows, in overgrown rubble in abandoned fields, or in clumps of dense conifers. These Owls tend to roost in trees only when snow covers the ground. During migration, Short-eared Owls will move through high mountain passes, flying at great heights.
The individual spacing of short-eared owls is poorly known, but owls in communal winter and post-breeding season often roost within 1 meter of each other. There is a wide range in the size of breeding territories. Nomadism in search of food, migration, and juvenile dispersal may be confused.
The short-eared owl is a bird of open country that is often seen during the day. It exhibits a type of moth-like or irregular flapping flight. Perhaps the most aerial owl, the Short-eared courses low over fields and marshes at dawn and dusk with floppy, moth-like rowing wingbeats. Outside breeding season, they may gather in communal roosts. This owl is largely a nomadic vole-specialist.
In contrast with many other owls, Short-eared owls begin foraging during daylight or early evening. These owls may continue to be active into the night, but usually cease activity after nightfall. They have a tendency to form communal roosts during the winter months. In different times of the year, they may live alone or together, but they always hunt alone.
Short-eared Owls are silent on the wintering grounds. They are generally quiet, owing to their diurnal nature and the wide open habitats where visual displays would be more effective than in forests. However, they have a scratchy bark-like call. Raspy waowk, waowk, waowk or toot-toot-toot-toot-toot sounds are common. A loud eeee-yerp is also heard on breeding grounds. The male's territorial song is a pulsing "voo-hoo-hoo", resembling an old steam engine. This song is given mainly during flight displays and the female responds with a barking "kee-ow". Both sexes give hoarse cheeaw calls when disturbed in their nesting territory. When excited near the nest, both sexes squawk, bark, hiss and squeal. Short-eared owl nestlings give high pitched calls from within the egg and from hatching until they are about 7 days old. These are probably begging calls or perhaps expressing discomfort. The vocal pitch changes at about 7 days and becomes lower. Adults sometimes direct calls at human territorial intruders.
Short-eared owls have keen vision, especially in low light. They also use their excellent sense of hearing to help locate and capture prey.
Short-eared Owls hunt mainly at night and during the morning and late afternoon. They fly over open areas, a few feet above ground, and pounce when prey is located. In dense vegetation they will hover over prey, often for extended periods when facing into the wind, before pouncing. They occasionally hunt from a perch or while standing on the ground.
Short-eared owls are vulnerable primarily to mammalian predation due to the type of open habitat they occupy and their ground nesting habit. They fly fast and directly at an intruder, pulling up and presenting their talons at the last moment. They often use thermal updrafts during skirmishes and rise vertically, chasing and interacting with intruders.
Short-eared owls are generally thought to be monogamous; however, the pair bond probably does not last beyond the breeding season. The difficulty of owl reproduction lies in their usually individualistic habits; a great amount of the effort goes into learning mutual recognition as mating partners rather than prey or predator. They even have some difficulty identifying the gender of prospective mates from a distance.
Courtship and territorial behavior is spectacular for an Owl. Males perform aerial displays by rising quickly with rhythmic and exaggerated wing beats, hovering, gliding down, and rising again, often 200 to 400 meters (650 to 1,300 feet) above ground. Wing claps, in bursts of 2 to 6 per second, are often made during this flight and some singing occurs. The flight can be ended with a spectacular descent where the male hold his wings aloft and shimmies rapidly to the ground. Two birds may engage in flight, locking talons, and fighting briefly. Often, a display where one bird flashes its light underwing towards another is used during territorial and courtship flights. Males also may offer food to females; this prevents females from considering the male as food.
Pair formation begins in mid-February and continues through June. Breeding usually begins in April.
The Short-eared Owl nests on the ground, unlike most other owls. Nests are usually situated in the shelter of a grass mound, under a grass tuft, or among herbaceous ground cover. Nests are loosely constructed by the female, who scrapes a spot on the ground and then lines the scrape with grass stems, herb stalks, and feathers plucked from her breast. Clutch sizes range from 4 to 14 eggs (average 5 to 7), with large clutches laid during years of high food abundance. Clutch size increases from south to north. Eggs are laid every 1 to 2 days and incubation commences with the first. Incubation is done largely by the female, with the male bringing food to the nest and occasionally taking a turn incubating. Young grow very rapidly after hatching, and begin to wander from the nest as soon as 12 days, an adaptation for a ground-nesting species to reduce the amount of time they are vulnerable to predation. Young fledge at about 4 weeks.
