The peat-brown, almost black forms of hoarsely screaming Swifts as they flutter and cruise through the great blue dome of air in the warmth of June is a wonderful sight. Witnessing such aerial perfection, the ultimate flying organism, as it speeds through the sky on knife-edge wings, as easily as we walk along the ground (and a lot more gracefully) is awe-inspiring. They have such different moods too; they can be speck-like arrowheads twisting effortlessly above you as they snatch up the tiny creatures that make up their diet, then on another day they are low-flying squealing demons shattering the peace and maniacally pelting at full speed between buildings in seemingly never-ending chases, no wonder people used to call it the ‘Devil-bird’.
Most birds fly, but none like the Swift; its mastery of the air is challenged only by the Albatross – and that is more of a glider than a proper flyer. Once a juvenile bird has left the nest it does not reach breeding age until it is four years old, during which time it has no reason to land at all – so for four solid years a swift will be airborne. Even when they do breed they only settle on the nest to incubate the eggs or feed the young, which will last around 56 days in total, so after that the adults are free once more and will probably start getting ready to migrate (almost all of our swifts will be gone by the end of August).
Although Swifts superficially resemble the swallows and martins they are not closely related at all, their similarity arises from the fact that they all share the same habitat so are shaped to be best adapted to it. Swifts are actually most closely related to the Hummingbirds, sharing the ability to swivel their wings at the shoulder and both possess very small, weak feet – which is why their order is Apodiformes and the Swift’s scientific name is Apus apus as both mean ‘without feet’. Unlike Hummingbirds however Swifts can sleep in flight; they can shut down half of their brain at a time whilst gliding at great heights, they also mate on the wing from time to time and collect all their nesting material in the air – if it was possible to nest in the air then they probably would!
As to what Swifts eat it is surprising what floats around in our atmosphere; beetles, aphids, flies, craneflies, moths, butterflies, thrips, leafhoppers, ants, lacewings and even spiders that float on strands of silk. In late summer large groups of Swifts can be seen flying at speed, screaming blue murder, it is thought these are juveniles engaging in social activity or looking for future nest sites though they could be adults gathering pre- aerial sleep.
You may have noticed this yourself already, I know I have, but Swifts are actually declining in the UK and other parts of Europe (though they seem common enough in the south), it would seem that suitable nest sites are in short supply – modern buildings rarely have gaps in the roof or under tiles where swifts could nest. Some older buildings that are suitable have been knocked down too and Swifts are notorious for being reluctant to occupy new nest sites even if they are provided, which is why pre-existing colonies are so important as pairs mate for life and will return to the same nest. New developments need to incorporate swift nest boxes or gaps to allow swifts to breed. Another possible cause behind their decline is a reduction in invertebrate prey; it is very difficult to monitor insect populations but considering the reduction in green spaces, wetlands and flowers (combined with an increase in pollution and insecticides) it would be an educated guess that the organisms Swifts feed on have massively reduced in number. Let’s hope that we can get our act together to help this species before it takes the same route as the Turtle Dove.