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The swallows and martins or Hirundinidae are a family of passerine birds found around the world on all continents except Antarctica. Highly adapted to aerial feeding they have a distinctive appearance. The term Swallow is used colloquially in Europe as a synonym for the barn swallow. There are around 83 species in 19 genera with the greatest diversity found in Africa which is also thought to be where they evolved as hole-nesters. They also occur on a number of oceanic islands. A number of European and North American species are long-distance migrants by contrast the West and South African swallows are non-migratory.

This family comprises two subfamilies Pseudochelidoninae and Hirundininae. Within the Old World the name martin tends to be used for the squarer-tailed species and the name swallow for the more fork-tailed species however there is no scientific distinction between these two groups. Within the New World martin is reserved for members of the genus Progne.

The swallows and martins have an evolutionarily conservative body shape which is similar across the clade but is unlike that of other passerines. Swallows have adapted to hunting insects on the wing by developing a slender streamlined body and long pointed wings which allow great maneuverability and endurance as well as frequent periods of gliding. Their body shape allows for very efficient flight the metabolic rate of swallows in flight is 49–72% lower than equivalent passerines of the same size.

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