Alpha codes are four-letter codes used by birders and bird banders as abbreviations for bird names.

According to http://www.birdpop.org/alphacodes.htm, the American Ornithologists' Union (AOU) developed a new set of alpha codes in 2003 to replace those used by The U.S. Bird Banding Laboratory (BBL). See the preceding link for complete details.

http://www.birdpop.org/DownloadDocuments/Alpha_codes_english.pdf is the AOU list in PDF format sorted alphabetically by English Name, and

http://www.birdpop.org/DownloadDocuments/Alpha_codes_tax.pdf is the AOU list in PDF format sorted in phylogenetic order.

http://www.pwrc.usgs.gov/bbl/index.cfm is the BBL website and,
http://www.pwrc.usgs.gov/bbl/manual/speclist.cfm are the BBL codes.

The BBL list is not the same as the AOU list; e.g. BBL for Barn Owl is BNOW and AOU is BANO.

The index in the back of the Crossley ID Guide to Eastern Birds, (p518 in 2011 Edition)  has an alphabetic list of the codes. [Editor: I don't know if this is based on AOU or BBL or some other list]

In many cases of 2-word names, the alpha code is the first two letters of the first word followed by the first two letters of the second word. However, that is not always the case as in BANO for Barn Owl, CARW for Carolina Wren, and CANW for Canyon Wren.

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