J. F. Gmelin, 1788,
Has been considered to belong to the B. bubo species-group (see that species, below). Formerly included B. magellanicus as a race, but DNA, voice and morphology found to differ. N populations lagophonus and heterocnemis possibly not separable from saturatus, and perhaps better merged with latter. Boundaries of races often obscure, and problem further complicated by birds of intermediate appearance; pacificus and pallescens intergrade in California. Numerous geographical races named, many poorly differentiated, or apparently result of individual variation, or of wandering individuals from other parts of range: forms described from C Canada (scalariventris), Venezuela (scotinus), E Colombia (elutus) and C Colombia (colombianus) considered not acceptable; also, name occidentalis, used for birds from Rocky Mts of WC Canada to WC USA, now synonymized with subarcticus; older name wapacuthu formerly applied to populations of W & C Canada and N USA (limits uncertain), but validity questioned as it cannot be certainly associated with present species#R. Fifteen races tentatively recognized.
Introduced (nominate race) to S Marquesas Is (Hiva Oa), in S Pacific.
45–60 cm#R; male 985–1585 g#R, female 1417–2503 g#R; wingspan 91–152 cm#R. Large, powerful owl, ear tufts large and erect, plumage distinctly greyish to grey-brown or more buffy-brown, mottled and vermiculated above, barred below, with white throat; wings long and broad, pointed towards tip. Nominate virginianus with f acial disc dull tawny-buff to distinct orange-buff, whitening around eyes, black rim broken by grey-buff flecking at lower edge; crown and hindneck dark; upperparts brownish with rufous tinge, mottled dark sooty-brown, broken by transverse mottlings of tawny grey-white, wing coverts and scapulars mottled with buff- to grey-white; flight-feathers and tail distinctly and regularly barred dark slate-grey to brown-black; underparts usually slightly sooty grey-buff with bold and somewhat erratic barring of brown-black, bars more pronounced on flanks and lower belly, and broad area of pure white on throat narrowing to upper breast; tarsus and feet fully feathered tawny to buff, often with black barring; irides brilliant yellow; cere and bill grey; talons brownish yellow-horn, darkening to black at tip. Juvenile somewhat more ruddy brown-orange, bars farther apart, white throat patch duller and much less extensive, ear tufts shorter. Races vary in size, tending to become smaller from NE to SW, small in S of range, and tend to be darker in more humid regions: lagophonus rich tawny-grey, feet barred; saturatus dark brownish-grey, heavily barred below; pacificus fairly dark, suffused tawny, less heavily barred, elachistus similar but much smaller; subarcticus pale whitish-buff, variably barred below, feet more or less plain; pallescens small, pale, barring above and below relatively indistinct, feet whitish; heterocnemis dark grey-brown, heavily barred below, feet mottled; mayensis small, short-winged, rather pale, mesembrinus similar but larger and darker; nigrescens dark, heavily blotched; nacurutu browner, longer-billed.
Wide range of wooded habitats, mainly open, from deciduous to mixed and coniferous forest, second growth, swamp-forest, farmland with patches of woodland, larger parks in towns, and mangroves; generally with open fields adjacent or nearby; also roadsides; locally, desert and rocky areas with some woodland; avoids dense rainforest and cloudforest#R. Foraging areas typically relatively open, but also include some woodland or groves, or at least scattered trees for perching. Sea-level to c. 4000 m; in Andes to 4400 m#R.
Food and feeding
Very diverse range of prey includes small mammals, birds, amphibians, reptiles, fish, and insects and other invertebrates; sometimes takes carrion when weather conditions severe. Mammals generally most important, often c. 90% of diet; lagomorphs, mice and waterbirds major food in many areas. Birds average c. 10% of food, range in size from small passerines up to geese and Great Blue Heron (Ardea herodias), and include other raptors; also nestlings. In N Canada, snowshoe hares (Lepus) represent 83–86% to 13% of diet, depending on hare density; alternative prey mainly voles (Microtus), ground squirrels (Spermophilus) and birds. In one study in Argentina, mammals also majority of prey (69%) and arthropods an alternative, with beetles (21%) and scorpionids (5%) most common, and birds, reptiles and amphibians poorly represented; in another study from that country, mammals constituted 89% of diet, and birds (6%) and amphibians (5%) comprised the remainder#R. In S Brazil, mammals (34% by number) and birds (38%) made up most of diet, followed by fish (<1%), amphibians (8%), reptiles (2%), and insects (18%)#R. Forages mostly at dusk and during night, rarely in daylight, usually in fairly open areas offering wide view, e.g. forest edge or clearings, or along wetland margins, also over open water. Hunts from perch, dropping steeply to ground and levelling off just above it; also flaps and glides over places where prey likely to be; occasionally forages by walking on ground, and reported to wade into water. Prey seized in talons; smaller items swallowed whole, larger ones dismembered first.
