Recovery Plan for the Northern Spotted Owl - DRAFT

Distribution of Habitat and Populations. There are several concerns aboutthe distribution of habitat and owls in the western Washington Cascadesprovince. In the northern portion, no large clusters of spotted owls currentlyoccur. Much of the habitat in lower elevation areas has been eliminated, andinterchange among remaining individuals or small clusters of spotted owlslikely is inhibited by nonforested, high-elevation ridges, peaks, and glaciers.As in the northern portion, no large clusters of spotted owls currently occur inthe 1-90 corridor. Distribution concerns are primarily with north-to-southinterchange of dispersing young and adults. With greatly reduced levels ofsuitable spotted owl habitat in this region, there is significant isolation of thenorthern and southern portions of spotted owl populations in the WashingtonCascades. North-to-south interchange is further restricted by narrowing offederal ownership in the 1-90 corridor area.In the southern portion of the province, two significant distributional concernsoccur. Spotted owl populations in Washington and Oregon are separatednaturally by the Columbia River. Historically, spotted owls probably werelocated along the northern and southern banks of the Columbia River. Loggingand urban development in lowland areas of western Washington and Oregonhave resulted in a restricted area of interchange, or "bottleneck" betweenspotted owls in both states. Currently, interchange between spotted owlpopulations in the two states likely occurs only in a 18- to 20-mile zone in theColumbia Gorge, if at all. Primary ownership on the Washington side of thegorge includes state, private, and federal lands. It is unknown to what degreespotted owls in the two states interact. State and private lands are importantin addressing these distributional concerns in the I-90 corridor and the ColumbiaGorge.The northwest portion of the Gifford Pinchot National Forest represents anotherdistributional concern. The Mineral Block is critical to potential geneticand demographic interchange between the Olympic Peninsula province and thewestern Washington Cascades province. Currently, 10 known spotted owlterritories are located in this checkerboard ownership block. Nonfederal landscurrently support spotted owls, and are important for long-term developmentof a stable subpopulation in this area.Province Isolation. The two provinces that comprise the Washington Cascadesare connected by contiguous habitat and owls in only a few high-elevationareas, such as Steven's, Snoqualmie, and White Passes. The extent ofdemographic interchange over these mountain passes is unknown. Thenorthern portion of the province is virtually at the edge of the species' currentrange. Spotted owls in southern British Columbia are found in low numbersand densities, and are unlikely to provide demographic support to owls innorthern Washington. The degree of province isolation in the Columbia Riverarea is unknown. Spotted owls in the Washington Cascades probably areisolated demographically at present from owl populations on the OlympicPeninsula.Vulnerability to Natural Disturbances. The eruption of Mount St. Helenseliminated a large forested region containing a number of spotted owls. Theblast zone is similar in size to an area that might support a large cluster of 20or more pairs of spotted owls as described by Thomas et al. (1990). A volcaniceruption of Mt. Baker, Mt. Rainier, Glacier Peak, or Mt. Adams could result inelimination of one or more conservation areas, and local isolation of subpopulationcenters.46