Common swift

The common swift is a medium-sized bird often mistaken for swallows, though they're not closely related. These aerial acrobats spend most of their lives in flight, even sleeping on the wing. Their closest relatives are actually hummingbirds and treeswifts, despite looking quite different.

• Can sleep while flying by gliding on air currents
• Their wing shape evolved separately from swallows through convergent evolution
• Closely related to hummingbirds despite very different appearances