A Swift Word About Swifts

But first, how do you know they are swifts and not swallows or martins?  At this time of year the hirundines (that’s swallows, house martins and sand martins), and swifts, triple or quadruple their numbers with the addition of all this season’s offspring. Dozens or even hundreds are often seen perching on overhead wires. If you are lucky enough to witness this you can be absolutely certain of one thing: you are not looking at swifts! They are swallows and/or martins – probably house martins as we have fewer sand martins hereabouts. 

The scientific name for the swift is apus; this was the bird’s Latin name and translates as ‘without a foot’. Although swifts do have feet, on the end of very short legs, they are only functional for clinging – onto the side of a rock face or stone building for example. They are not able to perch on a twig or wire. It’s not really surprising that a bird that spends its whole life in the air (sleeping and even mating on the wing) has evolved by reducing the size of body parts it hardly uses. Thus, if it were to end up on the ground, the unfortunate bird’s legs are too short, and weak, for it to stand on. Without being able to lift itself well clear of the ground by standing, its wings (evolved to be extra long for super efficient flying) have not enough space to flap. Hence the bird would be stranded and quickly fall victim to predators. 

For that reason you won’t see them on telephone wires, a sort of evolutionary footnote. 

Neither will you see them much after the first week or so of August.  For a bird that doesn’t normally arrive here until around the first week of may, it is one of our shortest-staying summer birds. As soon as it finishes raising its clutch, it is on its way to its winter quarters. Until a few years ago we had no idea where these were – how would we if they don’t breed in the winter so spend their time high in the sky? It was the arrival of tiny geolocators (like a little button battery for a watch) small enough for a bird to carry, that we discovered they spend their time circling above central and South Africa interspersed with long flights out into the Atlantic Ocean. 

So, one of our best known summer birds (like the cuckoo) is only actually with us for a small fraction of it. 

That’s no help of course during May, June and July when swallows, martins and swifts are whizzing round above our heads, all with their legs and plates of meat tucked up under them! Although their wings look superficially similar, swept back for speed, the swifts’ are significantly longer – making them look truly ‘sickle- or scythe-like’. Swallows are more slender and have long tail streamers, those with the longest being males (of course, men showing off again as usual). Although all the species are lighter underneath, that’s not a lot of help when you’re looking at them above you against a bright sky. A rule of thumb might be that the higher up they are, the more likely they are to be swifts as they are consummate aerial feeders, quite capable of flying several hundred miles in a day in search of insects if the weather is poor. During this time, if they have any, their chicks can become torpid to survive the extended time without food. 

But whether they be swifts, swallows or martins, they are there to be marvelled at and enjoyed while they still fly thousands of miles to bring our shared planet alive. They are to be welcomed, as Shakespeare called them, as true guests of summer.