Barn swallow: facts & profile

Barn swallows are so common, they are usually just called swallows. Despite their prevalence, however, there is a lot to learn about this colourful songbird. Get all the facts on swallows here.

The barn swallow (Hirundo rustica), alongside the house martin, is one of our most common swallow species. So common in fact, that a barn swallow is often simply referred to as a swallow. An elegant flyer, swallows have adapted excellently to man-made environments. Normally seeking shelter in cowsheds and farmyard barns, swallows feed on insects that fly above agricultural land and utilise the clay puddles found on farmers’ tracks to build nests. This is all changing, however. Small farms are few and far between, dirt roads are often covered with asphalt, and insect populations are drastically declining. On top of all this, swallows migrate to Africa during the winter months, and here they are hunted. As a result, swallow numbers are steadily declining and are in some regions endangered. Here, we’ll tell you everything you need to know to identify, understand and help protect this beautiful bird.

Swallow: key facts

How to recognise a swallow

Recognising a swallow in flight is easy. Look for pointed wings and a very long, forked tail with narrow ends. In flight, a swallow’s back and throat are uniformly dark, whilst the breast, abdomen and underside of the wings are comparatively light. Have a closer look, however, and you’ll notice that the back of the swallow is in fact featuring a metallic blue-black, and the throat is a metallic rust-red.

How to tell the difference between barn swallows and house martins

You will often see barn swallows and house martins flying together over fields or bodies of water. Being such graceful flyers, and often incredibly fast, it is sometimes difficult to notice the differences between them. Once you know what to look out for, however, it’s not so hard to differentiate a swallow from a martin. First, a house martin lacks the swallow’s long, forked tail. What’s more, house martins and barn swallows are different colours: house martins have light throats, while a barn swallow’s is rust-red and dark. Further, the house martin’s rump glistens white in flight, which contrasts to its otherwise blue-black back. Swallows have a much less conspicuous rump.

How to recognise a young swallow

You can recognise a young swallow by its bright abdomen and dark, blue-black back. Its throat will also be dark, distinguishing it from a young house martin. Do note, however, that young swallows lack their parents’ intense, rust-red throat and long, forked tail. 

Where do swallows build their nests?

Swallows prefer to build nests in barns and cowsheds made of wood. But they are known to use other buildings and protected facades. Swallow nests attach to the top of vertical walls, just under a roof. This construction requires a lot of clay and rough substratum. If they cannot find a suitable building, swallows will breed under bridges and attach their nests to the supporting beams.

How to recognise a swallow egg

A swallow’s egg measures on average 2 x 1.4 centimetres and is white with dark, reddish speckles. Females lay between four and six eggs in a bowl-shaped nest made of clay and plant fibres, and padded with fine feathers.

How to tell the difference between male and female swallows

At first glance, male and female swallows look very similar. As is often the case, however, the males do stand out a little more, with more vibrant throats and, on average, longer tails. It is this long tail that is used to court the females. The tails are, after all, an expression of vitality.

What is the perfect habitat for swallows?

The ideal habitat for swallows is a rural area with small cowsheds and barns, plenty of insects and clay puddles. However, swallows also feel at home in urban areas if there are suitable buildings or facades for nesting, and natural foraging grounds.

When is the breeding season for swallows?

Swallows start breeding in May. Given the right conditions, they can rear up to three broods per season. As such, breeding season can extend into August. Mothers incubate their eggs for at least two weeks, before both parents provide the new hatchlings with a diet of insects. Young swallows need 18 to 23 days before they can leave the nest.

Where do swallows spend winter?

Swallows take refuge in warmer climates during the colder months. Our native populations spend the winter mainly in South Africa, and, in preparation for the long trip, begin to form large flocks in autumn. Often, you will find hundreds of swallows, packed together on trees or power lines in autumn.

What does a swallow’s song sound like?

The song of the swallow consists of a lively, unstructured twittering. In flight, you should also be able to hear a lively chirping sound: “Witt-witt-witt”.

Help the swallow!

In recent decades, the swallow population has declined dramatically due to a lack of food and nesting sites. If you want to support swallows in your garden, look no further.

What do swallows eat?

Swallows are extremely good hunters, who catch flying insects in mid-air with spectacular flight manoeuvres. You can watch flocks of sparrows pulling off this feat over farmland or bodies of water. Since insects are scarce in winter, however, swallows travel long distances in the colder months, following the food supply to more southern regions. As such, attempting to feed swallows during winter is relatively futile. 

Which birdhouses are suitable for swallows?

Typical birdhouses are not suitable for swallows. However, it is possible to support the barn swallow by providing it a bowl-shaped nest, made of plaster, and placing the nest in a barn, shed or on the eaves of a building. It is important to differentiate between a house martin and a swallow nest, because many swallow nest aids on the market are in fact enclosed with a small entrance hole, and designed for martins.

Whenever possible, allow swallows to make their own nest. You can help, though, by creating a small puddle over loamy soil. Swallows will use this to collect building materials, which are often scarce. If your soil is rather sandy and does not stick, lay out a bowl full of clay soil and water, or create a pile of loamy soil somewhere in the garden.

How can I support swallows even more?

Besides locating nesting material, the decline in insects is a big problem for swallows. If you can, avoid using chemical sprays, and create a flower meadow to promote a long-lasting and continuous insect supply.

How can I help swallows in need?

If you happen to find a young swallow outside the nest, don‘t panic! It may be okay; it depends on the health and age of the bird. Fully-feathered, healthy chicks most likely left the nest independently and should be left alone. If the chick is unfeathered, it most likely fell from the nest, and should be carefully checked for injuries. If possible, return it to the nest. However, if the chick is injured or the nest cannot be located, contact the RSPB.

This is true for almost all other bird species. If you would like to learn more about native UK garden birds, take a look at our other bird profiles, including starlings, blackcaps and blackbirds.