Tiny ruby-throated hummingbirds weighing less than a nickel fly from the upper Midwest to Costa Rica every fall, crossing the six-hundred-mile Gulf of Mexico without a single stop. One of the many creatures that commute on the Mississippi Flyway as part of an annual migration, they pass along Chicago's lakefront and through midwestern backyards on a path used by their species for millennia. This magnificent migrational dance takes place every year...