The familiar Barn Swallow (Hirundo rustica) is a common breeding bird across North America, Europe, and Asia and winters in South America and southern Africa (it is possible that the variation across this enormous distribution may actually represent more than one species). In the New World, Barn Swallows breed from Canada to Mexico. They are also now established as breeders in northeastern Argentina, where a small number of breeding pairs were first documented in 1980 and the species has since been well established (Billerman et al. 2011). They winter from Mexico and Panama, Puerto Rico, and the Lesser Antilles south throughout South America to Tierra del Fuego. In Eurasia, the breeding range extends from Iceland, the British Isles, the Faeroe Islands, Scandinavia, northern Russia, and northern Siberia south to the Mediterranean region, northern Africa, the Near East, Arabia, Iran, the Himalayas, China, Taiwan, and Japan; these Old World populations winter south to tropical Africa, the East Indies, northern Australia, and Micronesia. Winter range can be difficult to delineate due to late fall records (as late as December) and early spring migrants.

Barn Swallows live in open or semi-open country (farms, fields, marshes, lakes), often near water, and capture and eat most of their food (mainly flying insects) in the air.

Courtship involves aerial chases. On a perch, the members of a mated pair sit close together, touch bills, and engage in mutual preening. Several Barn Swallow pairs may nest in the same immediate area, but Barn Swallows do not form dense colonies as some swallows do. Originally, Barn Swallows nested in crevices in cliffs or shallow caves, but today most nest sites are in open buildings, under eaves, under bridges or docks, or in similar situations. The nest, which is built by both sexes, is a cup of mud and dried grass lined with feathers. The 4 to 5 (sometimes 6, rarely 7) eggs are white, spotted with brown. Eggs are incubated by both sexes (but especially by the female) for 13 to 17 days. Both parents feed the young. One or two additional birds, the pair's offspring from previous broods, may attend the nest and sometimes feed the nestlings. Young leave the nest around 18 to 23 days after hatching.

Barn Swallows migrate in flocks, mainly by day.

(Kaufman 1996; AOU 1998; Dunn and Alderfer 2011)