No one doubts that both sexes of many birds have had their colours
adapted for the sake of protection; and it is possible that the females
alone of some species may have been modified for this end. Although it
would be a difficult, perhaps an impossible process, as shewn in the
last chapter, to convert one form of transmission into another through
selection, there would not be the least difficulty in adapting the
colours of the female, independently of those of the male, to
surrounding objects, through the accumulation of variations which were
from the first limited in their transmission to the female sex. If the
variations were not thus limited, the bright tints of the male would be
deteriorated or destroyed. Whether the females alone of many species
have been thus specially modified, is at present very doubtful. I wish
I could follow Mr. Wallace to the full extent; for the admission would
remove some difficulties. Any variations which were of no service to
the female as a protection would be at once obliterated, instead of
being lost simply by not being selected, or from free intercrossing, or
from being eliminated when transferred to the male and in any way
injurious to him. Thus the plumage of the female would be kept constant
in character. It would also be a relief if we could admit that the
obscure tints of both sexes of many birds had been acquired and
preserved for the sake of protection, for example, of the hedge-warbler
or kitty-wren (Accentor modularis and Troglodytes vulgaris), with
respect to which we have no sufficient evidence of the action of sexual
selection. We ought, however, to be cautious in concluding that colours
which appear to us dull, are not attractive to the females of certain
species; we should bear in mind such cases as that of the common
house-sparrow, in which the male differs much from the female, but does
not exhibit any bright tints. No one probably will dispute that many
gallinaceous birds which live on the open ground, have acquired their
present colours, at least in part, for the sake of protection. We know
how well they are thus concealed; we know that ptarmigans, whilst
changing from their winter to their summer plumage, both of which are
protective, suffer greatly from birds of prey. But can we believe that
the very slight differences in tints and markings between, for
instance, the female black-grouse and red-grouse serve as a protection?
Are partridges, as they are now coloured, better protected than if they
had resembled quails? Do the slight differences between the females of
the common pheasant, the Japan and gold pheasants, serve as a
protection, or might not their plumages have been interchanged with
impunity? From what Mr. Wallace has observed of the habits of certain
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