The Incredible Journey of the Swallow

Migration, Survival and the Return Home

We recently posted about the painted lady butterfly and their amazing, multi generational migration. Well, at Wildlife Food Co HQ, we are incredibly fortunate to have swallows (Hirundo Rustica) that migrate to us every Spring. In our previous home, we also had swallows but sadly they gradually stopped returning over a couple of years. The reasons for this could be many and their incredible journey is something that I would like to talk about.

This year we had two pairs that successfully raised two broods each, bringing a total of 12  swallows into this world. This was, of course, incredible to see and filled us with hope that most of those swallows will return next year.

Right now, across the UK, our swallows are preparing to leave — and where they're going, and how they get there, is nothing short of extraordinary.

Mating -

Males without a mate will often visit the nests of other swallows to associate themselves with females that are already paired.

However, the majority of the time, the only way a female will accept a new male is if their current mate dies or if the nest fails, thereby ‘divorcing’ the established pair.

Rogue males sometimes take things into their own ‘wings.’ For example, if there is an unattended nest with young chicks in it, it has been known for a male to kill the entire brood, ensuring the nest fails and making it more likely that the female will look for another male elsewhere.

Most songbirds use a nest for just a single clutch or season, then build a new one – if they survive to breed again. But one study showed that most swallows returned to the same colony, with 44 per cent of pairs reoccupying the same nest. “This is remarkable given the length of a swallow’s return migration from its wintering grounds in South Africa,” says Rob Robinson, associate director of research at the BTO. Robinson has studied this iconic species’ unusually strong nest-faithfulness, a phenomenon called philopatry.

A 6,000-mile flight to the other end of the earth

They nest in the UK in the summer, but as they only feed on aerial insects (the majority of which are large flies, such as horseflies and bluebottles), their food source starts to run out in the autumn.

Faced with the prospect of little or no food, they start to head south during September and October.

Every autumn, the swallows that spent their summer raising chicks in our barns, garages and outbuildings set off on a migration of around 6,000 miles (about 10,000km) to southern Africa — as far as South Africa and Namibia. It's one of the longest migrations of any small bird on the planet, undertaken by a creature that weighs about the same as a two-pound coin.

It’s no walk in the park for our departing swallows as their extreme migration takes them south through Europe and across the Sahara desert.

They cover approximately 200 miles a day, generally at about 20mph – the maximum flight speed recorded was a whopping 35mph.

The route: a journey through a dozen countries

There's no single flight path — different populations take slightly different routes — but a typical journey for a UK swallow runs something like this:

• Southern England to France and Spain, following the coastline and river valleys where insects are easiest to find
• Across the Strait of Gibraltar into Morocco — one of the narrowest, and busiest, crossing points for millions of migrating birds each autumn
• South through Western Africa, skirting or crossing the western Sahara — around 2,000km of desert with almost nothing to eat or drink
• Into the Sahel and tropical West and Central Africa, where food becomes abundant again
• On to the open grasslands and farmland of southern Africa — South Africa, Namibia and Botswana — arriving as the southern summer is just beginning

Some birds take a more easterly route, passing through Italy, the Balkans or the eastern Mediterranean and down through the Nile Valley or East Africa instead — which, as you'll see below, brings its own dangers.

Natural dangers along the way

It's a beautiful story, but not always a happy one. As few as one in six young swallows are thought to survive their first migration south. Starvation if insects are scarce, exhaustion over open sea and desert with nowhere to rest, sudden storms, and predators such as hawks and falcons all take their toll.

Human dangers along the way

Alongside the natural hazards, swallows face threats that are entirely down to us:

Illegal trapping and hunting. The Mediterranean basin is one of the most dangerous stretches of the entire journey. It's estimated that somewhere between 13 and 43 million birds are illegally killed or trapped there each year, using mist nets, lime sticks (branches coated in glue) and tape lures that play recorded birdsong to draw flocks in. Cyprus, Egypt, Malta, Italy, Lebanon and Syria see particularly high numbers — Cyprus alone is thought to lose hundreds of thousands of birds a year to illegal trapping in a single district.

Power lines. Collision and electrocution on power lines is a recognised threat along migration routes through Europe, the Middle East and Africa, particularly where lines pass near roosting or feeding sites. Conservation groups in several countries are now working with power companies to insulate the most dangerous stretches.

Habitat loss. Wetlands, hedgerows and open farmland along the route — vital stopover sites where exhausted birds refuel — are steadily being lost to development and agricultural intensification, leaving fewer safe places to rest.

Pesticides. Because swallows feed entirely on flying insects, anything that reduces insect populations along their route — at home or abroad — directly reduces their chances of survival.

It's a sobering reminder that a swallow's journey isn't just a test of endurance against nature, but increasingly, a test of survival against us.

Life in the African summer

Once they arrive, southern Africa's summer is just beginning — so our swallows effectively get two summers a year. They favour open habitats: savanna, farmland, and in parts of South Africa, recently burnt or harvested sugarcane fields, where disturbed insects make for easy feeding.

While there, they moult their flight feathers — essential maintenance after such a demanding journey, and preparation for the return still to come. Some overnight roosts are staggering in scale; one historic South African roost was estimated to hold around a million birds in a single reed bed.

Coming home

From February or March, the whole journey reverses. Remarkably, many swallows return not just to the same country or region, but to the very same nest — a trait called philopatry. Studies have found around 44% of pairs reoccupy the exact nest they used the year before, a striking feat for a bird that's just flown 6,000 miles through some of the most hazardous terrain — and countries — on earth.

One ringed swallow, tagged at a roost in South Africa, was recorded back in north east England just 27 days later — averaging well over 200 miles a day, non-stop.

What you can do

Swallows feed entirely on flying insects caught on the wing, so the single best thing any of us can do for them is protect the insect populations they depend on — avoiding pesticides where possible, leaving some of the garden a little wild, and providing clean, shallow water through the summer months when they're here. 

If you have swallows nesting in an outbuilding, resist tidying up too early in the season — and if there's an old nest from last year, leave it in place. There's a good chance the same pair will be back for it.