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Recognizable Forms 64 Recognizable Forms Subspecies of the Great Horned Owl by Ron Pittaway Introduction literature of the distinctive northern The Great Horned Owl (Bubo Ontario subspecies B. v. scalariventris virginianus) is found throughout most (Snyder 1961). See Figure 1. of Ontario, north almost to Hudson Bay IJames 1991). Its deep bass Taxonomy hooting, Whoo, hoo-hoo, whooo, Geographical variation is whooo is a familiar night sound. pronounced in the Great Horned During the day, it often roosts in Owl. Here I follow the treatment of a secluded, thick evergreen and most James (1991) who lists four of the time would go undetected but subspecies (races) in Ontario: the for the keen eyesight of its tormentor, rufous nominate race B. v. virginianus the American Crow (Corvus of southern Ontario; the grayish race brachyrhynchos). A flock of crows, B. v. scalariventris of most of northern cawing loudly, often betrays the Ontario; the whitish race B. v. presence of a roosting Great Horned subarcticus of extreme Western Owl. Ontario; and the blackish Labrador Getting a good look at resident race B. v. heterocnemis which wanders birds in southern Ontario is generally to Ontario in winter. difficult because they are usually James (1991) follows Snyder wary of humans. However, the (1961) in treating B. v. scalariventris as northern forms of the Great Horned a valid subspecies, distinct from B. v. Owl which wander to southern subarcticus. In April 1993, I examined Ontario in winter, are often less wary the large series of scalariventris in the and more easily observed. Speirs Royal Ontario Museum. I believe that (1985) noted that the periodic scalariventris would be widely movements of northern Great Horned accepted as a valid subspecies today Owls into southern Ontario are if Snyder (1961) had published his associated with population description in the more widely fluctuations in the Snowsboe Hare available Auk, and perhaps if the (Lepus americanus). However, some American Ornithologists' Union had (particularly young) may move south updated the 1957 list of subspecies every winter (Houston 1978). (now urgently in need of revision). In this note, I discuss the In the Fifth Edition of the occurrence and identification of the American Ornithologists' Union recognizable forms of the Great Check-list (1957), B. v. subarcticus is Horned Owl in Ontario. In addition, listed as B. v. wapacuthu. However, this is the first time that a description the original description of wapacuthu and photograph appear in the birding is confusing and cannot with ONTARIO BIRDS AUGUST 1993 65 certainty be associated with either the dark coloration with distinctive Great Horned Owl or the Snowy Owl amount of redness in the plumage" (Nyctea scandiaca) so the name (Godfrey 1986). As well, the black­ wapacuthu is invalid and should be rimmed facial discs are usually a discarded "into the waste bin of clear rusty colour (Taverner 1942). synonyms" (Manning 1952, Todd For a typical example of this southern 1963, Browning and Banks 1990, race, see John Crosby's illustration on Dickerman (1991a). Most authors Plate 42 in The Birds of Canada now use subarcticus instead of (Godfrey 1986). wapacuthu. In addition, Godfrey (1966, 1986) "Snyder's"Great Horned Owl noted that the large series of pale Great Horned Owls in the Canadian (B. v. scalariventris) Museum of Nature from the southern L.L. Snyder (1961) of the Royal parts of the prairie provinces referred Ontario Museum described the to B. v. occidentalis in the A.O.D. population of pale Great Horned Check-list (1957) "is not separable Owls breeding in most of northern from subarcticus from farther north". Ontario (except the extreme western Dickerman (1991b) also concluded parts) as distinct from B. v. that occidentalis was not a valid subarcticus, and named it B. v. subspecies and that it should become scalariventris. See Figure 1. Taverner synonymous with subarcticus. (1942) was aware of this form, stating that it was "too dark for subarcticus, See the comments on subspecies too white for any other race ...with on page 310 in Godfrey (1986) and pages 48,91 and 92 in James (1991). little or no red of virginianus' '. He regarded it as an intergrade Plumages population of subarcticus x The sexes of the Great Horned heterocnemis. However, the large and Owl are similar in appearance, except uniform series of scalariventris in the that females on the average are larger Royal Ontario Museum from across than males. First year birds and 800 kilometres of northern Ontario adults are also similar in colouration. strongly supports its recognition as a "The downy young moult directly valid subspecies (Snyder 1961). into the colors of the adults" Consequently, James (1991) also (Taverner 1942). accepted scalariventris as a valid race. Snyder's race breeds in northern "Nominate" Great Horned Owl Ontario from near the Manitoba (B. v. virginianus) border eastward to the Quebec border (and probably