Weather Conditions in Relation to Grouse 187 



chicks died within ten days after exposure. Some of the broods 

 cited by Bump {op. cit.) lost from half to three quarters of their 

 numbers within a few days after the bad weather. Prompt and ade- 

 quate brooding by the mother grouse no doubt aids in preventing 

 such losses. 



If we assume that adverse weather in June will cause excessive 

 chick mortality, we might expect that the reverse conditions— warm, 

 dry weather in June— would be particularly beneficial, other things 

 being equal. However, 1933, a good season from this standpoint in 

 New York, had a very high brood loss. Other instances also provide 

 a full range of inconsistencies in respect to this factor. 



The best opportunity that we had to evaluate the possibilities of 

 excessive rainfall affecting grouse brood survival occurred in 1935. 

 On July 7 and 8, at a time when grouse broods were past the usual 

 period of high mortality, came the most severe cloudburst in the 

 recorded history of southern New York. During this two-day period, 

 approximately ten inches of rain fell (a summer's normal supply), 

 about eight inches of it the first day. This storm caused unprece- 

 dented floods and destruction over an area of about ten counties. 

 It was immediately apparent that disaster had overtaken the young 

 grouse. Observations both in and out of the flood area clearly showed 

 that the abnormal brood losses were in the area of high rainfall. As a 

 result of this one storm, an additional twenty per cent of the grouse 

 chicks were lost over what would have been expected to perish. 

 This meant that the survival of chicks was only fifty per cent of the 

 normal, as an increase in mortality from the normal sixty per cent 

 to 1935's eighty per cent left only twenty per cent of maturing birds 

 instead of forty per cent {N. Y. S. Cons. Dept. Ann. Rep., 1936). This 

 extra loss resulted in a marked decrease in grouse on the area that 

 fall and illustrated how a moderate addition to the normal mortality 

 will cause a big loss in the proportion of birds maturing. 



Hence, while severe cold and rain can prove disastrous to very 

 young grouse, the average annual early-season losses are only partly 

 explained. A normal, healthy grouse chick, with proper maternal 

 care, can get along pretty well in spite of the chilly nights, rain- 

 storms, and periods of protracted cloudiness. 



Effects of Winter Weather on Adult Losses. Throughout the year 

 the condition of the weather causes marked changes in the selec- 



