Managing habitat for dispersing northern spotted owls—are the current management strategies adequate?

Abstract

When the northern spotted owl (Strix occidentalis caurina) was listed under the Endangered Species Act (ESA) as threatened in 1990, a number of challenges immediately became apparent. One of the first to surface was the need to develop definitions of suitable habitat that could be used in the regulatory environment. Consequently, in the early years following ESA listing, much attention was directed at defining habitats that spotted owls used for nesting, roosting, or foraging. The emphasis of research on various aspects of the structure, quality, quantity, or landscape configuration of nesting habitats throughout the owl's distribution was considerable (e.g., Carey et al. 1990, Lehmkuhl and Raphael 1993, Buchanan et al. 1995, Meyer et al. 1998, LaHaye and Gutierrez 1999) and overshadowed efforts to investigate the habitat conditions used by owls during dispersal (Miller et al. 1997). After the Northwest Forest Plan was adopted to manage spotted owl populations on federal lands (Forest Ecosystem Management Assessment Team [FEMAT] 1993), regulations were implemented for the management of nonfederal lands in the region. In Washington, for example, the Northwest Forest Plan and state forest practices rules (in 1996) identified key landscape where the emphasis of spotted owl conservation would be the management of nesting, roosting, foraging, and dispersal habitats. On federal lands, spotted owl nesting habitat would be managed in late-successional reserves (LSRs). Federal lands between the LSRs would be managed largely for timber production (within the matrix) or a combination of wildlife and human needs in adaptive management areas (FEMAT 1993). Areas between the LSRs would need to facilitate movement by juvenile and adult spotted owls among the LSRs. Nonfederal landscapes designated as Spotted Owl Special Emphasis Areas (SOSEAs) would provide demographic support, dispersal support, or a combination of these 2 functions under the state's forest practices rules (Washington Administrative Code 222-16-086). The SOSEAs are all adjacent to federal lands, and several are expressly designated as, or contain sub-units designated as, landscapes where spotted owl dispersal is of primary management importance. In 1992 the United States Fish and Wildlife Service (USFWS) approved the first Habitat Conservation Plan (HCP) for spotted owls in the region (Simpson Timber Company 1992). This was followed by implementation of additional HCPs, many of which provided dispersal habitat as mitigation for incidental take permits that allowed harvest of forest used by territorial spotted owls for nesting, roosting, or foraging. These dispersal-based plans have been implemented on hundreds of thousands of hectares in the Pacific Northwest. Despite this shift from retention of mature and older forests to management of younger forests as dispersal habitat, an interest in investigating the effectiveness of dispersal management plans has not emerged. This is surprising because dispersal long has been recognized as an essential component of spotted owl management (e.g., see Appendix P in Thomas et al. 1990). Moreover, dispersal has been an important ecological and management consideration for other listed species. Researchers and managers in the southeastern United States learned, for example, that poor landscape connectivity required the translocation of red-cockaded woodpeckers (Picoides borealis) to establish or maintain population clusters (DeFazio