tion, or
is pleasing to the other sex. The only remaining supposition is that it
is transmitted from the other sex, without being of any use. From the
number of examples above adduced of bright colours in the female, this
would imply that colour-characters acquired by one sex are generally
(but not necessarily) transmitted to the other. If this be the case it
will, I think, enable us to explain the phenomena, even if we do not
admit that the male bird is ever influenced in the choice of a mate by
her more gay or perfect plumage.

The female bird, while sitting on her eggs in an uncovered nest, is much
exposed to the attacks of enemies, and any modification of colour which
rendered her more conspicuous would often lead to her destruction and
that of her offspring. All variations of colour in this direction in the
female, would therefore sooner or later be eliminated, while such
modifications as rendered her inconspicuous, by assimilating her to
surrounding objects, as the earth or the foliage, would, on the whole,
survive the longest, and thus lead to the attainment of those brown or
green and inconspicuous tints, which form the colouring (of the upper
surface at least), of the vast majority of female birds which sit upon
open nests.

This does not imply, as some have thought, that all female birds were
once as brilliant as the males. The change has been a very gradual one,
generally dating from the origin of genera or of larger groups, but
there can be no doubt that the remote ancestry of birds having great
sexual differences of colour, were nearly or quite alike, sometimes
(perhaps in most cases) more nearly resembling the female, but
occasionally perhaps being nearer what the male is now. The young birds
(which usually resemble the females) will probably give some idea of
this ancestral type, and it is well known that the young of allied
species and of different sexes are often undistinguishable.

_Colour more variable than Structure or Habits, and therefore the
Character which has generally been Modified._

At the commencement of this essay, I have endeavoured to prove, that the
characteristic differences and the essential features of birds' nests,
are dependent on the structure of the species and upon the present and
past conditions of their existence. Both these factors are more
important and less variable than colour; and we must therefore conclude
that in most cases the mode of nidification (dependent on st