The Descent of Man

in the air, in the presence of the female. Each
male drives away, or if he can, kills his rivals.
Hence we may conclude that it is the object of
the male to induce the female to pair with him,
and for this purpose he tries to excite or charm
her in various ways; and this is the opinion of
all those who have carefully studied the habits
of living birds. But there remains a question
which has an all important bearing on sexual
selection, namely, does every male of the same
species excite and attract the female equally?
Or does she exert a choice, and prefer certain
males? This latter question can be answered in
the affirmative by much direct and indirect
evidence. It is far more difficult to decide what
qualities determine the choice of the females;
but here again we have some direct and indirect
evidence that it is to a large extent the external
attractions of the male; though no doubt his
vigour, courage, and other mental qualities
come into play. We will begin with the indirect
evidence.