The Barn Swallow (Hirundo rustica) is the most widespread species of swallow in the world. 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. 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".

Barn Swallow, Boerenzwaluw, Rauchschwalbe, Adorinha-das-chaminés, Golondrina Común

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. Its huge range means that the Barn Swallow is not endangered, although there may be local population declines due to specific threats, such as the construction of an international airport near Durban.

The Barn Swallow is a bird of open country which 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. 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 conspicuous annual migration. The Barn Swallow is the national bird of Estonia.

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 (0.8–2.8 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.

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 more pale. The juvenile is browner and has a paler rufous face and whiter underparts. It also lacks the long tail streamers of the adult.

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. The alarm calls include a sharp siflitt for predators like cats and a flitt-flitt for birds of prey like the Hobby. This species is fairly quiet on the wintering grounds.

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. 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.

The preferred habitat of the Barn Swallow is open country with low vegetation, such as pasture, meadows and farmland, preferably with nearby water. This swallow avoids heavily wooded or precipitous areas and densely built-up locations. The presence of accessible open structures such as barns, stables, or culverts to provide nesting sites, and exposed locations such as wires, roof ridges or bare branches for perching, are also important in the bird's selection of its breeding range.

The Barn Swallow is similar in its habits to other aerial insectivores, including other swallow species and the unrelated swifts. It is not a particularly fast flier, with a speed estimated at about 11 m/s, up to 20 m/s and a wing beat rate of approximately 5, up to 7–9 times each second, but it has the manoeuvrability necessary to feed on flying insects while airborne. It is often seen flying relatively low in open or semi-open areas.

The Barn Swallow typically feeds 7–8 metres (23–26 ft) above shallow water or the ground, often following animals, humans or farm machinery to catch disturbed insects, but it will occasionally pick prey items from the water surface, walls and plants. In the breeding areas, large flies make up around 70% of the diet, with aphids also a significant component. However, in Europe, the Barn Swallow consumes fewer aphids than the House or Sand Martins. On the wintering grounds, Hymenoptera, especially flying ants, are important food items. When egg-laying, Barn Swallows hunt in pairs, but will form often large flocks otherwise.

The Barn Swallow drinks by skimming low over lakes or rivers and scooping up water with its open mouth. This bird bathes in a similar fashion, dipping into the water for an instant while in flight.

Swallows gather in communal roosts after breeding, sometimes thousands strong. Reed beds are regularly favoured, with the birds swirling en masse before swooping low over the reeds. Reed beds are an important source of food prior to and whilst on migration; although the Barn Swallow is a diurnal migrant which can feed on the wing whilst it travels low over ground or water, the reed beds enable fat deposits to be established or replenished.

The male Barn Swallow returns to the breeding grounds before the females and selects a nest site, which is then advertised to females with a circling flight and song. The breeding success of the male is related to the length of the tail streamers, with longer streamers being more attractive to the female. Males with longer tail feathers are generally longer-lived and more disease resistant, females thus gaining an indirect fitness benefit from this form of selection, since longer tail feathers indicate a genetically stronger individual which will produce offspring with enhanced vitality. Males in northern Europe have longer tails than those further south; whereas in Spain the male's tail streamers are only 5% longer than the female's, in Finland the difference is 20%. In Denmark, the average male tail length increased by 9% between 1984 and 2004, but it is possible that climatic changes may lead in the future to shorter tails if summers become hot and dry.

Males with long streamers also have larger white tail spots, and since feather-eating bird lice prefer white feathers, large white tail spots without parasite damage again demonstrate breeding quality; there is a positive association between spot size and the number of offspring produced each season.

Both sexes defend the nest, but the male is particularly aggressive and territorial. Once established, pairs stay together to breed for life, but extra-pair copulation is common, making this species genetically polygamous, despite being socially monogamous. Males guard females actively to avoid being cuckolded. Males may use deceptive alarm calls to disrupt extrapair copulation attempts toward their mates.

As its name implies, the Barn Swallow typically nests inside accessible buildings such as barns and stables, or under bridges and wharves. The neat cup-shaped nest is placed on a beam or against a suitable vertical projection. It is constructed by both sexes, although more often by the female, with mud pellets collected in their beaks and lined with grasses, feathers, algae or other soft materials. Barn Swallows may nest colonially where sufficient high-quality nest sites are available, and within a colony, each pair defends a territory around the nest which, for the European subspecies, is four to eight square metres (45 to 90 square feet) in size.

