The Body of a Bird 297 



to be found by plucking out a few of the feathers of the 

 young bird. Those which replace the ones pulled out 

 will show intermediate stages, which have long since been 

 dropped from the sequence of patterns, as observed in 

 the regular moults of the birds. 



Another important phenomenon is the seasonal moult, 

 which was spoken of in the chapter treating of feathers- 

 In the fall of the year the brilliant Scarlet Tanager assumes 

 the olive-green dress of the female, and the Indigo Bunt- 

 ing and the Bobolink likewise don the dull garb of their 

 mates. 



There is another very interesting cause of change in 

 colour, namely, the wearing off of the brittle tips of the 

 feather-vane. An excellent example of this is seen in the 

 Snowflakes, which come south in the depth of severe 

 winters, flying in small flocks about our fields, like an 

 animated flurry of the actual crystals. When we see 

 the birds at this time they are brownish and brow^nish 

 white. In the spring, in their northern home, they change 

 to a clear-cut black and white, not by shedding the entire 

 plumage, but merely by the breaking off of the brown 

 feather-tips. By a similar process the Bobolink changes 

 from the buffy female dress to his rich black-and-white 

 spring suit, and, as we saw in Chapter II, Fig. 35, the 

 English Sparrow gains his cravat of jet. 



Another excellent example is found in the Black Larks 

 of Siberia, the males of which, in winter, are of an almost 

 uniform sandy colour, like a Skylark, but by the wearing 

 off of the buff tips of the feathers, the birds become jet-black 

 in the summer — a most remarkable and radical change. 



