Western screech-owl (Otus kennicottii) COSEWIC assessment and status report: chapter 3
Species Information
Name and classification
The Western Screech-owl (Otus kennicottii) was formerly considered to be conspecific with the Eastern Screech-Owl (Otus asio) (AOU 1957). In 1983, the Western Screech-owl was recognized as a separate species (AOU 1983). It has been referred to as Kennicott’s Screech-Owl, although this is sometimes in reference to the subspecies Otus kennicottii kennicottii only. The French name for the species is Petit-duc des montagnes.
The taxonomy of subspecies of the Western Screech-owl remains complex and uncertain. The American Ornithologists’ Union (AOU 1998) recognizes two broad groups: O. kennicotti (Western Screech-owl) and O. vinaceus (Vinaceous Screech-Owl), which are now considered conspecific because they intergrade and because they have similar vocalizations. Those examining the subspecies taxonomy have divided the Western Screech-owl into numerous and differing numbers of subspecies: Cannings and Angell (2001) nine subspecies; Hekstra (1982) 18 subspecies; Marshall (1967) eight subspecies. Miller and Miller (1951) recognised eight races in the southwestern United States portion of their range, where there appears to be the greatest amount of variation within the species.
Within Canada, there are either two or three subspecies, depending on which authority is used. The British Columbia Conservation Data Centre (BCCDC), until recently followed Hekstra (1982), who recognized three subspecies: Otus kennicottii kennicottii (found in most of coastal BC), O. k. saturatus (primarily southeastern Vancouver Island), and O. k. macfarlanei (southern interior of BC). On the other hand, Cannings and Angell (2001), Godfrey (1986), and now the BCCDC recognize two subspecies only, O. k. kennicottii and O. k. macfarlanei , with O. k. saturatus subsumed under O. k. kennicottii . Similarly, Marshall (1967) considered O. k. kennicottii to occur on the coast and O. k. bendirei (into which he merged O. k. macfarlanei ) as occurring in the Okanagan.
In this status report two subspecies--Otus kennicottii kennicottii and Otus kennicottii macfarlanei--are considered to occur in Canada, following Cannings and Angell (2001) as the most current source.
Nationally significant populations
The two subspecies of Western Screech-owl, O. k. kennicottii and O. k. macfarlanei are considered separately throughout this report. This is because the two populations are uniformly recognized to be two different subspecies, the ranges of the two subspecies are not contiguous with one another and they occur in different ecological zones.
Description
The Western Screech-owl is a small streaked owl, with ‘ear tufts’ and yellow eyes. The length of the adults varies between 19 and 25.5 cm, while the weight ranges between 120 and 305 g (Cannings and Angell 2001). Females are generally larger and heavier than males (Earhart and Johnson 1970, Johnson 1997, Cannings and Angell 2001). Similarly, the more northern subspecies are often larger and heavier than the southern subspecies (Miller and Miller 1951, Johnsgard 1988). Females have the same plumage as the males. The overall coloration of the species is grey-brown, with fine dark vermiculations on the breast overtop an off-white background, and a streaky mottled effect throughout most of the remainder of the plumage. A small percentage of O. k. kennicottii birds are reddish-brown (Johnsgard 1988, Cannings and Angell 2001). O. k. macfarlanei are generally paler than O.k. kennicottii (Bent 1938, Godfrey 1986).
The Eastern Screech-owl looks almost identical to the Western Screech-owl, but in Canada the ranges do not overlap, so confusion is unlikely. Also, one can easily distinguish the species by their vocalizations. The most typical territorial call of the Western Screech-owl is a series of quick hoots on one pitch that gradually speed up throughout the call. The corresponding call of the Eastern Screech-Owl is a descending whinny. Both species also give long trill calls; the Western Screech-owl’s is a double trill, while the Eastern gives a long single trill. The vocalizations of neither species sound like screeches or shrieks despite the common name.
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