Tweet of the Day is a series of fascinating stories about our British birds inspired by their calls and songs.
Bill Oddie presents the alpine swift. Alpine swifts are impressive anchor-shaped birds, the colour of coffee above and milk-white below. In the UK Alpine swifts are annual visitors, appearing in Spring, but they don't breed here. They spend the winter in Africa and on their journey north in spring some birds overshoot their breeding areas. Alpine swifts can be seen as they arc through the skies and because they travel so fast they can turn up almost anywhere from central London to Shetland.