320 CALIFORNIA ACADEMY OF SCIENCES. 



GENUS MNIOTILTA. BLACK AND WHITE WARBLER. 



(7) Male more conspicuously colored than female; 

 young similar to adult female. 



Prevailing colors, black, white, brownish (in young). 



This bird presents one of the best examples of black 

 and white as cognate colors. The markings are modifi- 

 cations of the primitive streaked plumage, the streaks 

 having simply been defined and accentuated, but whether 

 chiefly by sexual selection or by other factors, I am un- 

 able to surmise. 



GENUS PROTONOTARIA. PROTHONOTARY WARBLER. 



(7) Adult male more conspicuously colored than 

 female; young similar to adult female. 



Prevailing colors, white, bluish gray, olive green, 

 yellow. 



The markings of this genus are probably due to sexual 

 selection, which has not yet reached the end of its spe- 

 cializing influence. Individual variation in the head of 

 the male throws considerable light upon the law of the 

 assortment of pigments and correlative colors. In the 

 young the top of the head is olive green, but with the 

 assumption of a full plumage the tendency is for it to 

 become more and more pure yellow in color. In full 

 plumed individuals the yellow becomes an intense cad- 

 mium, sometimes tinted with orange.* 



GENUS HELINAIA. SWAINSON'S WARBLER. 



GENUS HELMITHERUS. WORM-EATING WARBLER. 



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



Prevailing colors, black, white, brown, buff, yellowish. 



These two genera may represent forms which have 

 degenerated in respect to their color markings, but per- 

 haps are species which have not yet attained the degree 



* Kidgway's Manual, p. 484. 



