| OCR Text |
Show 232 SEXUAL SELECTION : BIRDS. PAUT IT. covered with snow. On the other band we have re~son to believe that whiteness bas been gainocl by wany buds as a sexual ornament. W o may therefore conclude that an early progeuitor of tho Anlea asha and tho Buphus acquired a white plumage for nuptial purposes, and transmitted this colour to their young; so that tho vounrr and the old became white like certain existiug e• rrret~ · the whiteness bavinrr afterwards been retained b ' . b by the young whilst exchanged by the adults for mo~·e strongly pronounced tints. But if we could look .still further backwards in time to the still earlier progomtors of these two species, we should probably sec the adult.· dark-coloured. I infer that this would be the case, from tho analogy of many other birds, which are dark ''"~i1st Younrr and when adult are white; and more ospocmlly from bt'h e case of tho A'l'·dea gula1·is, the colours of wb 1' c 1 l are tho reverse of those of A. asha, for the yonng are dark-coloured and the adults white, tho young having retained a former state of plumage. It appears therefore th::1.t the progenitors in their adult condition of tho Ardea asha, the Buphus, and of some allies, have under-gone durin()' a lono- line of descent, the following changes ' 0 b . of colour: firstly a dark shade, secondly pure wlnte, and thirdly, owing to another change of fashion (if I may so express myself), their present slaty, reddish, or golden-buff tints. These successive changes are intelligible only on tho principle of novelty having been admired by birds for the sake of novelty. Summary of the Four Chapters on Birds.-Most male birds are highly pugnacious during the breeding-season, and some possess weapons especially adapted for fighting with their rivals. But the most pugnacious and the best-armed males rarely or never depend for success solely on their power to ch·ive away or l\ill their rivals, CHAP. XVI. SUMMAH.Y. 233 but have special means for charming the female. \Vith some it is the power of song, or of emitting strange cries, or of producing instrumental music, and the males in consequence differ from the females in their vocal organs, or in the structure of certain feathers. From the curiously diversified means for producing various sounds we gain a high idea of the importance of this means of courtship. l\fany birds endeavour to charm tho females by love-dances or antics, performed on the ground or in the air, and sometimes at prepared places. Bnt ornaments of many kinds, the most brilliant tints, combs and wattles, beautiful plumes, elongated feathers, top-knots, and so forth, are by far the commonest means. In some cases mere novelty appears to have acted as a charm. The ornaments of the males must be highly important to them, for they have been acqnired in not a few cases at the cost of increased danrrer from enemies, and even at some loss of power in fiO'htj~ g with their rivals. The males of very many ~peCJC~ do not ass~me their ornamental dress until they arnve at matunty, or they assume it only during the breeding-season, or the tints then become more vivid. Certain ornamental appenda~:?·es become enlarrred turo-id '-' t- ' b ' :mel brightly-coloured during the very act of courtship. Tho males display their charms with elaborate care and to the best effect; and this is done in the presence of the _females. The courtship is sometimes a prolonged affair, and many males and females congregate at an appointed place. To suppose that the females do not appreciate the beauty of tho males is to admit that their splendid decorations, all their pomp and display, are useless; and this is incredible. Birds have fine powers of discrimination, and in some few instances it can be shewn that they have a ta te for the beautiful. The females, moreover, are known occasionally to |
