The field guide information is extracted from the online species descriptions on the Gaia Guide website (http://www.gaiaguide.info/).
The species lists are based upon Avibase (http://avibase.bsc-eoc.org/), which includes many species that are only very occasional visitors or are only found in captivity or because of escapes from captivity.
Almost all species descriptions include one or more identification photos or drawings. All descriptions include detailed and searchable distribution data, based upon recent information from the Global Biodiversity Information Faclity (http://gbif.org/).
Descriptions also include comprehensive color data for each species so you can search by color, as well as location and size. Progress has been made on extending size data and wingspan data but that information remains incomplete for many families of birds. A number of species now also include sound recordings.
As the guide matures, it will include more information about distinguishing features for species, habitat preferences and a wide range of other information and links to external resources that assist with confirming identifications.
Note that the species descriptions are the result of collaboration by many contributors. All users of this app are welcome to contribute to species descriptions by adding identification photo, sound recordings and other information. Contributions can be made by submitting records through this app or they can be made directly through the Gaia Guide website.
"US Birds" uses large amounts of distribution data to provide location search and distribution mapping functions. That data can take a few minutes to load into the app database tables. Until fully loaded, the location search and distribution map functionality will be limited.