292 CALIFORNIA ACADEMY OF SCIENCES. 



the wing bars white. Intense examples of Xantho- 

 cephalus have the head orange or more rarely pinkish 

 saffron, while the intense races of the Icterus cucullatus 

 group have the head varying from orange to red. The 

 principal difference in color distribution is that in the 

 former bird the black is on the posterior portion of the 

 under parts of the body, while in the latter it is upon 

 the anterior portion. 



GENUS AGELAIUS. THE RED-WINGED BLACKBIRDS. 



(6) Plumage of male in summer different from winter 

 plumage; female different from either; young similar to 

 female. 



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



The adult males of this genus are highly specialized, 

 no generalized color being left, in fact. Like most birds 

 with black plumage, the members of this genus are gre- 

 garious. Gregarious birds, from their very habits, would 

 hardly be benefited by protective colors, and, accord- 

 ingly, instead of acquiring a protective plumage with 

 some distinctive markings, the black color itself be- 

 comes a recognition mark. Whether the red shoulder 

 patch is primarily a recognition mark or a character 

 developed by sexual selection is difficult to determine. 

 From the fact that it is so inconspicuous in the female, 

 it seems that it cannot be a directive mark, and was 

 probably developed primarily by sexual selection upon 

 the wings where it would attract the most attention. 

 Plate XIV shows the different phases in the development 

 of the wing patch. The differences between the adult 

 males of the three species, A. phoeniceus, gubernator and 

 tricolor, may have been developed by sexual selection, or 

 else are discriminative marks as a result of physiological 

 selection. They certainly do not appear to have been 

 produced by geographical isolation. That these wing 

 markings are associated with the breeding habits, is 



