Subspecies of Great Horned Owl in Ontario

by Ron Pittaway

Snyder's Great Horned Owl (scalariventris) on Manitoulin Island on 8 April 2006. Digiscoped from public road.


Revised January 2014. First published in Ontario Birds 11(2):64-69, August 1993.



The Great Horned Owl (Bubo virginianus) is found throughout most of Ontario, north almost to Hudson Bay (James 1991). Its deep bass hooting, whoo, hoo-hoo, whooo, whooo is a familiar night sound.

During the day, it often roosts in a secluded, thick evergreen and most of the time would go undetected but for the keen eyesight of its tormentor, the American Crow (Corvus brachyrhynchos). A flock of crows, cawing loudly, often betrays the presence of a roosting Great Horned Owl.

Getting a good look at resident birds in southern Ontario is generally difficult because they are usually wary of humans. However, the northern subspecies of the Great Horned Owl that wander to southern Ontario in winter are often less wary and more easily observed. Speirs (1985) noted that the periodic movements of northern Great Horned Owls into southern Ontario are associated with population fluctuations in the Snowshoe Hare (Lepus americanus). However, some (particularly young) may move south every winter (Houston 1978)

In this note, I discuss the occurrence and identification of the subspecies of the Great Horned Owl in Ontario. In addition, this is the first time that a description and photograph appear in the birding literature of the distinctive northern Ontario subspecies B. v. scalariventris (Snyder 1961). See Figure 1.


Figure 1. Four subspecies of the Great Horned Owl: From left to right are Labrador Bubo v. heterocnemis, Nominate B. v. virginianus, Snyder's B. v. scalariventris (type specimen) and Arctic B. v. subarcticus in the Royal Ontario Museum in Toronto on 21 January 2014.



Geographical variation is pronounced in the Great Horned Owl. Here I follow the treatment of James (1991) who lists four subspecies in Ontario: the rufous nominate subspecies B. v. virginianus of southern Ontario; the grayish subspecies B. v. scalariventris of most of northern Ontario; the whitish subspecies B. v.subarcticus of extreme Western Ontario; and the blackish Labrador subspecies B. v. heterocnemis which wanders to southern Ontario in winter.

James (1991) follows Snyder (1961) in treating B. v. scalariventris as a separate subspecies, distinct from B. v. subarcticus. In April 1993, I examined the large series of scalariventris in the Royal Ontario Museum. I believe that scalariveniris would be widely accepted as a subspecies today if Snyder (1961) had published his description in the more widely available Auk, and before the American Ornithologists' Union (1957) last revised its list of subspecies - now much in need of revision.

In the A.O.U Check-list (1957), B. v. subarcticus is listed as B. v. wapacuthu. However, the original description of wapacuthu is confusing and cannot with certainty be associated with either the Great Horned Owl or Snowy Owl (Bubo scandiacus) so the name wapacuthu has been discarded (Manning 1952, Todd 1963, Browning and Banks 1990, Dickerman 1991a). 


In addition, Godfrey (1966, 1986) noted that the large series of pale Great Horned Owls in the Canadian Museum of Nature from the southern parts of the Prairie Provinces referred to B. v. occidentalis in the A.O.U. Check-list (1957) "is not separable from subarcticus from farther north". Dickerman (1991b) also concluded that occidentalis should be synonymous with subarcticus. See the comments on subspecies on page 310 in Godfrey (1986) and pages 48, 91 and 92 in James (1991).



The sexes of the Great Horned Owl are similar in appearance, except that females average larger than males. First year birds and adults are similar in coloration. “The downy young moult directly into the colors of the adults” (Taverner 1942).


"Nominate" Great Horned Owl (B. v. virginianus)

The nominate subspecies breeds in southern Ontario (James 1991). It is usually a permanent resident being less prone to wander than the northern subspecies.

It is distinguished from the northern subspecies by its "medium dark coloration with distinctive amount of redness in the plumage" (Godfrey 1986). Some are quite rufous as shown in Figure 1. As well, the black rimmed facial discs are usually a clear rusty colour (Taverner 1942). A typical individual of this southern subspecies is illustrated by John Crosby on Plate 42 in The Birds of Canada (Godfrey 1986).


