244 THE GROUSE IN HEALTH AND IN DISEASE 



Although healthy Grouse are at a much lower ebb, as 

 evidenced by their average weight, during certain months of 

 the year than during others, Strongylosis does not necessarily 

 kill them off at these seasons. It kills off the hens when they 

 ought to be at their flood tide of health and vitality ; and the 

 cocks when they ought to be on a good rising average tide. 



We have thus a paradox which may be stated in the following 

 terms : 



More hens die of Strongylosis during April and May than 

 in any other month of the year, notwithstanding the fact that 

 the healthy hen is then at her best so far as weight, fat, and 

 plumage go. 



More cocks die of Strongylosis during April and May than 

 in any other month of the year, notwithstanding that the healthy 

 cock is then already recovering the weight which he lost during 

 courtship, and is at a fair average and rising weight. 



And although one might expect cock birds to die in March and 

 September, when the average weight is at its lowest, this does 

 not occur. 



And whereas one might expect hen birds to die in June and 

 July, or in November, when the average weight in health is 

 at itsjbwest, this also does not occur. 



In attempting to explain this paradox, it is necessary to 

 recapitulate shortly the conditions which lead to an over- 

 infection of the Grouse with the larval Strongylus. 



Elsewhere it has been pointed out that, owing to the small 

 proportion of heather which produces good food during the 

 months of February, March, and April, all the birds upon a 

 moor "are forced to concentrate upon small areas of feeding 

 ground. 1 Consequently there is a tendency for these small 

 areas to become heavily infected with Strongyles even from the 

 droppings of healthy birds. At first there are no evil results, 

 for the eggs take some weeks to go through the necessary 

 stages of metamorphosis without which they cannot become 

 actively dangerous to the health of the bird. 2 Thus, even by 



1 Vide chap. iii. p. 90. 2 Vide p. 233. 



