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It is reasonable to believe that diseases increase in 
virulence along toward the end of a so-called die-off. This 
should be expected on the basis of pathological conditions 
which would tend to build up such a condition. 
!Rhat is true of rodents is undoubtedly true of the common 
species of grouse throughout Idaho, and I believe to a greater 
or less extent throughout the continent of North America. Food, 
cover, and weather are the governing physical factors over which 
we can exercise some degree of control. Age, numbers, and dis- 
tribution of breeding stock are factors which determine the 
amount of use that can be made of favorable food, cover, and 
weather conditions. 
It is my opinion, based on close observation over a period 
of 25 years, that the most important step in the management of 
grouse of any species is to aim at a supply of an abundance of 
suitable food and cover for grouse. The next step is to keep 
the resident breeding stock young and in sufficient numbers to 
insure fair sized coveys and maintain covey or community habits 
in grouse. 
'hen the populations of rodents or grouse fall below a 
given minimum, natural enemies play a tremendous part on com- 
munity or covey havits and the rate of increase. The safety 
for sustained yield in the case of grouse is to maintain 
reasonable numbers of young, virile breeding stock well distri- 
buted over all suitable feeding and breeding areas. I do not 
believe that it serves any useful purpose at any time, or at 
any place, to allow grouse numbers to build up beyond a reason- 
able point if we would continue to keep them on a sustained 
yield basis and if we would perpetuate distribution of grouse 
over any given area. 
It is my opinion that if we would keep the grouse popula- 
tions on a sustained yield basis, we must keep the breeding 
stock young, the food supply ample, and the control of natural 
enemies at a very low point if we would avail ourselves of maxi- 
mum production and utilization. On this basis there would not 
occur any of the so-called cycles in grouse. I could make this 
statement without fear of subsequent research proving it untrue. 
There might be a semblance or a tendency in the direction of what 
might be called the so-called cycle as a result of favorable or 
unfavorable feeding, nesting, and breeding conditions, but this 
would not be and could not be termed a true cycle.