Often times, experienced birders use a specialized code when taking notes about the various bird species they have seen. This code may seem confusing to novice birders but there really is a logical system at work.
The codes are alphabetic (hence the name alpha codes) and have long been used by ornithologists as a quick and accurate way of recording data when doing bird surveys. They are also very useful as spreadsheet entry codes and as such, have been adopted by the U.S. Bird Banding Laboratory and other bird science organizations. Consequently, their use has spread beyond the confines of professional science and into the realm of the amateur birder.
If nothing else, using alpha codes in your field notebook saves time when writing notes, and it avoids the confusion which may arise if you are asking someone to read your notes and you have used a personalized bird naming system which differs from theirs.
This is not to say that you cannot devise your own naming system and in fact, many longtime birders have done just that. But the use of standard alpha codes is becoming more widespread.
There are two kinds of standard alpha codes. One is a six-letter code based on the scientific name of a bird. It is most often used by ornithologists and bird research programs, so as to avoid any confusion over exactly which species is being referred to.
The other system uses a four-letter code based on a bird’s common name. This is the system most often used by birdwatchers as it conforms nicely with how most people first learn their birds and it does not require them to learn the scientific name of each species.
In many other regions of the world outside of North America, the six-letter code is preferred as there is no firm agreement on the common names of each species. So while each bird will have a unique scientific name, it may have several different common names.
In North America, the common names of each species have long been established, with only occasional changes as new species are recognized from former sub-species, or a name is changed to account for more enlightened, cultural sensibilities (i.e., the recent renaming of the Oldsquaw Duck to the Long-tailed Duck).
The current standard alpha code list was devised by Peter Pyle and David DeSante (both of the Institute for Bird Populations in Point Reyes, California) in 2003, with regular updates to account for changes made to the Checklist of Birds of North America by the American Ornithologists Union as recently as 2006. The list includes the 2038 species recorded from the American Ornithologists’ Union checklist area plus 91 non-species forms (i.e., subspecies, races, etc.) which have standardized English names.
This means the four-letter alpha code list based on common bird names covers 2129 species found in Canada, the United States, Mexico, the Caribbean and Central America.
Generally, the way the code is devised is by using letters from the bird’s name. For birds with a two-part name, the code includes the first two letters of the first name and appended to that, the first two letters of the second name. So, the alpha code for the American Robin is AMRO, that of the Wilson’s Warbler is WIWA, the Ruddy Turnstone is RUTU, and so on.
The code for birds with one name is simply the first four letter of its name. For example, the code for the Dunlin is DUNL, and that of the Veery is VEER.
For hyphenated names, the code incorporates the first letter or first two letters of each part of the name, although there is some variation here due to the character of the name. For example, the code for the Gray-cheeked Thrush is GCTH.
There are some species that do not follow these conventions exactly as there are some birds whose names are different but their alpha code would be identical. The designers of the alpha code were careful to ensure that no two species have the same code and so they made decisions on a species-by-species basis as to which code defined which species.
The entire list of all 2129 species and their alpha codes, listed alphabetically by the common name of each species, can be found here.