Bird Codes displays the four-letter and six-letter code for all birds on the A.O.U. Checklist. Two sets of alpha codes for use by North and Central American and Caribbean ornithologists are included. The first set contains four-letter codes, based on English names, broadly following the rules and strategies adopted by the U.S. Bird Banding Laboratory (BBL). This set differs from that of the BBL in two ways. First, all 2116 species recorded from the AOU area (according to the AOU’s 57th supplement) are included, as well as 98 non-species taxa (many of which were recognized by the BBL) for which standardized English names and codes are provided. Second, standardized, species-categorization definitions and conflict-resolution formulae (Pyle and DeSante 2003) have been strictly adhered to, with two or three exceptions where conflicts were not resolvable. The second set of codes follows the same basic principles except that it contains six-letter codes based on the scientific names (genus, species, and subspecies) of the species or taxon. This second set of codes will be useful for ornithologists, particularly those in Latin American countries, who prefer using scientific rather than English names. These two sets of codes will continue to be updated every year, following taxonomic and name changes adopted by the AOU in future annual supplements.