This vjas measured for each run. Also employed was the widely-used Shannon- 

 Wiener diversity index (Margalef 1958), which is calculated by the following 

 formula: 



n i n T 

 Species Diversity =H'=-Z _ In — 



N N 



This index provides a measure of equitability or evenness of distribution 

 of individuals among species. For example, consider two samples, each having 

 100 individuals of 10 species, but sample A has 91 individuals of one species 

 and one individual in each of the other 9 species, and sample B has 10 indivi- 

 duals in each of 10 species. In sample B, individuals are much more evenly 

 distributed among species, and the diversity value (H') is much higher. The 

 conditions listed by Margalef for use of this index were assumed to be met in 

 this analysis. 



Also calculated was evenness;or the ratio of observed diversity to the 

 maximum diversity possible (Pielou 1966): 



Evenness = e = H'/ln S 



and species richness (Margalef 1958): 



Species Richness = D = (S-l)/ln N. 



The above mentioned community parameters can be especially valuable in mon- 

 itoring long-term changes in impacted areas, especially the area sampled by the 

 Dreyer Ranch route in this case, using the unaltered routes as controls against 

 which to measure such changes. Changes in these parameters may be more readily 

 attributed to mine-related impacts over a period of years than would changes in 

 individual species numbers which would likely be masked by random or cyclical 

 fluctuations or other ecological noise. 



Beta (or between-habitat) diversity was calculated for each route (pooled 

 May-July data only) using Whittaker's (1972) formula: 



Beta Diversity = BD = Sc/S 



where Sc = the number of species encountered on the route, and 



S" = the mean number of species encountered per stop 



Pearson product-moment correlation coefficients, stepwise multiple regres- 

 sion, and principal component (factor) analysis (Nie et al . 1975) were employed 

 to reveal relations among the sample abundances of selected species at each stop 

 and certain habitat parameters in the .40 km (0.25 mi) radius circle surrounding 

 each stop. Independent variables used in the multiple regression were, in order 

 of insertion: time (in relation to start of route), percentage of cultivated 

 land, percentage of grassland, percentage of trees and tall shrubs, percentage 

 of big sagebrush badlands, percentage of silver sagebrush, percentage of little 

 bluestem, percentage of horizontal juniper and bluebunch wheatgrass, percentage 

 of saltgrass, percentage of marsh, percentage of snowberry-rose, and Percentage 

 of buildings and farmsteads. Species included in the analysis were the nng-necKe^ 



32 



