Country diary: millions of birds arrive on their autumn migration

Many birds migrate at night, using the stars to orient themselves. For some, Britain is the last stop - for others, a staging post

Waking in the small hours, I find my bedroom bisected by a ribbon of light. The waxing gibbous moon hangs like a beaten silver pendant, backlighting wisps of cloud that cling to the inky sky like cobwebs. As I raise my binoculars to view the moon's craters, I notice a tiny silhouette flutter across the lunar disc.

Nocturnal migration allows birds to spend the daylight hours fuelling up in preparation for the long distances they must travel. It is believed that birds use the stars to help orient themselves, and it is advantageous for them to fly at night when the air is cooler and the atmosphere less turbulent. The cover of darkness also helps them to avoid attack by avian predators.