Chap. XVI.] COLOR AND PROTECTION. 0^5 



different from that of their congeners. Both sexes of thir- 

 teen out of the twenty-six species are colored in the same 

 manner ; but these belong to genera in which this rule 

 commonly prevails, so that they tell us nothing about the 

 protective colors being the same in both sexes of desert- 

 birds. Of 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 spe- 

 cies, 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-colored 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 ; 

 while the lower surfaces of the males alone have been 

 diversified through sexual selection, for the sake of orna- 

 ment. Here, as both sexes are equally well protected, we 

 clearly see that the females have not been prevented 

 through natural selection from inheriting the colors of 

 their male parents : we must look to the law of sexually- 

 limited transmission, 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 colored. No doubt, if their colors had been 

 brilliant, they would have been much more conspicuous to 

 their enemies ; but whether their dull tints have been spe- 

 ;ially 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 ornament. We must, however, bear in mind that male 

 birds, though dull-colored, often differ much from their 

 females, as with the common sparrow, and this leads to 

 the belief that such colors have been gained through sex- 

 ual selection, from being attractive. Many of the soft- 



