How a kingfisher helped reshape Japan's bullet train

Japan's famous bullet train used to make a loud boom when it travelled through tunnels. But, thanks to a spot of bird-watching, an engineer was able to fix the problem after he was inspired by a kingfisher.

Listen to 30 Animals That Made Us Smarter to hear more about the kingfisher and the bullet train.

Digital producers: Jennifer Green and Anna Doble; Animator: Jules Bartl.