The barn swallow (Hirundo rustica) is a migratory passerine bird, recognized as the most widespread species of swallow in the world. It is a distinctive bird with blue upperparts and a long, deeply forked tail, known for its graceful flight and agile maneuvers. The adult male of the nominate subspecies is 17–19 cm in length, including elongated outer tail feathers, and has a wingspan of 32–34.5 cm. It is adorned with a rufous forehead, chin, and throat, which are set apart from the off-white underparts by a broad dark blue breast band. The outer tail feathers are elongated, contributing to the iconic "swallow tail."
The barn swallow favors open country with low vegetation, such as pastures, meadows, and farmland, often near water. It avoids heavily wooded or steep areas and densely built-up locations. The species typically nests in man-made structures like barns and stables, or under bridges and wharves.
The Barn swallow (Hirundo rustica) is the most widespread species of swallow in the world. In fact, it has the largest natural distribution of any of the world's passerines, ranging over 251 million square kilometers globally. 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".
The Barn swallow is a distinctive songbird with blue upperparts and a long, deeply forked 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 paler. The juvenile is browner and has a paler rufous face and whiter underparts. It also lacks the long tail streamers of the adult.
Barn swallows are found in Europe, Asia, Africa, and the Americas. These birds are long-distance migrants 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. The preferred habitat of Barn swallows is open country with low vegetation, such as pasture, meadows, and farmland, preferably with nearby water. These birds avoid heavily wooded or precipitous areas and densely built-up locations. On their wintering grounds, Barn swallows avoid only dense forests and deserts. They are most common in open, low vegetation habitats, such as savanna and ranch land, and in Venezuela, South Africa, and Trinidad and Tobago the birds are particularly attracted to burnt or harvested sugarcane fields and the waste from the cane.
Barn swallows are gregarious birds and in the absence of suitable roost sites, they sometimes roost on wires where they are more exposed to predators. Individual birds tend to return to the same wintering locality each year and congregate from a large area to roost in reed beds. These roosts can be extremely large and are thought to be a protection from predators. Barn swallows typically feed by day in open areas 7-8 m (23-26 ft) above shallow water or the ground often following animals, humans, or farm machinery to catch disturbed insects; they may also pick prey items from the water surface, walls, and plants.
During the breeding, season Barn swallows hunt in pairs, but otherwise form often large flocks. These birds are usually fairly quiet on the wintering grounds. At other times they communicate with constant twittering and chattering. The song of the male Barn swallow is a cheerful warble, often ending with 'su-seer'. Other calls include 'witt' or 'witt-witt' and a loud 'splee-plink' when excited (or trying to chase intruders away from the nest). The alarm calls include a sharp 'siflitt' for predators like cats and a 'flitt-flitt' for birds of prey like the hobby.
Barn swallows are monogamous and pairs stay together to breed for life; however, extra-pair copulation is also common (polygynous behavior). The males return to the breeding grounds before the females and select a nest site, which is then advertised to females with a circling flight and song. The breeding season of these birds varies with location. Both sexes defend the nest, but the male is particularly aggressive and territorial. Males guard females actively to avoid being cuckolded and may use deceptive alarm calls to prevent any attempts toward their mates. Barn swallows typically nest 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, with mud pellets collected in their beaks and lined with grasses, feathers, algae, or other soft materials. The female lays 2 to 7 reddish-spotted white eggs and incubates them for 14-19 days. Altricial (helpless) chicks fledge 18-23 days after hatching but stay with, and are fed by, the parents for about a week after leaving the nest. Young swallows usually start to breed in the first breeding season after they have born.
This bird has a vast global range, breeding across the Northern Hemisphere and wintering in much of the Southern Hemisphere. Its distribution spans Europe, Asia, Africa, and the Americas.
Barn swallows are semi-colonial and may settle in groups. They exhibit site fidelity, often returning to the same location annually for breeding. The species is known for its aerial insectivory, catching insects in flight with remarkable agility.
The barn swallow communicates with a variety of calls, including a "witt or witt-witt" and a loud "splee-plink" when excited or deterring intruders. Alarm calls include a sharp "siflitt" for terrestrial predators and a "flitt-flitt" for avian predators. The male's song, used for territory defense and mate attraction, consists of a twittering warble followed by a series of musical notes.
Barn swallows are monogamous and often mate for life, with the male arriving first at the breeding grounds to select a nest site. They build cup-shaped mud nests lined with soft materials, frequently in colonies where each pair defends a territory. The female typically lays two to seven spotted white eggs, with the clutch size varying by latitude.
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