98 The Ruffed Grouse 



RELATION OF COVER TO GROUSE MORTALITY BY PREDATORS 



It is generally recognized diat cover conditions affect predation. 

 Other things being equal, quality of shelter and loss from predation 

 are inversely proportioned— the better the cover, the lower the mor- 

 tality from this cause. It would logically follow then that different 

 cover types, since they vary in their shelter quality, would produce 

 different predation rates. Possibly otlier aspects of cover too may 

 affect predation mortality. Let us consider this problem from the 

 point of view of the locations where grouse are found killed. 



In the first place we must make a hazardous assumption: That 

 the locations where grouse remains are found are the places where 

 they were killed; or at least the occasions of difference will balance. 

 However, that assumption is invalid. Since a large number of grouse 

 kills are picked up in open fields, it is quite certain that the majority 

 were carried here by the predators from the location of the kill in 

 some other cover type. And from the habits of many of the predatory 

 species, especially in the spring of the year, we know that it is a 

 common habit to carry a kill some distance before consuming it, 

 and there leaving the waste parts. 



While we cannot depend too much on the locations where grouse 

 remains are found as an indication of cover type vulnerability, there 

 are some fairly dependable conclusions that can be drawn when 

 supported by field observations. Probably the most important cor- 

 relations are the relatively low vulnerability of the birds in conff- 

 erous woodland and overgrown land, in both cases a reflection of 

 high protective character of the cover types. 



Shelter as a Limiting Factor. We have seen that the ruffed grouse 

 has a rather complicated shelter requirement to satisfy its needs at 

 all seasons, under various conditions of climate and other physical 

 conditions and for all of its activities. Yet at the same time we are 

 impressed repeatedly with the remarkable adaptability of the bird 

 to different conditions and to the changes that bring about new 

 environments. With all its flexibility in meeting successfully a variety 

 of conditions, it is still limited very definitely by the shelter factor 

 of the environment. Shelter is probably the limiting factor in the 

 long run throughout most of the Northeast. 



