570 



FLUCTUATIONS IN GROUSE ABUNDANCE 



conforming to these individual coverts. The grouse populations of these compartments be- 

 haved quite indejiendently of one another and seasonal estimates of numbers were made for 

 each. The sum of these constituted the estimate for the whole area. 



In figure 60 the fall population density on each of these compartments has been plotted year 

 by year in terms of its percentage deviation from the mean for that compartment together 

 with the trend of that for the area as a whole. It is significant that there was a wide spread 

 in the degree of deviation among the different units each year and that each fall some units 

 were at a low level although the specific ones varied constantly. It is also significant, with 

 respect to those compartments which were low in various years, that the degree of deviation 

 from the mean was often as great when the aggregate population level was high as when it 

 was low. In fact in 1942, when the population as a whole fell to the lowest point since the first 

 year of the study*, all but two compartments were within the same range of deviation that had 

 been observed during other years. The diflereme lay in the fact that in 1942 a greater pro- 

 portion of all the units were "below the line". Similarly years of abundance were those in 

 which the coverts producing an above-average number of birds outweighed the ones below 

 average, but nevertheless each year witnessed some units below average. 



It is important, too, to realize that the relative rank of the different compartments, as shown 

 in figure 60, constantly varied from year to year. To give some idea of the lack of unison 

 observed a composite graph of the individual trends has been prepared (figure 61). 



400 



300 



O 

 QC 



O 200 



tc 



hi 

 d 



D 



Z 100 



I 

 I 



I 

 I 



400 



300 



200 



too 



'-' 



FIGURE 61. 



i_ 



-i- 



-L. 



_1_ 



1930 1931 1932 1933 



1934 1935 1936 1937 



YEAR 



1938 1939 1940 1941 1942 



TRENDS OF FALL i;ROLSE POPULATION DENSITIES FOR THE VARIOUS COMPART- 

 MENTS OF THE CONNECTICUT HILL AREA — 1930-1942 



Thl■^il■ data, although covering only a comparali\cl) siiorl pci ioil of time with respect to tlie 

 behavior of wildlife populations, seem to demonstrate that the abundance of grouse in iiidi- 

 \i(hiai coverts is conslanllv fluctuating and that, even during seasons when the birds are plen- 

 tiful over a tract as a whole, many such coverts are normally below average. It seems prob- 



* FraKnirntary data iniliratr thai t)ir populalinn on lliin arra was aomewhal lower atill in 1943 and 1944 but 1942 it the Uat year 

 fur which (lata comparable to the other year* of the Itudy are available. 



