changes of fashion with us. Thus the males of some parrots can hardly
be said to be more beautiful than the females, at least according to
our taste, but they differ in such points, as in having a rose-coloured
collar instead of a bright emeraldine narrow green collar ; or in the
male having a black collar instead of a yellow demi-collar in front,
with a pale roseate instead of a plum-blue head. (55. See Jerdon on the
genus Palaeornis, Birds of India, vol. i. pp. 258-260.) As so many
male birds have elongated tail-feathers or elongated crests for their
chief ornament, the shortened tail, formerly described in the male of a
humming-bird, and the shortened crest of the male goosander, seem like
one of the many changes of fashion which we admire in our own dresses.
Some members of the heron family offer a still more curious case of
novelty in colouring having, as it appears, been appreciated for the
sake of novelty. The young of the Ardea asha are white, the adults
being dark slate-coloured; and not only the young, but the adults in
their winter plumage, of the allied Buphus coromandus are white, this
colour changing into a rich golden-buff during the breeding-season. It
is incredible that the young of these two species, as well as of some
other members of the same family (56. The young of Ardea rufescens and
A. caerulea of the United States are likewise white, the adults being
coloured in accordance with their specific names. Audubon
( Ornithological Biography, vol. iii. p. 416; vol. iv. p. 58) seems
rather pleased at the thought that this remarkable change of plumage
will greatly disconcert the systematists. ), should for any special
purpose have been rendered pure white and thus made conspicuous to
their enemies; or that the adults of one of these two species should
have been specially rendered white during the winter in a country which
is never covered with snow. On the other hand we have good reason to
believe that whiteness has been gained by many birds as a sexual
ornament. We may therefore conclude that some early progenitor of the
Ardea asha and the Buphus acquired a white plumage for nuptial
purposes, and transmitted this colour to their young; so that the young
and the old became white like certain existing egrets; and that the
whiteness was afterwards retained by the young, whilst it was exchanged
by the adults for more strongly-pronounced tints. But if we could look
still further back to the still earlier progenitors of these two
species, we should probably see the adults dark-coloured. I infer that
this would be the case, from the analogy of many other birds, which are
dark whilst young, and when adult are white; and more especially from
521