BIRDS 107 



would also mean the destruction of the young. The bright 

 colors of the males may have been developed. as suggested, 

 or the brightest females may have always been most frequently 

 destroyed and the less conspicuous ones escaped, and thus 

 the subdued colors developed. This is probably not the 

 whole explanation of the difference in color in the sexes. 



Birds moult, that is, lose their feathers wholly or in part 

 every year, or even several times a year. This loss of feathers 

 has some connection with the putting on of mating colors 

 and decorations, and sometimes is for protection. Change 

 of plumage colors is chiefly due to moulting and renewal. 

 But the pigments in the feathers may change, and sometimes 

 the tips of the feathers wear away and the lower ends of the 

 feathers with a different color are exposed. This last is the 

 case with the house sparrow when the male puts on his black 

 bib in the spring. 



The young are generally not quite of the same color as 

 the adults, though full fledged. The colors and markings 

 are not as bright or as distinct. Sometimes there is a great 

 difference in color or marking, as in the young robin, which 

 has its breast mottled with brown spots, like a thrush, re- 

 vealing the connection of the robins with the thrushes. 



The colors in feathers are chiefly due to pigments. But 

 the changing iridescence displayed on the feathers of the 

 dove, blackbird, humming-bird, etc., is due to the interference 

 of light rays reflected from the surface of the feathers- 

 analogous to the iridescence on the mother-of-pearl. 



Besides color, there are other mating devices. Many male 

 birds go through curious and, to us, comical performances 

 before their lady-loves. We have all seen the strutting, 

 rustling, and spreading and snapping of feathers by the 



