306 INFLUENCE OF WEATHER 



thai certain conditions may occasion severe direct losses while both immature and adult grouse 

 may be aflectcd indirectly by temperature and precipitation. In its 13 years of study, the In- 

 vestigation has had opportunity to observe the effects of many weather conditions. Neverthe- 

 less, even this period is comparatively short in relation to wildlife cycles. Therefore, an attempt 

 has been made to correlate existing information over a longer period. To this end, fluctuations 

 in grouse abundance as recorded for New York by other observers and the records of the 

 Weather Bureau since 1890 were brought together. 



If periodic declines in grouse numbers have been directly related to weather conditions, 

 some unusual deviation from normal should be evident in the records for the years associated 

 with such lows. Conversely, similar deviations should not have occurred at other times. Exper- 

 ience on the Connecticut Hill study area, as already presented, indicated temperatures during 

 March and June have been most closely correlated with mortality. Therefore, data for these 

 months* were plotted against the recorded periods of grouse scarcity as shown in figure 23. 



Some degree of agreement is apparent in this graph between periods of grouse scarcity and 

 years when March and June temperatures were both unusually low, although there appears 

 to have been an unaccountable lag of a year between the two. In 1906, however, only March 

 was severe. On the other hand, in 1900, in 1912 and again in 1940, similar conditions occurred 

 without a decline in grouse being recorded, although only in 1912 was June below average. 

 Nevertheless, no major decline has been recorded in New York which was not preceded by 

 colder than average weather during one or both of these months. One must bear in mind, too, 

 that this is only one factor affecting grouse abundance and other influences may often outweigh 

 it. 



In considering the implications of this material, it becomes obvious that a great deal of data 

 of a much more |)rp(ise nature will need to be taken before definite conclusions can be reached 

 as to the relationships involved. Even knowledge gained from physiological studies in the 

 laboratory will be difficult to interpret without more detailed information with respect to the 

 specific conditions under which grouse live in their various habitats. 



The standard measurements of the Weather Bureau are taken by means of instruments placed 

 on a platform six feet above the ground in an open s])ot. \et few animals spend much time in 

 such a situation. Rather, they are constantly on the move satisfying the many necessities of 

 their daily life In doing this they naturally take advantage of the most favorable situations 

 atliirdcd l>y the environment. Thus the shaded thermometer at a "weather station" may regis- 

 ter 20 degrees below zero, but if a grouse occupies a protected nook on a sunny south slope 

 during the dav and resorts to a snow-roost at night, it has succeeded, to a considerable extent, 

 in minimizing the effect of that temperature. 



The problem is complex, to say the least. 



* The valiip used par\\ yrjir ronftistpd uf llir mint of the ili-viiiiiuii^ fnini the »tnndatil mruri of ihr uveragc lemperaturrt for 

 Marrh anit June. 







