As luck would have it, Oxfordshire is a great place to make a film about swifts.

Oxford University’s Museum of Natural History is home to one of the most extensive studies of swifts anywhere in the world.

As part of David Lack’s epic study of swifts nesting in the Museum Tower, Roy Overall has spent 48 years ringing the feet of the birds.

What Roy doesn’t know about the life-cycle of swifts would go way beyond the filmmakers meagre swift-brain. Some terrific baby-facts are shared.

Roy describes the build up to a young swift’s fledging: