Swifts: One UK species, three more in Europe, many more worldwide. Swifts have elongated, cigar-shaped bodies, short, forked tails, very small bills but wide mouths, long, stiff, scythe-shaped wings and tiny legs, with all four toes facing forwards. They can cling to an upright surface or (rarely) foliage, but are unable to perch or walk, unlike swallows and martins. Swifts in the UK are exclusively aerial except at the nest; they nest inside cavities, mostly in buildings. For most of the year, they are in Africa, visiting the UK from May to early September.
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Martins & Swallows: Mostly small, elegant, aerial species with long, tapered wings, forked tails (often with elongated outer feathers) and small bills but wide mouths, for catching insects in flight.
There are three regular species in the UK plus some rare visitors, and many species worldwide. They tend to fly lower and slower than swifts but different species exploit different levels of air space and different sizes of aerial insects. Unlike swifts, they perch frequently on wires and (less often) trees and may be seen on roofs, sometimes on the ground.
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