WITHIN-STAND NEST-SITE SELECTION BY SPOTTED OWLS IN THE EASTERN WASHINGTON CASCADES

We describe 83 nest sites (0.2-ha areas) of northern spotted owls (Str ix ocidentalis caurina) in mixed conifer forests on the eastern slope of the Cascade Mountains, Washington. Approximately 74% of the nest si tes were in forests in intermediate stages of succession, and 27% were in old-growth forests (median = 122 yr, range 54-700 yr). Most sites were naturally regenerated after fire, but 23% of the nest sites had b een partially harvested greater-than-or-equal-to 40 years ago. We test ed the hypothesis that habitat structure does not influence nest site selection within forested stands, because such knowledge would aid con servation strategies that may include silvicultural prescriptions for creating future habitat. We compared habitat characteristics at 62 nes t sites with those at 62 random sites within the same forest stands. C ompared with random sites, spotted owl nest sites had canopies of domi nant and/or codominant and intermediate trees that were farther aboveg round (P = 0.02 and 0.07, respectively), more 35-60-cm-dbh (diam at br east height) Douglas-fir (Pseudotsuga menziesii) trees (P = 0.03), gre ater basal area of Douglas-fir trees (P = 0.02), more 61-84-cm-dbh pon derosa pine (Pinus ponderosa) trees (P = 0.03), greater live tree basa l area (P = 0.09), greater basal area of Class IV snags (broken snags with no branches and little bark; P < 0.001), less basal area of a gro up of relatively uncommon conifer species (P = 0.02), fewer 10-34-cm-d bh uncommon conifer species (P = 0.08), and less basal area of Class I and II snags (intact or nearly intact snags with branches and most ba rk remaining; P = 0.08 and 0.095, respectively). Volume of coarse wood y debris (P > 0.13 in all decay classes) and percent canopy closure (P = 0.45) did not differ between nest and random sites. Data support th e hypothesis that nest sites are selected as part of an antipredator s trategy.