black ducks, and the mallards with emerald-green heads, quacked, the pintails whimpered—the air was full of duck-notes. As they swept southward, the different families took their places according to their speed. Well up in the van were the canvas-backs, who can travel at the rate of one hundred and sixty feet per second. Next came the pintails, and the wood-ducks, whose drakes have wings of velvet-black, purple, and white. The mallards and the black ducks brought up the rear; while far behind a cloud of blue-winged teal whizzed down the sky, the lustrous light blue of their wings glinting like polished steel in the sunlight. Flying in perfect unison, the distance between them and the main flock rapidly lessened; for the blue-winged teal, when it settles down to fly, can tick off two miles a minute. A few yards back of their close cloud followed a single green-winged teal, a tiny drake with a chestnut-brown head brightly striped with green, who wore an emerald patch on either wing.
In a moment the blue-wings had passed the quacking mallards and black ducks as if they had been anchored in the sky. The whistlers and pintails were overtaken next, and then, more slowly, the little flock, flying in perfect form, began to cut down the lead of the canvasbacks in front. Little by little, the tiny teal edged up, in complete silence, to the whizzing, grunting leaders, until at last they were flying right abreast of them. At first slowly, and then more and more rapidly, they drew away, until a clear space of sky showed between the two flocks,
