Chap. XVI. COLOUE AND PROTECTION. 225 



the other thirteen species, three belong to genera in 

 which the sexes usually differ from each other, yet they 

 have the sexes alike. In the remaining ten species, 

 the male differs from the female ; but the difference is 

 confined chiefly to the under surface of the plumage, 

 which is concealed when the bird crouches on the 

 ground ; the head and back being of the same sand- 

 coloured hue in both sexes. So that in these ten 

 species the upper surfaces of both sexes have been 

 acted on and rendered alike, through natural selection, 

 for the sake of protection ; whilst the lower surfaces of 

 the males alone have been diversified through sexual 

 selection, for the sake of ornament. Here, as both 

 sexes are equally well protected, we clearly see that the 

 females have not been prevented through natural selec- 

 tion from inheriting the colours of their male parents : 

 we must look to the law of sexually limited transmis- 

 sion, as before explained. 



In all parts of the world both sexes of many soft- 

 billed birds, especially those which frequent reeds or 

 sedges, are obscurely coloured. No doubt if their 

 colours had been brilliant, they would have been 

 much more conspicuous to their enemies ; but whether 

 their dull tints have been specially gained for the 

 sake of protection seems, as far as I can judge, rather 

 doubtful. It is still more doubtful whether such 

 dull tints can have been gained for the sake of orna- 

 ment. We must, however, bear in mind that male 

 birds, though dull-coloured, often differ much from 

 their females, as with the common sparrow, and this 

 leads to the belief that such colours have been gained 

 through sexual selection, from being attractive. Many 

 of the soft-billed birds are songsters ; and a discussion 

 in a former chapter should not be forgotten, in which 

 it was shewn that the best songsters are rarely orna- 



VOL. II. Q 



