PRODICTIVITY OF POPULATIONS 



529 



densities. In both cases the years included in each group were well distributed throughout the 

 period of study. 



TABLE 82. RELATIONSHIP OF DENSITY OF GROUSE CHICKS AT HATCHING TIME TO 

 SURVIVAL DURING BROOD PERIOD ON CONNECTICUT HILL AND 

 ADIRONDACK STUDY AREAS— 1930-1942 



* Croup I — years having a density of chicks at hatching oo Connecticut Hill of under 15 per 100 acres, on the Adirondack area 

 oi under 10. 



Croup II — years having densities between IS and 20. and over 10 reitprrtively. 



Croup III — years on Connecticut HiU with densities over 20. 



Nevertheless, the trend in the number <>f chicks left as of September 1 each year has fol- 

 lowed in general that of the number hatched (figure 44). This was not true on Connecticut 

 Hill in 1935, however, when a marked increase in the rate of mortality occurred as a result 

 of abnormal weather conditions. The same season witnessed a very low survival on the north- 

 ern area, too, although the number of chicks hatched was the lowest recorded. Survival was 

 poor on both areas in 1933 also. 



On the other hand, if the years are grouped according to the density of the breeding pop- 

 ulation — in which case wide ranges of chick abundance are included together — one finds an 

 inverse relationship with respect to the percentage of brood survival (table 83). The degree 

 to which this may represent cause and effect as well as the reasons which may be involved, 

 however, are not apparent. One possibility for speculation is that the forces responsible for 

 lowering the breeding population level may tend to result in an increase in the average stam- 

 ina of the remaining stock. A similar condition among the progeny of these birds might then 

 account for the better brood survival associated with them. 





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