564 FLUCTUATIONS IN GROUSE ABUNDANCE 



One must realize, however, the distinction between the above and the inter\'al between the 

 end of one period of general abundance or scarcity and the beginning of the next. The record 

 indicates that in the case of abundance this interval has most frequently been from four to 

 seven years in length while in the case of scarcity it has most often been six or seven years. 

 But this does not mean that there was any need for four to seven year closed seasons. Abun- 

 dance is used here to denote a quite uniformly high population level, while enough birds to 

 justify hunting have usually been present over longer periods with a corresponding shor- 

 tening of the intervals of acute shortage to which closed seasons would apply. 



So far the discussion of this topic has dealt with the trend of general abundance over areas 

 of regional size. In most years, however, different localities in the same region have exhibited 

 conditions diametrically opposed to each other as well as various intermediate gradations. 

 This raises the question of to what extent the same individual localities have been involved in 

 successive manifestations of this phenomenon. 



Unfortunately, few specific data based on actual censuses of the same area have been re- 

 corded covering a period of years sufficient for such analysis. Griddle's graph"" indicates a 

 fairly regular periodicity of close to ten years but the area involved comprised less than 50 

 acres with a correspondingly small number of birds and only the portion from 1914 to 1929 

 was based on numerical census figures. Furthermore, the latter are spring records and there- 

 fore not entirely comparable with fall data. In Michigan grouse population censuses on the 

 Pigeon River tract of 2.520 acres, begun by Fisher in 1932"' and continued until 1940 by the 

 Conservation Department, showed a steady decline from a high level in 1932 to relative 

 scarcity in 1935 followed by a gradual increase to moderate abundance in 1940. The only 

 other record long enough to be considered is that of this Investigation. 



In figure 58 have been plotted the fall population estimates for the two principal areas 

 studied. Tlie data for 1930-42 on the Connecticut Hill area and for 1932-42 on the Adiron- 

 dack area (approximately 2.200 acres and 816 acres respectively), represent actual censuses 

 conducted by the Investigation. The approximate trends for several years before and after 

 these dates have also been indicated on the basis of other information. 



These records reveal that the fall population levels on these areas lia\c fluctuated widelv 

 from year to year rather than following a steady course. That the trough of 1936-37 on the 

 Connecticut Hill tract was minor is evidenced by the fact that the populations of 1927-28-29 

 are known to have been below that of 1930. Furthermore abundance on this area in 1933 

 dropped to a level comparable to that of 1937 but immediatelv recovered the next year. Al- 

 though intensive field work became impossible after 1942. the limited data available clearly 

 indicate that the trend continued to decline at least through 1941 so that grouse numbers quite 

 probably fell to the 1930 level if not lower. 



On the Adirondack area initial work in Jainiar\. 1932. indicated lluit \\m' fall population of 

 1931 was comparable with, if not high(>r than, any recorded later. The most severe decline 

 occurred in 1935 but was of otdv one \ears duration. Siiue 1936 grouse abundance remained 

 generally high throughout the surve) and sup|)lemental information shows it was still high in 

 194-1.. 



In figure 58 smoothed curves* have been superimposed on the actual data in order to indi- 

 cate the general trend which has taken place. These, too, show the trough in 1936-37 on Con- 

 necticut Hill to have been rjiinor and that it was not until 1944 that the population again 



* Smoothing wan done orcurtting to tlii- (orniula a -4- 2b -4- r. in whirli )i i» the >fiir in (lucHlinn. a llir year brforc and r thr yc»T 

 alter. ^ 



