Swallows (Hirundinidae)

 The Hirundinidae, or swallows, martins, and saw-wings, are a family of passerine birds found on all continents, including Antarctica. They have a distinct appearance and are well adapted to aerial feeding. In Europe, the term "swallow" is used colloquially to refer to the barn swallow.

Hirundinidae are comprised of approximately 90 species divided into 19 genera, with the greatest diversity found in Africa, which is also thought to be where they evolved as hole-nesters. They can also be found on a number of oceanic islands. A number of European and North American species migrate long distances, whereas West and South African swallows do not.

The Hirundinidae have an evolutionary conservative body shape that is similar across the clade but distinct from other passerines. Swallows have adapted to hunting insects on the wing by developing a slender, streamlined body and long, pointed wings that allow for great maneuverability and endurance, as well as frequent gliding periods. Their body shapes allow for very efficient flight; swallows' metabolic rates in flight are 49–72 percent lower than comparable passerines of the same size.