The Northern Hawk Owl is unlike any other owl in British Columbia and is more likely to be mistaken for a hawk than for an owl. Its behaviour, structure, and plumage are so distinctive, however, that any confusion would likely be only momentary.
| Usually silent during the winter. During the breeding season, the male gives a prolonged (up to 12-14 seconds in length), trilling, rolling, whistled ululululululululululululu or popopopopopopopopopo that is sometimes broken into short, repeated phrases that are given at ~2 second intervals: tu-wita-wit, tiwita-tu-wita, wita, wita,…. The song is reminiscent of that of the Boreal Owl but is higher, sharper, and longer. Both sexes also give a variety of harsh, screeching alarm calls during the breeding season such as a rapid , shrill, chirping kee-kee-kee-kee-kee, a raspy, two-parted screeeee-yip, and a sharp, trilling kiiiiiiiirrrl. Both the female and juvenile give a weak, screeching tschooolP. Source: Duncan and Duncan (1998); Sibley (2000) |
Courtship
Courtship behaviour begins in late winter or early spring, during which the male advertises his presence through a variety of vocal and behavioural means. The male often sings or utters other advertising calls from an elevated perch (rarely from flight) within his territory, exposing the contrasting black and white pattern on the throat. The male often sings at night during the breeding season which is unlike its normally diurnal habits at other times of the year. The male also engages in “display flights”, during which he glides in circles at heights of up to 15 m on outstretched wings with his head raised, calling intermittently and subsequently returning to a primary perch. Once a female has been attracted to the territory, the pair engage in “dueting” as well as several physical displays such as “billing” and touching foreheads. Courtship-feeding and food-caching activities generally precede copulation. This species is usually monogamous during the breeding season.
Nest
Both sexes participate in selection of nesting sites. The nest is usually placed in a shallow hollow at or near the top of a large, dead, broken-top snag, although some nests are located in other microsites such as in a hollow in a burned-out stump, in a large abandoned woodpecker hole, or in the abandoned stick nest of a raptor or corvid. Birds in Scandinavia will sometimes use nest boxes if they are available, and North American birds would likely do the same. Most nests are located at heights 2.5-18 m from the ground, although some nests have been found that are <2 m in height. The nesting hollow is lined (up to 5 cm thick) with decomposed sapwood, feathers, fur from prey animals, and accumulated and matted pellets.
Eggs
A clutch of (3) 5-7 (13) eggs is laid in late April or May and is incubated for 25-30 days before hatching. This species is generally single-brooded, but may produce two clutches in years with a high abundance of prey on the breeding grounds. The eggs are smooth, slightly glossy, and unmarked white or off-white (sometimes with a faint yellowish tinge). Only the female incubates the eggs, although she is tended by the male (fed, etc.) throughout the incubation process. Eggs may be present in B.C. as late as June (possibly later for replacement clutches). This species vigorously defends the nest from predators and other intruders throughout the breeding season.
Young
The young are altricial at hatching, with short, dense, white or yellowish-white (sometimes grayish) down, and are tended by both parents. Beginning at 2-3 weeks of age, the nestlings acquire a second downy coat (‘mesoptile down’) as well as adult-like tail and flight feathers; this is the plumage that the young hold when they fledge from the nest at ~23-27 days of age. Young in this ‘mesoptile’ plumage are fluffy and overall grayish, with a relatively poorly-defined, blackish or dark grey facial disc, a whitish throat, faint grey barring on the underparts, and some suggestion of pale spots on the darker brownish-grey upperparts. The young are unable to fly upon leaving the nest, but clamber, jump, and climb among surrounding limbs and branches for the first several days after fledging, during which time they are fed by the parents. The young become fully independent from the parents at 10-12 weeks of age. Nestlings and dependent young are present in B.C. from late May to mid-August.
Source: Campbell et al. (1990b); Baicich and Harrison (1997); Duncan and Duncan (1998); Sibley (2000)
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Unlike most other owls, the Northern Hawk Owl forages primarily during daylight hours and tends to avoid hunting during the night except during winter in the far north where daylight hours are extremely brief. It feeds on a wide variety of small mammals such as voles, mice, rats, shrews, hares, squirrels, and weasels throughout the year, supplementing this diet with small to medium-sized birds such as ptarmigan, grouse, pigeons, and passerines during the winter when they are available. Voles are particularly important in the diet during the breeding season, and their abundance in any given year usually determines the success of Northern Hawk Owls breeding in an area. It rarely consumes carrion.
The Northern Hawk Owl detects its prey by scanning an area (usually a relatively open area) from an elevated perch such as a dead snag, telephone pole, transmission tower, or isolated tree. Once a potential prey item is detected, the Northern Hawk Owl either pounces on the prey below the perch or, if prey is further away, leaves its perch and engages in a low, fast flight with several bursts of quick flapping interspersed with glides. When returning to a perch, this species characteristically flies low and then abruptly swoops up to an elevated position. It typically captures prey on the ground or the surface of the snow, but occasionally engages in “snow-plunging” behaviour when targeting prey that is beneath the surface of the snow.
Source: Duncan and Duncan (1998)
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