Productivity and Populations 303 



mortality among these second nests will be about half. Hence, we 

 may anticipate that five of them may hatch. This brings average suc- 

 cess in nesting to sixty-five per cent, and the failure ratio to thirty- 

 five per cent. Fluctuations will, of course, follow the same course as 

 occurs in rate of first nest mortality. 



Another way of stating this fact is that on an average sixty-five 

 per cent of female grouse will hatch a brood. However, not all of 

 these hens will succeed in bringing their brood, even a single chick, 

 to maturity. Some will lose their entire family before the summer is 

 over. The facts on this matter may be derived by obtaining the num- 

 ber of female grouse with and without a brood at summer's end ( i.e., 

 when the chicks are mature). Generally only about half the hen 

 grouse succeed in bringing at least one youngster to adulthood. 

 About one female in sLx that hatches a brood fails to raise any of the 

 chicks, in an average year. The ratio of hens succeeding in rearing 

 broods varies widely in different years from about three-quarters 

 to only one-quarter of the females. 



Losses Among the Young Birds. Most baffling of all grouse mortal- 

 ity problems is that of the young in the first two or three weeks after 

 hatching. Our experience indicates that a loss of from one-quarter to 

 one-half of the chicks may be expected in the first month of life, and 

 that most of this loss usually occurs in the first three weeks. This 

 large initial loss was estimated by Sandys (1902) as likely being at 

 least one-third of the young before they attained the size of quail; 

 Forbush (1913) gave one half as the normal loss of young before 

 reaching maturity, while Roberts (1932) stated that young grouse 

 have so many enemies that even under normal conditions only a 

 small remnant of a brood escapes. The mean of twelve years' rec- 

 ords on Connecticut Hill for brood mortality up to September is 

 sixty per cent. Extremes have been fifty per cent and seventy-seven 

 per cent. Excluding two years of unusually high losses, 1933 and 

 1935, the annual loss has ranged from fifty to sixty-three per cent. 

 On the Adirondack area the mean loss over a ten-year period was 

 about SLxty-three per cent with extremes of forty-three per cent and 

 eighty-eight per cent (N. Y. S. Cons. Dept. Ann. Reports). Stud- 

 holme ( 1941 ) gave the brood loss in Pennsylvania as sixty-two and 

 six-tenths per cent. Thus the losses of young grouse are fairly con- 

 stant, with an occasional bad year when the results are apt to be 