Season approximately Dec–Jul#R, with late nests being second attempts after initial failures; female observed to incubate in sub-zero temperatures, with 30-cm snow cover on ground. Normally uses old nest of other large bird such as corvid or raptor, in N often Red-tailed Hawk (Buteo jamaicensis), high up in main fork of tree, sometimes in heronry; also hollow at broken-off snag, or human-made platform, or depression on cliff ledge or ground, or cave entrance (in Ohio study, 533 in hawk nest, 527 in snag, 125 on man-made platform); rarely on building, once on beam beneath railway bridge; no material added; may use same nest 2–3 years in succession. In courtship display, both sexes hoot while bowing and while simultaneously drooping wings and cocking tail. Clutch size 1–3 eggs, usually 2, up to 6 in food-rich years, laying interval averaging 72 hours; egg size ranges from 50–60 mm × 43–50 mm#R; clutch often replaced if first destroyed; incubation c. 28–30 days, sometimes up to 37, by female, fed regularly through night by male; two known cases of prolonged incubation of addled eggs lasting c. 75 days each#R. Chick with white down, pink apteria and feet; young brooded by female until c. 2 weeks, climb on nearby branches at 6–7 weeks, fly well from c. 10 weeks; subsequent parental care up to 5 months. In USA (Ohio), mean annual productivity 1·7 young per successful nest, 1·3 young per breeding attempt, 15% of breeding pairs failed, 38% of pairs did not attempt to nest, average 0·80 young per occupied territory; in one study, mortality highest during post-fledging period, with 13 deaths due to high levels of parasitism, 11 to predation (or with signs of scavenging), 9 to disease, starvation or cause unknown, 6 roadkills; survival in first 2 years of life low, but higher during peaks in hare cycle. First breeding probably at 2 years, sometimes 1. Maximum recorded longevity more than 28 years.
Mostly resident, but some movement by N birds. In Canada (Saskatchewan), substantial SE movement in Nov–Dec in some years, with 17 of 35 recoveries occurring beyond 250 km from point of ringing; evidently, moves farther S during years of decreased reproductive success and, presumably, reduced food supplies. Typically roosts singly or in pairs, but one known case of communal roosting in which 6 birds found together in small grove of deciduous trees adjacent to farm lot#R.
Status and conservation
Not globally threatened (Least Concern). CITES II. Widespread, but densities low; few population estimates; Partners in Flight estimates a global population of 5.3 million individuals, 43% of them in the USA and Canada#R. Commonest owl in S Quebec; in optimum habitat in North America, densities of 0·1–0·2 pairs/km²; in S of range rather scarce generally, but said to be quite common in S Mato Grosso in Brazil. Population levels closely associated with prey availability: when prey scarce, breeding density much lower and mortality sometimes very high; in periods of high prey abundance, higher survival leads to greater intraspecific (and interspecific) competition. Heavily persecuted in first half of 20th century, but totally protected in North America since 1970; probably reasonably stable now within limits of annual fluctuations. In Canada, however, presence of individuals referred to as “non-territorial floaters” (a “shadow” population that lives a secretive life, moves more often than territorial birds, and ranges broadly over territories of latter) can delay detection of population declines in traditional censuses. Roadkills, pesticides, collisions with man-made objects, electrocution from power lines, and indiscriminate and illegal shooting are major causes of mortality locally in USA (Utah); these factors likely to be applicable elsewhere in range. Habitat disruption apparently less of a threat, and range and numbers noted to have expanded in Pacific Northwest following opening-up of new areas by logging activities. Species’ continuing survival almost throughout range aided perhaps by its highly secretive nature and its high capacity for ecological adaptability; adapts well to changes in habitat, so long as suitable nest-sites and roost-sites remain.
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