most excited or attracted by the most beautiful, or melodious, or
gallant males. Nor need it be supposed that the female studies each
stripe or spot of colour; that the peahen, for instance, admires each
detail in the gorgeous train of the peacock she is probably struck only
by the general effect. Nevertheless, after hearing how carefully the
male Argus pheasant displays his elegant primary wing-feathers, and
erects his ocellated plumes in the right position for their full
effect; or again, how the male goldfinch alternately displays his
gold-bespangled wings, we ought not to feel too sure that the female
does not attend to each detail of beauty. We can judge, as already
remarked, of choice being exerted, only from analogy; and the mental
powers of birds do not differ fundamentally from ours. From these
various considerations we may conclude that the pairing of birds is not
left to chance; but that those males, which are best able by their
various charms to please or excite the female, are under ordinary
circumstances accepted. If this be admitted, there is not much
difficulty in understanding how male birds have gradually acquired
their ornamental characters. All animals present individual
differences, and as man can modify his domesticated birds by selecting
the individuals which appear to him the most beautiful, so the habitual
or even occasional preference by the female of the more attractive
males would almost certainly lead to their modification; and such
modifications might in the course of time be augmented to almost any
extent, compatible with the existence of the species.
VARIABILITY OF BIRDS, AND ESPECIALLY OF THEIR SECONDARY SEXUAL
CHARACTERS.
Variability and inheritance are the foundations for the work of
selection. That domesticated birds have varied greatly, their
variations being inherited, is certain. That birds in a state of nature
have been modified into distinct races is now universally admitted.
(33. According to Dr. Blasius ( Ibis, vol. ii. 1860, p. 297), there
are 425 indubitable species of birds which breed in Europe, besides
sixty forms, which are frequently regarded as distinct species. Of the
latter, Blasius thinks that only ten are really doubtful, and that the
other fifty ought to be united with their nearest allies; but this
shews that there must be a considerable amount of variation with some
of our European birds. It is also an unsettled point with naturalists,
whether several North American birds ought to be ranked as specifically
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