In late March 2015, ornithologist Bruce M. Beehler set off on a solo four-month trek to track songbird migration and the northward progress of spring through America. Traveling via car, canoe, and bike and on foot, Beehler followed woodland warblers and other Neotropical songbird species from the southern border of Texas, where the birds first arrive after their winter sojourns in South America and the Caribbean, northward through the Mississippi...