Interrelationships of Ruffed Grouse 221 



prevents a higher degree of survival so that further increases are pre- 

 vented. 



We have aheady seen that drastic control of predators may bring 

 about an increase of grouse when the density is quite low, and that 

 it fails to have that result when populations are high. When the 

 number of grouse is more than the envii-onment can safely accommo- 

 date, decline is inevitable. The conclusion seems to be that predators 

 may limit grouse populations when below the peak of their upward 

 trend, but still do not ordinarily prevent them from increasing to a 

 greater density that permits another limiting factor to bring about 

 declines beyond expected seasonal losses. These relations of popu- 

 lation densities to changes in population level are fundamental and 

 override all others including predator-prey relationship. 



REFERENCES AND CITATION SOURCES ON RELATIONS 

 OF RUFFED GROUSE TO OTHER ANIMALS 



Bennett, L. J., and English, P. F. Food Habits of the Grey Fox in Penna., 



Penna. Game News, Vol. XII, No. 12, March, 1942. 

 Bezdek, F. H. (Progress report on research into methods of increasing ruffed 



grouse populations), Pittman-Robertson Quarterly, Vol. 3, No. 4, Oct., 1943. 

 Cook, D. B., and Hamilton, W. J., Jr. The Ecological Relationships of Red 



Fox Food in Eastern New York, Ecology, Vol. 25, No. 1, Jan., 1944. 

 Dean, R. Unusual Abundance of American Goshawk, Auk, Vol. XXIV, No. 2, 



1907. 

 Dearborn, Ned. Foods of Some Predatory Fur-bearing Animals in Michigan, 



Univ. Mich., School of Forestry and Conservation Bull. No. 1, 1932. 

 Eadie, W. Robert. Food of the Red Fox in Southern New Hampshire, Journ. 



Wildlife Mgt., Vol. 7, No. 1, Jan., 1943. 

 Edminster, F. C. The Effect of Predator Control on Ruffed Grouse Populations 



in New York, Journ. Wildlffe Mgt., Vol. 3, No. 4, Oct., 1939. 

 English, P. F., and Bennett, L. J. Red Fox Food Habits Study in Pennsylvania, 



Penna. Game News, Vol. XII, No. 11, Feb., 1942. 

 Errington, P. L. Food Habits of Mid-west Foxes, Journ. of Mammalogy, Vol. 16, 



No. 3, 1935. 

 Errington, P. L., Hamerstrom, Frances, and Hamerstrom, F. N., Jr. The Great 



Homed Owl and Its Prey in North-central United States, Res. Bull. 277, 



Iowa State College Agr. & Mech. Arts., 1940. 

 Fisher, A. K. The Hawks and Owls of the United States in Their Relation to 



Agriculture, U.S.D.A. Div. Omith. & Mammal. Bull. No. 3, 1893. 

 Gerstell, Richard. The Pennsylvania Bounty System, Res. Bull. No. 1, Pa. Game 



Commission, 1937. 

 Gross, A. O. Food of the Snowy Owl, Auk, Vol. 61, No. 1, Jan., 1944. 



