Is there any animal that spells summer quite like the barn swallow? Do they even realise they are a harbinger of good things to come? I do not know if it’s them deciding summer or if it’s summer that brings them into being. I dare say it matters not one iota the order of things, simply that one could not co-exist without the other. If either were to disappear, I cannot see how we could avoid joining them in the dustbin of history.

People living at lower latitudes might not appreciate the symbolic power of that first glimpse of a solitary swallow gliding and weaving, banking and dipping above the river and high over the houses. We, however, who choose to inhabit the Northern outposts of the habitable world (i.e. England), place more attachment than we’d have ourselves believe on the return of these seasonal visitors. For us, whether we admit to it or not, the swallow is arguably a national treasure, the most welcome sight over the White Cliffs of Dover in an age where few are getting all excited at the prospect of incomers. After nigh on six months of monochrome, half-light, naked trees and continuous dampness, you can about bank on the swallows to slap an injunction on this dismal run of days. And, yes, to save the rest of us from death by despondency. We owe them much. We owe them a debt of gratitude for returning to us what they callously took from us when they left the previous early autumn. While a simple thanks doesn’t wash with them, busy as they are frantically gobbling up insects on the wing to power the trip home to South Africa, we can perhaps begin to appreciate them by first getting to grips with how mindbogglingly difficult their journey back and forth from latitude 40 degrees south to latitude 50 degrees north.

Weighing in at slightly under half the weight of a pouch of tobacco, and measuring half the length of a school ruler from beak to the tips of their famous forked tail, these little fighter pilots don’t actually require aeronautical engineers to build their means of transport. Nature did that for them over millennia. They are, no less, the complete article. Top Gun school cadets that arrive on the scene with their seventeen million dollar supersonic jet fighter on their back. The inspiration of humans wealthy enough to chase the sun on a perennial basis, swallows don’t need two mortgages in order to live the dream. They do, however, need astonishing levels of stamina, as well as innate GPS coordinates to find their way literally from door to door.

Take the Cape of Good Hope as their starting point. It wasn’t that long ago that humans discovered the verifiable truth that the barn swallows we see here in the British Isles nearly all originate in South Africa. The telemetry of migratory birds was always an elusive truth until tiny metallic bands started to be fastened onto their twig-like ankles. When a swallow was located 8,000 miles away wearing the same band, the connection was finally made. This feat of endurance, flying the length of Africa plus the length of Europe surprised many birders. For starters, how does something weighing fifteen grammes make it that far year after year? And more beguiling, how does an animal with a tiny brain remember how to get home? I mean it’s not like home is just round the corner either. To find its way from a nest in the eaves of a house in a hamlet in a valley in an English county back to a forest in Lesotho or a hole in a crag deep in the Drakensberg Mountains, first it has to find a suitable crossing point on the south coast of England. it then needs to fly at about 50kph, avoiding predatory birds, as well as birdshot from hunters’ guns, through France, over the Pyrenees, over the baking plains of Castille in Spain, up and over the Sierra Nevadas before making another crossing of the straits of Gibraltar. Presumably it doesn’t stop for very long en route, other than to feed where it can and to catch some zzzz’s before the big one across the Sahara. Is this beginning to sound like an epic journey? Well, we’re not properly underway quite yet.

Once into Morocco and over the Atlas Mountains, the landscape becomes disturbingly parched. The complex chain of organic life that begins with plants and eventuates in the presence of insects is on the wane by the time the swallows cross into Mauritania. By now they are well and truly at the mercy of the elements. These elements are always harsh, but sometimes brutal. Food disappears. Soil gives to dust, which swirls around in the lower atmosphere, blinding and choking everything. The heat is intense, even in autumn when the swallows are passing through. Shade at midday, shade at any time of the day becomes a rarity. The nights are frigid. There are so few reliable sources of insectivorous sustenance for them that ornithologists suspect that they make sizeable detours to arrive at Saharan watering holes, of which they are few and far between.

The winds on the open plains of the desert are hot blasts of angry air. The bird must take that wind head on, though if the little navigator gets sucked into a trade wind, he or she will end up blown far off course and into the depths of the Atlantic Ocean where its end is watery.

If the swallow survives the full-blown Saharan stage, by perhaps following the Niger river for water and sustenance, he will find himself entering the Sahel – that band of latitude south of the Sahara and north of the equatorial belt. You might think of the brave little swallow that his troubles are now behind him, but you would be wrong. This passerine bird needs to know it has not ventured off the ‘flyway’ (the corridor that they all traditionally take), but how does he know this when a) a sandstorm has most likely disrupted his passage; and b) when recognisable landmarks beneath them, used season after season to as reliable route finders, have been upended, scorched, moved, destroyed or otherwise fallen victim to man’s insatiable tinkering of his physical world? In the anthropocene age of man the job of swallow with homes in either hemisphere has become intolerably difficult.

