Shrill cries of little demons

Uncanny birds: swift and nightjar.
Uncanny birds: swift and nightjar.

Usually you hear them first, that wild, high-spirited screaming. Then you see them high above, speeding on scythe-shaped wings. Swifts are the quintessential bird of summer.

However, their shrill cries were not well received in the past. In contrast to those welcome visitors, swallows and house martins, swifts were thought to be little demons.

Common swifts live almost their entire lives in the air, catching insects and sleeping on the wing. Their strange eyes, shielded by prominent, horizontal brows, have evolved for looking downward. What else could they be, but Devil birds?

Even their feet are odd. Swifts’ feet are only able to cling — on the ground they contract into balls — so the only time the birds land is to nest. Young swifts spend at least three years flying continuously, day and night, before they are ready to breed.

This year they’ve had a difficult time. Hot dry weather is what swifts need, so their food rises high on warm currents of air. On cool, rainy, or windy days, flying insects are hard to find. But swifts can leave their eggs for quite a while without harm, and their nestlings will survive longer without food than most birds.

Swifts arrive from Africa at the beginning of May and head for the same nest site every year. This will be a small crevice under the eaves of a house, church, factory, or even in a multi-storey car park.

Once common, swift numbers have declined by almost half in the last 20 years. One reason may be that their nest sites are being destroyed during building renovations.

Swifts nest on a tiny ledge, accessed through a small gap under tiles or soffits. As the birds don’t go into the roof space, or harm the building, most people are happy with their summer lodgers. Find out about special swift bricks or nest boxes at http://swift-conservation.org

Swifts are birds of southern Africa that visit us for only three months. The young leave the nest in early July, so by August they could be gone. But summer wouldn’t be the same without those mysterious, screaming swifts.

Goatsucker

If Devil birds rule the summer days, summer nights belong to another uncanny visitor. This bird’s large eyes and wide, gaping bill give it the appearance of a frog, but that’s not the only odd thing about it.

During daylight hours the nightjar sleeps. Not perched across a branch, but lying along it. At dusk it wakes to send its weird, purring call across heath and moorland. A silent flyer, it wheels and swoops in the half-light, scooping moths and flying beetles into that gaping mouth.

In more superstitious times nightjars were regarded with something akin to horror. In Yorkshire they were the souls of un-baptised infants; in other counties, corpse birds or night ravens. Goatsucker was a commonly used name, because nightjars were thought to steal milk from goats and cows.

In reality, nightjars are amazing birds. The female nests on the ground, where her mottled brown-and-buff feathers blend seamlessly into the dead leaves and heather stalks. As she sits on her two eggs with eyes half-closed, the nightjar sways gently, resembling leaves ruffled by the wind. Like the swifts, her youngsters will fly south this month.