THE RED GROUSE 145 



disease. The latter scourge has been traced, thanks to 

 the exertions of the Grouse Disease Committee, to a 

 minute thread-worm, to which the imposing name of 

 Trichostrongylus pergracilis has been assigned. This 

 minute thread or round worm— the male is ^ to ^ inch, 

 the female | to I an inch in length — is not confined to 

 sickly Grouse alone, and the point should, I think, be 

 emphasized that practically every Grouse on every 

 moor harbours the parasites in larger or fewer numbers. 

 The thread-worms take up their stations among the 

 young leaves and flowers of the heather, where they 

 remain till swallowed by the bird with its food, and 

 when present in large numbers, set up acute appen- 

 dicitis in their victim. It is only, however, when the 

 Grouse on a moor become enfeebled either by injudicious 

 burning of the ground, overstocking of the moor, or by 

 an absence of food consequent upon a more than usually 

 severe winter, that the attacks of the Nematodes are 

 sufficiently virulent to affect the health of the birds. 

 Since it has been discovered that the larval forms of 

 Trichostrongylus are most prevalent on the young "food " 

 heather, it is important that the moor should hold as much 

 of this heather as possible, so as to give to the birds 

 extensive feeding ground. A few words as to the heather- 

 burning on a moor may not be out of place. The Grouse 

 Committee are of opinion that the great majority of 

 moors are insufficiently burnt. On most of the moors 

 the rotation for heather-burning is not less than fifty 

 years, which means that the amount of heather is only 

 eighteen per cent, of the total area. In their opinion 

 the burning of the moor on a fifteen-year rotation should 

 be practised, for then no less than sixty per cent, of 

 the ground would consist of heather affording good 

 feeding for the birds. Also, when heather under the age 

 of twenty years is burnt, the new crop usually springs from 



K 