Figure 2. Nominate Great Horned Owl (virginianus) at Thickson's Woods, Ontario, 20 May 2014.

"Snyder's" Great Horned Owl (B. v. scalariventris)

L.L. Snyder (1961) of the Royal Ontario Museum described the population of pale Great Horned Owls breeding in most of northern Ontario (except extreme western parts) as distinct from B. v. subarcticus, and named it B. v. scalariventris, which means scaly below. See Figure 1. Taverner (1942) was aware of this form, stating that it was “too dark for subarcticus, too white for any other race ... with little or no red of virginianus.” He regarded it as an intergrade population of subarcticus x heterocnemis. However, the large and uniform series of scalariventris in the Royal Ontario Museum from across 800 km of northern Ontario strongly supports its recognition as a separate subspecies (Snyder 1961). Consequently, James (1991) accepted scalariventris as a subspecies.

Snyder's Great Horned Owl breeds in northern Ontario from near the Manitoba border eastward to the Quebec border (and probably beyond), south to approximately Thunder Bay, Sault Ste. Marie and North Bay, where it intergrades with nominate virginianus (Snyder 1961, James 1991). In winter it wanders to southern Ontario. Most reports of pale (gray) Great Horned Owls in southern Ontario are referable to scalariventris.

Classic individuals of scalariventris (Figure 3) are distinguished from nominate virginianus by their distinctive gray coloration and general absence of rufous in the plumage. The facial discs are usually a pale gray, sometimes with a tinge of rufous. From the more whitish subarcticus, Snyder's is told by its darker coloration and broader, more regular and darker bars ventrally. In broad terms, scalariventris is more coldly grey with bolder bars below (Snyder 1961).


Figure 3. Snyder`s Great Horned Owl (scalariventris) in Toronto on 14 December 2008.

“Arctic” Great Horned Owl (B. v. subarcticus)


The Arctic subspecies breeds east of the Rocky Mountains, across the boreal forest and prairies to northern Ontario (Godfrey 1986). However, Snyder (1961) considered most of the northern Ontario population to be distinct from subarcticus and designated it as a separate subspecies, scalariventris. See Figure 3 and previous account of that subspecies. James (1991) stated that subarcticus breeds along the western fringe of the province where it intergrades with scalariventris. The Arctic subspecies (subarcticus) wanders elsewhere throughout the province (Taverner 1942), including specimens from near Algonquin Park (Tozer 2012) and Toronto, but it is very much rarer in southern Ontario than the Snyder's subspecies (scalariventris).

Classic examples of subarcticus as in Figure 1 are much more extensively white than scalariventris, “with more vague and sparse dark markings below” (Snyder 1961). The facial discs are “white to light ashy, rarely with a tinge of rufous” (Taverner 1942). Illustrations of the Arctic subspecies appear on page 239 of the National Geographic Guide (Dunn and Alderfer 2011), on Plate 32 in Birds of Canada (Taverner 1937), and on page 232 of Peterson’s Field Guide to the Birds of North America (2008). See Figure 4.

Occasionally a very whitish Great Horned Owl as in Figure 4 is sighted, almost as white as a dark Snowy Owl. Such birds are safely called subarcticus. However, keep in mind that most pale birds seen in Ontario are referable to scalariventris.


Figure 4. Arctic Great Horned Owl (subarcticus) by Allan Brooks in the Birds of Canada (Taverner 1937).

“Labrador” Great Horned Owl (B. v. heterocnemis)


The dark Labrador subspecies breeds in Newfoundland and Labrador south to central Quebec (Godfrey 1986). In winter heterocnemis wanders to southern Ontario (James 1991). Taverner (1942) listed specimens from Ottawa, Peterborough County, Peel Region, Toronto and St. Thomas. I saw a Labrador Great Horned Owl at Aylmer, Quebec, near Ottawa one winter when I was a teenager. It was tame (unlike most of the local birds) and allowed me to observe it closely. I identified it from the description in the subspecies section of the old Peterson's Field Guide (Peterson 1947) which is still a useful reference on subspecies.

The Labrador subspecies differs from the nominate subspecies by its much darker (sootier) coloration and heavier barring below. On classic individuals, “the barring often obliterates the white markings, giving a black breasted appearance” (Peterson 1947). In addition, the facial discs are usually a dark brownish-gray instead of a clear rusty as in the nominate subspecies.


