164 SEXUAL SELECTION: BIRDS. [Part II, 



of their habits, or through the natural selection of so* 

 called spontaneous variations of instinct, might readily be 

 led to modify their manner of nesting. 



This way of viewing the relation, as far as it holds 

 good, between the bright colors of female birds and their 

 manner of nesting, receives some support from certain 

 analogous cases occurring in the Sahara Desert. Here, as 

 in most other deserts, various birds, and many other ani- 

 mals, have had their colors adapted in a wonderful man- 

 ner to the tints of the surrounding surface. Nevertheless 

 there are, as I am informed by the Rev. Mr. Tristram, 

 some curious exceptions to the rule ; thus the male of the 

 Monticola cyanea is conspicuous from his bright-blue col- 

 or, and the female almost equally conspicuous from her 

 mottled brown and white plumage; both sexes of two 

 species of Dromolsea are of a lustrous black ; so that these 

 three birds are far from receiving protection from their 

 colors, yet they are able to survive, for they have acquired 

 the habit, when in danger, of taking refuge in holes or 

 crevices in the rocks. 



With respect to the above-specified groups of birds, 

 in which the females are conspicuously colored and build 

 concealed nests, it is not necessary to suppose that each 

 separate species had its nidifying instinct specially modi- 

 fied ; but only that the early progenitors of each group 

 were gradually led to build domed or concealed nests ; 

 and afterward transmitted this instinct, together with 

 their bright colors, to their modified descendants. This 

 conclusion, as far as it can be trusted, is interesting, 

 namely, that sexual selection, together with equal or 

 nearly equal inheritance by both sexes, has indirectly 

 determined the manner of nidification of whole groups of 

 birds. 



Bome curious observations on the nests of Italian Birds by Engenio Bot- 

 tom, in the ' Atti della Societa Italiana,' vol. xi. 1869, p. 487. 



