I do not, however, at all think the question can be settled by
individual cases, but only by large masses of facts.
The colours of the mass of female birds seem to me strictly analogous to
the colours of both sexes of snipes, woodcocks, plovers, etc., which are
undoubtedly protective.
Now, supposing, on your view, that the colours of a male bird become
more and more brilliant by sexual selection, and a good deal of that
colour is transmitted to the female till it becomes positively injurious
to her during incubation and the race is in danger of extinction, do you
not think that all the females who had acquired less of the male's
bright colours or who themselves varied in a protective direction would
be preserved, and that thus a good protective colouring would be
acquired? If you admit that this could occur, and can show no good
reason why it should not often occur, then we no longer differ, for this
is the main point of my view.
Have you ever thought of the red wax-tips of the Bombycilla beautifully
imitating the red fructification of lichens used in the nest, and
therefore the females have it too? Yet this is a very sexual-looking
character.
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