Millions of years ago, the island of Kaua'i began to bloom with life, color, and sound. In time, the 'o'o bird added its song to the island chorus. Then a new species arrived: people. The impact of more and more humans meant fewer and fewer Kaua'i 'o'o. When scientists realized these unique birds were disappearing from the island, they deepened their efforts to observe them, including by recording their song. In time, only a single Kaua'i 'o'o was singing, and inevitably, a day came when there were none: pau. Complete with clear back matter, this gentle and poetic portrait of a species that evolved over thousands of years, declined, and became extinct only a few decades ago touches lightly on key conservation topics like invasive species and island ecology. Illustrations drenched in tropical color will light up the imaginations of young naturalists and fuel their instinct to understand, protect, and defend our planet's biodiversity.