146 Game Survey of the North Central States 



Chart 9) respectively. Only those of my observers who contributed the cleanest- 

 cut dates, or per cent of mortality, are shown. In some cases, Grange's observers 

 and mine were identical persons, but the approach to them was wholly separate, 

 and these overlaps were not numerous enough to affect the validity of the state- 

 ment that his findings on the last Wisconsin cycle corroborate mine on cycles in 

 general. 



The dark sectors of the large circles indicate the estimated degree of mor- 

 tality, in per cent, by the end of the first year of pronounced scarcity. The re- 

 maining white sector is the estimated survival. The date above any large or 

 medium circle is the year of first pronounced scarcity, and the date below it the 

 first year of perceptible recovery. (From this map and the preceding charts any 

 investigator can make his own analysis. It is hoped that some more competent 

 biometrician will do this.) The very small broken circles are dates of extermina- 

 tion (see date to left, which gives the year last seen) . 



Map 12 repeats the boundary of the "regular range," to be given in Map 

 13, for the reader's convenience. 



Possible Causes. Inferences on the possible cause and mechanism of the 

 cycle are more properly drawn from continental than from State data. Accord- 

 ingly the writer's reflections on this question will be presented in the proposed text 

 on game management which is to follow this report. A preliminary discussion of 

 possible causes and mechanism is being published by King and Leopold in a cur- 

 rent periodical. 



Present Status. The first State to reopen the season on any cyclic species 

 after the last low was Michigan, which allowed a 11 -day open season on ruffed 

 grouse in 1929. Wisconsin and Minnesota will evidently not reopen on either 

 grouse or chickens until 1931. 



Such fragments of current information as are available at the present writing 

 (October, 1930), indicate that recovery in both ruffed grouse and prairie chickens 

 is more complete in Wisconsin than in Michigan and Minnesota. Ruffed grouse 

 have also been seen this year in the Ozarks in localities not frequented in recent 

 years. 



Evidence Against Pre-1907 Cycles. As against the foregoing evidence 

 must be set the unquestioned fact that most "old timers" do not remember old 

 cycles, nor have the Wisconsin ornithologists recorded them. Dr. Alexander Wet- 

 more, for instance, recalls no cycle during his boyhood in Sauk County, Wis- 

 consin, from 1896 to 1904. This, however, is in the southern territory charac- 

 terized by_ relatively mild fluctuations which might be overlooked, or ascribed to 

 ordinary causes such as weather. Prof. R. A. Moore recalls no cycles in Kewaunee 

 County from 1875 to 1895, but says that no species of grouse was ever abundant 

 there, so that this may represent another case of inconspicuous low-amplitude cycle. 



It seems probable that the non-recollection of cycles is due to human cir- 

 cumstances rather than to their absence in fact. 