If the 18g swallow has made it this far, his chances of reaching home do increase. But success is far from a certainty. In the Sahel, where acacias grow sporadically on impoverished soils, finding dinner is still a major issue. The swallow can try and seek out the brahmin cattle, for their tails are always swishing from the density of flies congregating around their shit. Still, remember, the swallow is a small bird who prefers a diet of gnats and midges and altogether smaller insects. The big-ass African variety, such as the tsetse fly remains a formidable mouthful. Now, beating his wings at upward of 70kph, the swallow powers its way past the Sahel to where green shoots grow. He has now reached the Equatorial belt somewhere around Northern Nigeria. His weary plight will be eased by the sight of forests coming into view. But they are merely a trap. Once he, and another few thousand of his brethren, have reached the forests of tropical West Africa they must be careful where they choose to take their traveller’s rest. The unfortunate will be snared in vast nets that locals booby trap the trees with. There is no hope for a swallow caught in the net. Even though he is only transiting, the swallow will be considered fair game and taken for the village pot.

For the brave few, they might follow the flyway (or skyway as i like to call it) out into the Gulf of Guinea. Once away from land the armpit of Africa can be a dangerous proposition. All it needs is a gust of wind and that’s it, game over. For the foolhardy if they stay the course, crossing the island group of Sao Tome and Principe, they can nail the short cut, reentering Africa in the primordial forests of Gabon, and further south to the mouth of the mighty Congo river. Here they might not be deprived the sustenance needed to power an 8,000-mile journey, but still they are not out of the woods yet. Dangers abound. The Gaboon Viper can strike while they are taking branch breather. Humans continue to predate them and every other piece of flying meat. The rains over the Congo come in torrents, the raindrops as heavy as concrete on their weightless bodies. The electrical storms over the world’s second largest contiguous forest are legendary. Do these pint-sized pilots feel fear?

Once beyond the Congo the swallows are beginning to home in on home. They are now in the southern hemisphere and there is every chance they know this, due to the Coriolis effect, magnetism, position of the sun and stars, and so on. Just when you thought they could hit the home straight for a ticker-tape parade celebrating their incredible marathon, another geophysical kraken emerges. Their voyage home comes to resemble Odysseus and his ten years of wandering. Angola treats them fairly well, providing the Goldilocks Effect for an exhausted bird. However, what lies beyond is in every way as rigorous and daunting as the Sahara. Except this desert is much older and much drier: the Namib.

South Africa is bordered by Namibia to the north. Namibia contains some of the highest dunes on Earth alongside a skeleton coast of nothing but bleached bones and shipwrecks. The ocean is an ice bucket under a burning sun. The dunes have disoriented weary travellers for eons. Only there can north be south and east be west. In the Namib desert can the swallow fall at the final hurdle. If he follows the coast south to the mouth of the Orange River, the swallow will have a fighting chance of making it home in time for supper, though how many lie dazed and confused in the red sands of the Namib no one knows, because no one ever ventures in there and comes out telling the tale.

By now, the great navigator has completed seven of the eight thousand miles. In the Western Cape he can perch on the fynbos, and while the vegetation might be on the prickly side, he will find a good square meal and a place to rest his weary wings.

He’s made it. Many have fallen by the wayside. And, to think, our magnificent young fledgling was only born in England in May, so how in God’s name did he cruise the flyway without having that internal map to guide him? The possibilities are too great, the implications of his amazing solo feat semi-mythical. Leave the answers unanswered. It’s all good. Some mysteries are well-kept for reasons known only to Gaia.

He’s home, South Africa are world rugby champions, the sun is shining as only the sun can in a waterworld southern hemisphere where the skies are cerulean blue owing to the amount of ocean. The earth has tilted away from north to south while he’s been on the wing for those breathless six weeks. He and his squadron of fellow travellers have literally pulled the Earth upward to let their hemisphere bask in the full glow of sunlight. They used invisible pulleys and guy ropes that we cannot see (I know that, because I decoded a conversation between two of them one day). Meanwhile we in the northern hemisphere batten down the hatches for another deathly winter until the swallows return in April or May.

Oh, yes, the return. Did I mention? They’ll be making the homeward journey north as well, about four months from now. That’s if we humans don’t mess up his time-honoured route along the invisible skyway by altering the landscape uprooting trees, exterminating insects, to plough yet another bloody field before he leaves again. Given how far we humans have redecorated the Earth’s surface, it’s a miracle they even find their way back and forth year after year.

So the next time you see one wheeling, darting and generally performing top-notch aerial acrobatics on the green and by the river, doff your cap and take a bow in his direction. For what this tiny frequent flyer does without leaving a carbon trail, we could only dream of.