I occasionally hang out in birding forums on the web, and I was a little surprised to encounter people using four-letter abbreviations for bird species, such as BCCH for Black-capped chickadee or AMCR for American crow. I did a little digging and it turns out that not only are these bird codes available in birding apps like eBird, they were standardized decades ago by North American ornithologists to make computerized bird banding observations easier and more accurate.

Bird banding (a.k.a. bird ringing) is a long-standing practice by ornithologists where wild birds are caught and tagged with a numbered band around one of their legs. This allows e.g. their movements to be studied when the bird is recovered many miles away after migrating.

Back in the 1960s, ornithologists and their clerical staff were having issues with managing the volume of data that bird banding required. To help solve this, they started using punch cards and computers to enter the data:

THE BANDING PROGRAM

The past year ended with the distinction of breaking all records in every phase of our operation. More birds were banded, more bands were issued (2.5 million) and more recoveries were received (nearly 59,000) than in any previous year.

Inasmuch as our clerical staff has remained the same size through- out this period of expansion, numerous difficulties have arisen in handling the increased volume of incoming data and processing recovery reports. Never before has the need been greater for all banders to give full cooperation in all aspects of their programs. If we do not receive banding records that are complete in every detail and adequately checked for accuracy, it will not be possible for us to handle the volume of data being received.

All banding schedules are now being summarized on machine record cards. Only by doing this it is possible for us to process such a large volume of data and retrieve it readily to be used for research purposes. During this summarization process all data pertaining to an individual band number, as given on the schedule, is punched into a card. For this reason, it is necessary that schedules be completed and neatly prepared so that no errors will result from the machine operators not being able to easily read the data given.

—Willet T. Van Velzen, “Bird Banding Notes”, April 1965

https://d9-wret.s3.us-west-2.amazonaws.com/assets/palladium/production/s3fs-public/media/files/Vol.5%20No.02_041965.pdf

However, one issue with this process of computerization was in recording the bird species. Bird information was recorded on banding schedules, but entering species was tricky and error-prone. Birders in North America use common names like “Black-capped chickadee”, not scientific names like Poecile atricapillus, and neither of these names are easy to write down quickly. Various banders used ad-hoc abbreviations but eventually they were standardized using a system called alpha codes, banding codes, or simply bird codes. These were first proposed in 1978 in a paper entitled “Standard abbreviations for common names of birds” by M. Kathleen Klirnkiewicz and Chandler S. Robbins. Unlike previous systems, these had a consistent four-letter code based on mnemonic rules. It might appear that four letters might not be enough as there are over ten thousand bird species worldwide, but this was only for the 1,686 species and subspecies of birds in the Checklist of North American Birds, 5th ed. (1957). [1]

The paper itself is just 10 pages, about 9 of which are tables of bird codes and appendices. The introduction succinctly explains what the purpose of the codes are:

During the past two decades banders have taken their work more seriously and have begun recording more and more information regarding the birds they are banding. To facilitate orderly record-keeping, bird observatories (especially Manomet and Point Reyes) have developed standard recording forms that are now available to banders. These forms are convenient for recording banding data manually, and they are designed to facilitate automated data processing.

Because errors in species codes are frequently detected during editing of banding schedules, the Bird Banding Offices feel that banders should use species names or abbreviations thereof rather than only the AOU [American Ornithologists’ Union] or species code numbers on their field sheets. Thus, it is essential that any recording form have provision for either common names, Latin names, or a suitable abbreviation. Most recording forms presently in use have a 4-digit field for abbreviated common names; however, abbreviated common names should not be used on banding schedules.

It’s especially interesting to see their comparison with previous systems:

The purpose of this paper is to make available a system for common name abbreviations.The system is presently being used by us and others, and it has decided advantages over the list published by Stamm (IBBA News 39:46-48) and other systems that have been developed by various banders for their own use.

Before developing the system described here, we had tried using the Stamm abbreviations but found that the codes had to be memorized individually since no standardized procedure had been followed. Thus, it was easy to inadvertently write down the abbreviation for the wrong species. The Stamm abbreviations are of variable length (1 to 4 digits). For example, he adopted C for Canvasback and CA for Cardinal. Under the proposed system every species is given a 4-letter abbreviation (CANV for Canvasback, CARD for Cardinal). In the Stamm list, the family name precedes the species name, but in the proposed system the name is written in the sequence in which it is given in ordinary speech (Song Sparrow rather than Sparrow, Song)

The system they propose is straightforward and easy to remember:

The system we propose follows five simple rules for abbreviating:

1. If the common name is a single word, use the first four letters, e.g., Canvasback, CANV.
2. If the common name consists of two words, use the first two letters of the first word, followed by the first two letters of the last word, e.g., Common Loon, COLO.
3. If the common name consists of three words (with or without hyphens), use the first letter of the first word, the first letter of the second word, and the first two letters of the third word, e.g., Pied-billed Grebe, PBGR.
4. If the common name consists of four words (with or without hypens [sic]), use the first letter of each word, e.g., Great Black-backed Gull, GBBG.
5. If the common name consists of five words, treat it as four words, e.g., Puget Sound White-crowned Sparrow, PSWS.

