The barn swallow Hirundo rustica

Dr Angela Turner, University of Nottingham

Issue 19, December 2000

Barn swallows - often just called swallows in Britain - are one of our most well known birds. They nest close to people in our barns, stables, garages and porches and are commonly seen flying over our fields and lakes.

They build their nests from mud pellets and dried grass, attaching them to a wall or wooden beam, and adding a lining of white feathers. Usually, four or five eggs are laid and pairs may have two or even three broods a year.

Barn swallows have a characteristically long, forked tail. The shape of the tail improves their manoeuvrability, helping them catch fast-flying insects Re bluebottles and horseflies. Flies make up about three-quarters of the diet while the remainder consists of other insects such as beetles, mayflies, aphids, moths and flying ants.

Male barn swallows have a longer tail than females. But some males have very long tails and others have shorter ones. The longer the tail, the more attractive the male is to females. Long- tailed males attract a mate and start breeding earlier, and have more nestlings, than short-tailed males. Long tails aren't particularly useful themselves but a male who can manage to grow an impressively long tail may be showing off to females that he will be an excellent partner. Males that grow long tails are also resistant to parasites such as mites and live for longer than short-tailed Five fascinating facts about males. They can pass their genes for good health and long life on to their offspring. So a female barn swallows mating with a long-tailed male will give her nestlings the best start in life. She won't have an easy time, however, as long-tailed males leave most of the work of feeding the nestlings to their partners whereas short-tailed males provide more help.

[Anyone wishing to know more about these birds could consult one of Dr Turner's books, namely Handbook to the Swallows and Martins of the World. 1994. London, Croom Helm.]

Five fascinating facts about barn swallows

• Until the late 19th century, swallows were thought to hibernate under water; now we know that British swallows spend the winter in South Africa
• The trip between the northern breeding areas and southern Africa usually takes a couple of months but one bird flew 12 000km from Johannesburg to Russia in just 34 days!
• Swallows often nested in chimneys before the advent of central heating!
• European female swallows incubate the eggs by themselves but in North America males and females share this task!
• A brood of swallows will have eaten some 150 000 insects by the time they fledge!