don't look if fowl things give you the willies
Question: Have you noticed ducks sleeping with their bills tucked under their feathers?
Bills obviously have no feathers, so they can lose a lot of heat. To solve this problem the duck just tucks the bill into some feathers. Think of it like putting your hands in a jacket pocket on a chilly day.
Look at those same ducks and if they are standing up I bet you will see that they often stand on one leg and tuck the other into their feathers. Same thing – saves heat.