ROLE OF PREDATION 



319 



significant, too, that less than half a dozen instances of this kind have been witnessed in 

 upwards of 50,000 grouse flushes observed by the Investigation's field crews. Unless dis- 

 turbed, these birds seldom resort to reckless bursting flight. The possibility that any large 

 number year after year bring about their own demise by crashing into trees or other obstruc- 

 tions in their environment seems quite remote. 



Turning to disease pathological examinations have shown a very low incidence of conditions 

 which might prove fatal to grouse, both on the study areas and elsewhere over the State*. 

 Of 143 specimens collected on Connecticut Hill less than 5 per cent could have been expected 

 to succumb from this cause. Throughout the survey on this area but 20 birds have been found 

 dead, showing symptoms of disease. Unquestionably many other instances occurred but 

 there is little likelihood that this factor has been responsible for more than a very minor part 

 .of the overwinter losses recorded during this study. 



Thus, by the process of elimination, one must conclude thai the great majority of the 

 specimens found each year are attributable to predation as the original decimating agent, 

 although it is implemented in varying degrees by a number of influences affecting the vul- 

 nerability of the birds. Unquestionably accidents, disease and other circumstances have 

 taken a small toll — perhaps upwards of 15 per cent. Assuming that these data are repre- 

 sentative of the total losses occurring it seems probable that predation may be considered 

 to have been responsible for something over 80 per cent of the annual mortality among adult 

 grouse, or in the neighborhood of 40 per cent of the fall population on the areas involved.'^ 



FEATHER REMAINS INDICATING THAT AN ADULT GROUSE WAS KILLED BY A HAWK OR OWL 



Losses during this period have differed considerably from year to year. Especially note- 



* See Chapter X, p. 410. 



A These areas were not shot over in the fall. 



