|_5o T lie Descent of Man. Part Ii, 



from their manner of nidification. According to this view, their 

 present manner of nesting was acquired before their present 

 colours. But it seems to me much more probable that in most 

 cases, as the females were gradually rendered more and more 

 brilliant from partaking of the colours of the male, they were 

 gradually led to change their instincts (supposing that they 

 originally built open nests), and to seek protection by building 

 domed or concealed nests. No one who studies, for instance, 

 Audubon's account of the differences in the nests of the same 

 species in the Northern and Southern United States, 20 will feel 

 any great difficulty in admitting that birds, either by a change 

 (in the strict sense of the word) 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 colours of female birds and their manner of 

 nesting, receives some support from certain cases occurring in 

 the Sahara Desert. Here, as in most other deserts, various birds, 

 and many other animals, have had their colours adapted in a 

 wonderful manner 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 Manticola cyanea is conspicuous from his bright blue colour, 

 and the female almost equally conspicuous from her mottled 

 brown and white plumage ; both sexes of two species of Dro- 

 niolsea are of a lustrous black ; so that these three species are far 

 from receiving protection from their colours, yet they are able to 

 survive, for they have acquired the habit of taking refuge from 

 danger in holes or crevices in the rocks. 



With respect to the above groups in which the females are 

 conspicuously coloured and build concealed nests, it is not 

 necessary to suppose that each separate species had its nidifying 

 instinct specially modified ; but only that the early progenitors 

 of each group were gradually led to build domed or concealed 

 nests, and afterwards transmitted this instinct, together with 

 their bright colours, to their modified descendants. As far as it 

 can be trusted, the conclusion is interesting, that sexual selection, 

 together with equal or nearly equal inheritance by both sexes, 

 have indirectly determined the manner of nidification of whole 

 groups of birds. 



According to Mr. Wallace, even in the groups in which the 

 females, from being protected in domed nests during incubation, 



29 See many statements in the the nests of Italian birds by Eugenic 

 'Ornithological Biography.' See, Bettoni, in the ' Atti della Societi 

 also, some curious observations on Italiana,' vol. xi. 1869, p. 437. 



