Bare Rock (Upland) . The nearly vertical rock cliffs forming the 

 river gorge between the footbridge and the concrete retaining wall were 

 used as nesting sites by rough-winged swallows, robins, and possibly 

 violet-green swallows. 



Gravel Bars . Spotted sandpiper breeding territories were typically 

 associated with gravel bars along the river; great blue herons, Canada 

 geese, mallards, American wigeon, common goldeneye, common mergansers, 

 and killdeer also used this habitat. 



Scree and Talus . Rockslides and talus slopes were most common on 

 the steep hillside to the north of the Falls; they were used occasionally 

 by bighorn sheep, and provided cover for golden-mantled ground squirrels 

 and yellow pine chipmunks. A single deer mouse was the only mammal 

 taken in pitfall traps set in loose rock, but both masked and vagrant 

 shrews probably occur there as well. Pikas have been reported to use 

 this habitat at unusually low elevations along the Fisher River near the 

 study area (Hoffman et al. 1979a), but none were observed during this 

 study. 



Rocky Outcrops (Upland) . A raven nest was located on a steep rock 

 outcrop above Highway 2. On the north side of the river, sparsely vege- 

 tated cliffs and rocky bluffs were used extensively by bighorn sheep, 

 and also by merlin, Townsend's solitaire, and bushy- tailed woodrat. 



Grassland and Marsh Habitats 



Riparian Grasslands and Hayfields . While these habitats were used 

 occasionally for feeding or loafing by a variety of birds from adjacent 

 tree and shrub habitats (e.g., American robins, common ravens, song 

 sparrows) and by Canada geese and common goldeneye, they supported no 

 typical grassland species (such as savannah sparrow or western meadowlarks) , 

 probably because of their limited extent. Nevertheless, such 

 habitats are characterized by relatively high primary productivity, and 

 are a prime food source for grazing herbivores , particularly voles (Mi crotus 

 spp.) and bighorn sheep. Figure 8 shows where relatively flat, grassy 

 slopes of this habitat occur adjacent to rocky areas used heavily by 

 bighorn sheep on the north side of the river. In tliese areas, bighorn 

 sheep occupy the lowest elevations in late March and early April ; these 

 highly productive grasslands provide a key food source. Small mammals 

 taken during the trapping effort in this habitat include the vagrant 

 shrew, meadow vole, long-tailed vole, and meadow jumping mouse. Burrows 

 of northern pocket gophers and Columbian ground squirrels were observed 

 in this habitat, and western garter snakes were found only in this habitat. 



Fescue Grassland . This grassland type is also an important source 

 of forage for bighorn sheep. It Is occupied oy yellow-pine chipmunks 

 and probably deer mice and vagrant shrews, as well as various birds 

 using adjacent timber and shrub habitats. 



75 



