LOCAL CONDITIONS AND HEALTH OF GROUSE 299 



NOTE 



Since the foregoing chapter was written an opportunity 

 has occurred of studying the effects of prolonged drought upon 

 the health of Grouse. The spring and summer of 1911 was one 

 of the driest ever recorded. From May till September the 

 drought was almost unbroken all over the country except for 

 a few days' rain in June in certain parts of Scotland. All 

 surface water disappeared, and all but the deepest springs 

 were dried up. 



The opportunity was a good one for putting to the test 

 the results of previous observations. This was specially desir- 

 able so far as related to young Grouse, for as we have stated 

 there were grounds for believing that heat and drought were 

 favourable to the development of the intestinal parasite Eimer- 

 ium (Coccidium) avium, which had been identified as a cause 

 of mortality among chicks. But although this suspicion was 

 supported by the circumstance that in very dry summers there 

 was often a mysterious disappearance of young Grouse, and 

 further by laboratory experiments which proved that this 

 parasite developed most quickly under the influence of dry 

 warmth, yet there was still a hiatus in the chain of evidence, 

 for it had never been clearly proved that the young Grouse 

 which had disappeared in previous dry seasons had actually 

 died of Coccidiosis. 1 



In studying the effect of the abnormal drought of 1911 the 

 following points were kept in view : 



(1) If a shortage of young Grouse was reported in the shoot- 



ing season, was this shortage due to mortality among 

 the chicks or to failure of the hatching season owing to 

 the eggs being few in number or unfertile? 



(2) If it could be shown that such shortage was due to mor- 



tality among the chicks, was there any cause other 



For fuller details regarding Coccidiosis see chap. ix. pp. 246 et seq. 



