EVOLUTION OF THE COLORS OF BIRDS. 221 



most notable illustrations of the class. When the male 

 is more conspicuously colored than the female and there 

 is no marked seasonal change, the young may differ to 

 a greater or less degree from the adults. The following 

 is a list of species in which (7) the young are like the 

 adult female: 



Mniotilta varia. Geothly pis Philadelphia. 



Protonotaria citrea. Geothly pis macgiUivrayi . 



Helminthophila chrysoptera. Sylvania mitrata. 

 Helminthophila pinus. Sylvania pusilla. 



Helminthophila ruftcapilla. Sylvania canadensis. 

 Parula americana. Vireo atricapillus. 



Dvndroica tigrina. Phainopepla nitens. 



Dendroica cestiva. Progne subis. 



Dendroica ccerulescens. Coccothraustes vespertina. 



Dendroica blaekburnicc. Pinicola enucleator. 



Dendroica ccerulea. Cardinalis. 



Dendroica virens. Pyrrhuloxia sinuata. 



Dendroica toivnsendi. Habia. 



Dendroica occidentalis. Piranga wstiva. 



Dendroica vigorsii. Icterus. 



Setophaga ruticilia. Quiscalus. 



Geothly pis agilis. Trochilus. 



It is a noteworthy fact that every species in this list 

 has some mark of specialization, while nearly all are 

 highly modified forms. This is the class which, more 

 than any other illustrates sexual selection the males 

 having been originally marked like the present females 

 and young, and the brilliant and varied hues of the male 

 warblers, humming birds, cardinals, andtanagers of to- 

 day have doubtless been assumed principally as sexual 

 charms. 



Of species in which the male is more conspicu- 

 ously colored and the young have a peculiar first plum- 

 age, the following are representative examples: 



