264 THE GROUSE IN HEALTH AND IN DISEASE 



It is significant that not one moor with a stock below the 

 average had high mortality among chicks, whereas nearly three- 

 fourths of the moors which were understocked were absolutely 

 healthy. 



These figures seem to imply that overcrowding is a contribu- 

 tory cause of Coccidiosis ; but there must be many other factors 

 which combine to influence the distribution of the disease, for 

 it will be seen from the table that many moors were very heavily 

 stocked and yet remained perfectly healthy. 



nmary of Considering Coccidiosis as the chief cause of high mortality 

 among Grouse chicks the evidence of the reports for 1906, 

 1907, 1908, and 1911, may be briefly summarised as follows : 



1. In wet, cold seasons Coccidiosis probably rarely 



occurs. 



2. In hot, dry seasons Coccidiosis is more frequently 



observed. 



3. Its intensity appears to be but little affected by the 



water supply on the moor. 



4. When the drought is universal, as in 1911, Coccidiosis 



is not universal. 



5. High mortality in chicks then is not caused by heat 



and drought, but when the coccidian infection is 

 present heat and drought seem to assist the develop- 

 ment of the disease. 



6. A heavy stock of birds appears to be one of the 



contributory causes of infection. 



Other deductions might be made from the reports which 

 might lead to further elucidation of the subject, and one or two 

 special features reported from individual moors might also throw 

 light upon the nature and effects of the disease. 1 For example, 

 on one moor where the outbreak was particularly severe the 

 young chicks died in large numbers at a few weeks old, the 

 survivors then seemed to make a partial recovery, but about 

 July they again commenced to die, and continued to do so till 

 late into September. On examination, it was found that the 



1 See also pp. 302-303. 



