Passenger Pigeon

"In the moments they had intercepted the multitude several hundred yards behind the leading edge, easily matching the sixty-mile-per-hour speed established by the leaders. So closely together did they fly that each bird's head was only inches behind the tail of the bird preceding him, his wing tips all but touched those of the birds to right and left and no more than two feet separated him from the birds above or below. Yet despite such tight formation there was no confusion, there were no collisions. There was in fact a remarkable unit of movement as each bird predicated his own actions by those of the birds in front of him as well as those at his sides and both above and below."