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 brownish 
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 I, 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. 
