140 THE GROUSE IN HEALTH AND IN DISEASE 



villous engorgement due to the irritating presence of thousands of Tricho- 

 strongylus (threadworms). In this state the bird is flushed and shot, and 

 forwarded for a diagnosis. 



And still one more perplexing item, namely, that scattered here and 

 there amidst a hundred thousand Trichostrongylus ova, in the contents of 

 the intestine, are encysted spores of Coccidia, showing that the bird may have 

 lost weight in the height of the summer by excessive Coccidiosis, and yet 

 have survived. 



Our investigations have established that one form of sickness commonly 

 called " Grouse Disease " is due to the excessive infestment of Grouse by 

 Trichostrongylus, and the most easily recognised symptom of this disease is 

 loss of flesh and weight. 



It is for this reason that the average weight of birds is the best indication 

 that can be obtained of the prospect of health or disease upon a moor in 

 the near future. 



The tradition, for it is probably nothing more, that in some outbreaks of 

 " Grouse Disease " birds have been found dying or dead well up to weight is 

 discussed elsewhere. 1 Birds do not die of Strongylosis without exhibiting loss 

 of flesh and weight. Neither do Grouse chicks die of Coccidiosis without losing 

 weight. Beyond these two diseases we have no knowledge of any other disorder 

 which attacks Grouse over considerable areas of country, and kills them in large 

 numbers. The reason for this loss of weight in Strongylosis and Coccidiosis 

 can be seen when a diseased bird is dissected. The post-mortem appearances 

 are fully described in other parts of this Report. 2 



The following list includes most of the conditions which commonly 

 " affect the weight of Grouse :- 



I. IN HEALTH. 



(a) Sex, generally in favour of the male, but in April and May rather 

 to the advantage of the female. 



(6) Late hatching, producing birds of both sexes unready for the 

 winter; birds which have missed the best growing months of 

 summer, and which therefore remain permanently undersized 

 and of a poor physique though not actually diseased. 



1 Vide chap. ix. pp. 204 et seq. 2 Vide chap. xii. p. 288 ; chap. xi. pp. 257 et seq. 



