POPULATION CHARACTERISTICS 521 



igan, in 1933, Ruhl* estimated 3,444 grouse in the township, or nearly 15 birds per 100 acres 

 (September). He states that the population on this area "during the 1933 season seemed to 

 be high although the number was less than observed during the 1932 season." For the same 

 area in September 1932 Fisher"' gives an estimated 191 grouse per section (sq. mi.) or 29.9 

 per 100 acres as well as 250 per section or 36.4 per 100 acres on a tract in Munuscong State 

 Park (Mich.) in November 1934. 



In Minnesota, Trippensee^' gave 269 birds as the pre-hunting season (October) population 

 of four sections of the Superior National Forest in 1934. or 10.5 birds per 100 acres, and 

 316 as the population of an area of the same size in the Chippewa National Forest, or a den- 

 sity of 12.3. 



King"' states that the maximum breeding season population observed near Cliquot, Minne- 

 sota, was a bird per four acres or 25 per 100 acres. The highest spring abundance recorded 

 by Fisher"' was 15.4 per 100 acres in April 1933 on the Munuscong Park tract. 



Saturation Point 



From time immemorial hunters and others interested in wildlife have dreamed of game 

 abundance far in excess of any it has been their fortune actually to encounter. Thus fanci- 

 fully populated were the "happy hunting grounds" of the American Indian. Today's sports- 

 men are no less given to wishful thinking. One of the prin(i|)al measures of the worth of a 

 game management program is its effectiveness in increasing the density of such species as 

 well as reducing the frequency and severity of periods of scarcity. 



Yet one must not expect the impossible. Regardless of how the habitat may be improved 

 or the impact of decimating agencies relieved, populations will not increase above certain 

 levels except sporadically. These levels and the ullimate limiting factors vary with the spe- 

 cies. Deer, for instance, and other animals and birds which are highly gregarious may become 

 very abundant before some environmental condition halts the advance. The rufled grouse, on 

 the other hand, appears to exhibit an intolerance of crowding above an average of about one 

 bird to four acres even in the best coverts. This has been termed the saturation point of the 

 species and is a property of the bird itself apart from the quality of its environment. 



Evidence of this characteristic lies in the fact that, when greater densities occur, disper- 

 sion of excess individuals to surrounding territory tends to take place immediately. The influ- 

 ence, however, does not apply to birds of the year until after they have reached adulthood. 

 Thus it seldom manifests itself except in the fall. While crowding almost invariably occurs 

 within a brood group at the end of the summer, its numbers are usually accommodated 

 within the same covert. But. when the covert a.^ a whole is overpopulated, wider movements 

 ensue. 



During the Investigation, behavior of this kind has been observed on several occasions. Out- 

 standing was the 187-acre covert which held 38.8 grouse per 100 acres as of August 31, 1931. 

 Censuses later that fall showed its population to have dropped to 21.8 while those of adjacent 

 units gained. Similarly in 1939 the density on a plot of 131 acres decreased from 29.5 to 

 20.6 while those of others nearby increased. 



That the birds will tolerate as many as 25 per 100 acres (approximately) was demon- 

 strated when a portion of the Connecticut HUl area held a breeding population of 22.3 in 

 1935. King'^" has reported the same conclusion for an area in Minnesota. 



* Ruhl, H. D., personal letter to the authors July 2. 1936. 



