Weather Conditions in Relation to Grouse 189 



tality rate was very high, from twenty-five to one hundred per cent 

 more than in normal years. The increased losses occurred in Febru- 

 ary and March, coinciding with the period of unusual snow-roost- 

 ing. Whereas the normal curve of mortality reaches a peak in April, 

 or is at about the same height for March and April, the years of in- 

 creased winter predation brought on by adverse weather show a 

 peak in February or March. In 1936 it occurred in March. 



Weather conditions other than snow and sleet are of little im- 

 portance in causing or inducing grouse mortahty. Low winter tem- 

 peratures, unless accompanied by a heavy snow, do not seem mate- 

 rially to aflFect the birds. The winter of 1933-34 gave ample chance 

 to learn of any possible connection between temperature and winter 

 loss. Over half the days of February gave below zero (Fahrenheit) 

 readings, with an extreme of thirty degrees below. The monthly 

 mean was thirteen degrees, which is twelve degrees below average. 

 Yet there was no indication of accelerated predation, and the mor- 

 tality records indicated only the normal winter losses. 



Extremes of summer heat send the birds to coniferous shelter, as 

 does cold weather. Mousley (1919) attributed a noticeable increase 

 in grouse in Stanstead County, Quebec, in the summer of 1919 to 

 a prolonged hot spell. If rain could cause any increase in deaths of 

 adults, this should have been reflected in the 1935 summer cloud- 

 burst that so affected the youngsters. No losses of grown-ups attrib- 

 utable to this storm could be recognized. 



Snow and Sleet in Relation to the Food Supply. The deep snows of 

 the northern winter conceal and largely render unavailable the 

 fruits and leaves on the ground and on low-growing plants. Under 

 these circumstances the birds resort to budding but it is remarkable 

 the quantities of food as ferns, wintergreen, Canada mayflower, and 

 the like that they manage to obtain under even the worst of condi- 

 tions. A man may be wholly rmable to see any of these plants, but 

 the grouse get at them somehow. The ability of the bird to subsist 

 on buds alone, for how long or how well we do not know, reduces 

 the chance of its being starved when so much of its preferred 

 foods is covered by snow. 



Occasionally a freezing rain will encrust a snow, making the food 

 supply on the ground even less available, and at the same time may 

 sheath the tree buds with ice. Under such a condition grouse may be 



