Racing Extinction contains many grisly examples of mankind’s impact on the natural world, but one of its most affecting touches is a snippet of birdsong. The movie considers the way various species have been driven to nonexistence in the past few decades, among them the Kaua‘i ?‘? bird. A research unit at Cornell University catalogues wildlife sounds, and they recorded the song of the ?‘?—that is, the very last one—before the type vanished in the late 1980s. It’s a plucky little cry, made all the more poignant because no other ?‘? is around to answer it. Later we see footage of people killing manta rays and a Hong Kong rooftop loaded with thousands of shark fins, but that extinct sound really brings home an overwhelming sense of absence.