An impressively agile flier, the barn swallow is capable of sharp turns and twists while pursing its flying insect prey. Typically, it hunts alone during the day over open areas, usually between one and ten metres above the ground, although insects are also plucked off the walls of artificial structures during periods of bad weather (3). It may also follow other animals and vehicles to take insects flushed by such disturbance (2). The barn swallow spends the majority of its time in the air, only descending to the ground to collect mud, grass or feathers to build its nest while breeding (3).
The barn swallow usually breeds between May and August depending upon the location. At the start of the breeding season, the male bird attracts a female mate by displaying its spread tail and by singing while circling high above the nest site (2) (3). Usually new pairs form each season, but partners may mate in successive seasons if they are successful in raising a brood the first time round (2). Both birds cooperate to build a cup-shaped nest, and the male bird defends a territory around this simple structure from other swallows by attacking intruders, chasing them and pecking at their feathers (3). Usually three to six eggs are laid and incubated, mostly by the female, for around 13 to 16 days. The chicks are brooded and fed by both birds, and the chicks grow quickly to become fully independent at only two weeks of age (2).
For a bird of such small size, the barn swallow undertakes hugely impressive, long-distance migrations. Birds are generally at the northern breeding grounds between April and October, before collecting into huge post-breeding flocks that sometimes number several hundred thousand, occasionally millions, of birds. The autumn southward migration takes several months, with most European birds travelling to Africa, while Asian birds travel to South Asia, Southeast Asia and Australia, and North American birds travel to Central and South America, as far south as northern Argentina. The timing of arrival back at the breeding grounds is dependant upon the severity of the weather, but the older males generally arrive first, with the females and younger males soon following (2).