Over the last 150 million years, birds have spread around the globe and evolved a multitude of flying abilities to become lethal hunters, formation flyers, and aerial acrobats. But there is a vast kingdom birds do not control: the night skies. Naturalist David Attenborough explores the highly advanced inhabitants that dominate our skies today. Follow him to the caves in Gomantong, Borneo, where today's birds and bats meet in a battle for supremacy.