Chap. XV. Birds — Colour and Nidijication. 455 



the remaining twenty-eight being inconspicuous. 18 Nor is there 

 any close relation within the same genus between a well-pro- 

 nounced difference in colour between the sexes, and the nature 

 of the nest constructed. Thus the male house sparrow (Passer 

 domesticus) differs much from the female, the male tree-sparrow 

 (P. montanus) hardly at all, and yet both build well-concealed 

 nests. The two sexes of the common fly-catcher (Masicapa 

 grisola) can hardly be distinguished, whilst the sexes cf the 

 pied fly-catcher (M. luctuosa) differ considerably, and both 

 species build in holes or conceal their nests. The female black- 

 bird (Tardus merula) differs much, the female ring-ouzel (T. 

 torquatus) 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 distantly-allied water-ouzel 

 (Cinclus aquaticus) builds a domed nest, and the sexes differ 

 about as much as in the riug-ouzel. The black and red grouse 

 (Tetrao tttrix and T. scoticus) build open nests in equally well- 

 concealed spots, but in the one species the sexes differ greatly, 

 and in the other very little. 



Notwithstanding the foregoing objections, I cannot doubt, 

 after reading Mr. Wallace's excellent essay, that looking to the 

 birds of the world, a large majority of the species in which the 

 females are conspicuously coloured (and in this case the males 

 with rare exceptions are equally conspicuous), build concealed 

 nests for the sake of protection. Mr. Wallace enumerates 19 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 (Capitonidae), plantain- 

 eaters (Musophagse), woodpeckers, and parrots. Mr. Wallace 

 believes that in these groups, as the males gradually acquired 

 through sexual selection their brilliant colours, these were 

 transferred to the females and were not eliminated by natural 

 selection, owing to the protection which they already enjoyed 



18 I have consulted, ou this sub- boarula (?); Erithacus (?) ; Fru- 



ject, Macgillivray's ' British Birds,' ticola, 2 sp. ; Saxicola ; Ruticilla, 2 



and though doubts may be enter- sp. ; Sylvia, 3 sp. ; Parus, 3 sp. ; 



tained in some cases in regard to Mecistura ; Anorthura ; Certhia; 



the degree of concealment of the Sitta ; Yunx ; Muscicapa, 2 sp. ; 



uest, and to the degree of con- Hirundo, 3 sp. ; and Cypselus. The 



spicuousness of the female, yet the females ot' the following 12 birds 



following birds, which all lay their may be considered as conspicuous, 



eggs in holes or in domed nests, can according to the same standard, 



nardly be considered, by the above viz., Pastor, Motacilla alba, Parol 



standard, as conspicuous : Passer, major and P. cseruleus, Upupa, Pieu^ 



2 species; Sturnus, of which the 4 sp., Coracias, Alcedo, and Merops. 

 female is considerably less brilliant 19 'Journal of Travel,' elited by 



than the male ; Cinclus ; Motacilla A. Murray, vol. i. p. 78. 



