212 The Ruffed Grouse 



ful with the honied owl, marsh hawk, and crow/ Species which 

 showed httle or no reduction the second year included the Cooper's 

 hawk, sharp-shinned hawk, sparrow hawk, red fox, gray fox, skunk, 

 domestic cat, red squirrel, and raccoon. Considering only the more 

 important grouse predators, control apparently showed some effect 

 on the horned owl, crow and small brown weasel; but made little 

 dent in the Cooper's hawk, sharp-shinned hawk, red fox, gray fox, 

 skunk, and raccoon numbers. 



Even though some of the most important grouse predators re- 

 mained as abundant the second year as the first, there may have 

 been an immediate effect on the grouse by the temporary reduction. 



The data indicate that the predator control reduced the nest 

 mortality markedly both years. During the first year the brood- and 

 adult-mortality records show a small differential favoring the trapped 

 sections, but in the second year the brood mortality was practically 

 identical on the two tracts and the adult mortality was actually 

 higher on the controlled portion. But even though the predator con- 

 trol proved unable consistently to lower the brood or adult losses, 

 the reduction in nest loss accomplished might produce a higher 

 shootable fall population. 



In the fall of 1931, while the grouse population of the area was 

 still well below carrying capacity, the predator-controlled portion 

 had a markedly higher population density. These additional grouse, 

 twenty-five per cent more than on the check area, may reasonably 

 be credited to the control of predators. Then the second year, with 

 a nearly peak population at hand, the effect of the predator control 

 was negligible, although still producing a slightly more dense popu- 

 lation than developed on the untrapped subarea. It appears then 

 that the increase in adult mortality on the controlled portion the 

 second year, presumably brought on by the higher population 

 density the first fall, almost completely offset the saving in nests. 

 That is to say, the inevitable inverse relationship of productivity to 

 breeding density canceled any possible benefits of predator control. 

 Thus the vital part that population level plays in determining grouse 

 losses indicates the futility of attempts to regulate them. 



The value of predator control in high population seems, from this 

 test, to be negligible. 



^ Since these species are migratory, the indicated results may have resulted merely 

 from variations in the annual flights. 