There are a few exceptions to the rules to distinguish two species that would otherwise have the same abbreviation. [ … ] The 28 exceptions to the five standard rules are listed in the Appendix.

The last thing they say is a warning not to use the abbreviations as actual names for bird species:

We must stress that the 4-digit abbreviations are strictly for the convenienceof banders in their own records and should never be used as a substitute for common or scientific names on schedules submitted to the Banding Offices.

In the decades since their 1978 publication, these abbreviations have been a roaring success. For shorter common bird names, like “blue jay”, the advantage of “BLJA” for recording purposes may not be so apparent, but for a longer name like “Double-crested Cormorant”, “DCCO” is much faster. These abbreviations have experienced a renaissance with birders in the smartphone era, as full species names are often tiresome to type out in full on a mobile touchscreen keyboard:

So, why would you want to learn these codes? Birders often use them when messaging each other, or in social media posts and comments, since full names can be cumbersome to type, especially on smartphones. Another big advantage to knowing them is that they are search shortcuts in many bird apps, such as the iOS Sibley and eBird apps (eBird works even if you don’t learn the exceptions).

https://www.lycobirds.com/articles/bird-alpha-codes

On the other hand, these abbreviations have changed a little since 1978 as names for some birds have changed, both common names and scientific names. In 2003 the Institute for Bird Populations created their own standard with tweaked codes kept up to date with the American Ornithological Society:

Alphabetic (“alpha”) codes, abbreviations of English or scientific bird names, have long been employed by ornithologists. They allow quicker data entry than filling out the entire English or scientific name of a species, and they can also serve to cross-check other recorded names or numeric data. The Bird Banding Laboratory (BBL) has long used alpha codes, which have become an integral part of large ornithological programs across North America. However, because of taxonomic and English-name changes and the application of different conflict-resolution strategies, the BBL alpha-code list has become increasingly inconsistent. Moreover, the BBL list excludes most resident species found in Mexico, Central America, and the Caribbean. Because current North American avian conservation efforts (e.g., NABCI - North American Bird Conservation Initiative) include resident species, expansion and revision of the BBL alpha-code list is appropriate. Here we propose two lists of alpha codes for use by North and Central American and Caribbean ornithologists. The first list contains four-letter codes, based on English names, broadly following the rules and strategies adopted by the BBL. This list differs from that of the BBL in that: 1) all 2030 species recorded from the American Ornithologists’ Union (AOU 2002) area are included, as well as 91 non-species forms, many of which were recognized by the BBL; 2) standardized, species-categorization definitions and conflict-resolution formulae have been derived and strictly adhered to; and 3) English names for subspecies, unidentified forms, hybrids, intergrades, morphs, and intermediate morphs, for which alpha codes have been assigned, have been standardized.

They also added a six-letter abbreviation for scientific names for easier identification of species in an international setting:

The second list 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 form. We hope that this list will be useful for ornithologists, particularly those in Latin American countries, who would prefer using scientific rather than English names. These lists can be downloaded from http://www.birdpop.org/AlphaCodes.htm and will be updated every two years, following taxonomic and name changes adopted by the AOU in future biennial supplements.

https://www.birdpop.org/docs/pubs/Pyle_and_DeSante_2003_Four_Letter_and_Six_Letter_NABB_Alpha_Codes.pdf

The differences in the four-letter codes are mostly minor, but personally I find the IBP abbreviations easier to remember:

Complications, and differences between the two systems, arise when two birds would have the same code according to these rules (known as a collision), e.g., Canada goose and cackling goose should both be CAGO. The BBL system gives this code to the Canada goose since it is the more common bird, and gives CACG to the cackling goose. In the IBP system, neither species receives the CAGO code. The cackling goose is still CACG, but the Canada goose is CANG.

https://en.wikipedia.org/wiki/Bird_codes

The current IBP abbreviations can be found here:

https://birdpop.org/pages/birdSpeciesCodes.php

e.g. as PDFs:

• https://birdpop.org/docs/misc/Alpha_codes_tax.pdf
• https://birdpop.org/docs/misc/Alpha_codes_eng.pdf
• https://birdpop.org/docs/misc/Alpha_codes_sci.pdf

It’s fun to look for English words in the abbreviations, such as:

• BREW (Blyth’s Reed Warbler),
• BRAM (Brambling)
• BRAN (Brant)
• BRAT (Bright-rumped Attila)

Relevant links:

• https://en.wikipedia.org/wiki/Bird_codes
• https://scbirdcl.org/AlphaCodes.html
• https://www.birdpop.org/docs/misc/Alpha_codes_eng.pdf
• https://www.carolinabirdclub.org/bandcodes.html
• https://www.vaworkinglandscapes.org/wp-content/uploads/AlphaCodes.pdf
• https://www.lycobirds.com/articles/bird-alpha-codes
• https://birding-world.com/bird-species-alpha-codes/
• https://www.bsbo.org/uploads/3/0/8/0/30807041/banding_codes.pdf
• https://schechterguides.com/bird-codes
• https://alphacodes.net/about.html