Inspired by musician and eco-philosopher David Rothenberg's book of the same title, this documentary explores the intriguing, charming, complex and often conflicting theories on why birds sing like they do and why humans are so attracted to the sound. The film features contributions from musicians including Laurie Anderson, Jarvis Cocker and Beth Orton; enlightening and often startling analysis from some of the world's most eminent birdsong scientists; a literary guide to birdsong in poetry; a bizarre birdsong-themed art 'happening'; the creation of a new musical composition from the Afro-Celt Sound System, entirely made up of manipulated birdsongs; and a strange musical duet at New York's Bronx Aviary, featuring humans and birds.