A sighting in the field is just one way birders can identify bird species. Observant nature-lovers can discover what birds are where by examining tracks, trails, and a variety of bird sign: discarded feathers, feeding leftovers and caches, pellets, nests, droppings, and skulls and bones. This fully illustrated guide is the first of its kind for North American birds and presents thorough and straightforward instruction for identifying bird families or individual species by careful examination of the unique sign they leave behind. It also offers keys to the birds' behavior in the wild.