Recovery Plan for the Northern Spotted Owl - DRAFT

Table B.14. Habitata within 1.3 miles of 21 northern spotted owl nests on managedlands in the eastern Klamath province (Self and Brown, pers. comm.).IAverage Canopy Area Number Nests perDiameter Cover (m, 2 ) of nests m1 2>24" >60% 12.26 10 0.8211-24" >60% 4.94 3 0.61>24" 40-60% 4.23 1 0.2411-24" 40-60% 36.12 7 0.21a Area covered by stands of Douglas-fir with an understory of tanoak and madrone or by stands of Klamath mixed conifers (white fir, Douglas-fir,ponderosa pine, incense cedar, and sugar pine with an understory of oak and maple).. .stand is well below the mean in old-growth stands. This hypothesis should beinvestigated carefully because it has important implications for the design ofstrategies to protect owls in managed forestlands.The combination of density (and demographic) data and structural features atthe nest site and in the nest stand provides a powerful data set for analyzinghabitat preferences. Similar information from other parts of California, and onthe east side of the Cascades will be particularly useful in the future.Demographic Rates in Different HabitatsResultsThomas et al. (1990) reported that proportion of territories with pairs andreproductive success declined as the amount of old-growth declined. Thisconclusion was based both on Forest Service monitoring data and on landscapestudies. Results appearing since Thomas et al. (1990) are described inthe next section.Meyer et al. (1992) did not find any consistent relationships between thenumber of years that sites were occupied by owls and various measures offorest fragmentation.We reanalyzed the data from Meyer et al. (1992) to determine whether turnoverof adults varied with the amount of older forest (i.e., more than 120 years)present in the circle. Persistence of adults was defined as the probability thata bird present in a circle at the start of a year would be found at the site thenext year, given that the site was revisited in the following year. The consensusamong spotted owl biologists is that adults rarely change breeding sites (Lintpers. comm., Franklin pers. comm., Gutierrez pers. comm., Miller pers. comm.,Wagner pers. comm.). For example, in the Andrews study area in the westernOregon Cascades, during 305 pair-years, divorce and settlement elsewhereoccurred in, at most, four cases and was never established with certainty(Swindle and DeStefano pers. comm.). Persistence, as measured above,probably indicates adult survivorship, although we believe this issue needsfurther study. We obtained data from the 50 circles studied by Meyer et al.(1992), and Johnson (pers. comm.) supplied us with similar owl and habitat309