MOOR MANAGEMENT 329 



shoots, the area of ground on which the birds can feed is reduced, 

 and there may be therefore both a lowering of the Grouse 

 vitality through a shortage of the food supply, and an increased 

 danger of infection by the Strongyle worm through the conges- 

 tion of the birds upon a small area of feeding-ground. The 

 old stick heather, ragged and sparse, is the first to suffer from 

 frost, and is therefore of little use for food during the winter 

 and spring. It is only in the thick six- to fifteen-year-old 

 heather that green shoots can be found under the browned tops. 1 

 On a badly-burned moor this may mean a very great curtail- 

 ment of the food yield of the moor ; greater perhaps than the 

 health of the weaker birds will stand. 



Second Theory. It is stated that disease comes every seven (2) Period 

 years : that it is a recognised order of creation, and that no una void- 

 effective steps can be taken to alter the periodicity of its recur- able - 

 rence. This theory, like the preceding frost theory, is quite 

 beside the point. In the first place, " Grouse Disease " does 

 not occur on any moor in the regular order of once in seven 

 years. The examination of some hundreds of Grouse records 

 show that the disease occurs, on those moors which are 

 liable to the epidemic, at irregular intervals of three to eight 

 years. 



The ordinary sequence of events is, one year of disease, 

 one or two years of recovery, two or three average seasons, 

 one or occasionally two bumper years, followed by disease 

 in the following spring. Disease after a record year is due 

 partly to a heavy Strongyle infection in the winter months, 

 resulting from an overstock at a time when the birds are packed 

 together on the lower portions of the moor, partly also to the 

 Grouse's decreased power of resistance arising from a heavier 

 stock without a corresponding increase of the food-supply 

 As has been already pointed out this food shortage is most 

 marked in spring, and the outbreak of the disease accordingly 

 occurs at that time. 



1 See chap. iii. p. 83. 



