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Show 198 SEXUAL SELECTION: BIRDS. l'AR'l' II. tints of both sexes of many birds had been acquired. and preserved for the sake of protection,-for exam~le, of the hedo-e-warbler or kitty-wren (Accentor modular~s and Troglod;tes vulgaris), with respect to which we have. no sufficient evidence of the action of sexual selectwn. We Ouaht however to be cautious in concluding that <Colours b wh' ich appea'r to us dull, are not att~·act•l :e to the females of certain species ; we should bear m ~md s~ch .cases as that of the common house-sparrow, m which the male differs much from the female, but d.oes not exhibit any bright tints. No one probably will dispute that many gallinaceous birds which live on tl~e op~n ground have acquired their present colours, at east m part, for the sake of protection. vVe know h_ow well tl~ey .are thus concealed ; we know that ptarmigans, whllt:it changing from theie winter to their summer. plum~ge, both of which are protective, suffer greatly from bn·ds of prey. But can we believ~ that the ver~ sl~ght differences in tints and markings between, for mstance, the female black and rcd-geouse serve as a protection? Are partridges, as they are now coloured.' better protected than if they had resembled qua1ls? Do the slight differences between the females of the common pheasant, the Japan and golden pheasants, serve as a protection, or might not their plumages have been interchanged with impunity? From what Mr. vVallace has observed of the habits of certain gallinaceous birds in the East he thinks that such slight difference · are beneficial. For myself, I will only say that I am not convinced. Formerly when I was inclined to lay much stress 011 the principle of protection, as accounting for the less bright colours of female birds, it occurred to me that possibly both sexes and the young might aboriginally have been brightly coloured in an equal degree; but CHAP. XH THE YOUNG LIKE THE ADULT FEMALES. 1:99 that subsequently, the females from the danger in? urred .during incubation, aud the young from being mexpenenced, had been rendered dull as a protection. But this view is not supported by any evidence, and is not probable; for we thus in imagination expose during past times the females and the young to danger, from which it has subsequently been necessary to shield their modified descendants. vVe have, also to reduce thronah ' ' 0 a gradual process of selection, the females and the young to almost exactly the same tints and markings, and to transmit them to the corresponding sex and period of life. It is also a somewhat strange fact, on the supposition that the females and the young have partaken during each stage of the process of modification of a tendency to be as brightly coloured as the males, that the females have never been rendered dull-coloured without the young participating in the same change; for there are no instances, as far as I can discover, of species with the females dull-coloured and the young bright-coloured. A p~rtial exception, however, is offered by the young of certam woodpeckers, for they have "the whole upper.part "of the head tinged with red," which afterwards either decreases into a mere circular red line in the adults of both sexes, or quite disappears in the adult femalesP Finally, with respect to oul' present class of cases, the most probable view appears to be that successive variations in brightness or in other ornamental characters, occurring in the males at a rather late .period of life have alone been preserved ; and that most or all Qf these variations owing to the late period of life at which they appeared, have been from the first transmitted only to the adult male offspring. Any varia- 1 • 2 A~1dubon, ' OrniLh. Biography,' vol. i. p. 193. Macgillivray, 'Hist. Bnt. llmls,' vol. iii. p. So. Sec also the case before given of Indopicus ca1'lolta. |
