Word formation

The common swift spends almost its entire life on the wing, a fact that many people find frankly 1.. Once a young bird leaves the nest, it may not touch the ground again for ten months, feeding, drinking and even sleeping in flight. Such feats of 2. were long suspected but only recently confirmed, when researchers fitted birds with tiny data loggers whose 3. would once have been unthinkable. The results were 4.: some individuals had not landed once during the entire non-breeding season. Scientists are still debating how the birds manage to rest. One theory holds that they snatch brief periods of sleep while gliding at altitude, where they remain 5. safe from predators. Swift numbers are, nonetheless, falling 6. in many parts of Europe. Modern buildings, with their sealed roofs and smooth walls, offer few of the cracks and crevices in which the birds traditionally nest, and the 7. of older properties has removed countless sites. Conservationists now encourage developers to install special nest bricks, a measure that is cheap, virtually 8. and, where it has been tried, remarkably effective.