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53210 Federal Register/Vol. 69, No. 168/Tuesday, August 31, 2004/Rules and Regulations but specific data describing this habitat structure are not available. Forsman et of. (1984) and Geo- Marine (2004) have reported high site fidelity by owls. Once dispersing male owls settle in a territory (the area defended by an owl), they rarely make additional movements outside of their home range. However, Arsenault et al. (1997) reported that three sub -adult females paired temporarily with adult males in their first summer, but left in the fall, suggesting that dispersal can continue through an owl's second year. Sufficient habitat must occur within owl home ranges to provide vegetation of appropriate size and cover for roosting, sheltering, rearing, and foraging. The area must be adequate to provide for the needs of the owl on a year -round basis. Population growth can only occur if there is adequate habitat in an appropriate configuration to allow for the dispersal of owls across the landscape. Food Owls typically hunt from perches in trees with dense foliage using a perch- and-wait strategy; therefore, cover must be present within their home range for them to successfully hunt and survive (Service 1995). Their diverse diet includes small mammals, birds, lizards, and insects. The primary owl prey species are woodrats (Neotoma spp.), peromyscid mice (Peromyscus spp.), and microtine voles (Microtus spp.) (Service 1995; Young et al. 1997; Delaney et al. 1999; Seamans and Gutierrez 1999). Research indicates that woodrats are the most important prey species based on relative biomass (Young et al. 1997; Delaney et al. 1999; Grubb et al. 1999; Seamans and Gutierrez 1999). However, owls also utilize different groups of prey species on a seasonal basis. The density of annual plants and grasses, as well as shrubs, may be important to enhancing the owl's prey base (Ward and Block 1995; Delaney et al. 1999; Ward 2001). Vegetation communities which provide a diversity of structural layers and plant species likely contribute to the availability of prey for owls (Willey 1993; Gutierrez and Rinkevich 1991). Therefore, conservation of the owl should include consideration of the habitat needs of prey species, including structural and species diversity. Owl habitat must provide sufficient prey base and cover from which to hunt in an appropriate configuration and proximity to nest and roost sites. Water Owls are typically. found in close proximity to water (Ganey and Balda 1989; Zwank et al. 1994; Ganey et al. 1998; Young et al. 1998; Geo- Marine 2004). Even small sources of water such as tiny pools or puddles create humid microsites that may influence an owl's use of an area (Geiger 1965 in Gutierrez and Rinkevich 1991). Gutierrez and Rinkevich (1991) reported that owls in Zion National Park were always in areas with some type of water source (i.e., perennial stream, creeks, and springs, ephemeral water, small pools from runoff, reservoir emissions). Over 80 percent of the nests located by Forsman (1976) were within 984 ft (300 m) of permanent water. Barrows (1981) reported spotted owls roosting close to surface water in xeric sites in the San Bernardino National Forest. Geo- Marine (2004) reported finding most owls within 531 ft (162 m) from the nearest stream and all owls within 0.25 mi (0.4 km) of a stream. Tarango et al. (1997) reported cliff -roost site ranges of 33 ft (10 m) to 722 ft (220 m) from the nearest spring. Tree -roost sites ranged from 50 to 991 ft (15 to 302 m) to the nearest spring ( Tarango et al. 1997). Owls have not been reported to drink water, so it is likely that owls meet much of their biological water requirements through the prey they consume. However, the presence of water does provide related benefits to owls as the availability of water may contribute to improved vegetation diversity and structure which improves cover and possibly prey availability. Reproduction and Rearing of Offspring Male and female owls began roosting together in February and began nesting in March ( Zwank et al. 1994; Service 1995). Territories in mature mixed - conifer forests and pine -oak forests normally contain several potential nest and roost trees (Ganey and Balda 1989b; Ganey et al. 1999; Geo- Marine 2003, 2004). Canyon habitat normally contains several potential nesting cavities, crevices, and ledges. Hence, mature coniferous trees, riparian vegetation, and cavities, crevices, and rock ledges may be important criteria for habitat selection. Recent information throughout the owl's range indicate nests were predominately located in mature coniferous trees (mostly Douglas -fir) (Ganey 1988; Fletcher and Hollis 1994; Zwank et al. 1994; Seamans and Gutierrez 1995; Young et al. 1998; Peery et al. 1999; Ganey et al. 2000; Geo- Marine, Inc. 2003, 2004) and cavities, crevices and ledges in canyon habitat (Gutierrez and Rinkevich 1991). Owls exhibit a high degree of site fidelity once territories (the area defended) and home ranges (the area used throughout the year) have been established ( Forsman et al. 1984, Bond et al. 2002; Geo- Marine 2003, 2004). Therefore, it is important that habitat characteristics within territories and home ranges be maintained over time in order for them to remain suitable. This is important for established owl PACs, as well as new sites established by dispersing owls. Large trees also provide protection against predators, cover for foraging, and thermal cover (Gutierrez 1985; Carey et al. 1992; Service 1995; Ganey and Dick 1995; Caney et al. 1997; Delaney et al. 1999; Geo- Marine 2003, 2004). Predators include great horned owls (Bubo virginianus) and northern goshawk (Gutierrez et al. 1995). Owls may be particularly vulnerable to predation and other threats during and shortly after fledging (Geo - Marine 2003, 2004). Therefore, cover near nest sites may be important for young to fledge successfully. Conditions which promote the proliferation of great horned owls (reducing overstory and canopy cover) may contribute to this mortality factor. Habitat that provides for successful reproduction and rearing of young provides large trees, high basal area of large diameter trees (e.g., in mixed - conifer about 140 sq ft basal area per ac, with 20 or more trees per ac that are 18 in dbh or greater), high canopy cover (e.g., 40 or greater), uneven aged trees (e.g., 3 or more age classes), multistory layers and high volume of down and dead woody material of adequate size to provide nesting structures in proximity to foraging, roosting, sheltering and dispersal habitats, in addition to adequate cover for protection from climatic elements and predators in an appropriate configuration in relation to the nest site. We determined the primary constituent elements for the owl from studies of their habitat requirements (see "Background" section above) and the information provided in the Recovery Plan and references therein (e.g., Skaggs and Raitt 1988; Ganey et al. 1988; Ganey and Balda 1989a; Gutierrez and Rinkevich 1991; Willey 1993; Fletcher and Hollis 1994; Seamans and Gutierrez 1995; Service 1995; Gutierrez et al. 1995; Recovery Plan; Ward et al. 1995; Willey 1998; Geo - Marine 2004). Since owl habitat can include both canyon and forested areas, we identified primary constituent elements in both areas. We have made some changes to the description of the primary constitute elements listed in the proposed rule in order to make them easier to understand; however, we did not alter their meaning. The primary constituent elements which occur for the owl