This month our columnist welcomes the return of a harbinger of summer – and marvels at the supreme effort it takes to reach our shores

In the last days of February this year an early pair of swallows was sighted, the first to arrive from southern Africa and well in advance of the mass invasion which normally takes place from late March onwards.

Barn or chimney swallows, like their cousins the house martins, have a special affinity with man and his dwellings. There was a time when these steel-blue birds with their elongated tail streamers and red throats would have nested in caves or rocks, but for hundreds of years they have built their mud nests inside stables, barns and sheds, darting through doorways and narrow openings at 35mph with casual ease.

For a decade, several pairs of swallows nested in our stable and tack room, each rearing two broods over the summer months and we felt honoured by their swooping flights round the house and yard and took delight in their twittering song. Yet for the past two seasons we have been deserted, as too have our neighbours. For some inexplicable reason the mud nests have remained untenanted and though a pair of swallows was seen surveying our premises last year, they did not remain.

Now, as I write, a single swallow, the first I have seen this year, has taken post on a telegraph wire and, perhaps waiting for its mate, is contemplating the stable for its summer sojourn. This bird will have spent the past five or six weeks, flying at up to 190 miles a day, in a headlong dash from southern Africa to be amongst the first to find a breeding site in these isles. It is in complete contrast to the bird’s migration south in September, a leisurely journey which may take up to four months before reaching its final destination in South Africa, Namibia or Botswana.

That this tiny slip of a bird can survive a journey of over 5,000 miles, across territory as hostile as the Sahara Desert, is a miracle of nature. In late August we will see clusters of swallows, adults and young, assembling on telegraph wires to make short flights, gradually to work their way down to the Channel coast. Thence, hopping over the sea to France, the birds will fly by day, over the Pyrenees, down the eastern side of Spain and across the Mediterranean towards the Sahara. The major hazard they will encounter is in Nigeria where over 100,000 will be killed to be eaten. Caught as they roost at night in elephant grass, this is one of several similar hazards to be encountered on their journey south.

The migratory flight south is leisurely and insect-filled to help sustain reserves of fat and energy. Then, around four months after leaving our shores they will arrive at their Southern African destinations. Here, they will remain for only two months before heading north to their breeding grounds in a swift flight of only five or six weeks, spurred on by the instinct to find breeding grounds and mates.

On several occasions in the past I have been fortunate enough to have been in either South Africa or Namibia when “our” swallows have been present and have often wondered whether I am seeing birds that have honoured me with their presence at home.

The migratory habits of “our” swallows long puzzled our ancestors. Where did they go? Why did they vanish? Many theories were proffered, the most notable of which was the pronouncement by Dr Johnson that “A number of them conglobulate together by flying round and round and then, all in a heap, throw themselves under water and lie in the bed of a river”. Even the renowned 18th century naturalist Gilbert White of Selborne was not entirely convinced that swallows did, in fact, migrate and he would, I fancy, have been astonished had he known the extent of their autumn journey.