SEXUAL SELECTIOX 223 



was no longer an object of preference or the cause of specially violent 

 excitement, so that a new process of selection would begin in reference 

 to some other part of the body. We thus understand how, among 

 male birds of Paradise and humming-birds, such a marvellous 

 diversity of colours and of decorative feathers is found combined 

 in one and the same species. 



Whoever has seen the Gould Collection of humming-birds in 

 London must have observed with amazement that among the 130 or 

 so species of these beautiful little birds nearly every group of feathers 

 in the body has been affected by the decorative colouring. In one 

 species the little feathers on the region of the throat are emerald 

 green, metallic blue, or rose ; in another the feathers of the neck have 

 been transformed into an erectile collar of rose-coloured feathers with 

 a metallic sheen ; or, again, it is the little feathers round the ear that 

 stand erect and are brilliantly coloured. Sometimes we find that the 

 feathers of the tail are lengthened, it may be only two of them, or the 

 various lengths may l)e graduated like steps ; sometimes the tail has 

 assumed the form of a wedge, or is fan-like, or is shaped like the tail 

 of a swallow, and all this in combination with the most diverse colours 

 and patterns, black and white, ultramarine blue, and so forth. Or it 

 may be the outermost tail-feathers which are the longest, the inner 

 ones the shortest, or the four outer feathers are broad, pointed, directed 

 outwards, and only half as long as the other two, which are very long 

 and straight. Some species exhibit a sort of fine swan's down on the 

 legs, others have a gorgeous metallic red cap on the head — in short, 

 the variety is beyond description, just as we should expect it to be if 

 now this and now that chance variation attracted the favourable 

 regard of the selecting sex, and thus attained to its highest pitch 

 of development. 



The decorative colouring of male birds may be replaced, not only 

 by the p(]»wer of song, but in other ways also. Not all the male birds 

 of Paradise possess the familiar feather ornaments. The Italian 

 traveller Beccari has called attention to a species, the males of which 

 are simply coloured brown, like the females of other species. This 

 AmUyornis inornata entices its mate to itself in the pairing time in 

 a very peculiar manner, for it arranges in the midst of the primitive 

 forests of New Guinea a little ' love garden ' or bower, a spot several 

 feet in extent, strewn with white sand, on which it places shining- 

 stones and shells, and brightly coloured berries. In this case a special 

 instinct has developed, which has replaced the personal charm of the 

 bird in the eyes of the female. For this very reason the case seems 

 to me to have some theoretical importance, for it serves indirectly to 



