330 BIRDS OF DUMFRIESSHIRE 
The causes of the disease to which this species is from time 
to time subjected are still much discussed ; and the Com- 
mission to inquire into the question has as yet only issued 
an interim report. The germs of disease, we are told, are 
always present in all birds, and the outbreak is beheved 
to occur when their condition has become lowered, as by 
lack of food. Grouse feed all day, and their food-supply 
is a vital question. Since they do not eat what is known as 
*' frosted " heather, their food-supply becomes diminished 
when it gets into this state, and they therefore fall off 
in condition. It may here be noted that this " frosted " 
appearance of the heather is due not to frost but to the 
attacks of the larvce of a small beetle (Lochmma suturalis)* 
February and March are the least well provided months, 
and should a moor be overstocked it cannot then produce a 
sufficiency of food for the abnormal numbers of birds, 
whose health suffers in consequence. Under these conditions 
disease may break out ; the infected birds become more 
sluggish, their plumage appears duller, and they frequently 
leave the moors for the grass-fields. The cocks succumb 
in spring ; the hens after incubation in late summer ; each, 
it will be observed, " at the time when it would be expected 
that their vitaHty and power of resistance would be at its 
lowest, and when any shortage of food would be most 
felt."t Dumfriesshire does not appear to have suffered as 
extensively from disease as many other counties (though 
a bad outbreak in May, 1852, is recorded), and this may be 
attributable to the fact that our moors are seldom allowed 
to get overstocked. There is a local idea that the ups and 
downs of good and bad seasons are contained in a cycle of 
seven years. Late frosts and early summer " thunder- 
plumps " do much to deprive us of these good seasons, and 
the protection of the nests and eggs themselves demands 
a constant war against the Crows, and nowadays the Rooks 
as weU. 
* Ann. Scot. Nat. Hist.y 1898, p. 27. 
t Grouse Disease Inquiry. Interim Report, August, 1908. 
