Note: Information is dated. Do not rely on it.Swallow. Anyone of the numerous passerine birds of the family Hirundinidae. In the United States the best known species are the barn swallow, the cliff, eaves, or chimney swallow, the white bellied or tree swallow, and the bank swallow. The species usually described by naturalists as the type of the family is Hirundo rustica, a well-known European visitor whose arrival from Africa (usually about the middle of April) is eagerly looked for as a sign of approaching summer. Swallows usually arrive in pairs - a male and a female - though several pairs often form a small flight; but if a single bird is seen to arrive, there is a strong presumption that it has lost its mate. They return with unfailing regularity to their old haunts, and in May commence building their nests, which are in shape somewhat like a flattened cup, divided perpendicularly; they are made of clay, mud, and straw, lined with horse-hair or feathers; and the eggs, which are from four to six in number, are white, spotted with purplish-red.