Decades of research has been dedicated to the impressive navigation skills of homing pigeons. To explain how these pigeons are able to find their way home from unfamiliar, distant sites, scientists have arrived at various theories. These include the ideas that pigeons have a "map sense" that helps them follow roads, a solar compass and/or an ability to detect and use the earth's magnetic field. In this video segment from Nature, learn how homing pigeons are used as couriers by business owner Dave Costlow. [2:34]