the case of the Ardea gularis, the colours of which are the reverse of
those of A. asha, for the young are dark-coloured and the adults white,
the young having retained a former state of plumage. It appears
therefore that, during a long line of descent, the adult progenitors of
the Ardea asha, the Buphus, and of some allies, have undergone the
following changes of colour: first, a dark shade; secondly, pure white;
and thirdly, owing to another change of fashion (if I may so express
myself), their present slaty, reddish, or golden-buff tints. These
successive changes are intelligible only on the principle of novelty
having been admired by birds for its own sake.
Several writers have objected to the whole theory of sexual selection,
by assuming that with animals and savages the taste of the female for
certain colours or other ornaments would not remain constant for many
generations; that first one colour and then another would be admired,
and consequently that no permanent effect could be produced. We may
admit that taste is fluctuating, but it is not quite arbitrary. It
depends much on habit, as we see in mankind; and we may infer that this
would hold good with birds and other animals. Even in our own dress,
the general character lasts long, and the changes are to a certain
extent graduated. Abundant evidence will be given in two places in a
future chapter, that savages of many races have admired for many
generations the same cicatrices on the skin, the same hideously
perforated lips, nostrils, or ears, distorted heads, etc.; and these
deformities present some analogy to the natural ornaments of various
animals. Nevertheless, with savages such fashions do not endure for
ever, as we may infer from the differences in this respect between
allied tribes on the same continent. So again the raisers of fancy
animals certainly have admired for many generations and still admire
the same breeds; they earnestly desire slight changes, which are
considered as improvements, but any great or sudden change is looked at
as the greatest blemish. With birds in a state of nature we have no
reason to suppose that they would admire an entirely new style of
coloration, even if great and sudden variations often occurred, which
is far from being the case. We know that dovecot pigeons do not
willingly associate with the variously coloured fancy breeds; that
albino birds do not commonly get partners in marriage; and that the
black ravens of the Feroe Islands chase away their piebald brethren.
But this dislike of a sudden change would not preclude their
appreciating slight changes, any more than it does in the case of man.
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