SPOTTED OWLS - RESOURCE AND SPACE USE IN MOSAIC LANDSCAPES

Home ranges of 14 pairs of spotted owls (Strix occidentalis) were stud ied over four to six seasons in three southwest Oregon landscapes that differed in prey base and degree of forest fragmentation. The general theory of space use and the biology of spotted owls was used to const ruct a scheme for spatiotemporal analyses that provided insights beyon d those possible with polygon home-range methods. Landscape units, pre cisely defined by habitat type and aspect, were classified as not used , used less than or equal to expected based on area, and used > expect ed (selected). Selected units were categorized further by consistency of use: frequent, intermittent, and sporadic. Ratios of use categories and costs of use based on distances to units from activity centers re vealed that spotted owls adopted different tactics depending on prey b ase and degree and type of fragmentation. Strategies were in accordanc e with predictions for central-place foragers exploiting patchy enviro nments. Owls generally concentrated their foraging in old forests, but selectively used particular young forest units, especially when dusky -footed woodrats (Neotoma fuscipes) were present. Costs of fragmentati on were high, equivalent to the zoogeographic gain of adding the dusky -footed woodrat to the prey base. Selective use of young forests sugge sts that manipulation of young forests to provide habitat for prey and foraging by the owl would be of value in conservation efforts in this region.