368 THE GROUSE IN HEALTH AND IN DISEASE 



than on any tendency of the birds to eat the plant more in 

 one month than another. 



From statistics collected, blaeberries appear to form 30 per 

 cent, of all the foods taken by the Grouse in Derbyshire ; 22 

 per cent, in Yorkshire ; and 11 per cent, in some of the counties 

 of Scotland. Undoubtedly a good deal could be done to increase 

 the food-yield of the moor by encouraging the growth of this 

 hardy plant, either by fencing off areas where it is eaten down 

 by sheep or by planting it in suitable places. 



DRAINING. 



Close observers of " Grouse Disease " have always held the 

 idea that the mortality has been in some way connected with the 

 wet, undrained portions of the moor. Scientific investigation 

 shows that there is probably a good deal of truth in this view. 

 The Strongyle larvae have been shown to pass the free-living 

 portions of their lives in damp surroundings. Even in frozen 

 water they appear to live for an indefinite period, whereas 

 complete drought may kill them in a very short time. 1 



Without putting drainage forward as an absolute specific 

 against disease, it can be urged with confidence that a well- 

 drained moor is less liable to dangerous infection of nematode 

 worms than a moor with stagnant pools and great stretches of 

 flow ground. 



Draining should be. done on a well considered plan. Nothing 

 is more common than to see the water carefully drained from 

 the top of a hill-face descending only to flood a much larger 

 acreage below, owing to there being insufficient drainage 

 arrangements for carrying off the surface water thus collected. 



It will generally be found advisable to employ a professional 

 sheep-drainer, and allow him to work by contract at a fixed 

 price per chain. The specifications must ensure that the drain 

 is clear cut, at least the breadth of a spade at the bottom, 

 that the sides are at a slope of not more than one in two, and 



1 Vide, chap. viii. pp. 234, 235. 



