EVOLUTION OF THE COLORS OF BIRDS. 279 



the smallest species and the fratercule of G. inda the next 

 larger in the group. These two are green above and 

 rufous below, but the male has a pectoral band of white 

 and dark green bars. The next in size is C. cabanisi, 

 the fratercule of C. amazona. In these two the back is 

 green but the under parts of the male are white with a 

 pectoral band of green. In the female the rufous per- 

 sists posterior to the green band. In C. alcyon the 

 fratercule of C. torquatus the green is replaced by 

 blue while in the female the rufous still persists, but to 

 a less degree than in C. cabanisi, posterior to the blue 

 pectoral band. 



If, as suggested, the red and green colors are aggres- 

 sive resemblance marks, concealing the bird from fish 

 in muddy water, they would naturally be the primitive 

 color because streams were more universally muddy 

 in earlier geological ages when erosion was greater. 

 Furthermore, the rufous color would naturally persist 

 the longest on the posterior parts of the body, for there 

 it would be invisible to the fish as the bird plunged from 

 above. 



ORDER PICI. THE WOODPECKERS, WRY- 

 NECKS, ETC. 



FAMILY PICID^E. THE WOODPECKERS. 



This cosmopolitan group is especially interesting in 

 connection with the evolution of colors. Tropical species 

 are frequently very brilliantly colored, while all the 

 species found in North America show at least some 

 traces of a bright plumage. The different genera may 

 be divided into two groups those which appear to have 

 lost much of the former brilliancy of their markings, 

 either from degeneration or the need for protection, and 

 those which are to-day either becoming more brilliant, 



