220 
SEXUAL SELECTION: BIRDS. 
Part 1 
e %ed with brown . 48 So that the very same featli er * 
which in the young blackbird assume their mature 
racter and become black after the others, in these t"'° 
species assume this character and become blue be^ 
the others. Ihe most probable view with reference t 
these cases is that the males, differently from ^ 
occurs in Class I., have transmitted their colours b 
their male offspring at an earlier age than that 
which they themselves first acquired them; for if ^ 
bad varied whilst quite young, they would probate 
have transmitted all their characters to their offs]- 11 '' 11 ' 
of both sexes . 49 
In Aithurus pohjtmus (one of the humming-b' 1 ^.' 
the male is splendidly coloured black and green, 
two of the tail-feathers are immensely lengthened; * ' , 
female has an ordinary tail and inconspicuous colon 113 ’ 
now the young males, instead of resembling the . 
female, in accordance with the common rule, bet? 
from the first to assume the colours proper to tb el 
sex, and their tail-feathers soon become elong a * el 
I owe this information to Mr. Gould, who has g> v< f 
me the following more striking and as yet unp uD 
lished case. Two humming-birds belonging to /. 
genus Eustephanus, both beautifully coloured, inb ab \ 
the small island of Juan Fernandez, and have al' Vi ’k 
been ranked as specifically distinct. But it has l« te ; 
been ascertained that the one, which is of a rich 
PT W 'isM, in ‘Ibis,’ vol. vi. 1864, p. 65. Jerdon , lJ}it * 
of India/ vol. 1 . p. 515. 
“i lh f‘ ollo "' m S additional casos may be mentioned: the 7°^ 
males ot Tana,jm ruhra can be distinguished from the young 
(Audubon, * Onuth. Brogmphy,’ vol. iv. p. 392), and so it is 
nestlings of a h ue nuthatch, Dendrophila frontalis of India {3ef 
‘Brrds of India, vol. i. p. 389). Mr. Blyth al,o informs me th»* ‘ 
sexes of the stoneehat, Saxicola ruUcola, are distinguishable at » Vl " 
early age. 
