168 



Game Survey of the North Central States 



Only sharp declines not followed by recovery are admitted as evidence in the 

 above computation. These represent but a small fraction of the total number of 

 lows on which the cycle dates are based. 



The summarized result of the computation is as follows: 



TABLE 29. Temporary lows in relation to dales of permanent decline in prairie chickens 



Lows, prairie chicken, Wisconsin 



Dates of decline, prairie chickens. 

 All States 



All of this caption deals with both species collectively. 



The coincidence between declines and lows is the more striking when one 

 considers the fact that the "low" dates a decade or more ago are based on a 

 rapidly decreasing number of localities, and to that extent probably do not repre- 

 sent true means. Thus, if there had been a decline associated with the last true 

 mean trough of the cycle (1927), and we attempted to correlate it with one or 

 two localities which happened to fall off early (let us say 1925), we would con- 

 clude it did not fall within the 3-year period 192627-28. The fact that despite 

 this we get a 66 per cent correlation seems to me to strengthen the conclusion 

 that sharp declines, not followed by recovery, are usually skipped cycles, that is, 

 lows not followed by recovery. 



Types of Present Range. The present habitats of the pinnated grouse 

 clearly fall into two classes and five types: 



