Habitat

These passerines exploit a wide variety of habitats and are mainly dependent on the availability of food and nesting sites. Their main hunting habitats include forest ecosystems near lakes, rivers and swamps, wooded savannahs and grasslands. Nesting sites vary between species: some nest in tree cavities, others excavate nests in sand slopes and others build their nests in cliffs or human constructions.

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Behaviour

Swallows are expert fliers capable of impressive aerial manoeuvres, both for hunting and courting. Males usually choose and defend a nesting site and attract females through unique calls and flight patterns. Just as aerial manoeuvres are an important part of the mating ritual, coloured patches on the plumage are also crucial for attracting females. The size of each pair's territory varies between species. While gregarious species have smaller territories and these may be restricted to the nesting site itself, solitary species may have considerably larger territories. Migratory individuals may return to the same nesting site year after year if they have previously been successful.

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Food ecology and diet

Most swallows are exclusively insectivorous, catching their prey in flight. The Tree Swallow (Tachycineta bicolor) is an exception: this species also consumes plant matter, including berries and other small fruits. The type of insects eaten by swallows varies considerably. While the larger swallows can feed on dragonflies and butterflies, the smaller species feed mainly on medium-sized insects such as flies, small beetles and flying ants. Swallows also feed on spiders. The type of prey depends on the species that are available, thus varying with the weather conditions. These birds feed in places where food availability is greatest, flying over open habitat areas, water reserves or forest canopies. During the breeding season these birds tend to feed close to their nesting sites and do not stray more than a few kilometres from them, unlike swifts. Swallows may feed in large flocks or individually.

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Reproduction and life cycle

In general, these passerines form monogamous breeding pairs. However, some males with promiscuous behaviour may try to copulate with several females. This behaviour is typical in places where these birds form large flocks. On the other hand, females of some colonial species, such as the Common House Martin (Delichon urbicum), that try to maximise their reproductive success, lay some eggs in the nests of other pairs, who take care of them as if they were their own. Regarding the breeding behaviour, nest construction is highly variable among swallow species. Some species use pre-existing cavities, like old woodpecker holes, to build their nest of mud and twigs. Other species dig tunnels up to two metres long in sandy slopes, building the nest at the inner end of the tunnel. There are also some species that build mud nests that are attached to cliffs, caves or artificial structures, such as viaducts and buildings. These mud nests can have different shapes, being open bowls, like the characteristic nests of the Barn Swallow (Hirundo rustica), or being completely closed and have an entrance tunnel, like the nests of the Red-rumped Swallow (Cecropis daurica). These mud nests are renewed and used year after year. Swallows, unlike most swifts, can lay multiple clutches during a nesting season. These may range from 3 to 8 eggs, which are incubated for 11 to 20 days. In some species the eggs are incubated by both sexes. The development of the young takes between 2 and 3 weeks.