218 



The Ruffed Grouse 



We may fairly conclude that the numbers of several of the preda- 

 tory animals are responsive to changes in the numbers of their chief 

 prey species. The response in decline of predators may take up to 

 two years following marked changes in rodent numbers to become 

 significantly apparent. 



PREDATORS 

 (Primarily foxes, weasels, 

 horned owls and hawks) 



RUFFED GROUSE 



1930-31 1931-32 1932-33 1933-34 



1934-35 

 YEARS 



1935-36 1936-37 1937-38 1938-39 



Fig. 10. Generalized Population Trends of Ruffed Grouse, certain Predators, 

 and certain Rodents New York State 1930-1939 (Based on State Game Kill 

 Records and field data) 



Turning now to the trends in ruffed grouse in comparison with 

 those of rodents and predators, there are both correlations and lack 

 of correlations. We find that the Connecticut Hill trends indicate 

 that the population drop in 1933 was probably not associated with 

 predator-buffer trends, the 1935 decline is definitely not so associ- 

 ated, while the 1937 decline is quite probably linked with these 

 trends. In examining the state-wide game kill records ^ there appears 



^ These records are well-known to be inaccurate; but since the sources of error are 

 the same each year, tlie trends indicated may be quite reliable. 



