EVOLUTION OF THE COLORS OF BIRDS. 283 



In the feather here shown (fig. 4) the pigment is along 

 one side only, it being in fact a lateral hybrid, producing 

 a line of demarkation for a definite color patch. 



The prevailing colors of the family are black, white, 

 brown, red and yellow. The relation of the plumage of 

 the sexes and young has already been discussed (see 

 ante, p. 224). 



ORDER MACROCHIRES. THE GOATSUCK- 

 ERS, SWIFTS, ETC. 



FAMILY CAPRIMULGID^E. THE GOATSUCKERS. 



The colors of this family are remarkably homogeneous 

 in general style, being mottled brown, gray, ochraceous 

 and white. There are no marks of sexual adornment 

 among North American forms, the general colors being 

 very perfect protective marks, and the variously dis- 

 tributed white marks affording a beautiful illustration 

 of several classes of recognition marks. As these were 

 discussed somewhat fully in the preceding pages (see 

 ante, pp. 207-209) it is unnecessary to repeat what was 

 there stated. It need only be added that there is 110 

 group which appears to present less difficulty in the 

 elucidation of color marks. 



FAMILY MICROPODID^E. THE SWIFTS. 



(1) Adult male like female; young similar to adult. 



Prevailing colors, blackish, grayish, brown, white. 



Like the hawks, the colors of this family do not seem 

 to have been greatly influenced by natural selection. 

 From their crepuscular habits and swift flight, they can 

 can hardly have any enemies, nor do they need aggres- 

 sive colors for the capture of their prey. Cypseloides 

 and Chaetura have not even a suggestion of a recogni- 

 tion mark, apparently, and their colors do not appear to 



