Recovery Plan for the Northern Spotted Owl - DRAFT

Kerms (1989) measured habitat structure at one roost site in each of 10 homeranges in redwood forests of the California Coast province (Humboldt County).The roost stands were in second-growth with few snags or old-growth treesremaining. Roost stands were considered "used" if an owl was present on morethan one daytime visit; owls were present in most used stands during two orthree daytime visits. Owl use was documented in 1988, and vegetation wassampled in 1989. One 0.5-acre vegetation plot was centered on the roost treeor, for smaller stands, in the stand (Kerns pers. comm.).LaHaye (1988) measured habitat structure in six nest sites and stands inredwood forests of the California Coast province and in 38 nest sites andstands in the Klamath province (32 in Douglas-fir/tanoak/madrone forests,and six in mixed conifer forests of incense cedar/sugar pine/black oak). Thenests were widely distributed throughout the owl's geographic range in California.Nest stands contained patches of remnant older trees that had escapedfires and other natural catastrophes, and in which the nests were usuallylocated. The nest site was characterized by one plot centered at the nest treeand four plots located 75 feet from the nest tree and at equal distances fromeach other. Nest stands were characterized by plots at several distances fromthe nest. We used the data from four plots 450 feet from the nest tree and fourplots 600 to 4500 feet from the nest. All plots were of variable radius.Pious (1989) measured habitat structure on seven nest sites and 22 roost sitesin coastal redwood forests of the California Coast province in MendocinoCounty. The sites were in second-growth stands in a landscape lacking anyextensive, unharvested stands more than 200 years old. The location of roostsites was determined April-July 1989 through a series of nighttime callingsurveys and daytime visits: the roosts were on 22 home ranges (Pious pers.comm.). Nest sites were described using two 0.17-acre strips placed perpendicularto one another and each centered at the nest. Nest stands and rooststands were described using two or three plots: each plot was a 0.25-acre strip,randomly placed within each stand.Self and Brown (pers. comm.) described habitat structure on 21 nest sites inthe Klamath province, in northeentral California. Most of the sites were locatedduring the preparation of timber sales, and thus the surveys were concentratedin dense stands with large trees, rather than being fully representative of thelandscape. The nests were in second-growth stands of Douglas-fir or Klamathmixed conifers (white fir, Douglas-fir, ponderosa pine, incense-cedar, andsugar pine). Most areas were under even-aged management regimes composedof a mixture of partial harvest techniques (selective, seed tree, shelterwood,thinning). All but one of the areas studied had some clear-cut regenerationharvests during the previous 10 years. Within-stand diversity was generallyhigh due to the history of partial harvesting. Nest sites were described usingtwo 0.17-acre strips centered on the nest tree.Simpson Timber Company (1991) published a draft habitat conservation plancontaining results of their owl monitoring and research program. Surveys todetermine owl abundance, distribution, and reproductive success have beencarried out annually on Simpson's land in the California Coast province since1989.Sisco and Gutierrez (1984) and Sisco (1990) characterized the winter (October-February) roosting and foraging sites of five radio-transmittered owls duringfall 1982 and winter 1983 on the Six Rivers National Forest (Humboldt County,California) in the Klamath province. Most home ranges were in Douglas-fir/tanoak/madrone forests, although parts of some home ranges at higherelevations were in montane forest (white fir, ponderosa pine, sugar pine, andincense cedar). Most roosting and foraging stands were unmanaged, although292