Swallow

Swallow, common name for many species of a family of passerine birds, distinguished by their long and pointed wings, round heads, and small legs and feet. Like the unrelated swifts (see Swift), which also feed on flying insects, swallows have short bills but wide mouths. The family is cosmopolitan in distribution and contains about 80 to 85 species (species relationships of several swallows are unclear). Swallows are gregarious, and some species nest colonially. They are almost wholly insectivorous and include many flies, mosquitoes, gnats, and agricultural pests in their diet.

Only eight species breed in North America, and two of these are also found widely in Eurasia. One of these, the barn swallow, is probably the most abundant swallow in the world. The other, the bank swallow, is called sand martin (see Martin) in Europe; it is the smallest North American species, and nests in colonies in holes in earthen banks. The largest North American swallow is the purple martin, which takes readily to apartment-style nest boxes. Two species that will also nest in boxes are the violet-green swallow, of the western states and provinces, and the widely distributed tree swallow, which is steel blue or green above and pure white below. It is able to winter farther north than any of the other species, since after insects have disappeared for the season, tree swallows feed heavily on bayberries and other small fruits. Superficially similar to the bank swallow and also a nester in holes in banks, but less gregarious, is the northern rough-winged swallow. Two species that construct nests composed of little mud pellets are the cliff swallow, whose nests, often placed in rows on the outside walls of barns near the eaves, are closed and flask-shaped, and the cave swallow, whose nests are open at the top. The latter is a tropical species that reaches the southeastern United States.

Scientific classification: Swallows belong to the family Hirundinidae of the order Passeriformes. The barn swallow is classified as Hirundo rustica, the bank swallow as Riparia riparia, and the purple martin as Progne subis. The violet-green swallow is classified as Tachycineta thalassina, the tree swallow as Tachycineta bicolor, and the northern rough-winged swallow as Stelgidopteryx serripennis. The cliff swallow is classified as Hirundo pyrrhonota and the cave swallow as Hirundo fulva.