Interrelationships of Ruffed Grouse 213 



Following the two-)'ears' study of predator control in 1931 and 

 1932, a year was allowed to elapse and then the experiments were 

 resumed. With the possibility in mind that the results of the first 

 experiments may have been affected by factors peculiar to the two 

 subareas, the trapped and untrapped areas were reversed in the 

 second series of tests beginning late in 1933. 



Trapping and shooting were carried on from October 1, 1933, to 

 April 30, 1934, rather than for the full year as previously. The 1934 

 experiments continued the complete control with a no-trapping 

 check area. A total of one hundred and one birds and ninety-four 

 mammals were taken, including thirty-seven homed owls, fourteen 

 foxes, nineteen skunks, ten weasels, and twenty accipitrine hawks. 



As in the earlier experiments, the outstanding species taken was 

 the homed owl, which is probably the most efficient ( if not always 

 most important) of the common grouse predators. The mammalian 

 predators showed practically the same abundance as in the first 

 experiments, with the two species of foxes being most important. 



The nest mortality on the subareas for 1934 was twenty per cent 

 for the trapped portion and forty per cent for the untrapped. The 

 following summer, the brood mortalities were fifty-two and three- 

 tenths per cent and fifty-six and three-tenths per cent respectively. 

 By calculation, the loss of adults on the trapped area was twenty- 

 three and seven-tenths per cent and that on the untrapped thirty- 

 two and two-tenths per cent. 



In reversing the trapped and untrapped areas the results, too, have 

 been reversed. Nest mortality was decreased by one half, brood 

 mortality slightly lessened, and adult losses lowered appreciably. 

 We conclude that the predator-control-effect data were not seriously 

 confused by other factors, although detailed accuracy of the results 

 cannot be claimed. If comparability of the results of the two experi- 

 ments was maintained, the 1934 fall population densities on the two 

 subareas should have shown little difference, as was the case in 1932, 

 since 1934 was another peak year. The density on September 1 on 

 the trapped area proved to be a bird to five and six-tenths acres 

 while on the untrapped portion the ratio was five and five-tenths 

 acres per grouse. Thus, we find the result repeated that in a peak 

 year even effective reduction of the nest mortalitv bv predator con- 

 trol does not appreciably increase the fall population on unshot 

 areas. 



