Swallows and martins head back to the UK but a changing climate threatens their future | Birds

During the first week of April each year, regular as clockwork, I get a very welcome phone call. When I answer, the voice at the other end simply says: “It’s Andrew. They’re back! ” That’s the moment I know our local swallows have returned, having survived their epic 6,000-mile journey from South Africa to Somerset.

Andrew Ratcliffe and his brother Duncan run a car repair workshop in a village down the road from me. Here, for almost four decades, swallows have made their nests on the crossbeams beneath the roof. All day long, they fly in and out, bringing back beakfuls of insects for their hungry chicks, seemingly oblivious to the constant noise and the comings and goings of customers.

But this spring, the swallows did not arrive back at the workshop until 10 April – the latest they have ever returned in nearly 40 years. Numbers are down, too. At the turn of the millennium, at least 20 pairs nested here; nowadays, there are just five.

Swallows were late back to my village, too. In the 16 springs we have lived here, the average return date has been 8 April – but this year I did not see one over my garden until the 25th. How different from that gloriously fine lockdown spring of 2020, when the first swallow appeared a full three weeks earlier than this year.

At Portland Bird Observatory in Dorset, where many of our swallows make their first landfall in the UK, Martin Cade, a warden, confirms that this has been a very slow year for spring migrants. “The first half of April was rubbish,” he tells me. “There were virtually no birds – and a lot of very grumpy birders.” Some may have been passing overhead thanks to fine weather, but nevertheless numbers of birds were far lower than usual.

The good news is that, from last weekend onwards, the tide appears to have turned. The observatory logged roughly 10,000 swallows, and other long-distance migrants such as sand martins and willow warblers also passed through in good numbers. However, other familiar species, such as the house martin, have been very few and far between, continuing the declining trend of the past few decades.

Cade estimates that, this year, the main arrival of migrants has been roughly 10 days later than usual, peaking in late April, rather than the middle of the month. The latest nationwide figures from BirdTrack, organized by the British Trust for Ornithology, confirm this, showing that swallows, sand martins and house martins are all arriving between one and two weeks later than expected this spring.

In the Scottish Highlands, house martins usually arrive by mid-April, with swallows a week or so afterwards. But the conservationist and nature writer Sir John Lister-Kaye tells me that, this spring, neither have yet returned to their breeding sites; although wood and willow warblers – which also come here from sub-Saharan Africa – have returned more or less on time.

There are two reasons for the lateness of the swallows and martins. Unlike many other migrants, which fatten themselves up before they depart, these species feed as they travel, replenishing lost energy by catching flying insects. For that reason, they are especially vulnerable to bad weather en route. And the weather in southern Europe this spring – notably in southern Spain, which these birds cross after leaving Africa – has been very unsettled, with heavy rainfall, strong winds and even falls of snow across parts of Andalucía.

Migrating barn swallows perch on power lines.
Migrating barn swallows perch on power lines. Photograph: Patricia Fenn Gallery / Getty Images

The second reason is that, here in Britain, although the weather has been mostly dry, there have been persistent easterly and north-easterly winds, which also slow down the birds’ progress as they head north.

How might this affect these global travelers in the longer term? Songbird migrants usually live for only one or two years, so they need to get down to raising a family as soon as they return. This means that delays of even a week or two can lower their chances of breeding successfully. Swallows, which usually start nesting in early April, may only be able to raise a single brood this year, rather than two (or even three), as they do in most years.

I have seen swallows all over the world, and discovered just how important they are as a sign of spring: not just in Britain but right the way across the northern hemisphere. Since Aristotle noted that “one swallow does not make a summer make” – a sentiment echoed by Shakespeare and many others – millions of us have celebrated their annual return as the true sign of spring.

Yet I am concerned that rapid changes in the world climate – including more frequent and extreme weather events – pose a real threat to these birds’ long-term future. Disturbingly, this year some swallows even attempted to overwinter in Cornwall, suggesting that the climate crisis is already having a major impact on their behavior.

Fortunately, warm weather and clear skies have finally come to southern Europe, and the migration floodgates have opened. Earlier this week, down on the Somerset coast, I saw a steady passage of swallows, together with a few sand and house martins, all heading steadily northwards. Some will breed nearby, others elsewhere in the UK, while a few might even venture beyond the Arctic Circle in Scandinavia.

If we enjoy a fine late spring and summer, with warm sunshine and enough rain to produce a glut of insects, the swallows might be able to make up for lost time. Then, as the autumn winds begin to blow, and flying insects become increasingly scarce, they will head off once again, on their incredible global journey to the southern tip of Africa.

Stephen Moss is a naturalist and author. His book, The Swallow: A Biography, is published by Square Peg

Leave a Comment