WEATHER AS A DIRECT DECIMATING AGENT 



301 



many others exist but more detailed study will be required to reveal them. Even with those 

 noted so far, however, it is impossible to establish the exact degree to which they represent 

 cause and effect. Nevertheless, they indicate relationships, a knowledge of which is highly im- 

 portant to an adequate understanding of the pattern of wildlife existence. 



WEATHER AS A DIRECT DECIMATING AGENT 



In general, weather appears to be of negligible importance as a direct cause of death among 

 grouse. During the period of egg laying*, snow and freezing temperatures, both potentially 

 destructive, have frequently occurred. In one instance a low of 21° F. was accompanied by 

 two inches of snow which remained on the ground for four days. \et no increase in the 

 failure of eggs to hatch has been associated with such conditions on the areas studied. Prob- 

 ably their location, close to the ground, which did not freeze, was largely responsible. Un- 

 doubtedly, however, temperatures much lower than this would kill eggs. 



Similarly, losses among grouse chicks, in the experience of the Investigation, have rarely 

 been attributable directly to this factor. Many times, contacts with the same brood, both before 

 and after cold, rainy periods, have shown no evidence of higher mortalitv ihan that occurring 

 under seemingly more favorable conditions. Deliberate flushing of young broods, under ten 

 days of age, during rain storms has not been followed by an immediate loss, although in sev- 

 eral instances the chicks were known to have been soaked. That such a wetting can be serious 

 is indicated, however, in that two broods of very voung chicks at the Catskill {{caring Station 

 lost most of their numbers through failure of the mother grouse to brood tlii-ni throughout 

 severe thunder storms. 



On another occasion weather did appear to have a direct effect. In central New York, in the 

 summer of 1935, a relatively cold, wet June was followed, on July 7 and 8. by the worst cloud- 

 burst in the history of the region. On the Connecticut Hill study area, approximately 10 

 inches of rain fell in the two days, some 8 inches of it coming the first day. Despite backward 

 conditions during June, no indication of an above average brood mortality had been observed 

 ])rior to the storm. Yet, by July 15, losses had jumped to 66.1 per cent, by far the highest 

 recorded up to this date. There is little doubt that the July flood, culminating the none too 

 favorable June, was primarily responsible for the excessive mortality. But such storms are 

 extremely rare. 



In this connection, on the other hand, in 1937, over 6 inches of rain fell in 24 hours during 

 the latter part of August, resulting in nearly as severe a flood as occurred in 1935. The young 

 birds at this time were approximately 12 weeks old and their adult plumage was essentially 

 Complete. No increase in mortality was observed. Thus it would seem that chicks, up to 

 about six weeks of age, are vulnerable to severe rain storms, but that, sometime between then 



* A clutch begUD as early as April 7 has been recorded for the Adirondack region. 



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