Читать книгу A Parliament of Owls - David Tipling - Страница 17

STRIX VARIA

APPEARANCE

Medium-large owl with wide, rounded head, dark eyes, yellow bill, and no ear tufts; pale gray-brown facial disk indented at top and bottom; plumage largely grayish-brown; upper parts barred with white and spotted on wing coverts; pale under parts densely barred on upper breast and more finely streaked below; flight feathers heavily barred. size

length 19 – 22 in. (48 – 56 cm)

weight 1.1 – 2.3 lb (500 – 1,050 g)

wingspan 42 – 44 in. (107 – 111 cm)

females larger than males.

DISTRIBUTION

Eastern North America, from southern Canada to Florida and south to southern Mexico; range expanding in northwestern United States; northerly populations make irregular southward migrations.

STATUS

Least Concern

IT IS NOT OFTEN THAT THE GOOD FORTUNES of one owl species spell misfortune for another. However, the advance of the Barred Owl in the northwestern United States—following a trail blazed by the loggers—is giving conservationists a headache, because it may be at the expense of the much rarer Spotted Owl. The two species belong to the Strix genus, but the Barred Owl is larger and more aggressive. In the past, the Spotted Owl was secure in the large, untouched tracts of forest in the northwest, while the Barred Owl flourished further east. However, the logging and fragmentation of these northwestern forests have produced a forest structure better suited to the Barred Owl. The more common species has been quick to accept the invitation, ousting its cousin in the process.

Four subspecies of the Barred Owl are recognized, of which the nominate race, S. v. varia, is the largest and most northerly, occurring from southeast Alaska to North Carolina. This bird frequents moist, dark, mature forests, typically in wooded swamps or woodland fringing lakes. It thrives in large parks with old trees and will take to old-growth forest where this has been opened up by logging. It is a nocturnal species that hides away by day in dense foliage, usually close to a tree trunk. Here, it can escape the attentions of the irate songbirds that are often drawn to mob it. After dark, however, this owl need fear no such persecution. Like most Strix species, it is largely a sit-and-wait hunter, watching and listening from its high perch, then swooping down to grab the prize. Prey comprises small rodents, notably meadow voles (Microtus pennsylvanicus), but it may take larger mammals, including possums and weasels. It hunts birds, such as jays and pigeons, by ambushing them in flight as they settle at their roost, while smaller owls, including the Eastern Screech Owl (Megascops asio) and Long-eared Owl, also sometimes fall victim. Among other interesting observations, this species has been seen wading in shallows to capture fish, plucking baby alligators from swamps, and visiting campfires to capture large insects drawn to the light. At peak nesting, it may also hunt by day.

The Barred Owl is easily identified by its territorial call: a resonant “hoo, hoo, too-HOO; hoo hoo too-HOO, ooo” phrase. A male tends to repeat this call in bursts of eight and then fall silent, waiting for a female’s reply. Once the two meet, the male pursues the female, giving a variety of calls and displays, swaying on a branch and sidling up to her with wings raised. This is a very vocal species, and the pair communicates throughout courtship with hoots, yelps, barks, and monkey-like shrieks, cementing their bond with feeding and mutual preening. Unpaired birds may call in fall, but an established pair does not get going until late winter. The pair usually selects an old stick nest from a hawk, crow, or squirrel but may also choose a natural cavity. The female lays two to four eggs and incubates them for twenty-eight to thirty-three days while the male provides food. The parents care for their chicks for four months, longer than most owls.

In captivity, the Barred Owl has been known to live thirty-two years. With an estimated population of 600,000, it is classed as Least Concern. Indeed, its recent range expansion in the northwest is a worry for conservationists, who fear the impact on the Western Screech Owl and rare Spotted Owl. In a contentious initiative of the U.S. Forest Service, considerable numbers of Barred Owls have already been culled.

A pair of Barred Owls inflate their throats as they call in duet.

Prey for this species ranges from small rodents, as here, to mammals as large as opossums.