SEXUAL. SELECTION 587 



merula) differs much, the female ring-ouzel {T. torquatua) 

 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 ring-ouzel. 

 The black and red grouse (Tetrao tetrix 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 colored (and in this 

 case the males with rare exceptions are equally conspicu- 

 ous) build concealed nests for the sake of protection. Mr. 

 Wallace enumerates" 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 (Oapitonidse), plantain -eaters (Musophagse), wood- 

 peckers and parrots. Mr. Wallace believes that in these 

 groups, as the males gradually acquired through sexual 

 selection their brilliant colors, these were transferred to 

 the females and were not eliminated by natural selection, 

 owing to the protection which they already enjoyed from 

 their manner of nidification. According to this view, their 

 present manner of nesting was acquired before their present 

 colors. 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 colors of the male, 

 they were gradually led to change their instincts (supposing 

 that they originally built open nests), and to seek protection 

 by building domed or concealed nests. No one who studies, 

 for instance, Audubon's account of the differences in the 

 nests of the same species in the Northern and Southern 



'» "Journal of Travel," edited by A. Murray, vol. i. p. 18. 



