Sex Ratios in Pigeons. 
473 
age period at time of death being known for 1,676 birds* whose sex 
was determined as well. Of these 1,676 pigeons, 866 were males 
and 810 were females, the ratio being 106.9 : 100. While this 
ratio is slightly higher than that (105 : 100) which has been taken 
as normal, the difference is not great enough to be of much significance, 
and for present purposes we only therefore consider the changes in 
a population assumed to consist at hatching of 866 males and 810 
females, all other birds being left out of consideration for the time 
being. In Period A, that is, within five days of hatching, 115, or 
13.3% of the original number of males died, and 114, or 14.1% of the 
females. The number of deaths of each sex is almost equal (100.9 : 
100), there being one more male death than female, but the percentage 
of female deaths is slightly greater. 
Subtracting the deaths in Period A leaves the population in Period 
B composed of 751 males and 696 females, or 107.9 : 100, a 
slightly higher proportion of males than before. In this period the 
number of male deaths considerably exceeds the female deaths, there 
being 228 of the former and 193 of the latter (118.1 : 100). The 
proportion of the males which died in Period B is 30.4%; of the 
females, 27.7%. The distinctly higher death rate of males in the 
nestling period is reflected in the composition of the juvenile popula¬ 
tion (523 males, 503 females), where the proportion of males 
(105 : 100) is lower than at the start. Period C is the only one in 
which the actual number of female deaths exceeds the male deaths, 
i 
and the only one in which the percentage of female deaths is in excess 
to any appreciable degree. The ratio of male to female deaths is 
95.1 : 100; expressed in percents, 25.8% of the males composing 
the population died, 28.2% of the females. Allowing now for all 
previous deaths we find that the adult population (Period D), consist¬ 
ing of 749 birds, comprises 388 males and 361 females, or only a 
slightly, and probably insignificantly higher ratio of males (107.5 : 
100) than that with which we started. 
*In addition to the 1,227 birds mentioned on page 468 there are here included those birds which 
were killed after they were six months of age, and birds over six months of age alive on December 1, 
1914, whose sex had been determined by their breeding behavior. It is certain, therefore, that all 
these belonged to Group C. 
