When Steve Gosser heard the song of a scarlet tanager in the woods, he knew to look for a bright-red bird with black wings. But when he laid eyes on the singer, he saw instead a dark-colored head, black-and-white body, with a splash of red on its chest. "Well, that sort of looks like a first-year male rose-breasted grosbeak," he said. The song of one bird coming out of the body of another suggested this little guy could be a rare hybrid. Gosser enlisted the help of some pros, including biologist David Toews, who conducted a genetic analysis to see if this was truly the offspring of t...