Recovery Plan for the Northern Spotted Owl - DRAFT

tion of spotted owls to a portion of the province, generally at higher elevations.The long-term stability is unknown for these populations that once inhabited awide range of ecological conditions, but are limited now to high-elevationhabitat.Predation and Competition. Levels of predation by great homed owls andcompetition with barred owls and northern goshawks on the Olympic Peninsulaare not understood well. Barred owls are present on the peninsula, butno evidence of competition has been documented. Predation by great homedowls may have increased over historic levels with an associated decrease in thesurvival of northern spotted owls.Province Isolation. The Olympic Peninsula province is isolated on three sidesby coastline; the Pacific Ocean to the west, the Straits of Juan de Fuca to thenorth, and Hood Canal to the east. To the south, timber harvest in the lowlandsof western Washington virtually has eliminated spotted owls. Currently,approximately 60 miles separate owl subpopulations on the Olympic Peninsulaand subpopulations in the western Cascades. Distance between currentlyknown reproductive pairs is approximately 75 miles. Isolation may decreasethe number of successfully dispersing juveniles and inhibit movement of adultsamong populations (Thomas et al. 1990).There is little or no dispersal between this and other populations, and demographicrescue would be unlikely in the event of a population decline on theOlympic Peninsula. Following such a decline, inbreeding could become aconcern.Offsetting a demographic decline on the peninsula or restocking a populationareawhere spotted owls have become locally extirpated due to catastrophic orstochastic events would be assisted by demographic connectivity betweenspotted owls on the Olympic Peninsula and those in other provinces. Thislikely would require establishment of groups of breeding pairs in the westernWashington lowlands province.Vulnerability to Natural Disturbances. Wind is the dominant disturbancefactor along the western coast of the peninsula and as far as 20 to 30 milesinland. Historic stand-replacing wind events occurred in 1921 and 1962(Appendix F). Logging within the past 30 years has resulted in increasedfragmentation on Forest Service, state, and private lands. Exposed forestedges are much more susceptible to wind damage than are relativelyunfragmented patches. The potential is high for a large-scale wind event toadversely affect spotted owl habitat in this region (Appendix F). Fire is also asignificant threat on the Olympic Peninsula, particularly in the eastern portion.Recent fires, such as the Forks Burn, were stand-replacement events thateliminated significant tracts of spotted owl habitat. Agee (1991b) suggests thatunder a worst case scenario, wind and fire could reduce the capability of theOlympic peninsula to support spotted owl pairs by up to 30 percent during thenext 100 years.Western Washington LowlandsOwnership in this province is largely nonfederal and includes major urban,industrial, and agricultural areas. Most forestland is owned by the State ofWashington or large industrial timber corporations. This province includesthe Puget Trough and southwest Washington physiographic provinces asdelineated by Franklin and Dyrness (1973) because these regions show similaritiesin spotted owl densities, land ownership patterns, and ecologicalconditions.43