124 
SEXUAL SELECTION: BIRDS. 
PAS 1 " 
0 
«w 
wing-feathers, and erects his ocellated plumes in 
right position for their full effect ; or again, ho"' 
male goldfinch alternately displays his gold-bespat®*^ 
wings, we ought not to feel too sure that the h’ 11 ^, 
does not attend to each detail of beauty. W e l 
• i i i i i pi- , • ,.,-erw 
judge, as already remarked, of choice being es 01 
only from the analogy of our own minds ; and 
mental powers of birds, if reason be excluded, <1° . 
considerations we may conclude that the pair 111 
I 
birds is not left to chance ; hut that those males, "^ ft 
are best able by their various charms to please or eS f. 
the female, are under ordinary circumstances accsf 
If this be admitted, there is not much difficult) fl | 
understanding how male birds have gradually acfi’j j r I 
their ornamental characters. All animals present "h. 
vidual differences, and as man can modify his don ;l ^, 
cated birds by selecting the individuals which &l’^,, r 
to him the most, beautiful, so the habitual or even 0 
sional preference by the female of the more attrs 1 
i" 
:ajL 
males would almost certainly lead to their modifi caI *' p 
and such modifications might iu the course of tif e ^ 
augmented to almost any extent, compatible wi^ 1 
existence of the species. 
Variability of Birds, and especially of their seco ,u ^ , 
Sexual Characters . — Variability and inheritance 9,16 f 
foundations for the work of selection. That doP 1 '.,^ 
cated birds have varied greatly, their variations 
inherited, is certain. That birds in a state of n* 1 ^ 
present individual differences is admitted by e \ $ 
one ; and that they have sometimes been modifi 01 ^ 
distinct races, is generally admitted. 31 Variation 5 
the!® 6 i 
81 According to Dr. Blasius (< Ibis,’ vol. ii. I860, p. 297), 
425 indubitable species of birds which breed in Europe, b eSl 
