262 The Ruffed Grouse 



cent. Since these samples are only indicators of a general condition 

 we may conveniently use twenty per cent of the prehmiting season 

 population as the normal anticipated loss from hunting. 



An interesting sidelight on grouse hunting is the success ratio— 

 the proportion of flushed birds brought to bag by the hunters. 

 About one grouse in a dozen flushed was retrieved. This is con- 

 siderably less tlian the success ratio of birds actually shot at, which 

 is a more correct indication of shooting skill. This was from two to 

 three times the ratio of flushed birds bagged, or about one bird in 

 four or five shot at was taken. 



The effect of hunting on grouse populations varies with the density 

 of the population, as well as with the local intensity of hunting 

 pressure. Whether the hunters kill twenty per cent of the grouse, or 

 more or less, is important mainly as it affects tlie continued abun- 

 dance of the species. During the years of moderate-to-high abun- 

 dance, the twenty per cent of kill effected is of little importance in 

 changing the trend of grouse abundance. 



Ordinarily there are about two and a half grouse produced for 

 each pair of grouse in the spring. Thus two and a half birds from 

 each four and a half living in the fall may be removed and still 

 maintain the normal number of spring breeders. If there were no 

 other sources of loss, the hunter could thus safely take fifty-five per 

 cent of the fall population. This represents the upper potential safe 

 limit of kill, but actually it cannot safely be approached owing to 

 unavoidable losses from other causes. It has already been noted that 

 winter losses from predation are low when fall populations are low, 

 other things being equal. Under such circumstances the probability 

 of predation may be twenty-five per cent or less, even where no 

 hunting has taken place. Following Errington's theory of vulner- 

 ability, which seems to hold fairly well with grouse, hunter take 

 would displace a loss from some other cause for all birds in an inse- 

 cure position. This becomes effective only in years of high abun- 

 dance. From both theory and practice we may conclude that a 

 hunter kill of twenty-five per cent is safe in all but years of scarcity, 

 and that this figure may be increased somewhat in years of abun- 

 dance. Surely the record of increased take and increased populations 

 in New York from 1930 to 1938, along with specific field data, show 

 that hunting as currently practiced has not been a factor in causing 

 serious grouse declines. 



Tlie rather small part that hunting plays in total grouse mortality 



