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H-14 <br />n <br />U <br />in the study area was the Brewer's sparrow. Its density was higher in <br />three habitat types (greasewood-sage bottom, sagebrush, chained pinyon- <br />juniper) than the density of any other species in any habitat. Other <br />common species included the black-throated gray warbler, solitary <br />vireo, mountain chickadee, and chipping sparrow in the pinyon-juniper <br />habitats; green-teliled towhee, vesper sparrow, and meadowlark in <br />sagebrush habitats; and green-tailed towhee, blue-gray gnatcatcher, and <br />sage thrasher in greasewood-sage bottom. <br />Songbird density was highest in the greasewood-sage bottom habitats <br />(about 8 birds/ha). The density of songbirds in other habitats was <br />considerably lower: pinyon-juniper, chained pinyon-juniper, and <br />sagebrush had about. 3.5, 3.3, and 2.6 birds/ha, respectively. Total <br />songbird population in the study areas was estimated to be about 23,643 <br />individuals. <br />• Species diversity--estimated using the Shannon-Wiener index (Pielou <br />1966)--was highest in the pinyon-juniper habitat type -- H' = 1.93. <br />There was little difference indicated among the other habitat types: <br />chained pinyon-juniper, H' = 1.33; sagebrush, H' = 1.41; and grease- <br />wood-sage bottom, H' = 1.24. <br />Songbird species frequently prefer certain types of habitats; this is <br />usually based on the vegetation height and density (Odum 1945, Bond <br />1957, Hilden 1965, Balda 1975, Buttery and Shields 1975, Peterson <br />1975). The most frequently used classification consists of grassland, <br />shrubland, and tree cover. The habitat preference of common species <br />of songbirds (based on density estimates) in this study is listed in <br />Table H-2. <br />Pianka (1973) described the niche breadth index (B) which indicates a <br />species flexibility of habitat occupation. Species which occur in a <br />• larger variety of habitats are characterized by a higher B value. From <br />the data gathered in the Emlen study, the green-tailed towhee (B = <br />THIS DOCUMENT COIJT AINS TRADE SECRETS AND PRIVILEGED, CONFIDENTIAL AND M' ~• ~ ~ .,, <br />ROPRIETA RY COMMERCIAL, FINANCIAL, GEOLOGICAL AND GEOPHYSICAL DATA AND ~Yl~y~ ~ ~ ~ ~~ ~] <br />INFORMATION. PURSUANT TO LAW, THOSE PORTIONS MARKED "CONFIDENTIAL" u 1- 7 <br />MAY NOT BE DISCLOSED, COPIED OR MADE AVAILABLE FOR PUBLIC INSPECTION. <br />