380 



THE GROUSE IN HEALTH AND IN DISEASE 



fully feathered ; in every case the spring balance has indicated that 

 the birds referred to were below the normal weight, and visceral 

 examination has shown that the cseca were charged with Strongyle 



(4) Midges 

 or caats. 



Small stock 

 does not 

 secure 

 immunity. 



Congestion 

 duringtirae 

 of snow. 



worms. 



Piners are found in every outbreak of disease, and experience 

 on the Frimley observation area, as well as research in the field, 

 goes to show that there are always some birds wholly or partly 

 able to combat the disease, owing either to their previous good 

 condition of health, or to their being less heavily infected by the 

 Strongyle worm. 



Fourth Theory. — The fourth theory put forward is that when birds 

 die of disease on lightly-stocked moors it is impossible that they 

 should die of shortage of food or by parasitic infection, and that 

 therefore midges or gnats must be the cause of death. This theory 

 is not supported by any ascertainable facts or data, and, as far as 

 examination of the blood goes, there is strangely little evidence in 

 it 5 favour. 



It cannot be admitted that a shortage of stock on a moor is neces- 

 sarily a guarantee of immunity from infection by the Strongyle worm, 

 although it may lessen the risk of such infection. It will be shown 

 later that moors in Yorkshire, which one hundred years ago w^ere 

 unable to carry three hundred brace to ten thousand acres without 

 a certainty of disease, have by careful burning been made to carry 

 ten times that stock without risk. 



Infection of a ligrht stock can be brought about in various 

 ways : — 



(l) If, in a hard winter, the birds are driven by snow oft' their own 

 ground and congested on a small feeding-area for a long enough 

 time for the larval nematode to aro throuorh its changes and infect 

 the heather, the birds may become so charged with Strongyle that 

 they die as soon as thev return to their own ground, however lightly 

 stocked that ground may be. 



There are very few owners of high-lying moors who have not 

 heard the remark : " The birds were quite healthy before the last 

 winter storm ; as soon as they returned to the high ground they 

 besfau to die." 



