Most of the time when you see birds, they're flying around, chirping, eating food, splashing in the water, and being very busy. Here's the inspiration for this article - a downy woodpecker fluffed up and resting at the side of my suet feeder. He wasn't hungry, he just sat there for quite a while, taking a nap. His little feet clung easily to the side of the tree.
Most birds sleep at night, although there are some, like owls that sleep during the day.
Birds have to be very light sleepers, because even at night there are predators that would love to gobble them up for a snack. Some birds sleep resting on a branch, while others find a nest or birdhouse to sleep in. Some birds can even close one eye for a while and rest part of their brain, then shift eyes to rest the other part. Most birds take short naps during the day, as well. This helps them get through the night withough a long, sound sleep.