Riverby by John Burroughs — Read

I have often had occasion to notice how much more intelligence the bird carries in its eye than does the animal or quadruped. The animal will see you, too, if you are moving, but if you stand quite still even the wary fox will pass within a few yards of you and not know you from a stump, unless the wind brings him your scent. But a crow or a hawk will discern you when you think yourself quite hidden. His eye is as keen as the fox's sense of smell, and seems fairly to penetrate veils and screens. Most of the water-fowl are equally sharp-eyed. The chief reliance of the animals for their safety, as well as for their food, is upon the keenness of their scent, while the fowls of the air depend mainly upon the eye.

A hunter out in Missouri relates how closely a deer approached him one day in the woods. The hunter was standing on the top of a log, about four feet from the ground, when the deer bounded playfully into a glade in the forest, a couple of hundred yards away. The animal began to feed and to move slowly toward the hunter. He was on the alert, but did not see or scent his enemy. He never took a bite of grass, says the sportsman, without first putting his nose to it, and then instantly raising his head and looking about.