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and yellowth oat.' Of these species, only the yellowthrvae was observed in <br />sufficient numbers to exhibit an affinity for the type. <br />Upland sagebrush. The sagebrush vegetation type supported a total of eight <br />passerine species during the June, 1979 census. The violet -green swallow <br />and red - winged blackbird Were the most abundant species observed. The <br />sagebrush habitat supported the lowest total avian population of all types <br />sampled (22.7 individuals/km). The Shannon - Weiner 'species diver- <br />sity index (1.52) was relatively high because the number of observations was <br />equally distributed among species. Bullock's oriole and the barn swallow <br />were observed only in the sagebrush; however, neither were observed in <br />sufficient numbers to indicate an affinity for this habitat. <br />Grassland pasture. The grassland pasture vegetation type was the most homo- <br />geneous vegetation type sampled and accordingly, the least diverse in terms <br />of numbers of bird species observed (4). The western meadowlark represented <br />at least 75% of all sightings during the June, 1979 census. Due to the low <br />number of species observed and the dominance by the western meadowlark, the <br />Shannon-Weiner species diversity index in this type was lowest (0.69) of <br />all types sampled. The total avian population supported by this habitat <br />was 26.0 individuals/km, the lowest of all species sampled after upland <br />sagebrush (22.7 individuals/kin). <br />Tnvortant breeding passerine birds. Twenty -two different avian species <br />were encountered along the breeding bird transects conducted in the five <br />vegetation types surveyed. Abundant passerine species in decreasing order <br />of relative abundance during June, 1979 census were: red winged blackbird, <br />violet -green swallow, cctte on craw, and western meadowlark. All of these <br />species except western meadowlark were observed in at least four of the five <br />vegetation types sampled. <br />Red-winged blackbird. The red - winged blackbird was the most abundant species <br />observed on the study area averaging 19.5 invididuals/km over all habitats. <br />This ubiquitous species was encountered on all five vegetation types and was <br />the most abundant species in each type. The red- winged blackbird is gre- <br />garious and Feeds, flys and roosts in flocks. It was most abundant in ripar- <br />ian and alfalfa field habitats and showed an affinity for these types. <br />-33- <br />JUN 1 1 1980 <br />