Table 35. Beta diversity for 1977 runs of five roadside wildlife survey routes, 



y 



Average value for June 15 and June 22 runs, 



high ranking of the Prairie Elk route in terms of bird diversity is due largely 

 to beta (between-stop) diversity, or to the wide range of habitats sampled along 

 the length of the route, rather than to richness of the habitats themselves. 

 Second, the high ranking of the Missouri River route is due largely to alpha 

 (within-stop) diversity, that is, to the high species richness of the cottonwood, 

 tall shrub, and marsh habitats sampled, rather than to the variety of different 

 habitats sampled by the route. Third, the principal habitats sampled by the 

 Flowing Well route are very species-poor, and much of the gamma diversity of this 

 route would be even lower in relation to the other routes than it was observed to 

 be. 



Similarity of Routes . A similarity dendrogram for the five June runs of the 

 five roadside routes is shown in figure 47. The Prairie Elk and Dreyer Ranch 

 routes are seen to be most similar (0.692), although the Circle and Dreyer Ranch 

 routes have nearly as high a similarity value (0.691). The Circle and Flowing 

 Well routes were most dissimilar (0.40). 



Between-year similarities for 1968-1977 runs of the Circle route A ranged 

 from 0.32 to 0.89. This wide variation may reflect ecological differences in 

 breeding bird populations, but is more likely due to changes in observers and 

 observer bias. Figure 48 shows an increase in similarity between 1968 and 1970 

 and between 1972 and 1975 runs, as the observers became more familiar with the 

 route. A sharp drop in similarity is evident between 1970 and 1972 runs and 

 between 1975 and 1977 runs, corresponding to a change in observers. This demon- 

 strates the importance of maintaining the same observer for the route for as many 

 consecutive years as possible during monitoring of the roadside routes, in order 

 to minimize differences due to observer bias. 



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