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Show 170 SEXUAL SELECTION: BIRD'. PART II. us conspicuous to a dangerous degree, th~ remaining twenty-eight being inconspicuous.17 Nor 1~ there a~y close relation between a well-pronounced difference m colour between the two sexes, and the nature of tho nest constructed. Thus the male house-sparrow (Pass?r domesticus) differs much from the female, the male tree-sparrow (P. montanus) diifers hardly at al1, and yet both build well-concealed nests. The two sexes of the common fly-catcher (Muscicapa grisola) ?an hardly be di~tinguished, whilst the sexes of the p1ed. fly~catcher (llf.l~wtuosa) differ considerably, and both b~1ld m holes. The female blackbird ( Turdus merula) dtffers much, the female ring-ouzel ( T. tm·quat~£s) differs less, and the female common thrush (T. musicus) hardly at all from their respective males ; yet all build open nests. On the other hand, the not very distantlyal1iod water-ouzel ( Oinclus aquaticus) builds a domed nest, and the sexes differ about as much as in the case of the ring-ouzel. The black and red grouse ( Tetrao tetrix and T. Scoticus) build open nests, in equally wellconcealed spots, but in the one species the Eexes differ greatly, and in the other very ~ittle. . . Notwithstanding the forogomg obJectJOns, I cannot donbt, after reading 1\'Ir. Wallace's excellent essay, 11 1 have consulted, on this subject, Macgillivray's 'British Dircls,' auu though doubts may bo entertained in some cases in re~ard to the do.,.roo of concealment of the nest, and of tho degree of consptcuousncss of tho female, yet tho following birds, which all lay t~eir eggs in holes or in domed nest~, can hardly bo considered, accordmg to th~ above standard, as conspicuous: Passer, 2 species; Sturu~s, of whwh ~ho female is considerably less brilliant than the malo; Cmclus; Motactlb boarula (?) ; Erithacus (?) ; Fruticola, 2 sp.; Saxicoll\; Ruticilla~ 2 sp.; Sylvia, 3 sp.; Parus, 3 sp.; Mccistum; Anorthura; Ccrt~10. ; Sitta; Yunx; .M:uscicapa, 2 sp.; llirunclo, 3 sp.; and Oypsclus.. The fcmules of the following 12 birds muy b considered as conspicuous uccoruing to the same standard, viz., Pastor, Motacillu alba, Parus mujor andr. crorulcus, Upupa, Pious, 4 sp., Corncias, Alccdo, and .M:crops. GliAl'. X\". COLOUR AND NIDIFICATION. 171 that looking to the birds of the world, a large majority of tho species in 'rhich tho females are conspicuously coloured (and in this case the males with rare exceptions are equally conspicuous), build concealed nests for the sake of protection. 1\'Ir. Vvallace enumerates 18 a long series of groups in which this rule holds good; but it will suffice here to give, as instances, the more familiar groups of kingfishers, toucans, trogons, puff-birds (Capitonidre), plaintain-eaters (1\'Iusopbagre), woodpeckers, and parrots. l\lr. Wallace believes that in these groups, as tho males gradually acquired through sexual selection their brilliant colours, these ·were transferred to the females and wore not eliminated by natural selection, owing to the protection which they already enjoyed from their manner of nidi:fication. According to this view, their present manner of nesting was acquired before their present colours. But it seems to me much more probable that in most cases as the females were gradually rendered more and more brilliant from partaking of the colours of the male, they were gradually led to change their instincts (supposing that they originally built open ne .. ts), and to seek protection by building domed or concealed nests. No one who studies, for instance, Audubon'::) account of the differences in the nests of the same species in the N ortbern and Southern United States/9 will feel any great difficulty in admitting that birds, either by a change (in tho strict sense of the word) of their habits, or through the natural selection of so-called spontaneous variations of instinct, might readily be led to modify their manner of nesting. 18 'Journal of Travel,' edited by A. l\'lurrny, vol. i. p. 78. 10 See many slatemcnts in the' Ornithological Biography.' Sec, also, .. some curious observations on the nests of Italian birds by Eugenio Ddtoni, in the 'Atti dcl111 Societa Italiana,' vol. xi. 18GO, p. 487. |