534 



PRODUCTIVITY OF GROUSE POPULATIONS 



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CONNECTICUT HILL 



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ADIRONDACK 



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NUMBER LOST 

 PERCENT DEVIATION FROM MEAN 



FIGURE 40. RELATIONSHIP OF FALL POPULATION LEVEL TO NUMBER OF ADULTS LOST ON 

 CONNECTICUT HILL AND ADIRONDACK AREAS — 1930-31 TO 1941-42 



25 



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 50 

 25 

 O 

 25 

 50 

 75 



-50 o +50 -50 o +50 



PERCENT LOST 



PERCENT DEVIATION FROM MEAN 



FIGURE 47. RELATIONSHIP OF FALL POPULATION LEVEL TO PROPORTION OF ADULTS LOST ON 

 CONNECTICUT HILL AND ADIRONDACK AREAS — 1930-31 TO 1941-42 



failed to conform to such a pattern may be traced to the fact that mortality is conditioned by 

 a number of hitrhly variable environmental forces in addition to the more stable ones of ranpe 

 quality. The relative number of birds surviving to breed in any year appears to be determined 

 to a large extent by the particular complex prevailing at the time. Thus, on the areas studied 

 by the Investigation, the relatively constant number of adult birds which the shelter and food 

 conditions should enable to survive each spring has been modified from vear to year by the 

 varying effect of these forces, especially weather and the availability of buffers. 



Fluctuations in the fall population level have been directly correlated with the relative num- 

 ber of maturing chicks each season. On Connecticut Hill the ratio of adults to these birds of 

 the year has averaged 1 :1.0, but has ranged all the way from 1 :1.6 to 1 :0.4. On the Adiron- 

 dack area the average has been 1:1.4, while the extremes have been 1:3.0 and 1:0.4 respec- 

 tively. It has been suggested that the younger birds might be more vulnerable and accord- 

 ingly represent an important factor in the above inverse relationship. 



