30 FORM AND HABIT: THE BILL. 
these birds are largely ground-haunters, and most of them 
inhabit regions where the snowfall is heavy, the toes in 
winter acquire a comblike fringe on either side. Practi- 
cally, therefore, Grouse don snowshoes in the fall, and 
wear them until the following spring. 
The Bill.—Of the four organs we are considering, 
the bill is beyond question the most important. We | 
have seen that a bird may be wingless and practically 
tailless, and may almost lose the use of its feet; but 
from the moment the bill breaks the eggshell and 
liberates the chick, the bird’s life is dependent upon its 
services. The variety of offices performed by the bill, 
and the correspondingly numerous forms it assumes, are, 
doubtless, without parallel in the animal world. 
The special modification of the fore limbs as flight- 
organs deprives birds of their use for other important 
services, and consequently we have a biped which, so far 
as their assistance goes, is without arms or hands. As a 
result, the duties which would naturally fall to these 
members are performed by the bill, whose chief office, 
therefore, is that of a hand. 
Occasionally it is sexually adorned, as in the Puffins, 
several Auks, Ducks, and the White Pelicans, which, 
during the nesting season, have some special plate, knob, 
or color on the bill. With the Woodpeckers it is a 
musical instrument—the drumstick with which they beat 
a tattoo on some resounding limb. Owls and some other 
birds, when angry or frightened, snap their mandibles 
together like castanets. But it is as a hand that the 
bill gives best evidence of adaptation to or by habit. 
Among families in which the wings, tail, and feet are 
essentially alike in form, the bill may present great vari- 
ation——proof apparently of its response to the demands 
made upon it. 
All birds use it asa comb and brush with which to 
