EVOLUTION OF THE COLORS OF BIRDS. 303 



GENUS CALCARIUS 



. THE LONGSPURS. 

 GENUS RHYNCHOPHANES ) 



(5) Adult male in breeding plumage differs from 

 female; young with a peculiar first plumage. 



Prevailing colors, white, black, gray, brown, chestnut, 

 buffy. 



This genus is closely allied to the preceding in regard 

 to its colors, but has not resided so long or been so much 

 confined to the Arctic regions, and hence has not ac- 

 quired the same amount of white. It is a significant 

 fact in this connection, I think, that in this genus al- 

 though the plumage does not become white in winter 

 the black markings are largely obscured either by white 

 or buffy tips to the feathers. This might .well be in- 

 terpreted as the commencement of a climatic influence 

 which will culminate in a white plumage. Natural 

 selection would favor this change as resulting in a 

 warmer winter dress. The characteristic marks of the 

 different species are apparently directive and discrim- 

 inative recognition marks. 



GENUS POOC^TES. THE VESPER SPARROWS. 



(1) Adult male like female; young like adult, but 

 markings duller. 



Prevailing colors, brown, rufous, gray, white. 



This is one of the plainly attired ground birds in 

 which very little specialization of marking has been at- 

 tained, the colors being protective in nature. The only 

 recognition mark is the white outer tail feathers, unless 

 the rufous patch on the wing coverts be considered as 

 such. This latter may be a discriminative mark, al- 

 though it seems hardly conspicuous enough. On the 

 other hand it cannot well be looked upon as the result 

 of sexual selection, for it is not highly enough developed 

 to have been completely transmitted to the female. 



