The Descent of Man and Selection in Relation to Sex HTML version

Choice exerted by the female--Length of courtship--Unpaired birds--Mental qualities and
taste for the beautiful--Preference or antipathy shewn by the female for particular males--
Variability of birds--Variations sometimes abrupt--Laws of variation--Formation of
ocelli--Gradations of character-- Case of Peacock, Argus pheasant, and Urosticte.
When the sexes differ in beauty or in the power of singing, or in producing what I have
called instrumental music, it is almost invariably the male who surpasses the female.
These qualities, as we have just seen, are evidently of high importance to the male. When
they are gained for only a part of the year it is always before the breeding-season. It is the
male alone who elaborately displays his varied attractions, and often performs strange
antics on the ground or 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.
The lengthened period during which both sexes of certain birds meet day after day at an
appointed place probably depends partly on the courtship being a prolonged affair, and
partly on reiteration in the act of pairing. Thus in Germany and Scandinavia the balzen or
leks of the black-cocks last from the middle of March, all through April into May. As
many as forty or fifty, or even more birds congregate at the leks; and the same place is
often frequented during successive years. The lek of the capercailzie lasts from the end of
March to the middle or even end of May. In North America "the partridge dances" of the
Tetrao phasianellus "last for a month or more." Other kinds of grouse, both in North
America and Eastern Siberia (1. Nordman describes ('Bull. Soc. Imp. des Nat. Moscou,'
1861, tom. xxxiv. p. 264) the balzen of Tetrao urogalloides in Amur Land. He estimated
the number of birds assembled at above a hundred, not counting the females, which lie
hid in the surrounding bushes. The noises uttered differ from those of T. urogallus.),
follow nearly the same habits. The fowlers discover the hillocks where the ruffs
congregate by the grass being trampled bare, and this shews that the same spot is long
frequented. The Indians of Guiana are well acquainted with the cleared arenas, where
they expect to find the beautiful cocks of the Rock; and the natives of New Guinea know
the trees where from ten to twenty male birds of paradise in full plumage congregate. In
this latter case it is not expressly stated that the females meet on the same trees, but the
hunters, if not specially asked, would probably not mention their presence, as their skins
are valueless. Small parties of an African weaver (Ploceus) congregate, during the
breeding-season, and perform for hours their graceful evolutions. Large numbers of the
Solitary snipe (Scolopax major) assemble during dusk in a morass; and the same place is