332 PRE DAT ION 



winter mortality of which predation has been the chief agent. Moreover, since there is an 

 inherent maximuin to the carrying capacity of each covert the elimination of predation would 

 only result in some other factor, possibly disease, sooner or later assuming its role. It can- 

 not be emphasized too strongly that no data so far give any promise that the principle of 

 compound interest can be applied to grouse or similar game populations. 



On the other hand predation during the nest and brood periods does represent a factor 

 limiting the fall abundance which might otherwise occur. Under primeval conditions such a 

 staggering of the total reduction which must take place is advantageous. Where man's pursuit 

 of the bird for sport — being, as it is, confined to the fall — is important, however, the advan- 

 tage is less real. But this point of view is valid only where such sporting activities are suf- 

 ficient to utilize the bulk of any additional surplus it might be possible to produce. Unless 

 so utilized they might better furnish dessert for some predator as eggs or chicks since few 

 would survive to breed. 



Another function of predation is that of culling crippled, sick or otherwise defective stock. 

 The Investigation has little direct evidence, however, of the importance of this service. In 

 the first place crippled birds have not been present on the study areas since no shooting has 

 been allowed. Furthermore, the incidence of disease has been negligible. Then, too, one marked 

 female, in spite of a broken wing was known to have hatched her clutch of eggs and success- 

 fully reared her brood. Nevertheless, such relationships may at times be highly valuable. 

 Some effect of this kind probably occurs during the brood period since a large proportion 

 of the losses at this time appear to result from causes other than predation. It is also likely 

 that the effect of weather on adult mortality suggested in Chapter VI, if real, operates through 

 fostering the decimation of the weaker individuals. Certainly there can be little doubt that 

 over the period of its evolution the constant necessity of eluding its natural enemies has been 

 a major influence in developing the very qualities which today make the grouse so prized a 

 game bird. 



Finally, in considering its significance one must make a distinction between the fact of 

 predation on individual grouse and the effect of predation on populations of this game bird. 

 Obviously the inevitable reduction of its potential productivity must involve the death of a 

 large number of individuals in one form or another, many by predators. But only under 

 very unusual circumstances does such decimation endanger the maintenance of population 

 levels in accordance with the carrying capacity of the habitat. Perhaps the greatest obstacle 

 to an understanding of the role of this factor has been the failure to appreciate this difference. 



APPRAISAL OF THE VARIOUS SPECIES 



In addition to an understanding of the role of predation as a factor in the life equation 

 of grouse the game manager must also know what predators occur in his locality and what 

 their relative importance is. An appraisal of the various species in New York has been an 

 integral part of this study. 



CHdisK Predators of the Northeast 



At one time or another <;rouse have probably fallen prey to nearly every carnivorous bird 

 and animal occurring within its range, except those entirely incapable of attacking it. Be- 

 yond this its eggs are often destroyed by a number of other species. 



Among wild mannnals the Investigation has recorded the red fox fVulpes fiilva), gray 

 fox (Urocyon cinereoargenteus). New York weasel (Mustela noveboracensis), Bonaparte 



