Swifts live almost entirely in the air. They eat, drink, sleep, mate and gather their nesting materials on the wing, fly thousands of miles across the world, navigating their way around storms, never lighting on tree, cliff or ground, until they return home with the summer.Sarah Gibson has written a fascinating story of discovery, exploring what is known about these mysterious birds, their ancient ancestry and how they have been regarded through history. But the swifts are in