How long can a bird fly without touching the earth? To find out, Swiss scientists attached sensors to Alpine Swifts. The sensors showed long periods when the swifts were gliding and not flapping their wings. Were the birds asleep? Scientists don’t know for sure. It could be that Alpine Swifts sleep during the summer breeding season — and don’t sleep at all during migration. But why do they stay aloft so long? Swifts can’t perch because they have very short legs. So if they can manage it, avoiding touching down makes perfect sense. Learn more at BirdNote.org.