158 ON THE CLASSIFICATION OP BIRDS. 
(136.) The most extraordinary shaped foot among the 
Grallatorial birds is that of the jacanas^ or spur-winged 
water-hens. These birds, whose geographic range 
appears restricted to the tropical latitudes of both hemi- 
spheres, are particularly common on the low and in- 
undated grounds of Brazil; and we have frequently 
seen twenty of them at once, in different parts of a 
swamp, walking almost upon the water. Such, at least, 
is their appearance ; and, although startling to one who 
is a stranger to their habits, the deception can be thus 
explained : — More than two- thirds of tlie surface of these 
swamps, where the water is generally shallow, is partially 
covered with the broad leaves of water lilies and other 
aquatic plants : it is upon these that the jacana walks 
while seeking the aquatic insects upon which it feeds. 
It is clear, however, that, to accomplish this, it must 
have a very ])eculiar shaped foot; for, otherwise, the bird 
would sink in the soft mud below by its own weight. 
The toes and claws are therefore developed to a most ex- 
traordinary length, in order that the bird should lie sup- 
ported by the great extent of surface which its foot covers. 
The African jacana*, whose body is about the size of 
S6 
our green woodpecker, has yet such an enormous foot 
that its fore toes measure no less than three inches and a 
quarter, and its hind one 86. a) two inches and a 
half: the claws are obviously constructed for the sole 
purpose of supporting the bird upon a smooth and level 
plain ; they are perfectly straight, and of such uncom- 
mon length, that the hinder one measures at least 
two inches. By this remarkable structure the bird is 
enabled to walk upon half floating leaves, which would 
* Zoological Ulus. vol. il pL 2. 
