‘Chap. XVI. 
COLOUE AND PKOTECTION. 
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- 
Ttion 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 
fheir 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 
