Friday, July 30, 2021

Short-eared owls: Wide-ranging, funny in flight

Photo by Joe Kostoss

Short-eared owls are one of the most widely ranging members of the Strigidae owl family, absent only from Australia and Antarctica. They favor grasslands, fields, tundra, meadows, airports, marshes and bogs, any open habitat home to their favorite prey, moles, voles, deer mice, shrews, small birds, and insects.

Breeding all over Canada and Alaska, short-eared owls are permanent residents of the Midwest and Northwest, while wintering in the southern U.S through Mexico. They are endangered in New York and other northeastern states with reforestation and the decline of non-agricultural, open habitat suitable for supporting prey. Short-eared owls nest on the ground in unmowed grassy areas with shallow dense vegetation cover, and roost there, on fence posts, saplings, or natural rises, scanning for prey.

Territory sizes vary widely, from 40 to 350 acres, probably based on prey density and the number of owls. Prey numbers, such as voles, may be cyclic, which not only affects the number of owls supported by the availability of prey, but may result in territory shifting as owls try to locate the areas with the most prey. During the breeding season, clutch size may be affected by the number of potential prey available. In the nonbreeding season, short eared owls may roost communally, flying off to respective territories to hunt.

short-eared owl

Photo by Anne Fraser

A medium-sized, round-headed owl with greatly reduced ear tufts, short eared owls are from 13 to 17 inches long, weighing in between 11 and 18 ounces, and as with other owls, females are slightly larger than males. Short eared owls have a wingspan of about 42 inches, making them stubby owls whose flight appears erratic and almost comical. The most diurnal of northeastern owls, short-eared owls are often seen at dawn and dusk, swooping over each other, emitting sharp yip like cries, and flying off to hunt, gliding a few feet off the ground, sometimes hovering, pouncing or diving at prey. Day hunting increases during breeding season when more prey is required to raise the brood.

Short-eared owls don’t make a great deal of noise, but their repertoire, especially around the nest area, includes hoots, barks, scream-growls, hisses and whines. The male makes a hoo-hoo-hoo territorial call, but the “hoos” are rapid, muffled and regular, not broken up as in the call of a great horned owl. As with other owls, short eared owls snap their beaks sharply and loudly in defensive mode.

Their wide facial disk features bright yellow eyes, with whitish to grayish bristle feathers between the eyes and surrounding the dark cere and beak. The whitish ring marking the outer edge of the facial disk surrounds stiff, radiating tawny, brownish streaks over dark feathers, hence the species designation, asio flammeus. The under sides are whitish on males and tawny on females, each streaked with brown, while the back and tops of the wings are brownish blotched with white. In flight, dark streaks mark the underside of the wings at wrist and wing tips. Male underwings are whitish, females more buff. Tarsi and toes are tawny to whitish feathered, while talons are light grey with darkening tips. Juveniles tend to be darker colored overall.

The facial disk acts as a sound receptor, directing sounds to the ears, which are behind the eyes. The “ears” of great horned, long-eared and short-eared owls are display feathers, which may reflect mood, but have nothing to do with hearing. Since owls’ eyes are fixed in position within the eye socket, and can not swivel, triangulation of sound source with each ear providing a slightly different sound direction, results in the owl generally staring at the location the prey must be, whether the prey is visible or not.

The contrast between the broad wings and the short body gives the owl an odd, flapping boomerang-like shape during flight, with the deep, slow motion wavering suggesting the erratic flight of a large moth. The lack of elegant flight aside, short eared owls have very high success rates when diving on prey from perches or while flying, often exceeding twenty percent, while most hawks have success rates of only about ten percent. During courtship and territory defense, particularly when young are in the nest, the owls may circle above female prospects or intruders in exaggerated flight, with the wings extending high above the back, and the wing tips audibly clapping beneath the owl. When perching, the wings extend beyond the tail.

short-eared owl

Photo by Deb MacKenzie

Preying mainly on small mammals like voles, mice and shrews in dry, open habitats, when hunting in freshwater bogs or marshes, short eared owls will go after small birds, such as meadowlarks and blackbirds, and small gulls and terns along coastal areas.

Courtship displays are elaborate and noisy, with males rising with vigorous wing flaps from 600 to 1,200 feet, clapping their wings together, hovering and gliding down, then repeating, sometimes singing, and sometimes joined by females, who may lock talons and tumble with the males, as red-tailed hawks do.

Females create simple nests by scraping the ground and spreading tufts of grass, lining them with breast feathers. Clutch sizes range from four to fourteen eggs, the latter in times of high prey density. The eggs are laid sequentially, every other day, and there’s an advantage in being born earlier as the chick will be larger, and more apt to monopolize food. Unfortunately, ground nesting results in high degrees of mortality, with nests often raided by skunks, fox and coyotes, and a replacement clutch may be laid. Clutch sizes increase the further north nesting takes place, and In the southern breeding range, two clutches are often raised in a single season. Females do most of the early incubation, while males bring food to the nest. Young often leave the nest when only twelve days old and fledge when four weeks old.

Short-eared owls face competition from northern harriers, which often steal the food which the short-eared carries in the talons, as opposed to the more normal carrying with the beak practiced by other owls. Short-eareds are often preyed upon by larger raptors, such as Bald Eagle, Red-tailed Hawk, Northern Goshawk, Gyrfalcon, and Snowy Owl. Gulls, ravens, jaegers and crows may steal eggs and grab small chicks. Short eared owls can live up to about thirteen years in the wild, but with the constant dangers they face, a shorter life is the norm.

The conversion of open habitat to housing, agriculture and areas that are routinely mowed has taken a large toll on short eared owls and other grassland birds, such as snowy owls, northern harriers and kestrels, along with bobolinks, meadowlarks, sand pipers and hundreds of other birds, as well as insects, the base of the food chain, and pollinators like bees and butterflies, with estimates that we’ve lost 700 million grassland birds since the seventies. Grasslands are the fastest disappearing habitats in North America. Grasses filter carbon out of the air, storing it in soil and roots which survive fire, making grasslands more effective carbon sinks than forests. An important organization for the preservation of grasslands is the Grassland Bird Trust.

short eared owl

Pastel by Wendy Hall

 

Related Stories


Steve Hall

Steve and Wendy Hall run the Adirondack Wildlife Refuge and Rehab Center in Wilmington. They've been rehabbing and releasing wild animals for over 45 years, specialize in predators, keep wolves as the cornerstone of their educational program, and have lived in the Adirondacks for the past 20 years. The Adirondack Wildlife Refuge became a non-profit about 10 years ago.

Visit www.AdirondackWildlife.org to learn more.




One Response

  1. Boreas says:

    Great article Steve! I used to like to watch them in winter on some farm fields close to Lake Ontario. That time of the year I could usually only hear their barks.

Leave a Reply

Leave a Reply

Your email address will not be published. Required fields are marked *