The Descent of Man

confined to the females, have been in most cases
specially gained for the sake of protection.
There can, however, be no doubt, as formerly
remarked, that both sexes of many birds have
had their colours modified, so as to escape the
notice of their enemies; or in some instances, so
as to approach their prey unobserved, just as
owls have had their plumage rendered soft,
that their flight may not be overheard. Mr. Wallace
remarks (49. 'Westminster Review,' July
1867, p. 5.) that "it is only in the tropics, among
forests which never lose their foliage, that we
find whole groups of birds, whose chief colour
is green." It will be admitted by every one, who
has ever tried, how difficult it is to distinguish
parrots in a leaf-covered tree. Nevertheless, we
must remember that many parrots are ornamented
with crimson, blue, and orange tints,
which can hardly be protective. Woodpeckers
are eminently arboreal, but besides green species,
there are many black, and black-and-white
kinds—all the species being apparently expo-