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corridor. WRFO nest records indicate that these territories have historically low rates of nest occupancy (less than 15 percent) and low nest success rates (about 7 percent). Adults return in February and begin nesting in early April. Young are generally fledged by mid -July. The lease tract's limited support of burrowing owl nest activity is associated with those prairie dog towns in and near the lease tract. Most recently, from late April through mid -May, a single bird was noted in 2006 along the Staley Mine Road (burn on western end of lease) and a single bird and pair of birds (failed nest attempt) were documented in 2006 and 2009, respectively, off the southeast corner of the lease tract. Burrowing owl nesting activity is closely associated with the availability of intact prairie dog b -LuTow systems. The utility of prairie dog burrows for owl nesting may be largely lost within three years of burrow inactivity. Occupancy rates and nest densities of burrowing owl tend to be positively correlated with the density of active prairie dog burrows (Klute et al., 2003). Small Mammals Small mammal populations are poorly documented however, recent BLM and CPW surveys found essentially all shrub- steppe communities in the WRFO are dominated by deer mouse and least chipmunk. Region - specific species that are likely to occur in this area (e.g., Merriam's shrew, sagebrush vole, rock squirrel, northern grasshopper mouse) are less common, but display broad ecological tolerance and are widely distributed throughout the region. No narrowly distributed or highly specialized species or subspecific populations are known to inhabit this area. Environmental Consequences of the Proposed Action: Direct and Indirect Effects: The existing infrastructure associated with the mine has not been implicated in serious or noteworthy influences on terrestrial wildlife populations or habitat in GMU 10. The development of infrastructure attributable to the proposed lease tract addition would remain consistent with the long - established rate, intensity, and distribution of disturbances attributable to the mine's operation, and in particular, its subsurface ventilation system. Based on 2009 aerial photography, the long -term accumulation of surface facilities attributable to adjoining lease development was considered representative of those surface facilities that may eventually be constructed on the proposed lease tract. Collective surface disturbance associated with ventilation facilities on the proposed lease tract would amount to about 1.8 percent of the land base (e.g., about 24 acres attributable to access and 32 acres cleared for pads) over the life of the lease. This acreage figure does not account for the staggered development or progressive reclamation of these sites with perennial bunchgrasses and forbs. At the present time, much of the lower Red Wash watershed, and especially its alluvial bottomlands, are represented by ground cover dominated or heavily influenced by invasive annual weeds, primarily cheatgrass, which fail to provide effective wildlife - related forage or cover. After reclamation of these disturbances, vegetation would be expected to be comparable to or superior to pre - disturbance ground cover in terms of forage value and ground cover. Although elevating the ecological status of the existing plant community represents an incremental benefit to virtually all forms of terrestrial wildlife, including small mammals, as forage or cover, the overall contribution to improving community trends would be negligible. DOI- BLM -CO- 110- 2012- 0023 -EA 55