How fast does time fly for migrators?

THE songbirds of Europe are well studied, but some aspects of their lives are shrouded in mystery. Most small birds migrate at night, when we can’t see them; their flocks appear on radar screens.

Roosting places would be impossible to find in the dead of night in unfamiliar terrain, so birds probably fly non-stop, using the stars as a guide.

How far can a small bird travel in a single flight, and, after a long journey, does a bird take the next night off? Carrying extra fat adds to a bird’s work-load, and, as with humans, being overweight is dangerous; a fat bird is slower, less manoeuvrable and more easily seized in a hawk’s talons. A migrating bird might only carry enough fuel for one flight. Being as light as possible and refuelling at each stopping point may be the best option. But is it?