162 SEXUAL SELECTION: BIRDS. [Part II. 



her. About forty of our British birds (excluding those of 

 large size which could defend themselves) build in holes 

 in banks, rocks, or trees, or construct domed nests. If 

 we take the colors of the female goldfinch, bullfinch, or 

 blackbird, as a standard of the degree of conspicuousness, 

 which is not highly dangerous to the sitting female, then, 

 out of the above forty birds, the females of only twelve 

 can be considered as conspicuous to a dangerous degree, 

 the remaining twenty-eight being inconspicuous. 17 Nor 

 is there any close relation between a well-pronounced dif- 

 ference in color between the two sexes and the nature of 

 the nest constructed. Thus the male house-sparrow 

 (Passer domesticus) differs much from the female, the 

 male tree-sparrow ( P. montanus) differs hardly at all, and 

 yet both build well-concealed nests. The two sexes of the 

 common fly-catcher (Muscicapa grisola) can hardly be 

 distinguished, while the sexes of the pied fly-catcher 

 (3f. luctuosd) differ considerably, and both build in holes. 

 The female blackbird (Tardus merula) differs much, the 

 female ring-ouzel (T. torquatus) differs less, and the female 



m 



common thrush (T. musicus) hardly at all, from their re- 

 spective males ; yet all build open nests. On the other 

 hand, the not very distantly-allied water-ouzel (Cinclus 



17 1 have consulted, on this subject, Macgillivray's ' British Birds,' 

 and though doubts may be entertained in some cases in regard to the 

 degree of concealment of the nest, and of the degree of conspicuousness 

 of the female, yet the following birds, which all lay their eggs in holes or 

 in domed nests, can hardly be considered, according to the above stand- 

 ard, as conspicuous : Passer, 2 species ; Sturnus, of which the female is 

 considerably less brilliant than the male ; Cinclus ; Motacilla boarula (?) ; 

 Erithacus (?) ; Fruticola, 2 sp. ; Saxicola ; Ruticilla, 2 sp. ; Sylvia, 3 sp. ; 

 Parus, 3 sp. ; Mecistura; Anorthura; Certhia; Sitta; Yunx; Muscicapa, 

 2 sp. ; Hirundo, 3 sp. ; and Cypselus. The females of the following 12 

 birds may be considered as conspicuous according to the same standard, 

 viz., Pastor, Motacilla alba, Parus major and P. coeruleus, Upupa, Picus, 

 4 sp., Coracias, Alcedo, and Merops. 



