Recovery Plan for the Northern Spotted Owl - DRAFT

ITable B.9. Snag density (number of snags per acre) by dbh class in Oregon andWashington provinces.dbh Nest Nest Roost/ Old-Province (inches) Site Stand Forage GrowthOregon >0 1 6 aCoastRange >20 7Western >0 25aOregonCascades >20 11Western >0 30aWashington >4 42b 33C 41 dCascades >20 18 7 7 15Olympic >4 25 ePeninsula >20 10Eastern 4-13 1 f 13fWashington 14-23 4 6Cascades >23 2 2>10 59>20 1a Spies et al. (1988)b Hamer (1988)C Allen et al. (1988) (Mt Baker-Snoqualmie National Forest)d Allen et al. (1989) (Gifford-Pinchot National Forest)e Allen et al (1989) (Olympic National Forest)f Buchanan (1991)9 Benson (1991b).~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~........../This type of information is particularly useful in defining habitat categories.These efforts, however, must proceed with caution. For example, the resultssuggest that utilized sites studied to date tend to have trees of several differentdiameters (including some large trees), high canopy cover, and dominance byconifers, and that a hardwood understory is usually present in California butis not present in Washington and most of Oregon. As we have stressed, however,these generalizations describe average values in the study; they do notnecessarily describe the features present at each site. Thus, birds might usesome sites with a few large trees and few other trees but use other sites with nolarge trees but many smaller trees. This differential use might occur within orbetween home ranges. In either cases, the study-wide averages would be asreported earlier. Bingham (pers. comm.) has suggested that the values inTable B. 10 may characterize utilized sites in mature stands but may notcharacterize utilized sites in old-growth stands very well. This suggestioncould be investigated by comparing results for home ranges dominated by oldgrowthstands with home ranges dominated by mature stands.Improved descriptions of utilized sites might be obtained by defining a habitatcategory using several habitat variables. For example, we might examine thestudy-wide averages reported in Tables B.2 through B.9 and then define ahabitat category as including stands with canopy cover exceeding 80 percent301