Swift (Apus apus)
At this time of year, if you suddenly see some black crescents, scything through the sky, it means that the Swifts have arrived back for the summer.
Swifts are renowned as being superb flyers and in fact, spend most of their lives on the wing, feeding, sleeping and mating in flight. They can ‘snooze’ with one side of their brain and then switch to the other side.
Food is flying insects and spiders which are collected in the back of the throat in a special food pouch and bound together with saliva into a ball called a bolus which can contain over a thousand insects. Birds drink either by catching raindrops in the air, or by flying low over water, skimming a mouthful from the surface.
Swifts nest in holes and crevices, particularly inside old buildings and under rooves where they can still gain access. Increasingly, specially-designed swift nest boxes are used. After leaving the nest, the youngsters will keep flying non-stop for three years! Late in the summer, family parties of birds can be seen screaming through the air in aerial chases.
With the ability to fly more than 800 km a day (500 miles), Swifts can avoid areas of bad weather and so keep feeding.
However, they have suffered a dramatic decline in recent decades, perhaps 50% in the last 20 years. The reduction in insects due to pollution and pesticides, habitat destruction and the modernisation of many buildings has resulted in loss of nesting sites.
While Swifts are one of the last migrants to arrive in the UK, they are also one of the first birds to depart and by late July and early August, will have left Barnes and be migrating through France and Spain to spend the winter in Africa, south of the Sahara.
Photo credit: A Podmore