Spotted owl (Caurina subspecies) COSEWIC assessment and status report: chapter 4

Distribution

Global range

The Spotted Owl occurs in western North America from southwestern British Columbia to Mexico. The Northern Spotted Owl subspecies occurs from the southwest mainland of British Columbia through western Washington, western Oregon and the coast ranges of California to San Francisco Bay (Figure 1). The species occurs from the Pacific Ocean east to the eastern slopes of the Cascade Mountain Range, and can be found from sea level up to 2,250 m in elevation in southern portions (USDI 1992) and up to 1,370 m in northern portions of its range. Although the current range is similar to the historic range, the distribution and abundance of Northern Spotted Owls within this range has been significantly altered (USDI 1992; USFWS 2007).

Figure 1. Distribution of the Spotted Owl in North America. (Chutter et al. 2004; adapted from Gutiérrez et al. 1995).

Figure 1. Distribution of the Spotted Owl in North America.

Canadian range

In Canada, the range of the Northern Spotted Owl is restricted to British Columbia (Godfrey 1986; Campbell et al. 1990). The entire Canadian population of the Northern Spotted Owl occurs in about 32,800 km² in the southwest mainland of British Columbia (Harestad et al. 2004), from the international border north 200 km to Carpenter Lake, west to Howe Sound, and east to near Lillooet and eastern Manning Park, just beyond the height of land of the Cascade Mountain Range.

Two historic records (Laing 1942) of Northern Spotted Owls as far northwest as Bute Inlet, on the mainland coast, were discounted because specimens were not collected and the observations were only audible detections (Dunbar and Blackburn 1994). Between 1985 and 2005, Northern Spotted Owls had been observed at 72 different locations in British Columbia (Chutter et al. 2007).

Canadian Northern Spotted Owl populations are continuous with populations in Washington; however, this linkage has been severely reduced by forestry, urban, and agricultural uses that has limited the connectivity to the foothills of the Cascade Mountain range. Large gaps in distribution occur within the Canadian range (Harestad et al. 2004). Northern Spotted Owls formerly occurred in much of the lower Fraser River valley but no longer do so because suitable habitat has been largely replaced by human development. It is likely that this owl formerly nested in the Greater Vancouver Regional District watersheds but is apparently absent now. Northern Spotted Owls are also absent from much of the Squamish River/Whistler area (Blackburn and Godwin 2003). Other portions of its range have concentrations of records: Pemberton to Lillooet area and Chilliwack Lake north through the Fraser Canyon area (Harestad et al. 2004).

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