CHARACTERISTICS 561 



Grouse abundance on the study areas used in this Investigation has exhibited both gradual 

 and abrupt rates of change (figure 58). On Connecticut Hill the fall population, after the 

 low point of 1928, climbed steadily upward until a high level of abundance was reached in 

 1932. Then in 1933 a sharp set-back took place but was followed by an immediate recovery 

 the next year. This was succeeded by a 3-year decline and a 2-year recovery ending in 1939. 

 Since that date the trend has been downward, sharp losses taking place in 1940 and 1942. It 

 must be pointed out, however, that the low points reached in 1933, 1937 and 1940 repre- 

 sented only about half the differential between the levels of 1928 and 1932. Not until 1942, 

 three years after the high density of 1939, did the population again approach real scarcity. 



On the Adirondack area the population did not exhibit any sustained decline during the 

 Investigation. Rather it reversed its trend almost annually. .Nevertheless it is noteworthy that 

 the year of greatest scarcity (1935) followed immediately after that of greatest abundance* 

 and was succeeded by recovery to a high level the next year. 



In Michigan, Fisher's data'" show a generally gradual rate of decline in grouse abun- 

 dance on the areas he studied between 1932 and 1936, although in 1933 the population of 

 his Area IV dropped much more sharply than those of the other study tracts while that of 

 his Area III did not begin to decline until 1934. King, however, working in Minnesota in- 

 terpreted his data as indicating a progressive increase from srarcitv to abundance covering 

 seven years followed by a 3-year decline to scarcity again'". 



Thus it is evident that local populations also have failed to exhibit a uniform rate of 

 change with respect to their fluctuations in abundance. Moreover, although often following 

 a trend roughly in harmony with that of the surrounding region, they have also been sub- 

 ject more frequently to rather abrupt intermediate fluctuations. 



Duration ok Abundance and Scarcity 



The foregoing discussion has dealt with the rate of change between high and low levels 

 of abundance. Of interest also is how long periods of abundance and scarcity have lasted. 

 On each occasion, although some one year witnessed the highest or lowest average density 

 reached, there have usually been several years during which the general status of grouse 

 abundance has been either good or poor. 



The duration of such periods has been from two to four years in most instances. By far 

 the most frequent period of scarcity has been three years. Such periods, of course, include 

 the last year of decline and also the initial year or so of recovery. With respect to general 

 abundance sufficient to afford good hunting, three and four year periods have predominated. 

 Here again an overlap occurs since the first year of abundance corresponds to the last year 

 of recovery. That they may last longer, however, was shown by the 1924-28 scarcity in 

 Minnesota and by the good years of 1939-44 in Vermont and New Hampshire. Furthermore, 

 in case of a minor depression, like that experienced in New York in 1936-37, grouse may be 

 generally numerous throughout such a region for js many as thirteen years or more'''. 



Periodicity 



As evidence of the recurrent nature of these fluctuations accumulated, sportsmen and natura- 

 lists alike become interested in their degree of regularity. One of the earliest observers to sug- 

 gest a fairly constant interval was Hatch, whom Forbush"" quotes as saying "that there is an 



* As mentioned eUe^liere there is some indication tlial the density in tlie fall of 1931 may have been as high or higher than 



that in 1934 but specific data are lacking. 

 A The current period in New York began about 1932 ami, disregarding the minor depression of 1936-37, had not abated in 1944. 



