230 
BIRD-LIFE. 
curved arm-bone, we find long, hard, and yet very elastic 
feathers, which are furnished with short, compact webs, 
and are somewhat curved; the wing can be moved very 
rapidly, by means of the short, mobile arm. The tail is 
long, broad and forked, probably to allow of the most 
varied movement of this rudder, so necessary to the 
Swift, and to permit of an instantaneously greater or 
less powerful use of the same. These wings and this 
tail combined, render it not only possible for the bird to 
cleave the air with incredible swiftness, but in a certain 
degree for it to live in that element, so to speak. With 
these creatures flight is but sport: the Swift is never 
tired. The structure of the organ with which it captures 
its prey is naturally much simpler than that of the true 
Raptores, though equally well adapted to the work they 
have to perform. The eye, placed forward in the head, 
is very large and somewhat flat, and is deposited in 
a shell-shaped orbit, which is clothed on the outside 
with feathers to the very edge. With this organ the 
Swift can discern the smallest insect at a considerable 
distance, and the mandibles are so constructed as to be 
able to capture the same with certainty. The beak 
itself is small, but the gape, reaching far back under 
the eye, is a regular abyss ! The feet, on the contrary, 
appear stunted; the tarsi very short, and all four toes 
are turned forward and are provided with sharp nails. 
They cannot be used for walking, but enable the bird 
to cling to and crawl into those places which it frequents 
exclusively for the purposes of roosting and breeding, 
principally holes in towers or rocks. They are use¬ 
less for any other purpose, if we except fighting with 
its rivals during the courting season. If the two 
combatants fall together on the ground, one powerful 