beyond), south The widespread nominate to approximately Thunder Bay, Sault subspecies is the breeding form in Ste. Marie and North Bay, where it southern Ontario (James 1991). It is intergrades with nominate virginianus usually a permanent resident being (Snyrer 1961, James 1991). In winter less prone to wandering than the it wanders to southern Ontario. Most northern forms. reports of pale (gray) Great Horned It is distinguished from the other Owls in southern Ontario are Ontario subspecies by its "medium referable to scalariventris. VOLUME 11 NUMBER 2 66 Classic individuals of scalariventris on page 239 of the National are easily distinguished from Geographic Guide (Scott 1987), on nominate virginianus by their Plate 32 in Birds of Canada (Taverner distinctive gray colouration and 1937), and on page 173 of A Field general absence of rufous in the Guide to the Birds (Peterson 1980). plumage. The facial discs are usually Also see Figure 1. a pale gray, sometimes with a tinge of Occasionally a very whitish Great rufous. From the much more whitish Horned Owl (almost as white as a subarcticus, Snyder's race is dark Snowy Owl) is sighted. These distinguished by its darker typical birds are probably safely colouration and "broader, more called subarcticus. However, keep in regular and darker bars ventrally". In mind that most pale (gray) birds seen broad terms, scalariventris is "more in southern Ontario are referable to coldly grey with bolder bars below" Snyder's race, scalariventris. (Snyder 1961). See Figure 1. "Labrador" Great Horned Owl "Arctic" Great Horned Owl (B. v. heterocnemis) (E. v. subarcticus) The dark Labrador race breeds in The Arctic race breeds east of the Newfoundland and Labrador south to Rocky Mountains, across the boreal central Quebec (Godfrey 1986). In forest and prairies to northern winter heterocnemis wanders to Ontario (Godfrey 1986). However, southern Ontario (James 1991). Snyder (1961) considered most of the Taverner (1942) listed specimens northern Ontario population to be from Ottawa, Peterborough County, distinct from subarcticus and Peel Region, Toronto and St. Thomas. designated it as a separate subspecies, I saw a "Labrador" Great Horned scalariventris. (See Figure 1 and Owl at Aylmer, Quebec, near Ottawa previous account of this race.) James one winter when I was a teenager. It (1991) stated that subarcticus breeds was tame (unlike most of the local along the western fringe of the birds) and allowed me to observe it province where it intergrades with closely. I identified it from the scalariventris. The Arctic race wanders description in the subspecies section elsewhere in the province, especially of the old Peterson's Field Guide in winter; for example, Taverner (Peterson 1947) which is still a useful (1942) listed specimens from reference on subspecies! Algonquin Park and Toronto, but it is The Labrador race differs from much rarer in southern Ontario than the nominate race by its much darker Snyder's race. (sootier) colouration and heavier Classic examples of subarcticus barring below. On classic individuals, are much more extensively white "the barring often obliterates the than scalariventris, "with more vague white markings, giving a black­ and sparse dark markings below" breasted appearance" (Peterson (Snyder 1961). The facial discs are 1947). In addition, the facial discs are "white to light ashy, rarely with a usually a dark brownish-gray instead tinge of rufous" (Taverner 1942). of a clear rusty as in the nominate Illustrations of the Arctic race appear race. ONTARIO BIRDS AUGUST 1993 o<: t""' c:: ~ t'j ...... z...... c:: ~ to Figure 1: Three subspecies of the Great Horned Owl: (left to right) Bubo viginianus virginianus, B. v. scalariventris, t'j :;lj and B. v. subarcticus. Photo by Ross James (Royal Ontario Museum). Q) N '"" 68 An illustration by Roger Tory Browning, M.R. and R.C. Banks. 1990. The Peterson of a "Labrador" Great identification of Pennant's "Wapacuthu Owl" Horned Owl can be found on Plate 18 and the subspecies name for the population in The Birds ofNewfoundland (Peters of Bubo virginianus from the western Hudson Bay. journal of Raptor Research 24: 80-83. and Burleigh 1951). The same Dickerman, R. W. 1991a. Specimens of the illustration, but not labelled as the subarctic nesting populations of Great Horned Labrador race, is found on Plate 21 of Owls from New York, New jersey and the more widely available Birds of Connecticut. Kingbird 41: 154-157. Nova Scotia (Tufts 1986). Dickerman, R. W. 1991b. On the validity of Bubo virginianus occidentalis Stone. Summary Auk 108: 964-965. Godfrey, W.E. 1966. The Birds of Canada. Four well-marked forms of the National Museum of Canada Bulletin 203. Great Horned Owl are found in Godfrey, W.E. 1986. The Birds of Canada. Ontario. Although intergrades occur, Second Edition. National Museum of Canada, typical individuals of these forms are Ottawa. distinctive and recognizable in the Houston, C.S.
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