550 PRODUCTIVITY OF GROUSE POPULATIONS 



portion, as discussed earlier in this chapter (p. 538), observations indicate that about half, or 

 9 per cent, represents a loss which would occur anyway. Therefore, in the diagrams the 

 hunter take is shown in full while 9 per cent has been deducted from the overwinter mor- 

 tality as derived from the study area data. The data indicate that this degree of hunting is 

 seldom a decisive factor. Even under the situations represented by figures 55 and 56 its 

 elimination would still fail to prevent a net loss of breeding stock. 



On the other hand, as populations approach scarcity in an area the importance of hunting 

 increases and may become limiting. Under such circumstances a low degree of productivity 

 by the end of the brood period would be the cue for reducing hunting pressure. But while 

 the general population level remains high even failure of the increment of young birds does 

 not necessarily mean that shooting should be curtailed. For example, while the September 

 ])roduction ratio on the Connecticut Hill area in 1933 was only 0.96, it followed the highest 

 breeding population recorded and the actual fall density was greater than those of 1937 and 

 1940 when the production ratios of lower breeding populations were 2.21 and 1.50 respec- 

 tively. There seems little doubt that in all three of these years the birds could have withstood 

 average hunting without endangering the prospect of a good crop the following season. 



The possibility that a greater harvest might on occasion be permitted, withort impairing 

 the breeding potential, depends on the size of the fall crop. The foregoing equation may 

 be modified to indicate the latter by restricting the term AL (adult losses) to cover only 

 the period from April to the beginning of the hunting season. But practical interpretation 

 of estimates at this time depends on a knowledge of the portion constituting a surplus. Means 

 of evaluating this point are discussed in the section of this report dealing with 

 management*. 



THE BIOLOGICAI, BALANCE SHEET-^ 



In preceding chapters the observations of the Investigation with respect to the major fac- 

 tors controlling grouse abundance have been discussed individually. In the present chapter 

 the data relating to survival, productivity rates, and life equations have also been consider- 

 ed. It seems logical at this time to undertake a brief summary of the host of interactions 

 among the various competing influences involved. 



The situation may be likened to a picture puzzle composed of a great variety of pieces, 

 some large, some small, with a few still hiding unrecognized in the box. The title of the 

 picture is "The Grouse Crop." On the skill and accuracy with which the pieces can be 

 fitted together depends the solution. But the game is made more difficult and interesting 

 because Nature has provided an infinite variety of basic patterns, constituting grouse cover on 

 which the pieces, like semi-transparent overlays, may be fitted together. For each such pat- 

 tern the pieces combine a lilllc dilTcrcntlv so lliat. in reality, each one represents a puzzle in 

 itself. 



Standing at one"s elbow in this game are many players, both amateur and professional, 

 each convinced that the solution of the various puzzles requires a different arrangement of the 

 pieces (such as shelter, food, predalion or disease). Guiding rules as to the soundness of 

 conclusions regarding relationships must be developed through experience and study. It is 

 the intent of this book to define and explain as manv of these rules as the a<ithc)rs have conic 

 to know durin" the Investigation. 



• Sco Chaplcr XVU. p. 674. 

 ^ By Gardiner Bump. 



