Productivity and Populations 291 



found hatched nests to the hatched nests actually located. Know- 

 ing these items we calculate the fourth. However, this assumption 

 is not always vahd. 



Applying the above formula, and applying the corrective factor 

 for unfound destroyed nests, the nesting ratio ranged from well 

 below one hundred per cent to well over one hundred per cent. 

 Without the corrective factor, the nesting ratio was somewhat 

 below one hundred per cent. These latter figures are, of course, 

 conservative. At least some of the first set are excessive. 



From this wide variation we may conclude: (1) There was a 

 marked variation in nest-location success year by year; (2) the 

 proportion of hatched nests located exceeds that for broken-up 

 nests; (3) some grouse fail to nest, and this proportion seems to 

 vary in different years; (4) the nesting ratio is high, approaches 

 perfection (if not actually reaching it) in some, and probably in 

 most, years. 



Nimiber of Broods. The ruffed grouse raises one brood of young a 

 year. There are no exceptions to this rule in nature despite occa- 

 sional \ATJtten statements to the contrary. For example, Davie 

 (1898) concluded that grouse not infrequendy rear two broods 

 between the first of April and the middle of October, He was prob- 

 ably mistaking a late brood coming from a renest as a second brood. 

 When one considers that the mother bird cares for her young ones 

 for three months or more, and consumes more than another month 

 in egg-laying and incubating, it is obviously impossible to produce 

 more than one family in a season. 



Sex Ratio. The proportions of the sexes is most accurately obtained 

 in the spring during the breeding season when many types of data 

 that bear on it are availal^le. It is at this season that the sex ratio 

 assumes its greatest importance too, affecting as it does the breed- 

 ing and productivity of the species. 



All our evidence indicates that an approximate balance of the 

 sexes is normal,^ all seasons considered, but tliat there tends to be 

 a slight preponderance of males in the fall, and a small but con- 

 sistent excess of females in the spring. This adjustment of the ratio 

 from fall to spring results from the greater mortality of the male 



^ King advises (letter of October 5, 1943): "My work in Minnesota leads me to 

 believe that at some phases of the cycle there is far from a balanced sex ratio." 



