18 THE GROUSE IN HEALTH AND IN DISEASE 



a real menace, for if the nesting season is a dry one Grouse 

 have been known to nest in very unsuitable places, such as 

 the beds of burns and dried-up pools and water-courses often 

 with disastrous results when the weather breaks. 



But, if there has been no rain, the drowning theory must 

 be discarded, and its place is taken by the drought theory ; 

 in other words, the fine, dry, warm, sunny weather which is 

 credited with producing a healthy stock in a good year is the 

 cause of their wholesale destruction in a bad year. 



Nor do we know exactly what proportion of Grouse meet 

 their fate from vermin ; that a certain number are killed by 

 foxes, ravens, hoodie crows, stoats, weasels, and even gulls, 

 may be admitted ; but when we come to apportion the blame 

 we again find ourselves without sufficient evidence to amount 

 to proof. The subject of vermin is dealt with more fully in 

 a later chapter. 1 



Occasionally it is found that old birds as well as young 

 have disappeared, and when this happens it is customary to 

 ascribe the cause to " Grouse Disease " amongst the adult 

 birds, for it is well known that if a parent bird dies from disease 

 or any other cause there is little chance of her brood surviving. 



At a very early stage of the Inquiry it became evident that 

 the loss of young stock on a large scale had never hitherto been 

 properly accounted for, and required further investigation by 

 the Committee. 



The Committee were able to offer a solution of this 

 problem. During their Inquiry into the causes of mortality 

 in Grouse they discovered a certain unicellular intestinal para- 

 site, one of the Protozoa, a Coccidium, known as Eimeria avium, 

 which in certain cases is most destructive to the young chick, 

 but is rarely fatal to the adult bird ; this Coccidium is fully 

 described in chapter ix. 2 The discovery of the disease caused 

 by this pathogenic organism and known as Coccidiosis justifies 

 the view that when there has been extensive mortality amongst 

 the young stock which cannot be accounted for in any other 



1 Vide chap. xiv. pp. 403 et seq. 2 Vide chap. ix. pp. 246 et seq. 



