Three comprehensive online sources for identifying wild birds include All About Birds, Whatbird.com and the National Audubon Society. All three have a function where users can search birds by shape and other features and contain photos and recorded sounds for easier identification.
In addition to electronic field guides, traditional book field guides, such as Sibley's, Peterson's and Audubon's field guides, are also available. These field guides are easy to carry and are often helpful in conjunction with electronic apps. The disadvantage of traditional field guides is that the user needs some existing knowledge about birds to know where to begin searching.