MOOR MANAGEMENT 381 



(2) " Grouse Disease " occasionally appears the second and third 

 year after a severe epidemic, especially on wet, badly-drained moors, 

 and this notwithstanding the small stock that mav have 



■ 11,^ 1 , » , 1 1 ■ , After-effects 



survived the nrst outbreak. As has been shown m chapter of severe 

 X.,' the Strongyle worm flourishes best in damp surround- 

 ings, and it is possible that on a wet moor a smaller quantity of 

 ova may be sufficient to cause fatal infection. 



(3) On the west coast of Scotland a very light stock sometimes 

 contracts the disease. West coast heather is, as a rule, of ranker 

 growth and more open habit than what is found on the ^^^^^^^^ 

 east coast ; it is therefore more liable to be scorched by ^°°^^- 



the frost and cold winds of early spring. The food-supply in 

 consequence is apt to become so short that the normal quota of 

 Strongyle worms are enabled to become actively pathogenic with- 

 out the aid of further and outside infection. 



Fifth Theory. — Another theory put forward is that a hard winter affects 

 the health of a moor. This theory takes two forms. First, ,5, jj^^^ , 

 that a hard winter makes for a healthy stock, and secondly, ^^"•^'''"s- 

 that a hard winter causes disease in the following spring. 



These theories are mutually destructive, but, paradoxical as it 

 may appear, both are conceived on a certain basis of truth. A 

 hard winter tends to kill off sickly birds, to shift the stock and 

 to mix the breed ; snow lying on the heather till far into the 

 spring protects it from larval infection during the critical months 

 of February and March, and so ensures a fresh, untainted food- 

 supply in April and early May ; lastly, heavy snow followed by 

 floods tends to wash the moor clear of Strongyle larvse ; all these 

 are factors which benefit the moor. 



On the other hand, a hard winter may do incalculable harm 

 if the birds are driven off the whole of the hill - ground, and 

 massed for several weeks on a small area of feeding-ground. The 

 winter storms, especially in the Highlands, drive birds off great 

 tracts of heather land, with the result that when the food is at its 

 shortest the local feeding-area is reduced sometimes to a half, in some 



' Chap. X. p. 226. 



