214 
SEXUAL SELECTION : BIKDS. 
ParJ' ■ 
cause. Some birds moult so early, that nearly ^ 
the body-feathers are cast off before the first wing' 
feathers are fully grown j and we cannot believe th ;1 | 
this was the primordial state of things. When the peri° ( 
of moulting has been accelerated, the age at with’ 1 ' 
the colours of the adult plumage were first develops 
would falsely appear to us to have been earlier 
it really was. This may be illustrated by the practi ce 
followed by some bird-fanciers, who pull out a 
feathers from the breast of nestling bullfinches, 
from the head or neck of young gokl-pheasants, 
order to ascertain their sex ; for in the males tl> eS ° 
feathers are immediately replaced by coloured ones-'’ 
The actual duration of life is known in but few' birds ,® 0 
that we can hardly judge by this standard. And wi* 1 ’ 
reference to the period at which the powers of rep r °' 
duction are gained, it is a remarkable fact that vari°° s 
birds occasionally breed whilst retaining their iinmat ur ° 
plumage . 37 
The fact of birds breeding in their immature plunn'ty 
seems opposed to the belief that sexual selection b llS 
38 Mr. Illy til, in Clmrlesworth’s ‘Mag. of Nut. Hist.’ vol. i. I 837 ’ 
,100. Mr. Bartlett lias informed me in regard to gold-pheasants. . 
Sl I have noticed the following eases in Audubon’s ‘Ornith- 
graphy. the lledstart of America’ (Muscicapa rutieilla, vol. *' j 
20ii). The Ibis tantalus takes four years to come to full maturity- 0 
sometimes breeds in the second year (vol. iii. p. 133 . The (irus re 
canus takes the same time, but breeds before acquiring its foil 
(vol. iii. p. 211}. The adults of Arden cterulea are blue and the J' 01 " ", 
white; and white, mottled, an.l mature blue birds may all fl , r - 
breeding together (vol. iv. p. 58, : but Mr. Blytb informs me the* C A 
tain lierons apparently are dimorphic, for wliite and coloured iiulivR 11 
of the same age may be observed. The Harlequin duck j, u 
trionica, Tanu.) takes three years to acquire its full plumage, tfo’ 1 .',, 
many birds breed in the second year (vol. iii. p. 611). Th" " ‘j.,, 
headed Eagle ( Falco leucocephalus, vol. iii. p. 210) is lik6 'l r 
known to breed in its immature state. Some species of Oriol» s ^ 
cording to Mr. Blyth and Mr. Swinhoe, in ‘Ibis,’ July, 1863, P- 
likewise breed before they attain their full plumage. 
