Birds
Barn Swallow
Hirundo rustica · also called swallow
The barn swallow is the swallow of proverb and painting, the forked-tailed bird that twists low over a hayfield on a summer evening and vanishes into the gloom of a barn. It is also the most widely distributed swallow in the world, breeding across the whole Northern Hemisphere and wintering across the whole Southern one.
Overview
Hirundo rustica is a small, streamlined songbird with a glossy steel-blue back, a rusty-red forehead and throat, pale underparts, and a deeply forked tail with long outer streamers. It feeds entirely on flying insects, caught in fast, agile flight low over meadows, pasture, and water, and it drinks and bathes by skimming the surface without stopping.
A bird that moved in with us
The barn swallow once nested on cave ledges and cliffs. Today it builds its open cup of mud pellets almost exclusively on human structures — beams and walls inside barns, sheds, and porches, and under bridges and culverts — close to the open ground where its insect prey lives. The long tail streamers are longest in the healthiest males, and females choose mates partly on streamer length, so the tail is shaped by courtship as much as by flight.
The long haul
Barn swallows are extreme migrants. A northern European bird winters in southern Africa; a North American one reaches southern South America. Round trips of up to 20,000 km are made twice a year, mostly by day and at low level, and many birds return to the same nest each spring.
Status
The barn swallow is Least Concern on the strength of its vast global range, but the trend is a slow decline. Fewer flying insects from pesticide use and intensive farming, and the loss of old open barns, have cut its numbers across much of Europe and North America.
Barn Swallow: common questions
What is the difference between a swallow and a swift?
They look alike in the air and both catch insects on the wing, but they are not related; the resemblance is convergent evolution. A barn swallow perches readily on wires and rooftops, has a glossy blue back, a red face, a pale belly, and a long forked tail with streamers, and it flies with fluid, twisting glides low over fields. A swift is sooty brown all over, has a short forked tail and long stiff scythe-shaped wings, almost never perches, and spends nearly its whole life airborne, feeding, sleeping, and mating on the wing. Swifts also nest in cavities high on buildings, while swallows build open mud cups lower down.
Why do barn swallows build their nests in barns?
Because barns and similar structures offer what the swallow used to get from caves and cliff overhangs, namely a sheltered, rain-proof ledge or beam under a roof, safe from most ground predators, close to the open pasture and water where flying insects are abundant. Traditional livestock barns are especially good, since the animals attract flies and keep the building warm and open. The switch has been so complete that in many regions the barn swallow now almost never nests away from human buildings, which is also why the loss and conversion of old barns is one of the pressures on the species.
How far do barn swallows migrate?
Very far. Barn swallows are among the great long-distance migrants. Birds that breed in Britain and northern Europe fly the length of Africa to spend the northern winter in the far south of the continent, and those from Siberia may reach India or Southeast Asia, while North American barn swallows travel to central and southern South America. A one-way journey can be 8,000 to 12,000 km, undertaken twice a year, mostly by day at low altitude, feeding as they go. Many individuals show strong site fidelity, returning not just to the same area but often to the same nest.
Why are barn swallows declining if they are so widespread?
The global population is still huge, but in Europe and North America the long-term trend is downward, and the likely causes are linked. The intensification of agriculture has reduced the abundance of the flying insects swallows depend on, through pesticide use and the loss of mixed farmland, hedgerows, and rough pasture. The number of suitable nest sites has fallen as old open barns are demolished, converted to houses, or sealed up, and as cattle move indoors into closed sheds. Conditions on the African wintering grounds and hazards along the migration route, including droughts and severe weather, add further pressure.