My whole world has been turned upside-down: bird nests aren’t for sleeping in. Throughout my life, I’ve lived what I thought was an informed, meaningful existence, all the while mistakenly believing that after a long day of doing bird things, bird retire to their nests for a snooze. Now I know better.
Nicholas Lund of ‘The Birdist’ blog writes in Slate: “So where do birds sleep? Lots of places. When birds settle down to sleep, it’s called “roosting,” and the main things they’re looking for are safety and warmth. Songbirds have to keep off the ground to avoid cats and other dangers, and out of the open to avoid owls. Dense brush or foliage does fine. Bigger birds have more options and can sleep on the water, on a branch, or even just right on the ground.
Go figure: nests are for keeping eggs and chicks in one place, and not all birds even construct them. Many birds can use unihemispheric slow-wave sleep to literally sleep with one eye open—resting half of their brain while still remaining vigilant for predators while they roost in foliage or on the water. Amazingly, some seabirds and swifts spend their lives in flight except for when they come to land to breed. These species sleep while they’re flying.