pheasant, sharp-tailed grouse, horned lark, western meadowlark, black-billed 

 magpie, brown thrasher, rufous-sided towhee, vesper sparrow. Brewer's sparrow, 

 chestnut-collared longspur, yellow warbler, common yellowthroat , mule deer, 

 white-tailed deer, and proghorn antelope. The 200 individual stops of the 

 four standard roadside routes were treated as samples. Principal component 

 analysis ("factor analysis" as described by Nie et al . 1975) was applied to this 

 same set of variables to ordinate species along first and second principal com- 

 ponent axes. 



It is of interest to determine the total number of species of breeding 

 birds found in habitats sampled by the roadside routes. This was attempted 

 by analysis of the species-abundance relation, using numbers of individuals 

 of each species seen during the roadside counts (sample abundances) in place 

 of actual abundances. When the numbers of species falling into each abundance 

 class ("octaves" of 1 to 2, 2 to 4, 4 to 8, 8 to 16, etc., individuals per 

 species) are plotted, a lognormal curve as described by Preston (1948, 1962) 

 is closely approximated. 



where: S^ = Sq 



.-(aR): 



S^ = the number of species in the R^"^ category to the left 

 or right of the mode; 



r 



Sq = the number of species in the model category, and 

 a = a fitted constant. 



The terms S , a, and r^ (the coefficient of determination) were calculated 

 for: the pooled breeding season (May-July) data for four routes (excluding the 

 Dreyer Ranch route); and the pooled breeding season data for all five routes. 

 The theoretical total number of species (S^) present in each "universe" sampled 

 (i.e., the habitats sampled during the roadside counts) was calculated using 

 Preston's (1962) formula (see also Slocomb et al. 1977): 



S^ = SgV^/a. 



This method has an advantage over other diversity measurements (such as H') 

 in that it is largely independent of sample size as long as the mode of the 

 species curve has been withdrawn several octaves to the right of the ordinate 

 on veil line (Edden 1971). (Migrants and summer visitors v;ere excluded from analysis.) 



It should be emphasized that the number of registrations of each species seen 

 during these counts (n^-) in no way represent a census of true abundances, or even 

 true relative abundances, since species differ in conspicuousness and ease of 

 detectability. Also, a given species will differ in conspicuousness from month 

 to month. These figures represent, rather, a measure of sample abundance, as 

 discussed by Preston (1948), similar to the "audiovisual density index" of Seals 

 (I960), and can be thought of as a species-specific and season-specific index of 

 absolute or relative abundance. 



Since sample abundance data were obtained for ring-necked pheasants by this 

 method, it was not necessary to run pheasant crow count routes, which require 

 somewhat different methods (Kimball 1949). 



33 



