Recreating the sound of early 20th-century America

Naturalist Aldo Leopold took such detailed notes of the sounds he heard in 1930s Wisconsin — particularly bird calls — that researchers at the University of Wisconsin-Madison have been able to recreate what the environment sounded like back then. At least, what it sounded like around Aldo Leopold's house. His notes, and the recreated sound, are allowing scientists to learn more about species migration and how industrialization has changed ecology.