S56 I Li CTV AT IONS IN GROUSE ABUNDANCE 



Failure of the annual increment of young birds appears to he the key to such fluctuations. 

 (p. 571). 



It is not icnovvn what may be the underlying cause of synchronism among such losses. Of the 

 suggested hypotheses, a weather relationship of some kind seems most likely to be con- 

 trolling, (p. 576). 



Another contributory influence is population density although the nature of its effect is not 

 clear, (p. 576 1. 



The concept of cyclic behavior is tenable with respect to the fluctuations of grouse abun- 

 dance only if their variability and the uncertainty of prediction are recognized. I p. 579). 



That wildlife populations are subject to fluctuations in abundance has long been recognized. 

 History is full of accounts of plagues of rodents and insects. With respect to game, as Wing*" 

 has said, in times of plenty "the beknighted savage bowed down in pious supplication and 

 tendered offerings to the Gods and Spirits". During periods of scarcity, however, primitive 

 peoples as well as the pioneers of more civilized races have often had to shift their hunting 

 grounds or be faced with starvation. The, writings of the early explorers and historians record 

 innumerable instances of this kind. Sportsmen, too, although seldom dependent on such 

 species for the necessities of life, have become alarmed when numbers of their favorite game 

 dropped to low levels and have voiced their concern in contemporary sporting journals. 



But until comparatively recent years such fluctuations were principally of local concern 

 and were regarded as haphazard in occurrence. About the beginning of the present cen- 

 tury, however, observers began to realize that in many instances they had recurred in certain 

 species with considerable regularity. Perhaps the outstanding examples were the Norwegian 

 lemming (Lemmus lemmus) in Europe and the varying hare or snowshoe rabbit (Lepus amer- 

 icanus) in iNorth America. Among the first to call attention to the phenomenon were Mac- 

 Farlane°™, Seton"" and Hewitt"" who used records of the number of hare and other fur-bearer 

 pelts handled by the Hudson's Bav Company to illustrate it. Since then Fllton'^'. '"'. Leopold"' 

 and others have demonstrated fluctuations of more or less regular periodicity in these and a 

 variety of other species over the earth. 



It has been pdinlrd out in the preceding clmpli'r that grouse populations are in a constant 

 state of oscillation al)i)\e and below an average which is correlated with the quality of the 

 coverts invoKed. Beyond this, apparently more pronounced fluctuations at periodic intervals 

 have been reported. The recurrence, during the past half century, of several quite widespread 

 conditions of scarcity has led lo the suggestion that this behavior might follow a regular pat- 

 tern. It seems appropriate, therefore, to review the evidence brielh and lo discuss how the 

 (lata iif llie present Investigation relate to the problem. 



OCCURRENCE 



Many early accounts apparently refer to the occurrence of periods of abundance or scarcity 

 among ruffed grouse populations, but the data are scattered and fragmentary until the latter 

 part of the nineteenth century. It is interesting to note, however, that as early as 1721. the 



