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• layer, a shrub layer and ground cover. Although the latter two layers are not as <br />dense as in other habitats, they still attract a number of bird species that otherwise <br />would not be present. The total number of species (64) recorded from the aspen <br />habitat represents 50 percent of all the bird species observed on the mine complex. <br />Average summer bird abundance (37 birds per km) in the aspen ranks second and is <br />similar to that found in mountain shrub and sagebrush habitats. <br />In winter, abundance in the aspen still ranks second compared To other <br />communities but diversity is very low (Exhibit 2.7-4). Eight species were observed <br />in March and only two in November. There are, however, two winter residents which <br />were observed To occur only in The aspen: pine grosbeak (Pinicola enucleator) and <br />Lincoln's sparrow (Melospiza lincolnii). <br />Three other species ore primarily found in the aspen communities on and around <br />the mine: white-breasted nuthatch (Sitto canodensis), warbling vireo (Vireo gilvus), <br />and solitary vireo (V. solitarius). <br />Mountain Shrub -The mountain shrub community is similar to aspen <br />and sagebrush in summer bird abundance (ExibiT 2.7-4) while summer diversity is <br />intermediate between other transecis. Species richness (69 species) ranked second to <br />• the riparian area. Abundance in summer (36.4 bird/km) is considered moderately high <br />although much less (43 percent) than abundance in the riparian area. This difference <br />in abundance between mountain shrub and riparian habitats probably reflects the <br />difference in moisture availability. The mountain shrub habitat is drier resulting in <br />decreased food volumes available to birds. Summer bird diversity (less than riparian <br />and aspen) probably reflects the height diversity of the vegetation. There is no <br />overstory of vegetation higher Than 5 meters compared to aspen habitat where <br />foliage occurs at 10 meters above the ground. In winter, although abundance in the <br />mountain shrub is lower than in three other habitats, diversity is almost equal To that <br />of the riparian (Exhibit 2.7-4). <br />Four bird species on the mine complex appear to be primarily dependent on the <br />presence of the mountain shrub community. These species were not seen, or seen <br />only as accidentals, in other habitats. The four species are Columbian sharp-tailed <br />grouse (Pedioecetes phasianellus), short-eared owl (Asia flammeus), which probably <br />nests in mountain shrub, says's phoebe (Sayornis soya), and blue-gray gnatcatcher <br />(Polioptila caerula). <br />Sagebrush -The sagebrush bird tronsect data from the summer show <br />• abundance and diversity similar to that in the mountain shrub (Exhibit 2.7-3). This <br />is at least partially due to the presence of birds primarily associated with the <br />2.7-10 <br />