524 



PRODUCTIVITY OF GROUSE POPULATIONS 



survived on other occasions. Furthermore, analysis of these figures on the basis of their per- 

 centage deviation from the mean (figure 42) shows the variability on the two areas to have 

 been quite similar. 



loo 



I 



Connecticui Hill 

 Adirondack 



I 



loo 



15 



50 



Zb 



Z5 



bo 



7b 



I930 1931 193Z 1935 1934. (935 1934 (937 1938 1939 ,940 ,94, ,942. 



YEAR 



FIGURE 42. DEVIATION FROM MEAN OF SPRING POPULATIONS ON CONNECTICUT HILL AND 



ADIRONDACK AREAS — 1930-1942 



Apparently other factors such as weather and predation have varied sufficiently in their 

 effect to overbalance the influence of carrying capacity to a greater or lesser degree each 

 year. 



A much greater degree of definiteness has been reported by Errington'™ with respect to 

 marginal grouse range in certain north-central states. His data, covering seven years, in- 

 dicate a relatively stable survival of about 18 bird.'* on five square miles of such range in 

 Wisconsin. In the same paper he also records data taken by W. J. Breckenridge showing a 

 rather definite level of from eight to ten birds on a square mile tract in Minnesota over a 

 4-year period. Thus it may be that grouse on marginal range do exhibit a considerable 

 uniformity of survival. Scattered observations in connection with pheasant studies in New 

 York have shown one or two grouse usually present in isolated woodlots of 50 to 60 acres. 

 But in the better grouse habitats of the Northeast the data consistently refute it. 



Nevertheless some idea of the relative qualitv "f difTercnt coverts is afforded bv the spring 

 densities recorded. For the Connecticut Hill area as a whole, the residual i)o])ulation at this 

 time reached 10.7 birds per 100 acres in 1935 and on the basis of sample data exceeded 

 12 in 1933. A possibly more representative figure would be the average of the highest level 

 for each of the component units regardless of the year in which it occurred, or 12.7. Among 

 these units one held an estimated 22.3 birds per 100 acres in 1935 but this was believed to be 

 to a considerable extent the result of influx from surrounding terrilorv during late winter 

 rather than survival of the birds actually present in the fall. .Aside from this instance the 

 greatest number of grouse successfully wintered by such a habitat was 19.9 per 100 acres in 

 the same year. On the other hand other nearby coverts have never been able Id support cxcii 

 ten birds on the same scale. 



