The Diseases and Parasites of Wild Ruffed Grouse 249 



grouse by the New York study [N. Y. S. Cons. Dept. Ann. Reps., 

 1935-37) in the three years 1935 to 1937. None was found in other 

 years. No indication was given of any importance attached to these 

 infestations. 



TOTAL PARASITE INFESTATION 



In discussing each organism that parasitizes the ruffed grouse, the 

 conclusion was almost always reached that the species was not a 

 very serious mortality factor. Most have not been demonstrated to 

 be lethal even when prevalent and widespread in occurrence. None 

 of the afflictions known to cause death commonly is widely dis- 

 tributed. The stomach worm {Dispharynx spiralis) is apparently 

 restricted to parts of New England and the middle Atlantic states, 

 the blood parasite (Leucoctjtozoon bonasae) primarily to Ontario, 

 and tularemia to the north-central states. No one disease-producing 

 organism has been shown to cause major grouse declines over a wide 

 range. 



Possibly of more significance as an indicator of the importance of 

 disease as a mortality factor than each parasite by itself is the total 

 prevalence of all parasites and diseases. It is entirely logical that 

 there would be a cumulative effect when more than one organism 

 is attacking an individual bird. The effect of several species could 

 result in death whereas any one of them alone might not have caused 

 trouble. 



The proportion of grouse having one or more parasites or disease 

 organisms has varied with a clear-cut trend in New York in the 

 period 1930-42. The autopsy records are not available to corrobo- 

 rate the belief that parasitism was at a low ebb in 1930 and 1931 

 but circumstances indicate it to be true. Beginning with 1932 the 

 incidence of parasitism increased steadily; forty-eight per cent in 

 1932; sixty-four per cent in 1933 and sixty-one per cent in 1934; then 

 ninety-five per cent, ninety-two per cent and ninety-four per cent 

 in 1935, 1936 and 1937, respectively. Then followed a decline in 

 parasite incidence beginning with a seventy per cent rate in 1938, 

 followed by fifty-five per cent in 1939 and forty per cent in 1940. 

 The next two years indicate another period of increase, the 1941 

 rate being fifty per cent and that of 1942, sixty per cent. 



The periods of increase exactly parallel these of growth in the 



