All animals with a decent-sized brain engage in sleep – a period of rest when the brain enters an altered state of consciousness less immediately sensitive to its surroundings. But how animals sleep can differ. Some animals sleep standing up, some, like dolphins, sleep with one eye open, but what about birds? How do they manage? A lot depends on the species.
How do birds sleep?
So how do birds sleep? Can they sleep when flying? And how do they sleep in trees without falling out?
Birds’ feet are engineered to grip their perches even when relaxed, which prevents them from falling out of trees when roosting.
Some birds, such as swifts, sleep on the wing, which allows them to remain airborne for 200 days.
Swans can sleep on land or when floating on water and tuck their heads between their wings.
Frigatebirds - one of the world's weirdest birds - can sleep with one half of their brain at a time and with one eye open, while vigilant nesting chinstrap penguins fall asleep thousands of times a day, but only for seconds at a time.
Finally, rapid eye movement (REM) sleep has been demonstrated unequivocally in birds.