EVOLUTION OF THE COLORS OF BIRDS. 215 



that there is a slight difference in the shade or intensity 

 of color of adult and young: 



Dendroica doininica. Pica. 



Icteria virens* Cyanocitta.^ 



Vireo . Aphelocoma . 



Clivicola riparia. Pcrisoreus. 



Stelgidopteryx serripennis. Corvus. 



Spinus pinus* Sayornis.^ 



Ammodranius. Contopus. 



Melospiza. Empidonax. 



Passerella. Chaiura. 



Picicorvus. * Geococcyx. 

 Cyanocephalus . 



It is a noticeable fact that most of the birds in the 

 above list are more or less dull colored forms. The 

 yellow-throated warbler (Dendroica doininica) smd yellow- 

 breasted chat (Icteria virens) are the only two in which 

 yellow figures at all prominently, and the genera Cyano- 

 citta and Aphelocoma are the only ones in which blue 

 occurs. Besides these there are the highly specialized 

 crows and magpies, and all the rest are without distinct- 

 ive marks, save the peculiar Geococcyx, which, as will 

 be shown later, is doubtless a degenerate form, so far as 

 color goes, at least. This lack of forms with elaborate 

 patterns of color in this first list is what would naturally 

 be expected; first, because elaborate colors are generally 

 assumed first by the male, and only occasionally the 

 female has been enabled to acquire them; and second, 

 because these dull colors are apt to represent old estab- 

 lished types which have found their protection in their 

 insignificance, so that there would have been ample 

 time for the female to have acquired what small degree, 

 of specialization the male had attained. 



There are a large number of forms belonging to class 



