If you want to find one of the rarest birds in America, you have to start early. You also need to train your hearing. The Florida Grasshopper Sparrow is hiding in a field of palmetto and grass, and the only way you’ll find him, without scaring him away, is to listen for a call that sounds remarkably like that of a grasshopper. And to catch him, you must convince him you’re another male, come to claim his territory.