Leopold, regarded as the father of wildlife ecology, would sit on a bench before sunrise at his Wisconsin shack during the 1930s and '40s. He would jot down the morning chorus of birds, noting the light level and time when he heard the first calls. He even mapped the birds' distribution around his Sauk County, Wisc., home. Stan Temple, a University of Wisconsin-Madison emeritus professor of wildlife ecology, and Christopher Bocast, a UW-Madison graduate student and acoustic ecologist, worked with 30 minutes' worth of Leopold's notes and compiled a list of species and sounds. The recordings are compressed into a five-minute clip, so it's a bit more of a din than Leopold would have heard. The background noise comes from a rural Wisconsin setting, and the bird calls came from the Cornell Lab of Ornithology's Macaulay Library.