The common swift (Apus apus) has a top speed of around 63mph (100kph) - no other bird has been recorded faster in level flight. The scientific name Apus is Latin for swift – derived from the Ancient Greek apous which means without feet, based on the belief that these birds were a form of swallow that lacked feet. It is entirely blackish-brown except for a small white or pale grey patch on its chin which is not visible from a distance. Swifts have very short legs which they use primarily for clinging to vertical surfaces (hence the German name Mauersegler, literally meaning "wall-glider"). Almost entirely aerial, a young bird could fly for three years without landing on a solid object. An adult could fly around 4 million miles over its lifetime of around 5.5 years. The swift separated taxonomically from other birds around 70 million years ago, when they would have nested in gaps in rocks or trees alongside the last of the Tyrannosaurs. Common Swifts are migratory, and in midsummer they are found in Britain and northern Europe, while they winter much further south in southern Africa.