ROLE OF PREDATION 327 



Coincident with the grays the red squirrel {SciuTus hudsordcus) population on Connecticut 

 Hill has followed a closely parallel trend. In the Adirondack region also this species reach- 

 ed an abnormally high level of abundance in 1935 following which it fell off sharply. 



To sum up it seems evident that in New York bufiEers fluctuate markedly in numbers, sev- 

 eral approaching a cyclic pattern, but that these fluctuations are not harmonious. Fur- 

 thermore, even during periods of low abundance, an appreciable population remains, partic- 

 ularly since all species seldom hit the bottom together. 



Predator Pressure 



One might think that, so long as predator numbers remain relatively constant, their effect 

 on grouse should not change materially. Such is not the case, however. Relationships of 

 this kind are affected by innumerable other circumstances. The abundance of a game bird 

 or animal in comparison with that of its natural enemies and buffers as well as the quality 

 of the protection afforded by its habitat are major influences. In general the more abun- 

 dant a species is the more often it will be encountered by predators. On the other hand, 

 the smaller the game population the greater the significance of individual losses. Yet, as 

 Errington has reported for quail'"', a compensatory influence exists in that many prey species 

 appear to become more secure as the number living in a habitat approaches the level where 

 only the higher quality territories are occupied. 



But, even though the numbers of grouse and its predators did not vary appreciably, the 

 degree of predation would be increased or decreased as a result of a wide variety of other cir- 

 cumstances. As with upland game birds in general, grouse do not represent a staple food of 

 any predatory species. Rather they are taken as the opportunity presents itself although 

 they are preyed upon more heavily as buffers* become scarcer. Then loo changing weather 

 conditions continually affect the availability of prey of all kinds. 



The number of combinations of such circumstances is endless. Adequate appraisal of their 

 effect on the relative pressure exerted by various predators at different times is, according- 

 ly, difficult. The Investigation has revealed a few of these relationships, particularly with 

 respect to the Connecticut Hill study area. 



Throughout the period of survey certain coverts ])roved consistently superior to others in 

 their ability to support grouse populations over winter. Some tendency has also been noted for 

 snow-roosting birds at times to be more vulnerable to predation. Experimental predator 

 control brought about reductions in nest mortality during the seasons immediately involved. 

 During the winters in which goshawks appeared grouse kills attributable to them were found 

 but the net effect on overwinter loss was not appreciable^. 



Differences in the effectiveness of various buffers have also been observed. Thus squir- 

 rels are usually more difficult to secure than most of the others. Deep snow sometimes renders 

 mice and shrews largely unavailable. The residual numbers of varying hares during periods 

 of scarcity are much lower than is the case with respect to cottontails. Predilection among 

 predators seems largely a question of availability both as to presence and ease of capture. 

 Dislike for potential food species appears to be of minor consequence although there is some 

 indication that shrews are not well-liked by foxes. 



That unusual local abundance of grouse may cause a concentration of predator activity 

 was demonstrated when one section of the Comiecticut Hill study area attained a density of 



* See discusaion of Buffer Fluctuations, p. 325. 



A No pronounced influx of ttiis apecicB was experienced during the Investigation. 



