Hirundo rustica

The barn swallow (Hirundo rustica) is the most widespread species of swallow in the world.[2] It is a distinctive passerine bird with blue upperparts, a long, deeply forked tail and curved, pointed wings. It is found in Europe, Asia, Africa and the Americas.[2] In Anglophone Europe it is just called the swallow; in Northern Europe it is the only common species called a "swallow" rather than a "martin".[3]

There are six subspecies of barn swallow, which breed across the Northern Hemisphere. Four are strongly migratory, and their wintering grounds cover much of the Southern Hemisphere as far south as central Argentina, the Cape Province of South Africa, and northern Australia.[2] Its huge range means that the barn swallow is not endangered, although there may be local population declines due to specific threats.

The barn swallow is a bird of open country that normally uses man-made structures to breed and consequently has spread with human expansion. It builds a cup nest from mud pellets in barns or similar structures and feeds on insects caught in flight.[4] This species lives in close association with humans, and its insect-eating habits mean that it is tolerated by man; this acceptance was reinforced in the past by superstitions regarding the bird and its nest. There are frequent cultural references to the barn swallow in literary and religious works due to both its living in close proximity to humans and its annual migration.[5] The barn swallow is the national bird of Austria and Estonia.

Description 

The adult male barn swallow of the nominate subspecies H. r. rustica is 17–19 cm (6.7–7.5 in) long including 2–7 cm (0.79–2.76 in) of elongated outer tail feathers. It has a wingspan of 32–34.5 cm (12.6–13.6 in) and weighs 16–22 g (0.56–0.78 oz). It has steel blue upperparts and a rufous forehead, chin and throat, which are separated from the off-white underparts by a broad dark blue breast band. The outer tail feathers are elongated, giving the distinctive deeply forked "swallow tail". There is a line of white spots across the outer end of the upper tail.[4] The female is similar in appearance to the male, but the tail streamers are shorter, the blue of the upperparts and breast band is less glossy, and the underparts paler. The juvenile is browner and has a paler rufous face and whiter underparts. It also lacks the long tail streamers of the adult.[2]

Reported range from ornithological observations confirms the heavy migration pattern.     Year-round range     Summer range     Winter range

The song of the barn swallow is a cheerful warble, often ending with su-seer with the second note higher than the first but falling in pitch. Calls include witt or witt-witt and a loud splee-plink when excited (or trying to chase intruders away from the nest).[4] The alarm calls include a sharp siflitt for predators like cats and a flitt-flitt for birds of prey like the hobby.[6] This species is fairly quiet on the wintering grounds.[7]

The distinctive combination of a red face and blue breast band render the adult barn swallow easy to distinguish from the African Hirundo species and from the welcome swallow (Hirundo neoxena) with which its range overlaps in Australasia.[2] In Africa the short tail streamers of the juvenile barn swallow invite confusion with juvenile red-chested swallow (Hirundo lucida), but the latter has a narrower breast band and more white in the tail.[8]

Taxonomy 

The barn swallow was described by Linnaeus in his Systema Naturae in 1758 as Hirundo rustica, characterised as H. rectricibus, exceptis duabus intermediis, macula alba notatîs.[9] Hirundo is the Latin word for "swallow"; rusticus means "of the country".[10] This species is the only one of that genus to have a range extending into the Americas, with the majority of Hirundo species being native to Africa. This genus of blue-backed swallows is sometimes called the "barn swallows".[2][3]

The Oxford English Dictionary dates the English common name "barn swallow" to 1851,[11] though an earlier instance of the collocation in an English-language context is in Gilbert White's popular book The Natural History of Selborne, originally published in 1789:

The swallow, though called the chimney-swallow, by no means builds altogether in chimnies [sic], but often within barns and out-houses against the rafters ... In Sweden she builds in barns, and is called ladusvala, the barn-swallow.[12]

This suggests that the English name may be a calque on the Swedish term.

There are few taxonomic problems within the genus, but the red-chested swallow—a resident of West Africa, the Congo basin and Ethiopia—was formerly treated as a subspecies of barn swallow. The red-chested swallow is slightly smaller than its migratory relative, has a narrower blue breast-band, and the adult has shorter tail streamers. In flight, it looks paler underneath than barn swallow.