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.
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