576 FLUCTUATIONS IIS GROUSE ABUNDANCE 



Weather 



Regardless, however, of what governs it, or to what extent it may or may not be related 

 to the forces represented by sunspot changes, the evidence is becoming increasingly strong that 

 weather is a primary factor in governing variations in grouse abundance. Data from the Con- 

 necticut Hill study area indicate that both temperature and precipitation are important. Other 

 elements of weather are undoubtedly involved also. Despite its evident significance, however, 

 a great deal still needs to be explained regarding the specific ways in which weather functions 

 in affecting grouse productivity. 



With respect to roajor fluctuations, the data discussed in Chapter VI* with respect to 

 the relationship between March and June temperature trends in New York and recurrent 

 grouse scarcity in this State reveal some agreement in point of time. Furthermore, tempera- 

 ture records for other grouse states exhibit similar degrees of agreement. Perhajjs this was 

 coincidence for exceptions also occurred. Certainly the channels through which it may have 

 exerted its affect are not clear. Then, too, temperature is only one element in the complex 

 of factors, even with respect to weather, operating in any instance. All of them vary in 

 intensity and no one of them is likely to be the best index at all times. Nevertheless, the 

 possibility of a connection warrants serious consideration. 



To speculate regarding the modus operandi of such a relationship is hazardous. One pos- 

 sibility, though, is indicated by observations during this Investigation. In view of the fact 

 that the evidence points most strongly to failure of the increment of young as the key to 

 grouse scarcity of this kind, weather may function through some physiological efifect in which 

 the weather conditions involved would not cause direct decimation but rather would set the 

 stage for subsequent losses. It must be emphasized that this is mainly conjecture. A sugges- 

 tion of something of this kind, however, is found in the data from the Connecticut Hill study 

 area^ which indicate a correlation between temperature and precipitation during the three 

 weeks immediately following hatching and the brood mortality occurring during the latter 

 part of the sununer. In this connection, too. may be cited the observation that a lack of sharp 

 temperature changes from day to night ma) iiihiliit the mating of sheep and thus result in 

 failure of the lamb crop^". 



If weather should prove to be a significant factor in recurrently synchronizing grouse 

 scarcity throughout large areas, the fact that, in spite of general conditions, it varies greatly 

 from place to place because of such influences as irregular topography and shifting storm tracks 

 would help to explain the disparities between localities which have been so frequently re- 

 corded. ]}ut how much fire there may be under all this smoke must await further research. 



I'opiilntion Density 



Aiiiilher piece which must event iialK be fitted into the ])uzzle pertains to the role of pop- 

 iilalinn deiisilv in relation to Hue luatioiis in grouse abuiulafHC. As was discussed in the chap- 

 ter dealing with produc ti\ il\ a IciiiliricN was iiolcd during llic Iinestigation for high breeding 

 populations to be less pruductixc. relatively, than low ones and fur this to result from a lower 

 increment of young being produced". Moreover, on llu- Ciniiici licut Hill study area those 

 compartments which exhibited relatively high densities at limes when the general average 

 was low were often those whiili. for one reason or another, had been low the preceding year. 



• Sec figure 23. ji. 305. 

 A See Choplei VI. p. 303. 

 t See Clupler XU, p. S40. 



