POPULATION CHARACTERISTICS 513 



limit of susteiiancf. Iiis])ire(l by this |)rinciplp. Darwin liased on it his theory of natural 

 selection''. More recent study, however, has shown thai, aside from a few exceptions such as 

 deer which, in the absence of predators, have overbrowsed their winter range in certain locali- 

 ties, lack of food is seldom a limiting factor. As pointed out by McAtee'™, only rarely is the 

 solution so simple as Malthus supposed. 



Rather a host of interdependencies, both direct and indirect, are involved. Outstanding 

 among them are those associated with the factors of shelter, food, weather, and predation. 

 Less obvious are such influences as mating success, fertility and physiological resistance. Their 

 combined interaction tends, on a long-term basis, to maintain the numbers of wildlife species 

 in a state of equilibrium compatible with the biological niches to which they are adapted. 



In preceding chapters the various factors affecting grouse abundance have been considered 

 individually. It is proposed to discuss here their combined effect on populations of this game 

 bird as observed during this study. 



POPULATION CHARACTERISTICS 



As discussed in the chapter dealing with general habits, individual grouse exhibit certain 

 peculiarities of adaptation and behavior. In the same way grouse po])ulations also have a 

 typical pattern of composition as well as characteristic reactions to various influences and cir- 

 cumstances. A knowledge of these is of the utmost importance to the game manager because 

 in many respects they govern the extent to which management practices may be effective. 



Composition 



A fundamental factor in determining the productivity of any species is the age- and sex- 

 composition of the population. This is particularly true for those which, unlike the grouse, 

 do not breed their first year, but it is still of potential importance with these birds. 



According to Age 



In New York the great majority of grouse chicks hatch during the last week of May or the 

 first week of June. These young birds have been considered adult by September and are cap- 

 able of breeding the following spring. Therefore, populations of this species are made up 

 entirely of mature individuals except during the summer. 



At hatching time the chicks have always considerably outnumbered the adults, the actual 

 degree varying with breeding success and nest survival. On Connecticut Hill they have 

 averaged 2.6 times as many, while on the Adirondack area the proportion has been 3.1:1, 

 reflecting the usually lower nest mortality on this type of range. One should not assume, how- 

 ever, that a degree of nesting failure sufficient to cause a reversal of this situation may not 

 have occurred elsewhere or may not be experienced on the study areas at some future time. ' 



As the brood period progresses the preponderance of chicks diminishes until by the end of 

 August the young birds usually but little exceed the adults in number. On Connecticut Hill 

 the proportion* at this time has averaged 1.0:1, ranging from 1.6:1 in a year of high produc- 

 tivity (1934) to 0.4:1 following a season of brood failure (1933). On the northern tract the 

 average was 1.4:1 and the extremes 3.0:1 in 1936 and 0.4:1 in 1935. 



Data have not been sufficient to permit an analysis of age groups above the one-year level, 

 although there is considerable evidence that among wild populations few grouse live more than 

 three years'''. 



* Figures represent number of chicks for each adult, 

 A See Chapter VUI, p. 360. 



