The Swift is a medium-sized aerial bird, which is a superb flyer. Sleeping, eating, bathing and even mating on the wing (while flying), Swifts rarely touch the ground. They are also the fastest birds in level flight, with an impressive top speed of 69mph. Swifts are plain sooty brown, with a white throat, but in flight against the sky they appear black. They have curved wings and a forked tail. Swifts are summer visitors, breeding across the UK, but are most numerous in the south and east. Spending their winters in Africa, Swifts migrate 3,400 miles twice a year, stopping off to refuel in places like Portugal and France along the way.