292 The Ruffed Grouse 



birds in the early spring because of their courtship behavior. 



The spring records from 1931 through 1941 on the Connecticut 

 Hill area showed an extreme variation in percentage of males, rang- 

 ing from forty-two per cent to fifty per cent in different years, with 

 the corresponding proportion of females being from fifty-eight per 

 cent to fifty per cent. Sex ratio records on the Adirondack, Pharsalia 

 and Catskill areas of the New York investigation varied from forty- 

 five to fifty per cent of males in different years. 



The sex ratio has been watched with great care as it has been 

 suspected of being an indicator of abnormal mortality, possibly 

 having a correlation with cyclic losses. Forbush (1912) recognized 

 a differential mortality among the sexes of grouse during popula- 

 tion declines as early as 1906. Leopold (1933) attributes this dif- 

 ferential mortality, which results in an abnormally high loss of 

 females and correspondingly unbalanced sex ratio, to disease. 



The evidence I have observed has not shown this phenomenon. 

 However, the populations have not dropped precipitously in this 

 period either, and hence have not produced the conditions where 

 the unbalanced sex ratio is alleged to occur ( New York data derived 

 from N. Y. S. Cons. Dept. Ann. Reports). 



POPULATIONS IN RELATION TO PRODUCTIVITY 



We have discussed the fluctuations in the population of grouse 

 over periods of several years. These changes took place in specific 

 sets of conditions, but do not correlate the grouse populations to 

 the cover, or enable us to compare the populations with those on 

 other areas. To reduce population figures to a common basis, we 

 may obtain the ratio of birds and cover, either on a units-per-acre 

 or an acres-per-unit basis. Since grouse densities are relatively low 

 (compared with many rodents and small birds for example), the 

 figures will be most easily handled if derived as an acres-per-grouse 

 unit. 



Grouse Nest Densities, If all females nest, and the sex ratio is fifty- 

 fifty, the density of nests would be half that of the adult birds in 

 the spring season. Due to the difficulties in locating the nests, the 

 entire number on a sizable area is never formd, hence the actual 

 density of nests is never determined with full accuracy. Evidence 



