A small songbird soars above Ithaca, New York, on a September night. He is one of 4 billion birds, a great annual river of feathered migration across North America. Midair, he lets out what ornithologists call a nocturnal flight call to communicate w
In the late 1800s, scientists realized that migratory birds made species-specific nocturnal flight callsacoustic fingerprints. When microphones became commercially available in the 1950s, scientists … [+3025 chars]