Figure 5. Labrador Great Horned Owl (heterocnemis) by Roger Tory Peterson in The Birds of Newfoundland (Peters and Burleigh 1951).


Four subspecies of the Great Horned Owl are found in Ontario. Although intergrades occur, typical individuals of these subspecies are identifiable in the field. The type specimen of “Snyder'ssubspecies B. v. scalariveniris is shown and described here in the birding literature for the first time. This cold gray subspecies accounts for most of the reports of pale Great Horned Owls seen in Ontario.


Ron Pittaway holds the type specimen of Snyder`s Great Horned Owl (Bubo virginianus scalariventris) collected in Elsas, Algoma District, Ontario, 26 February 1948. Jean Iron and I visited the Royal Ontario Museum on 21 January 2014 to check Great Horned Owl specimens and revise my original article published in August 1993 in Ontario Birds 11(2):64-69.



I thank Bill Crins, the late Earl Godfrey, Michel Gosselin of the Canadian Museum of Nature, Phill Holder, Ross James, Mike King, Ron Tozer and Mike Turner for much valuable advice in the preparation of this note. Ross James, Jim Dick and Mark Peck kindly allowed me and Jean to examine skins in the Royal Ontario Museum. Jean Iron's colour photographs greatly enhance this revised version.


Literature Cited

American Ornithologists' Union. 1957. Check- list of North American Birds, 5th edition. American Ornithologists' Union, Washington, D.C.

Bent, A.C. 1938. Life Histories of North American Birds of Prey. Part 2. United States National Museum Bulletin 170. Washington, D.C.

Browning, M.R. and R.E. Banks. 1990. The identification of Pennant's “Wapacuthu Owl” and the subspecies name for the population of Bubo virginianus from the western Hudson Bay. Journal of Raptor Research 24: 80-83.

Dickerman, R. W. 1991a. Specimens of the subarctic nesting populations of Great Horned Owls from New York, New Jersey and Connecticut. Kingbird 41: 15157.

Dickerman, R. W. 1991b. On the validity of Bubo virginianus occidentalis Stone. Auk 108: 964-965.

Dunn, J.L. and J. Alderfer 2011. Field Guide to the Birds of North America. National Geographic Society, Washington, D.C.

Godfrey, W.E. 1966. The Birds of Canada. National Museum of Canada Bulletin 203.  

Godfrey, W.E. 1986. The Birds of Canada.Second Edition. National Museum of Canada, Ottawa.

Houston, C.S. 1978. Recoveries of Saskatchewan-banded Great Horned Owls. Canadian Field-Naturalist 92: 61·62.

James, R.D. 1991. Annotated Checklist of the Birds of Ontario. Second Edition. Life Sciences Miscellaneous Publications, Royal Ontario Museum, Toronto.

Manning, T.H. 1952. Birds of the west James Bay and southern Hudson Bay coast. National Museum of Canada Bulletin 125: 1·114.

Peters, H.S. and T.D. Burleigh, 1951. The Birds of Newfoundland. Department of Natural Resources, St. John's.

Peterson, R. T. 1947. A Field Guide to the Birds. Houghton Mifflin Company, Boston.

Peterson, R.T. 2008. Field Guide to the Birds of North America. Houghton Mifflin Company, Boston.

Snyder, L.L. 1961. On an unnamed population of the Great Horned Owl. Life Sciences Division, Royal Ontario Museum, Contribution No. 54: 1-7.

Speirs, J.M. 1985. Birds of Ontario. Volume 2. Natural Heritage/Natural History Press, Toronto.

Taverner, P.A. 1937. Birds of Canada. The National Museum of Canada, Ottawa.

Taverner, P.A. 1942. Canadian races of the Great Horned Owls. Auk 59: 234-245.

Todd, W.E.C. 1963. Birds of the Labrador Peninsula and Adjacent Areas. Carnegie Museum and University of Toronto Press.

Tozer, R. 2012. Birds of Algonquin Park. The Friends of Algonquin Park, Whitney, Ontario.


Ron Pittaway, 9 Lichen Place, Toronto ON  M3A 1X3 or email:

Great Horned Owl in Toronto on 14 December 2008