HIGH FLIERS

Swallows, swifts and martins are busy in the summer skies above the Dales. Brian Pike investigates these intriguing aerial acrobats

Dozens of species of migratory birds that spend the winter in warmer climes have now arrived on our shores to nest and raise their young.

Of these fair-weather visitors, the nation’s favourite is undoubtedly the swallow. One swallow may not make a summer, but no sunny summer’s day in the country would be complete without the sight of these elegant birds wheeling and diving above our fields, parks and village greens.

Swallows are expert fliers and feed by snatching small insects from the air. There are three other summer visitors that make their living in much the same way, namely house martins, sand martins and swifts. Sometimes it can be difficult to tell the different species apart, though, so let’s start with the easiest distinction to make: swallows and martins versus swifts.

COMINGS AND GOINGS

Swallows and martins generally arrive in the Dales in early-to-mid April, and set off back to Africa in September. Swifts are here for a far briefer time. They arrive about a month later, in May, and leave a month earlier, in August.

A swift on the wing appears to be black all over (although in reality swifts are a very dark brown) whereas swallows and martins are blue-black with prominent splashes of white. And swifts have long, narrow, sickle-shaped wings, whereas swallows and martins have stubbier, triangular ones.

Astonishingly, swifts spend virtually their whole lives on the wing, even sleeping in the air. Swallows and martins, by contrast, will readily perch on telephone wires and fences. Swifts can’t do this – their legs and feet are simply too weak.

If you’re still in doubt about whether you’re looking at a swift, use your ears. Swallows and martins twitter or chirp, whereas swifts call to each other with piercing high-pitched screeches, especially when they gather together into larger groups after a day spent foraging individually.

Telling the difference between swallows, house martins and sand martins requires slightly keener eyes – unless, that is, you happen to see them on their way to their nests. Swallows like to nest on ledges under bridges or inside buildings that are open to the outside world, such as stables, outhouses, carports or sheds. House martins prefer the sides of buildings, typically tucking their nests up under the eaves. And sand martins nest in tunnels in sandy river banks, gravel pits and sea cliffs.

PATTERN MATCHING

Without a nesting site as a clue, take a good look at the bird’s tail and plumage. Swallows have long, forked tails, whereas both species of martin have short, stubby tails. And whilst all three are predominantly black and white, swallows – unlike martins – have red chins.

As for telling the difference between house martins and sand martins, it’s the precise pattern of black and white that is key. Both birds have white undersides, but the sand martin has a black bar across its chest. The two species are equally distinctive when seen from behind: the house martin has a prominent white rump. By the way, don’t assume your job is done once you’ve identified a single bird in a group. Swifts keep themselves to themselves, but swallows, house martins and sand martins often form mixed flocks, especially as summer draws to a close. All three species frequently mingle on telephone wires and migrate together.

Although swifts, swallows and martins all feed on flying insects, they have different foraging patterns. Martins tend to stay fairly low, skimming a foot or two above fields, lakes and streams. Swallows, with their longer wings and more powerful flying style, often climb higher.

Swifts, however, are the ultimate aeronauts, with a top speed of 70mph and a head for heights. You’ll often see them circling at high altitude, especially in the evenings, but just how high they venture wasn’t appreciated until a First World War French airman on night operations flew into a party of swifts asleep on the wing at a height of 10,000 metres.

Other species of bird may fly higher than the swift – the current record is held by a Rüppell’s griffon vulture that collided with an aircraft at 37,000 feet – but none stays aloft for longer. Swifts touch down only to nest, and researchers tracking the birds with electronic monitors discovered that some individuals stayed airborne for a whole ten months straight. Even birds that landed for short periods still spent over 99 percent of their time in the air.

CHANGING FORTUNES

The number of swallows, martins and swifts arriving in the UK varies considerably from year to year depending on weather conditions and the relative abundance of the insect populations on which they feed.

In terms of long-term trends, British Trust for Ornithology statistics suggest that populations of swallows and sand martins are just about holding their own, but that numbers of house martins and swifts are declining rapidly. Swifts have suffered especially badly, and there are now less than half the number arriving in the UK than there were when surveying began in 1994.

Swifts mate for life and return to the same nest sites year after year, and the ongoing refurbishment of old buildings has deprived them of many of the traditional nest sites they occupied for centuries. Installing swift nesting boxes in suitable locations may help to reverse the trend. Both the RSPB (rspb.org.uk) and Swift Conservation (swift-conservation.org) provide useful information on how to do this.

ABOVE Sand martin hawking for insects over a lake BOTTOM House martins resting on power lines before migration LEFT House martin collecting mud for nest BOTTOM LEFT Common swift flock in flight Opening image © Klein & Hubert, all others © RSPB Images

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