Читать книгу A Parliament of Owls - David Tipling - Страница 11

AEGOLIUS FUNEREUS

APPEARANCE

Small, with large head and cat-like face; dark marks above eyes and bumps on facial disk give expression of surprise; coloration varies from reddish-brown to gray; upper parts dark with white spots; under parts pale and streaked; in flight, shows short tail and broad wings.

SIZE

length 8.7 – 10.6 in. (22 – 27 cm)

weight 3.3 – 7.6 oz (93 – 215 g)

wingspan 20 – 24 in. (50 – 62 cm)

female much larger than male

DISTRIBUTION

Northern coniferous belt in Old and New World; in North America, from east to west coast, and down the Rocky Mountains to New Mexico; in Eurasia, from Scandinavia to Pacific coast; isolated populations in central Europe, w including southern France.

STATUS

Least Concern

“SURPRISED” IS A TERM COMMONLY USED to describe the facial expression of this small owl. The dark markings above its bright yellow eyes and the two bumps atop its facial disk convey a certain raised-eyebrows astonishment. You might be surprised, too, if you manage to spot one. This nocturnal bird inhabits deep woods and is very wary of people.

The Boreal Owl—known in Europe as Tengmalm’s Owl, after Swedish naturalist Peter Gustaf Tengmalm—is the size of a starling. It does not have true ear tufts but, when alarmed, compresses its facial disk to produce two bumps. The dark upper parts are boldly spotted in white (hence the Finnish name “pearl owl”) and pale under parts are streaked with arrowheads, providing excellent camouflage at its tree trunk roost. Females are much larger than males, showing the most extreme sexual dimorphism of any North American owl.

The deep boreal forests where this bird lives vary from pure coniferous in the north of its range to pure deciduous further south. In northern regions, the bird is more nomadic, making southward journeys of up to 620 miles (1,000 km) when conditions dictate. Males are less inclined to move than females, preferring to safeguard their breeding territory in readiness for the next year. In southern regions, this bird also inhabits high subalpine forests.

The Boreal Owl operates almost entirely between dusk and dawn, and voles make up the bulk of its diet. Its standard hunting technique is to perch on a low branch and move its head slowly from side to side to pinpoint the movement of a rodent by ear. This species has the most pronounced ear asymmetry of any owl, an indication of the exceptionally powerful hearing with which it finds food in dark forests. Once prey is located, the bird swoops down to secure the prize, sometimes plunging through layers of leaf litter or snow. It may also take other small mammals, including shrews, mice, and moles, and in poor vole years it will more regularly target small birds. Like some other owls, this species may cache food in a tree crevice larder. It has even been observed thawing out frozen prey by crouching on it, as though brooding chicks.

Although hard to see, the Boreal Owl is easily heard; the male’s courtship song is audible for 2 miles (3 km) on a still night. It comprises a series of six to ten “poop” notes, which resemble the call of a hoopoe (Upupa epops) and are repeated with three- to four-second breaks. This song varies between individuals in pitch and speed, so each male in a given area is easily identified. Once a female approaches, the male’s call becomes more stuttering and develops into a long trill as he shows her to a potential nest site. The female’s song is weaker and higher pitched. Both sexes also utter various barks, croaks, and other softer calls. Pair bonding is seasonal, with the male defending a small territory but finding new mates each year. The nest is often an old woodpecker hole, but natural cavities will also do and nest boxes are readily accepted. A female lays three to eight eggs, one day apart, and incubates her clutch for twenty-eight to twenty-nine days, while the male provides food. In good years, a pair may have a second brood.

With an estimated global population of two million, the Boreal Owl is classed as Least Concern. However, numbers are hard to assess and it is declining in some areas. Nesting birds often fall prey to martens, and other predators include the northern goshawk (Accipiter gentilis) and the Tawny Owl. Nevertheless, habitat loss through deforestation is a much greater threat.

A Boreal Owl peers out from its nest hole beneath the ever-changing night sky.

Burrowing Owls are often seen in pairs or family groups near the entrance to their burrows.