Sometimes he stands straight up on one leg, with the other drawn up out of sight in his feathers, but more often he sits down on the perch, still resting on his feet. Most wild birds of the perching kind sleep in the same way. It is only lately that we have begun to find out where birds sleep, because it is dark when they go to bed, and they get up before it is light enough for us to see them. The only way to catch them in bed is to go out in the evening, and start them up after they have gone to sleep. And this is not very kind to the poor little birds. Some men who are trying to learn about the habits of birds have tried this way, and so have found out some of their sleeping-places. One thing they have learned is that the nest is not often used for a bed, except for the mother, while she is sitting and keeping her little ones warm. Robins and orioles, and others, creep into the thick branches of an evergreen tree, close up to the trunk. Some crawl under the edge of a haystack, others into thick vines or thorny bushes. All these are meant for hiding-places, so that beasts which prowl about at night, and like to eat birds, will not find them. Tree sparrows like to sleep in holes in the ground like little caves. The men who found these cosy little bedrooms think they are places dug out by field mice, and other small animals, for their own use. And when they are left, the birds are glad to take them. When the weather is cold, some birds sleep under the snow. You may think that would not be very warm, and it is not so warm as a bed in the house with plenty of blankets. But it is much warmer than a perch in a tree, with nothing but leaves to keep off the wind. While the snow is falling, some birds find it as good as blankets for their use. Grouse, who live on the ground, dive into a snow-bank, and snuggle down quietly, while the snow falls and covers them all over, and keeps the cold wind off. Air comes through the snow, so they do not smother. Some birds creep into a pile of brush that is covered with snow, and find under the twigs little places like tents, where the snow has been kept out by the twigs, and they sleep there, away from the wind and storm outside. Water birds find the best sleeping-places on the water, where they float all night like tiny boats. Some of them leave one foot hanging down and paddling a little, while they sleep, to keep from being washed to the shore. Bob-white and his family sleep in a close circle on the ground, all with their heads turned outward, so that they can see or hear an enemy, whichever way he comes. Hawks and eagles are said to sleep standing, never sitting on the feet like a canary. Some ducks and geese do even more: they sleep standing on one foot. Woodpeckers and chimney swifts hang themselves up by their claws, using their stiff tail for a brace, as if it were a third leg.