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.
Some birds, like the crows, sleep in great flocks. They agree upon a piece of woods, and all the crows for miles around come there every night. Sometimes thousands sleep in this one bedroom, called a crow roost. Robins do the same, after the young are big enough to fly so far.
AMERICAN ROBIN
Audubon, who has told us so much about birds, once found a hollow tree which was the sleeping-room of chimney swifts. The noise they made going out in the morning was like the roar of a great mill-wheel.
He wanted to see the birds asleep. So in the daytime, when they were away, he had a piece cut out at the foot of the tree, big enough to let him in, and then put back, so the birds would not notice anything unusual.
At night, after the swifts were abed, he took a dark lantern and went in. He turned the light upon them little by little, so as not to startle them. Then he saw the whole inside of the tree full of birds. They were hanging by their claws, side by side, as thick as they could hang. He thought there were as many as twelve thousand in that one bedroom.