THE WINGS. 
87 
of the Swift’s wing. Sometimes, by carefully watch- 
ing these birds in clear water, opportunities occur 
of observing their progress beneath the surface, 
when they may be seen flapping with their short 
wings, as if flying, thus acquiring a much greater 
speed than they could by the use of their webbed 
feet alone. 
There is one bird, however, the Water Crow 
(T Urdus ductus ), in size, shape, and wings very 
similar to the Blackbird, which also dives ; but as it 
does not pursue fish, living on spawn or such sort of 
food, as may be collected without effort, the diver’s 
form of wing is not necessary, and accordingly the 
only use of its wing, under water, is by flapping or 
jerking it upwards to prevent its rising ; for as, like 
all other birds, it is much lighter than water, it 
must of course use some power to keep itself beneath 
the surface, and this it does by means of its wings. 
These birds are chiefly found in wild parts of the 
country, abounding in streams rushing over rocky 
beds. There they may be seen perched upon a 
stone on the edge or middle of the water, from 
whence they'wade beyond their depth, and continue 
their course along the bottom, where they may be 
observed struggling to preserve a footing, and pre- 
vent themselves from rising, by a strange tumbling 
sort of motion of their bodies, accompanied by 
quiverings of their wings, which, acting upon the 
water above, helps to keep them down. 
Before we proceed to speak of migration, or that 
instinct which induces birds to visit and retire from 
certain countries at particular times of the year, it 
is necessary to say a little on the speed with which 
