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Show 196 SEXUAL SELECTION : BIRDS. PAlt'l' II. auritum and Phasianus Wallic~ii) the two sexes closely resemble each other and thell' colo~rs are dull. . We may go so f:a r. as to Lu elieve that If any part do fb the lumaae in tho males of these two pheasants ha een tillia~tly coloured, this would not have been transfer~d to the females. These facts stro.ngly support r. Wallace's view that with birds whwh are exposed to much danger during nidification, the transference of ·bright colours from the male to the female has been checked through natural selection. . We must . not, however, forget that another explanatwn.' before. grven, 1· s poss1' ble., namely ' that the males whwh var1ed. and became bright, whilst they were young and mex-perienced, would have been exposed to much danger,. and would generally have been destroyed; th~ older and more cautious males, on the other hand, If they varied in a like manner, would not only have b~en ab~e to survive, but would have been f~v~ured 111 th.eir rivalry with other males. Now vanatwns occurnng late in life tend to be transmitted exclusive~y to .the same sex, so that in this case extremely bnght tmts would not have been transmitted to the females. On the other hand, ornaments of a less conspicuous kind, such as those possessed by the Eared and C~eer pheasants, would not have been dangerous, and If they appeared during early youth, would generally have been transmitted to both sexes. In addition to the effects of the partial transference of characters from the males to the females, some of the differences between tho females of closely-allied species may be attributed to the direct or definite action of the conditions of life.11 With the males any such n Sec, on this subject, chap. xxiii. in tho 'Variation of Animo.ls and Plants under Domestication.' CI!Al'. XVI. THE YOUNG LIKE THE ADULT FEMALES. 197 action would generally have been masked by the brilliant colours gained through sexual selection; but not so with the females. Each of the endless diversities in plumage, which we see in our domesticated birds is, of course, the result of some de:finite cause; and under natural and more uniform conditions, some one tint, assuming that it was in no way injurious, would almost certainly sooner or later prevail. The free intercrossing of the many individuals belonging to the same species would ultimately tend to make any change of colour, thus induced, uniform in character. No one doubts that both sexes of many birds have had their colours adapted for the sake of protection; and it is possible that the females alone of some species may have been thus modified. Although it would be a difficult, perhaps an impossible process, as shewn in the last chapter, to convert through selection one form of transmission into another, there would not be the least difficulty in adapting the colours of the female, independently of those of the male, to surrounding objects, through the accumulation of variations which were from the first limited in their transmission to the female sex. If the variations were not thus limited, the bright tints of the male would be deteriorated or destroyed. Whether the females alone of many species have been thus specially. modified, is at present very doubtful. I wish I could follow Mr. Wallace to the full extent ; for the admission would remove some difficulties. .Any variations which were of no service to the female as a protection would be at once obliterated, instead of being lost simply by not being selected, or from free intercrossing, or from being eliminated when transferred to the male and in. any way injurious to him. Thus the plumage of the female would be kept constant in character. It would also be a relief if we could admit that the obscure |