Strix occidentalis caurina

Fairly large range (British Columbia to northern California) but relatively few occurrences are of high quality, and population trend is downward, so this owl remains of significant conservation concern; decline is due to past and continuing loss and/or fragmentation of habitat resulting from timber harvest, effects of barred owls, and other factors.

Range extends from southwestern British Columbia (Dunbar et al. 1991) southward through the Coast Ranges and Cascade Range (both west and east sides) of Washington and Oregon to northwestern California north of San Francisco (Marin County) and northwest of the Pit River in northeastern Shasta County (the Pit River boundary between subspecies caurina and occidentalis is based on biogeographic considerations, rather than on adequate taxonomic data from that area) (Thomas et al. 1990). The population on the Olympic Peninsula appears to be reproductively isolated (by nonforested lands of the Puget Trough) from owls in the Cascade Range. The Columbia River may constitute an isolating barrier between the Cascades populations in Washington and Oregon. Population size and density are relatively low at the northern and southern ends of the range.

This subspecies is represented by a large number of occurrences (subpopulations).

In a major range-wide analysis, Lint et al. (2005) concluded that presence of barred owls (Strix varia), weather, past and present harvest of habitat, and wildfire and insect infestations that alter habitat are all possible contributors to declines in northern spotted owl populations. Lint et al. (2005) determined that barred owls, West Nile virus (Flavivirus sp.), and management of owl habitat in high-fire-risk areas are topics for future management consideration.

Habitat continues to be lost or degraded by logging and/or forest fragmentation, but the rate of loss has slowed. A perhaps conservative estimate is that habitat has been reduced by about 60% since 1800; habitat loss (including that due to fragmentation) has been due primarily to logging, but natural disturbances also have played a role (Thomas et al. 1990).

Spotted owls may be threatened by the recent expansion of the range of the barred owl into the Pacific Northwest; barred owls possibly could compete with or displace spotted owls. For example, Kelly et al. (2003) found that occupancy of spotted owl territories in Oregon and Washington declined after barred owls were detected within 0.80 kilometers of the territory center. Between 1974 and 1998, the authors estimated that 706 different barred owl territories were located in Oregon. From 1989-1998, an average of 60 new barred owl territories were located in Oregon each year. USFWS (2007) concluded that the most important threat currently facing the spotted owl is competition from the barred owl. Hybridization between spotted owls and barred owls has been detected but is relatively rare (Thomas et al. 1993, Hamer et al. 1994, Seamans et al. 2004) and has been recorded most often in Oregon.

Based on data from all three spotted owl subspecies, Bond et al. (2002) hypothesized that "wildfires may have little short-term impact on survival, site fidelity, mate fidelity, and reproductive success of spotted owls. Further, prescribed burning could be an effective tool in restoring habitat to natural conditions with minimal short-term impact on resident spotted owls."