swallow, common name for small perching birds of almost worldwide distribution. There are about 100 species of swallows, including the martins, which belong to the same family. Swallows have long, narrow wings, forked tails, and weak feet. They are extremely graceful in flight, making abrupt changes in speed and direction as they feed on the wing, catching insects in their wide mouths. Their plumage is blue or black with a metallic sheen, generally darker above than below. They nest in flocks in barns, sheds, chimneys, or other secluded places. The common American barn swallow, Hirundo rustica, is steel-blue above and pinkish beneath, with a rusty forehead and deeply forked tail. The purple martin, Progne subis, is deep violet with black wings and tail. Other American swallows, all with shallowly forked tails, are the cliff, or eave, swallow ( Petrochelidon pyrrhonota ), which builds jug-shaped nests of mud and clay lined with grass and feathers; the bank swallow or sand martin, which burrows into shore banks to nest; and the tree ( Iridoprocne bicolor ) and rough-winged ( Stelgidopteryx ruficollis ) swallows. The so-called chimney swallow is a swift. Swallows are classified in the phylum Chordata, subphylum Vertebrata, class Aves, order Passeriformes, family Hirundinidae.
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