Swallow

Bird of the Month July 2023: Swallow

Many people regard the swallow as their favourite summer migrant. This affection is probably down to the fact it has been living alongside us in our barns and under our eaves for thousands of years. Added to that is its exotic appearance, impressive migration and its acrobatic flight style. By July, many UK breeding swallows will be feeding their first brood, or maybe even thinking about a second. This means high summer is a wonderful time to spot them busily catching insects on the wing and rearing the next generation of this beautiful species.

Scintillating Swallows

Swallows are fairly unmistakeable with their glossy, dark blue backs, white bellies, red faces and throats and their long tail streamers. Females have shorter tails than males. There is also some variation in tail length between males. Scientists previously thought that females preferred males with longer tails purely because it showed they were healthy enough to grow a fairly useless bit of ornamentation. More recent research, though, shows they are a sign of greater flight skills, something a female would want to pass on to her offspring. Both sexes have a series of white spots running around the top of the tail edge. Juveniles are much duller in appearance, with the red and blues much more subdued. Their tails are also much shorter. The only similar birds in the UK are two fellow hirundines, house and sand martins, and the unrelated swift.

Swallow flying into barn
Swallows often nest in unused barns and sheds

Unlike swallows, sand martins are brown on top and pale below. House martins do have a similar glossy blue back, but they lack the red face. They also show an obvious white rump band when in flight, and both martins have shorter forked tails than the swallow. Nesting behaviour is also a good clue to identity. House martins, as their name suggests, do nest around houses like swallows. Their nests, though, are always constructed outside a building, never inside, with a mud cup hanging under eaves or an overhang of some kind. Sand martins, meanwhile, nest exclusively in holes dug into a soft cliff or bank. All three species commonly associate with each other, however, often feeding in the same habitats and even gathering together before migration.

Swallow nest
Swallows usually make nests of mud and line them with vegetation

Signs of Summer

Swallows typically arrive in the UK to breed each year in March and April, making them one of our earlier arriving migrants. Males usually get here first with females coming afterwards. In the summer, birds can be seen flying in and out of the open buildings they like to nest in. The bird’s full name, the barn swallow, reflects this. They will also nest in sheds, stables and under eaves or bridges. I have even seen them nesting in bus stop shelters and a Bronze Age burial chamber! Historically, they would have nested in caves or on cliff ledges. They usually make the nests from mud and a mixture of vegetation. Overall, they prefer more open country. Sites with a nearby water source, and therefore more insects, are also favoured. They are much less urban than house martins.

Young swallows
Young swallows sometimes help raise second broods

Most pairs raise two broods each year. Sometimes the first brood will hang around to help rear the second. In late August and September, birds often form large roosts as they prepare to head off on migration. Reedbeds and wetlands are typical sites. European birds then head to southern Africa for the winter. Here they will also commonly roost communally in reedbeds at night. Climate change and our milder winters mean, however, that a few birds have now begun to spend the winter on the UK’s south coast. Those that do leave are also increasingly delaying their departures later into the autumn and winter as insects are more abundant for longer. The species is actually the most widespread swallow globally and so also breeds in North America and across Asia. Birds breeding in the Americas head to South America for the winter. Asian breeders winter in India, South-east Asia and northern Australia.

Swallows and martins
Swallows and martins often gather in large groups before migrating south

Swallows and Us

Humans have been celebrating the swallow’s return each spring for centuries, even when we didn’t know where they disappeared to for the winter. Incredibly, ornithologists only confirmed in 1912 through bird-ringing that these small birds migrated at all, as well as where exactly they went. Before that there were a variety of theories. The Greek philosopher Aristotle thought that some migrated and some hibernated at the bottom of ponds and lakes. This idea of hibernation persisted for centuries. In the 18th century, scientist Carl Linnaeus believed it whilst naturalist Gilbert White was undecided. Others thought they hibernated under the sea and one theory even had them migrating to the moon. Not knowing where they went, though, certainly didn’t change the fact that humans have long felt a strong emotional connection to swallows.

Baby swallows
Swallows have been nesting alongside us for millennia

This has probably been helped not only by their habit of nesting close to us, but also by the fact they only eat insects and not crops of any kind. As a result, we have never seen them as pests. In Classical times, artists celebrated their return on frescoes and pottery. Some cultures considered it lucky if one nested in your house. Since at least the 19th century, sailors have employed swallow tattoos to represent a number of themes, despite the fact they aren’t seabirds. When people still thought they might hibernate under the sea, the fact they could do so without drowning was considered lucky by sailors. Later on, a swallow tattoo came to represent a safe return home, as well as a fellow long-distance traveller. One swallow tattoo meant a sailor had travelled 5,000 miles, while two stood for 10,000.

The Singular Swallow

The swallow’s fortunes in the UK have taken a turn for the worse in recent years. The BTO recorded a 23% decline in the breeding population between 1995 and 2020. Certainly, many people are noticing that less swallows seem to be gracing our skies each summer. A number of factors could be at play. Climate change and the availability of their insect food, however, are almost certainly the most likely problems facing them. The fear is that if these issues aren’t addressed, less and less of them will make it back each year. The prospect of one day not being able to celebrate the remarkable annual return of this beautiful bird is a sobering one indeed.

Swallow and mud
This swallow is collecting mud for its nest

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