EVOLUTION OF THE COLORS OF BIRDS. 331 



Like Setophaga, these two genera of brilliant red 

 warblers are tropical in their distribution, and the colors 

 have been produced by sexual selection in a hot climate. 



Genus Basileuterus. Brasher's Warbler, etc. 



(1) Adult male like female; young like the adult (?). 



Prevailing colors, black, yellow, olive green, chestnut, 

 orange-rufous. 



The colors in this genus are the conventional ones of 

 the family, and are to be accounted for as in the pre- 

 ceding instances. The different species appear to be 

 largely due to climatic influences. 



FAMILY MOTACILLID^. The Wagtails and 



Pipits. 



(5) Male in breeding plumage differs from female; 

 young with peculiar first plumage (Motacilla and 

 Budytes), or (4) both sexes change with season; young 

 differ from adults at any season (Anthus). 



Prevailing colors, black, white, gray, bluish, brown, 

 yellow, olive green. 



In this family a certain similarity to the colors of the 

 genus Dendroica is to be noted. The bluish ground 

 color is present in some of the species of Motacilla, 

 while in M. melanope and in the genus Budytes the 

 ground color is olive green, thus presenting the two 

 colors most often occurring in the generalized markings 

 of Dendroica. In this family also black and yellow 

 form the principal specialized marks. Sexual selection 

 has evidently been the factor which has produced the 

 markings in this group, although far less completely 

 carried out than in Dendroica. The terrestrial habits 

 of the members of the family may have had a tendency 

 to suppress the bright colors, Anthus in particular being 

 protectively colored. The gregarious disposition of these 



