214 
SEXUAL SELECTION : BIKDS. 
Part II. 
cause. Some birds moult so early, that nearly all 
the body-feathers are cast off before the first wing- 
feathers are fully grown ; and we cannot believe that 
this was the primordial state of things. When the period 
of moulting has been accelerated, the age at which 
the colours of the adult plumage were first developed 
would falsely appear to us to have been earlier than 
it really was. This may be illustrated by the practice 
followed by some bird-fanciers, who pull out a few 
feathers from the breast of nestling bullfinches, and 
from the head or neck of young gold-pheasants, in 
order to ascertain their sex ; for in the males these 
feathers are immediately replaced by coloured ones.^^ 
The actual duration of life is known in but few birds, so 
that we can hardly judge by this standard. And with 
reference to the period at which the powers of repro- 
duction are gained, it is a remarkable fact that various 
birds occasionally breed whilst retaining their immature 
plumage.^^ 
The fact of birds breeding in their immature plumage 
seems opposed to the belief that sexual selection has 
36 Mr. Blytli, in Cliarleswortli’s ‘ Mag. of Nat. Hist.’ vol. i. 1837, p. 
300. Mr. Bartlett has informed me in regard to gold-pheasants. 
37 I have noticed the following cases in Audubon’s ‘Ornith. Bio- 
graphy. The Kedstart of America’ (Muscicapa rutieilla, vol. i. p. 
203). The Ih's tantalus takes four years to come to full maturity, but 
sometimes breeds in the second year (vol. iii. p. 133;. The Grus Ameri- 
canus takes the same time, but breeds before acquiring its full plumage 
(vol. iii. p. 211). The adults of Ardea cserulea are blue and the young 
white; and white, mottled, and mature blue birds may all be seen 
breeding together (vol. iv. p. 58) : but Mr. Blyth informs me that cer- 
tain herons apparently are dimorphic, for white and coloured individuals 
of the same age may be observed. The Harlequin duck (Anas Ms- 
trionica, Linn.) takes three years to acquire its full plumage, though 
many birds breed in the second year (vol. iii. p. 614). The White- 
headed Eagle (Falco leucocephalus, vol. iii. p. 210) is likewise 
known to breed in its immature state. Some species of Oriolus (ac- 
cording to Mr. Blyth and Mr. Swinhoe, in ‘Ibis,’ July, 1863, p. 6Sy 
likewise breed before they attain their full plumage. 
