Many of his most interesting natural-history notes Thoreau got from his farmer friends--Melvin, Minott, Miles, Hubbard, Wheeler. Their eyes were more single to the life around them than were his; none of them had lost a hound, a turtle-dove, and a bay horse, whose trail they were daily in quest of. A haunter of swamps and river marshes all his life, he had never yet observed how the night bittern made its booming or pumping sound, but accepted the explanation of one of his neighbors that it was produced by the bird thrusting its bill in water, sucking up as much as it could hold, and then pumping it out again with four or five heaves of the neck, throwing the water two or three feet--in fact, turning itself into a veritable pump! I have stood within a few yards of the bird when it made the sound, and seen the convulsive movement of the neck and body, and the lifting of the head as the sound escaped. The bird seems literally to vomit up its notes, but it does not likewise emit water. Every farmer and fox-hunter would smile if he read Thoreau's statement, made in his paper on the natural history of Massachusetts, that "when the snow lies light and but five or six inches deep, you may give chase and come up with the fox on foot." Evidently Thoreau had never tried it. With a foot and a half, or two feet of snow on the ground, and traveling on snowshoes, you might force a fox to take to his hole, but you would not come up to him. In four or five feet of soft snow hunters come up with the deer, and ride on their backs for amusement, but I doubt if a red fox ever ventures out in such a depth of snow. In one of his May walks in 1860, Thoreau sees the trail of the musquash in the mud along the river-bottoms, and he is taken by the fancy that, as our roads and city streets often follow the early tracks of the cow, so "rivers in another period follow the trail of the musquash." As if the river was not there before the musquash was! Again, his mysterious "night warbler," to which he so often alludes, was one of our common everyday birds which most school-children know, namely, the oven-bird, or wood-accentor, yet to Thoreau it was a sort of phantom bird upon which his imagination loved to dwell. Emerson told him he must beware of finding and booking it, lest life should have nothing more to show him. But how such a haunter of woods escaped identifying the bird is a puzzle. In his walks in the Maine woods Thoreau failed to discriminate the song of the hermit thrush from that of the wood thrush. The melody, no doubt, went to his heart, and that was enough. Though he sauntered through orchards and rested under apple trees, he never observed that the rings of small holes in the bark were usually made by the yellow-bellied woodpecker, instead of by Downy, and that the bird was not searching for grubs or insects, but was feeding upon the milky cambium layer of the inner bark.