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AyIE'AL1NA <br />Passerine Birds. Breeding and resident wintering passerines in the Seneca II <br />study area were surveyed during early June, 1979 and mid February, 1980 along <br />1 km transects placed within major vegetation types represented in the study. <br />The census technique was designed to quantify passerine abundance; however, <br />all avian species, including raptors and game birds, observed along the <br />transacts were counted. The results of the breeding and wintering bird <br />surveys are provided on computer print-outs in Appendix B, Part 2 for each <br />of the five vegetation types sampled (mixed brush, upland sagebrush, Gimbel <br />oak, aspen and riparian). These printouts provide relative abundance indices <br />(number of individuals/km) and macmhabitat affinities for each species <br />encountered and Shannon-i~einer species diversity indices for each habitat <br />sampled. A list of all avian species positively identified for the Seneca II <br />study area during this and previous studies is pravided in Table 3. <br />u <br />Ztao major topics are considered in the discussion of breeding passerine <br />birds. First, the relative ittportance tb avifauna of each habitat type <br />sampled is described. DerA*++»nation of importance focuses on three parameters: • <br />species diversity, ccmq~osition, and abundance. Secmid, the occtisrence, <br />distribution and abundance of important passerine species is discussed. <br />Important species are defined as those with a high relative abundance in one <br />or more habitat type or those with a wide distribution (i.e., found in most <br />habitat types sampled). <br />Avian Habitats. The greatest rnmiber of avian species was encountered in the <br />aspen vegetation type (18 species). This type had the highest species <br />diversity index of any type surveyed on the study area (2.34) and the highest <br />total avian population (33.0 individuals/km). The structural heterogeneity <br />of the aspen type with its tree stratum provides more opportunities or <br />"niches" for nesting and feeding than other vegetation types in the area; <br />as a result, the type can support a greater variety of bins species and <br />greater population of birds. The most aburx3ant species observed in this <br />habitat in decreasing order of relative abL~a*+~e were house wren, green- <br />tailed towhee, tree swallow, mourning dove, and American robin. Six • <br />-36- <br />