Productivity and Populations 307 



culminating in a peak in the breeding season in March and April. 

 From then on to summer, the losses drop off rapidly. 



The increased mortality rate in winter is due in a large measure 

 to the greater vulnerability of the birds to predation resulting from 

 winter weather and poor cover conditions, and from the increased 

 intensity of hunting by predators. The continuance of the high mor- 

 tality into the breeding season is to a considerable extent the result 

 of increased losses of male birds resulting from exposure during the 

 courtship period. This differential mortality among the sexes seems 

 to be balanced at other times of the year by greater losses among 

 females than males. This is particularly true in the summer and fall. 



In most years the greatest immediate source of adult loss is preda- 

 tion. However, it is highly probable, in fact quite certain, that 

 predation takes more than its fair share of the blame. When there 

 is evidence of predator work on the remains of a grouse, the cause 

 of death is usually credited to the predator. Many times the predator 

 plays a secondary, and often unimportant part in causing the death 

 of the grouse. Grouse that are weakened by wounds from hunting 

 or from physical accidents are often taken by predators before suc- 

 cumbing from their injuries. I recall an occasion when a man winged 

 a bird and was unable to retrieve it. Over a month later my setter 

 dog pointed a grouse within a hundred yards of this same location 

 and, finally breaking point, caught the bird. It proved to be the one 

 winged some time before— still in good health but unable to fly. Or- 

 dinarily this bird would have been caught by a wild predator— and 

 its loss erroneously attributed to that animal. Likewise, some grouse 

 that die from disease or accident are eaten as carrion. These cases 

 too would have evidence of predator work, although many times 

 they can be identified as carrion from other evidence. 



Notwithstanding these facts, most adult grouse in the Northeast 

 wind up their lives as food for some other wild creature, as the Lord 

 intended they should. The exact proportion that die primarily at the 

 'Tiands" of claws or talons cannot be determined because of the 

 obscuring evidence already noted. And even among those that actu- 

 ally die directly and essentially from predation are many whose fate 

 was influenced by weather conditions, overpopulation, scarcity of 

 other prey species, etc. After an evaluation is made of all of the com- 

 plicating factors, we conclude that predators cause about fifty per 

 cent of the kflling of grown birds in normally hunted coverts and 



