PRODUCTIVITY OF POPULATIONS 525 



The situation on the Catskill and Pharsalia study areas has been quite similar to that on 

 Connecticut Hill, the highest spring densities for the entire tracts being 10.3 and 11.1 birds 

 per 100 acres respectively. 



The maximum noted on the Adirondack area, however, was 4.9 again indicating that the 

 carrying capacity of wilderness range is lower than that of more diversified territory. 



PRODUCTIVITY OF POPULATIONS 



Productivity may be defined as the relationship between a wildlife population and the 

 breeding stock which produced it. Usually it is considered to apply from one breeding sea- 

 son to the next. The game manager, however, is also interested in the production of as 

 great a fall surplus as possible. But whatever standard is used, the number of birds present 

 at any time is the resultant of the inherent reproductive capacity of the species modified by 

 a wide variety of delimiting conditions, environmental influences, and decimating agencies. 



The reproductive capacity of the species has already been considered*. The other major 

 influences have also been taken up separately. It remains to discuss their combined effect 

 on grouse populations as observed during the Investigation. The first source of loss to the 

 potential productivity of such a population is failure to breed. 



Breeding Success 



As has been discussed in Chapter VIII (p. 3551 non-breeding has been a difficult factor to 

 evaluate. Nevertheless there has been no indication that such a condition among male grouse 

 has been important. Among females, too, it appears to have been of negligible significance 

 during most years. In the seasons of 1933, 1935 and 1936, however, on the Connecticut Hill 

 study area less than 75 per cent of the females appear to have nested. Yet what influence 

 or combination of influences may have brought about these variations is as yet unknown. 



Beyond this point the principal yardstick of productivity is survival. 



Survival During Each Life Period 



Survival is best measured according to the three life periods of the bird. The data pre- 

 sented here pertain chiefly to observations on the Connecticut Hill and Adirondack study 

 areas. They are believed to be essentially representative of New York and similar sections 

 of the Northeast. Elsewhere over the range of the species, however, entirely different con- 

 ditions may exist. 



Nest Period 



As discussed in Chapter Vll (p. 312), nest losses of about 39 per cent have been experi- 

 enced over the State during this study. Survival, therefore, has averaged approximately 61 

 per cent, the degree varying more widely on individual areas (figure 24). Regarding the Con- 

 necticut Hill data, however, there is some indication that the mortality among nests under 

 observation has been slightly higher than among those not located. But while the actual 

 survival over this tract as a whole may have been somewhat greater than shown in the graph 

 the variations from year to year are still representative. 



Studies of certain other species, notably the ring-necked pheasant'™, have revealed that a 

 considerable proportion of the total nest mortality suffered each season is usually compen- 

 sated for by the renesting of birds whose initial attempts were broken up. In the experience 



* See Chapter VIM. 



