Darwin's Theory of Sexual Selection 197 
“In regard to color, hardly anything need here be said, 
for every one knows how splendid are the tints of many 
birds, and how harmoniously they are combined. The col- 
ors are often metallic and iridescent. Circular spots are 
sometimes surrounded ‘by one or more differently shaded 
zones, and are thus converted into ocelli. Nor need much be 
said on the wonderful difference between the sexes of many 
birds. The common peacock offers a striking instance. 
Female birds of paradise are obscurely colored and destitute 
of all ornaments, whilst the males are probably the most 
highly decorated of all birds, and in so many different ways, 
that they must be seen to be appreciated. The elongated 
and golden-orange plumes which spring from beneath the 
wings of the Paradisea apoda, when vertically erected and 
made to vibrate, are described as forming a sort of halo, in 
the centre of which the head ‘looks like a little emerald sun, 
with its rays formed by the two plumes.’ ” 
Male humming-birds are almost as splendidly colored as 
are the birds of paradise, some having the feathers modified 
in a truly extraordinary way. “Almost every part of their 
plumage has been taken advantage of, and modified ; and the 
modifications have been carried, as Mr. Gould showed me, to 
a wonderful extreme in some species belonging to nearly 
every subgroup. Such cases are curiously like those which 
we see in our fancy breeds, reared by man for the sake of 
ornament: certain individuals originally varied in one charac- 
ter, and other individuals of the same species in other charac- 
ters; and these have been seized on by man and much 
augmented —as shown by the tail of the fantail pigeon, the 
hood of the jacobin, the beak and wattle of the carrier, and 
so forth. The sole difference between these cases is that 
in the one the result is due to man’s selection, whilst in 
the other, as with humming-birds, birds of paradise, etc., it 
is due to the selection by the females of the more beautiful 
males.” 
