Recovery Plan for the Northern Spotted Owl - DRAFT

Table B.3. Percent hardwoods in the understory (based on density) by dbh class atsites used by northern spotted owls in California.Approx. Nest Roosting/Province DBH (in) Site Roosting and foraging ForagingCalifornia Coast 5-10 63a11-20 5020-35 1835 011-24 51 b24-3636605-16 78c 68c16 13 175-16 43d16 13Klamath 5-10 31e 86f 739 92g 68f 61911-20 32 70 66 83 49 4421-35 19 22 43 44 17 2735 17 0 8 4 6 45-10 - 58i 62i 91 56' 62i11-20 77b 30 30 8 28 3121-35 30 10 9 2 8 935 0 3 4 0 3 4aFolliard and Reese, (1991): Diller and Folliard, (pers. comm.)bLaHaye (1988) (intervals were 11-24", 25-36", and 36")CPious (1989)dKerns (1989)eSelf (1991)fSolis (1983)9Sisco and Guit6rrez (1984); Sisco (1990)hChavez-Leon (1989)'Bingham et al (1991)lAsrow (1983) (intervals were 1-10-, 11-17", 18-29" and 30")Other provinces: Fewer studies providing quantitative descriptions of utilizedhabitat are available from other provinces. Studies in the western WashingtonCascades, Oregon Coast range, and Olympic Peninsula revealed approximatelysimilar results for nest sites, roosting or foraging sites, and sites in old-growthstands, except that more large trees were found in the Olympic Peninsula thanin the other areas studied (Table B.8). In the eastern Washington Cascades,fewer large and medium-sized trees occurred in nest sites, nest stands, andforaging sites than in the other provinces.Maximum tree height was 103 feet in plots used for roosting and foraging inthe eastern Washington Cascades (Benson 199 lb). Spies et al. (1991) reportedmaximum tree heights in old-growth stands of 198 feet in the Oregon Coastprovince, 184 feet in the western Oregon Cascades, and 168 feet in the westernWashington Cascades. Maximum tree heights have not been reported forstands used by owls in these provinces.Total canopy closure averaged 83 percent for 11 nest sites in the westernWashington Cascades (Hamer). In the eastern Washington Cascades, totalcanopy cover averaged 75 percent in 62 nest sites and 72 percent in the standswithin which the nest were found (Buchanan 1991). In the same province,296