Every July, young common swifts leave their European roosts and migrate to western and central Africa. They’ll only be back in the following June, and they’ll spend the intervening 10 months almost continuously in the air. They might travel to Africa, but their feet never meet African soil.

“They feed in the air, they mate in the air, they get nest material in the air,” says Susanne Åkesson from Lund University in Sweden. “They can land on nest boxes, branches, or houses, but they can’t really land on the ground.” That's because their wings are too long and their legs are too short to take off from a flat surface.

As a result, common swifts are among nature’s greatest aeronauts, superbly