The Short-eared Owl routinely lays replacement clutches, because of high predation rates. In southern areas, it may raise 2 broods in 1 year. Because reproductive success is relatively poor, the ability to lay large clutches helps populations recover after periodic declines.
The Short-eared Owl is highly migratory, and nomadic, except in southern parts of its range. Movements of up to 2,000 kilometers (1,200 miles) have been documented. This Owl has relatively small nesting territories and home ranges, varying from 15 to 200 hectares (35 to 500 acres), and may nest in loose colonies in excellent habitat. Because of its nomadic tendencies, mate and site fidelity are very low. Breeders tend to wander until they find areas with high densities of prey before settling to breed. In winter, large numbers of Owls will occur in areas with lots of food. Communal winter roosts of up to 200 birds are known, with these birds ranging over nearby areas to hunt. Resident owls will defend winter foraging territories of about 6 hectares (15 acres), before expanding the territory size during the breeding season.
Short-eared owls hunt mostly at night, but this owl is diurnal and crepuscular as well as nocturnal. They rely mainly on auditory clues; using these alone, they can catch prey that is under continuous grass cover. Their food consists mainly of rodents, especially voles, but it will eat other small mammals and some large insects. Sometimes it even tends to eat smaller birds. Meadow voles (Microtus species) are the primary prey. Deer mice, shrews, ground squirrels, pocket gophers, pocket mice, moles, rats, bats, rabbits, and muskrats are also taken. Birds probably are more important when Short-eared Owls hunt in marshes and along coastal areas, where they can target shorebirds, terns, and small gulls and seabirds. In inland habitats they take mainly Horned Larks, meadowlarks, blackbirds, and pipits. A few insects such as roaches, grasshoppers, beetles, katydids, and caterpillars are also taken. Unlike most Owls, prey is normally carried in its talons.
Records are limited, but the longevity record for a wild Short-eared owl is 4 yrs, 2 months. Natural enemies include many diurnal raptors such as the Bald Eagle, Northern Goshawk, Gyrfalcon, Red-tailed Hawk, and Snowy Owl. Because they nest on the ground, they are vulnerable to mammalian predators such as skunks, dogs, foxes, and coyotes, while Jaegers, gulls, ravens, and crows steal eggs and small chicks. Collisions with vehicles account for a large number of deaths. Also, they are attracted to the wide open fields of airports and so many are killed by collisions with aircraft.
The Short-eared owl is listed as declining in the southern portion of its range. It is listed as of special concern, threatened, or endangered in some states and common in northern portion of breeding range. Numbers have declined in recent decades because of destruction and fragmentation of grasslands and riparian habitats. Like many species dependent on grasslands or other open lands, the primary threat to the Short-eared owl is the destruction and degradation of open habitat. From agriculture to human development to successional reforestation, this species is losing open fields, meadows, and marshes where it prefers to nest and spend winters. The species may also be affected by pesticides accumulated through its prey, especially during winter when Short-eared owls often occur in agricultural areas, but this has not been studied.
Conservation efforts undertaken are usually similar to those of other grassland breeding birds. Management protocols such as prescribed burns, periodic mowing, and efforts to maintain waterfowl breeding sites all lend aid to preserving habitat necessary for Short-eared owls. However, because these birds are partially nomadic in winter and could appear anywhere in suitable habitat, habitat should be preserved in both known and potential breeding and wintering sites.
Due to their wide distribution, short-eared owls are not a federally endangered species; however, in the Great Lakes region of the United States, conditions are worse. This species is threatened by the diminishing area of marshes, bogs, and open grasslands. Nesting habits and nomadism make this species particularly vulnerable to habitat loss during any season. Due to these factors, short-eared owls are endangered in Michigan, Illinois, and Pennsylvania. They are also threatened in Minnesota and of special concern in Indiana and Ohio. They are among the rarest nesting owls in Michigan. There are no major efforts to help them recover in these areas.
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