BIRDS. 515 



to the sexual coloration of birds. He believes that the 

 bright tints originally acquired through sexual selection by 

 the males would in all, or almost all cases, have been trans- 

 mitted to the females, unless the transference had been 

 checked through natural selection. I may here remind 

 the reader that various facts opposed to this view have 

 already been given under reptiles, amphibians, fishes and 

 lepidoptera. Mr. "Wallace rests his belief chiefly, but not 

 exclusively, as we shall see in the next chapter, on the fol- 

 lowing statement,* that when both sexes are colored in a 

 very conspicuous manner the nest is of such a nature as to 

 conceal the sitting bird; but when there is a marked con- 

 trast of color between the sexes, the male being gay and 

 the female dull colored, the nest is open and exposes the 

 sitting bird to view. This coincidence, as far as it goes, 

 certainly seems to favor the belief that the females which 

 sit on open nests have been specially modified for the sake 

 of protection; but we shall presently see that there is an- 

 other and more probable explanation, namely, that con- 

 spicuous females have acquired the instinct of building 

 domed nests oftener than dull-colored birds. Mr. Wallace 

 admits that there are, as might have been expected, some 

 exceptions to his two rules, but it is a question whether 

 the exceptions are not so numerous as seriously to invalidate 

 them. 



There is, in the first place, much truth in the Duke of 

 Argyll's remark f that a large domed nest is more con- 

 spicuous to an enemy, especially to all tree-haunting carniv- 

 orous animals, than a smaller open nest. Nor must we 

 forget that with many birds which build open nests the 

 male sits on the eggs and aids the female in feeding the 

 young; this is the case, for instance, with Pyranga (estiva^ 

 one of the most splendid birds in the United States, the 

 male being vermilion and the female light brownish-green. 

 Now if brilliant colors had been extremely dangerous to 

 birds while sitting on their open nests the males in these 

 cases would have suffered greatly. It might, however, be 

 of such paramount importance to the male to be brilliantly 

 colored in order to beat his rivals that this may have more 

 than compensated some additional danger. 



*" Journal of Travel," edited by A. Murray, vol. i, 1868, p. 78. 

 "Journal of Travel," edited by A. Murray, vol. i, 1868, p. 281. 

 j Audubon, "Ornithological Biography," vol. i, p. 233. 



