They do so, in order that the leaves may not obstruct their vision--thus giving them a wider range, and, consequently, a better chance of espying their prey.

But even with this advantage their chances of seeing their prey are circumscribed, when compared with that of hawks upon the wing; and they are frequently compelled to take to the air in order to discover it.
Now the kites are always in the air, or nearly so.

They, in fact, _live upon the wing_, eating their food as they fly, from their claws.

Living thus, they have many more chances of _seeing_ their prey than their cousins of the hawk species; and were they possessed of the power to _pounce_ upon it with as much certainty as the latter do, it is evident they would have greatly the advantage.

The want of that capability, however, brings them upon an equality; and, as I have said, Lucien perceived in this that peculiar equilibrium, or "balance of power," which constantly presents itself to the student of Nature.
These thoughts passed through his mind at the moment.