 Other synonyms

Afrikaans: Europese Swael, Swaeltjie
Asturian: Andarina
Breton: Ar simenelig, Gwennili, gwennili-siminal, Gwennol, Wennilienn
Catalan: oreneta, Oreneta vulgar, Oronella, Oroneta vulgar, Parpallò
Catalan (Balears): Oronella
Valencian: Parpallò
Czech: vlaštovka, Vlaštovka obecná
Welsh: Gwenfol, gwennol
Danish: Landsvale, svale
German: Rauchschwalbe, Rauschschwalbe, Schwalbe
Emiliano-romagnolo: Rundanena
English: Barn Swallow, Common swallow, Eurasian Swallow, European chimney Swallow, European Swallow, House Swallow, Rustic Swallow, Swallow
Esperanto: hirundo, kamphirundo
Spanish: golondrina, Golondrina bermeja, Golondrina Cola de Tijera, Golondrina Comun, Golondrina Común, Golondrina de Horquilla, Golondrina del Norte, Golondrina Ranchera, Golondrina Riberena, Golondrina ribereña, Golondrina Tijereta, Golondrina tijerita, Golondrina zapadora, Golondrna tijereta rojiza
Spanish (Argentine): Golondrina tijerita, Golondrina zapadora
Spanish (Bolivia): Golondrina zapadora
Spanish (Colombia): Golondrina Tijereta
Spanish (Costa Rica): Golondrina ribereña, Golondrina tijereta
Spanish (Cuba): Golondrina Cola de Tijera
Spanish (Dominican Rep.): Golondrina Cola de Tijera, Golondrina del Norte
Spanish (Honduras): Golondrna tijereta rojiza
Spanish (Mexico): Golondrina Ranchera, Golondrina Riberena, golondrina tijereta
Spanish (Nicaragua): Golondrina Común
Spanish (Paraguay): Golondrina tijereta, Golondrina tijerita
Spanish (Uruguay): Golondrina Tijereta
Estonian: Suitsupääsuke
Basque: enara, Enara arrunt, Enara arrunta, Oreneta vulgar
Finnish: Haarapääsky, pääskynen
Faroese: svala
French: hirondelle, Hirondelle de cheminée, Hirondelle des granges, Hirondelle rustique
Friulian: cisile, sisile
Frisian: Boeresweal, boereswel, swel
Irish: andoriña, fáinleog
Guadeloupean Creole French: Hirondelle
Gaelic: Gobhlan-Gaoithe
Galician: Andoriña, Oreneta vulgar
Guarani: Mbyju'i jetapa
Manx: gollan geayee
Haitian Creole French: Irondèl Ke Long
Croatian: Lastavica, Lastavica poku?arka
Hungarian: Füsti fecske, Füstifecske
Indonesian: [Layang-layang Asia], Layang-layang api, Layanglayang Asia, Layang-layang Asia
Icelandic: Landsvala, svala
Italian: Rondine, Rondine comune
Inuktitut: Tulugarnaq
Japanese: tsubame
Greenlandic: Tulugarnaq
Cornish: gwennel, Gwennol
Kwangali: Sisampamema
Latin: Chelidon erythrogastra, Hirundo erythrogaster, Hirundo rustica, Hirundo rustica rustica
Ladino: rondola
Malay: Burung Layang-layang, Layang-Layang Hijrah
Dutch: Boeren Zwaluw, Boerenzwaluw, zwaluw
Norwegian: Ladesvale, Låvesvale, Saksesvale, Sulu, svale
Occitan: ironda
Polish: Brzegówka
Portuguese: andorinha, andorinha das chaminés, Andorinha-da-chamine, andorinha-da-chaminé, Andorinha-das-chamin, Andorinha-das-chaminés, Andorinha-de-bando, andorinha-de-pescoço-vermelho, Andorinha-do-barranco
Portuguese (Brazil): andorinha-da-chaminé, Andorinha-de-bando, andorinha-de-pescoço-vermelho, Andorinha-do-barranco
Romansh: randulina, Randulina stgira
Romany: pitsagoy rindilashka
Russian: Derevenskaya Lastochka
Sardinian: arrùndine, mongixedda, pilloni de santa luxia, puzone de santa lughia
Scots: aileag, Gobhlan gaoithe
Northern Sami: láhtospálfu, spálfu, suorrespálfu
Slovak: lastovicka
Slovenian: kmecka lastovka, kme?ka lastovka, lastovka
Shona: Nyenganyenga
Albanian: Dallëndyshe, Dallëndyshe bishtgërshërë, dallëndyshja
Serbian: lasta, seoska lasta
Siswant: Inkonjane
Sotho, Southern: Lefokotsane
Swedish: Ladusvala, svala
Swahili: Mbayuwayu wa Ulaya
Tswana: Pêolwane
Tsonga: Nyengha
Sorbian, Lower: jaskolicka
Xhosa: Inkonjane
Zulu: iNkonjane