318 The Ruffed Grouse 



losses. There was no evidence of an undue preponderance of birds 

 of the year in these losses. Since these cases appear to deal with 

 noncyclic losses, they do not disprove the point. Since the evidence 

 that has been recorded supports this characteristic, we may accept 

 it. Certainly it checks with the breeding density-recovery inverse 

 ratio principle. 



7. Weather Conditions have no Correlation with Cyclic Grouse 

 Declines. 



Griddle ( 1930 ) says "that rainfall seems to be a far less influence 

 in accounting for grouse fluctuation than is generally supposed." 

 Braestrip (1940) concludes that "there is probably general agree- 

 ment today that it is impossible to explain the phenomenon by direct 

 climatic influence on the animals, as was at first supposed." Clarke 

 (1936), Middleton (1934) for British grouse cycles, and King like- 

 wise come to the conclusion that climatic factors do not affect the 

 cyclic die-off. 



Certain it is that some climatic factors, notably temperature and 

 precipitation, profoundly affect grouse survival. As we note in the 

 chapter devoted to weatlier in its effect on grouse, abnormalities 

 of weather conditions can bring about abnormally high losses of 

 grouse. These have been observed on Connecticut Hill both during 

 early summer ( on young grouse ) and in late winter. 



It has been suggested that adverse weather just after hatching 

 time may cause starvation of the young chicks by killing off their 

 insect food supply. Counts made on Connecticut Hill showed a 

 normal average insect density in the zone available to grouse chicks 

 of around 300,000 per acre in typical grouse brood cover types. 

 Since a large share of these insects live in the duff on the ground and 

 are types (such as ants) that are not greatly affected by weather 

 changes, this suggestion does not seem to offer much likelihood of 

 importance. 



8. Parasitic Infections and Diseases are not Correlated with 

 the Cycle. 



Following an early enthusiasm for disease as an answer to the 

 cycle problem resulting from the work of Allen and Gross (Allen, 

 1928; Gross, 1925) in the mid-twenties, most workers have dis- 

 counted the importance of epidemic sickness in giouse. However, 

 Clarke (1936) attributes to a particular blood parasite, Leuco- 

 cytozoon bonasae, primary association with grouse cyclic losses in 



