ere may be other causes besides the need for protection,
which prevent the female acquiring the gay colours of her mate, and
there is one curious circumstance which tends to elucidate it. The male
of Leptocoma zeylanica is said to assist in incubation. It is possible,
therefore, that the group may originally have used open nests, and some
change of conditions, leading the male bird to sit, may have been
followed by the adoption of a domed nest. This is, however, the most
serious exception I have yet found to the general rule.

6. Superb warblers (Maluridae). The males of these little birds are
adorned with the most gorgeous colours, while the females are very
plain, yet they make domed nests. It is to be observed, however, that
the male plumage is nuptial merely, and is retained for a very short
time; the rest of the year both sexes are plain alike. It is probable,
therefore, that the domed nest is for the protection of these delicate
little birds against the rain, and that there is some unknown cause
which has led to the development of colour in the males only.

There is one other case which at first sight looks like an exception,
but which is far from being one in reality, and deserves to be
mentioned. In the beautiful Waxwing, (Bombycilla garrula,) the sexes are
very nearly alike, and the elegant red wax tips to the wing-feathers are
nearly, and sometimes quite, as conspicuous in the female as in the
male. Yet it builds an open nest, and a person looking at the bird would
say it ought according to my theory to cover its nest. But it is, in
reality, as completely protected by its colouration as the most plainly
coloured bird that flies. It breeds only in very high latitudes, and the
nest, placed in fir-trees, is formed chiefly of lichens. Now the
delicate gray and ashy and purplish hues of the head and back, together
with the yellow of the wings and tail, are tints that exactly harmonize
with the colours of various species of lichens, while the brilliant red
wax tips exactly represent the crimson fructification of the common
lichen, Cladonia coccifera. When sitting on its nest, therefore, the
female bird will exhibit no colours that are not common to the materials
of which it is constructed; and the several tints are distributed in
about the same proportions as they occur in nature. At a short distance
the bird would be indistinguishable from the nest it is sitting on, or
from a natural clump of lichens, and will thus