Where Do Swallows Go in Winter? Swallow Migration Routes

Where European swallows spend the winter

The barn swallow, known in Britain simply as the swallow, winters across almost all of Africa south of the Sahara. Ringing and tracking studies show that birds from different parts of Europe tend to use different regions:

• Swallows from Britain, Ireland and western Europe mostly winter in southern Africa, especially South Africa, a journey of roughly 10,000 km (6,200 mi) each way.
• Birds from central and eastern Europe winter mainly in eastern and southern Africa, while some winter farther west.
• Swallows from western Siberia and central Asia also reach southern Africa, and others winter in Arabia and the Indian subcontinent.

In Africa, swallows feed over open grassland, savanna, farmland, wetlands and burned or harvested sugarcane fields. At dusk, huge numbers gather in reed beds to roost. A reed bed at Mount Moreland, near Durban in South Africa, is used by more than three million swallows each southern summer.

Where North American swallows go

North American barn swallows leave the United States and Canada in late summer and autumn and spend the winter from southern Mexico and the Caribbean through Central America to South America as far as Argentina and Chile. Many funnel through Central America on a narrow front, so they are abundant on passage along both coasts there.

Since about 1980, small numbers of barn swallows have stayed to breed in Argentina, raising chicks in their winter range during the southern summer. In mild areas of the southern United States, a few birds may linger through the winter.

Other American swallows have different winter homes:

The tree swallow is unusual: it can eat berries, such as bayberries, when insects are scarce, so it winters farther north and returns earlier than other swallows.

The migration route and timing

Swallows from Britain usually leave in September and October. They fly south through western France, cross the Pyrenees and eastern Spain to Morocco, then cross the Sahara before continuing through West and Central Africa to the south. They arrive in South Africa in October and November, stay through the southern summer and start back north in February and March.

Unlike many songbirds, swallows migrate by day. They feed on flying insects as they travel, often covering a few hundred kilometers a day, and roost in reed beds at night, where they can also feed and rebuild fat. The Sahara crossing is the most dangerous part, because there is almost nothing to eat for well over 1,500 km (930 mi).

Adults usually reach Britain again in late March and April, and males tend to return first so that they can claim a nest site. How swallows find their way over such distances is explained in how do birds know where to migrate?

The old belief that swallows hibernated

For more than 2,000 years, many people believed that swallows did not migrate at all. Aristotle wrote that some swallows hid in holes over winter, and in 1555 the Swedish churchman Olaus Magnus described fishermen pulling bundles of sleeping swallows out of frozen lakes in their nets. Even the careful English naturalist Gilbert White, writing in the late 18th century, was never fully sure whether swallows left or hid nearby.

The belief probably came from watching autumn flocks swirl down into reed beds at dusk and then seemingly vanish. In reality, they were roosting before leaving. Birds do not hibernate under water, and no swallow could survive months without food.

How ringing solved the mystery

The answer came from bird ringing, also called bird banding. A swallow ringed at a nest in Staffordshire, England, was caught in Natal, South Africa, in December 1912. It was the first proof that British swallows spend the winter at the southern tip of Africa.

Since then, hundreds of thousands of swallows have been ringed in Europe and Africa, and tiny light-sensitive data loggers called geolocators now record whole journeys. These studies show that individual swallows often return to the same wintering region, and sometimes the same roost, every year. They have also revealed surprises: one Danish breeding population was found to winter in two separate parts of Africa.

Why swallows fly so far

Swallows catch all their food in the air, and flying insects disappear in a northern winter. Africa and South America offer insects all year, while Europe and North America offer long summer days and plenty of food for raising chicks. Migration lets swallows enjoy both, as explained in why do birds migrate?

The journey is risky: storms, cold snaps on arrival and droughts in the Sahel kill many birds, especially young swallows on their first trip. Yet for a bird that can feed as it flies, the rewards of two summers a year outweigh the dangers.