Recovery Plan for the Northern Spotted Owl - DRAFT

I. IntroductionThe long-term protection of habitat for the northern spotted owl (Strix occidentalisspp. cawuina) revolves around large protected areas called designatedconservation areas (DCAs). This strategy assumes that by protecting fairlylarge blocks of suitable habitat, and spacing these blocks throughout the rangeof the species, there is a high probability that the viability of the subspecies willbe maintained. A major assumption of this strategy is that the DCAs willperpetually serve as suitable habitat for the spotted owl. A primary threat tothe owl to date has been clear-cutting of mature to old-growth stands; the DCAstrategy assumes elimination or major reduction in timber removal withinDCAs as well as between them. A primary threat in the future for establishedDCAs will be the probability of damage or destruction by a variety of natural"disturbance agents: fire, wind, insects, and diseases. The purpose of thisreport is to describe the nature of these threats, the probability of success of atotal protection strategy, and guidelines to increase the probability of successfulmaintenance of conditions within DCAs suitable for spotted owls in the faceof such threats.Definition of Suitable HabitatThe following description of habitat for the northern spotted owl is abstractedfrom the proposed critical habitat rules published in the Federal Register onMay 6, 1991 (vol. 56, no. 87). The northern spotted owl is known from most ofthe major types of coniferous forests in the Pacific Northwest. Spotted owlsseem to avoid subalpine forests, but have been found as low as 70 feet elevationin the Olympic Mountains and as high as 6,000 feet elevation in California.Spotted owls commonly use Douglas-fir (Pseudotsuga mrenziesiO andmixed-conifer forests in California. In that area habitat tends to be discontinuousin a mosaic pattern. In Washington's coastal forests, the spotted owl isfound in forests dominated by Douglas-fir and western hemlock (Tsugaheterophylk4. At higher elevations spotted owls use Pacific silver fir (Abiesamnabilis), while on the east side of the Cascades, Douglas-fir and grand fir(Abies grandis) are used.The age of a forest is not as important a factor in determining habitat suitabilityas are vegetational and structural elements. Components of northern spottedowl nesting habitat are: 1) moderate to high canopy closure (60 to 80 percent);a multilayered, multispecies canopy dominated by large (more than 30inches dbh) overstory trees: 2) a high incidence of large trees with various deformities(e.g., large cavities, broken tops, mistletoe infections, and other evidenceof decadence); 3) numerous large snags; 4) large accumulations of fallentrees and woody debris on the ground; and 5) sufficient open space beneaththe canopy for owls to fly (Thomas et al. 1990). Old-growth or mixed speciesstands typically require a minimum of 150 to 200 years to attain these aforementionedattributes. Attributes of breeding and roosting habitat are sometimesfound in younger stands, especially those with remnants of the earlierstand that was disturbed by fire, wind storms, inefficient logging operations, orhighgrading. However, nearly all nest and roost sites are found in the portionsof these stands with the oldest components. In the Oregon Coast Ranges, OregonCascades, Washington Cascades, Olympic Peninsula, and Klamath Province,owls use old forests more than expected for foraging and roosting.427