“The Red-tailed Hawk is a constant resident in the United States, in every part of which it is found.  It performs partial migrations, during severe winters, from the Northern Districts towards the Southern.  In the latter, however, it is at all times more abundant, and I shall endeavour to present you with a full account of its habits, as observed there.

Its flight is firm, protracted, and at times performed at a great height.  It sails across the whole of a large plantation, on a level with the tops of the forest-trees which surround it, without a single flap of its wings, and is then seen moving its head sideways to inspect the objects below.  This flight is generally accompanied by a prolonged mournful cry, which may be heard at a considerable distance, and consists of a single sound resembling the monosyllable Kae, uttered in such a manner as to continue for three or four minutes, without any apparent inflection or difference of intensity.  It would seem as if uttered for the purpose of giving notice to the living objects below that he is passing, and of thus inducing them to bestir themselves and retreat to a hiding-place, before they attain which he may have an opportunity of pouncing upon some of them . . .

The lively squirrel is seen gaily leaping from one branch to another, or busily employed in searching for the fallen nuts on the ground.  It has found one.  Its bushy tail is beautifully curved along its back, the end of it falling off with a semi-circular bend; its nimble feet are seen turning the nut quickly round, and its teeth are already engaged in perforating the hard shell; when, quick as thought, the Red-tailed Hawk, which has been watching it in all its motions, falls upon it, seizes it near the head, transfixes and strangles it, devours it on the spot, or ascends exultingly to a branch with the yet palpitating victim in his talons, and there feasts at leisure.”

–J. J. Audubon, Ornithological Biography, I (1831), 265-266 [excerpted].