“They always feed on the wing.  In calm and warm weather, they soar to an immense height, pursuing the large insects called Musquito Hawks, and performing the most singular evolutions that can be conceived, using their tail with an elegance of motion peculiar to themselves.  Their principal food, however, is large grasshoppers, grass-caterpillars, small snakes, lizards, and frogs.  They sweep close over the fields, sometimes seeming to alight for a moment to secure a snake, and holding it fast by the neck, carry it off, and devour it in the air.  When searching for grasshoppers and caterpillars, it is not difficult to approach them under cover of a fence or tree.  When one is then killed and falls to the ground, the whole flock comes over the dead bird, as if intent upon carrying it off.  An excellent opportunity is thus afforded of shooting as many as may be wanted, and I have killed several of these Hawks in this manner, firing as fast as I could load my gun.”

–J. J. Audubon, Ornithological Biography, I (1831), 369 [excerpted].