EVOLUTION OF THE COLORS OF BIRDS. 299 



GENUS ACANTHIS. THE REDPOLLS. 



(8) Adult male more conspicuously colored than 

 adult female; young with a peculiar first plumage. 



Prevailing colors, brown, white, gray, red, pink. 



The colors of the young, female and adult, represent 

 three stages in the assumption of the red color, first the 

 plain streaked bird, not unlike the pine goldfinch (Spinus 

 pinus), next with the red cap (acquired first by the male 

 as a sexual charm, and afterwards transmitted to the 

 female by heredity), and lastly the red on the rump and 

 under parts. There is a tendency towards the assump- 

 tion of an albinistic plumage in the northern forms of 

 this genus. Just as the two large forms, Pinicola and 

 Coccothraustes, seem to have come from the same stock, 

 and developed, one the red and the other the yellow 

 color, so also even more intimately the small forms 

 Acanthis and Spinus appear to be related. The probable 

 genealogical connections of the genera thus far con- 

 sidered, which seem to constitute a group by themselves, 

 may be indicated by the following diagram: 



