476 
Bulletin No. 162.—1915. 
Perhaps the most striking fact noticeable in this table is that from 
the age of six months to three years the number of females which died 
is strikingly in excess of the males. To a less extent the same is 
true (except in the six-month group)* of the number of females alive 
on December 1, 1914, as compared with the males. Beyond this 
age the numbers dead are so small that they have little meaning; it 
will be observed, however, that in the case of the birds alive at ages 
above three years the earlier condition is reversed, there being more 
males than females alive at each age above three years. The total 
number of female deaths in the adult period is greatly in excess of 
the male deaths, there being 78 of the former recorded and only 47 of 
the latter. By far the greater number of these occurred under the 
age of two years. At the bottom of the table the number of deaths 
for each sex is given as a percentage of the total number of birds which 
reached that age, the sexes again being considered separately. These 
show that the highest percentage of the females died between the 
ages of one and two years, and in each group up to three years the 
percentage of females which died is considerably greater than of 
males; beyond this point the figures are scarcely significant. 
Considering the birds alive, it will be seen that there are somewhat 
more one-and two-year-old females than males; but of the older ages 
the moles are always in excess, so that the total number of males 
slightly exceeds the females, being 197 as against 194, a ratio (101.6: 
100) distinctly lower than the normal ratio at hatching. 
Summarizing the results of Table II, they seem to show that there 
is a high mortality of both sexes during the first two or three years of 
their adult life, but that it is especially high in the females between 
the ages of one and two years. The difference between the percentage 
of female and male deaths is considerably greater at this age than at 
any other and it seems not unlikely that this may be associated with 
trouble connected with the onset of ovulation. This greater mortality 
of females in the early adult ages, together with the somewhat 
♦Living birds hatched before June in 1914, and consequently over six months old on December 1, 
are not included, since their sexes are undetermined. The one male less than one year old at this 
date was hatched in December, 1913. 
