Four-Letter Bird Codes (FLBCs)

Kent Fiala

Four-letter codes are commonly (and too often incorrectly) used as a short-hand way to write a bird name. Two different sets of codes are in use. The first codes were created by the Bird Banding Laboratory (BBL) for use by bird banders in submitting data; consequently the codes are frequently referred to as “banding codes”. A slightly different set of codes has been published by the Institute for Bird Populations (IBP).

The basic codes were derived from a simple set of rules for reducing a name to four letters. A major problem is that the rules can create “collisions”; cases where two (or more) different names reduce to the same four letters. In these cases, different codes had to be created ad hoc. Unfortunately, if you want to use the codes, you simply must memorize the special cases; there is no way around it. Worse, the BBL and IBP code sets differ in some of these ad hoc codes.

Here is a summary of the basic rules:

1. If the name is one word, the code is the first four letters.

      DICK Dickcissel
      SORA Sora
   

2. If the name is two unhyphenated words, the code is the first two letters of each word.

      MODO Mourning Dove
      AMRO American Robin
   

3. If the name is three words, the code is the first letter of each of the first two words, and the first two letters of the third word. A name of three hyphenated words is treated the same way.

      GCFL Great Crested Flycatcher
      AWPE American White Pelican
      CWWI Chuck-will's-widow
   

4. If the name is a word and a pair of hyphenated words, the code is the first two letters of the unhyphenated word and the first letter of each of the hyphenated words.

   Hyphenated word first (coded essentially the same as a three-word name):

      BTGR Boat-tailed Grackle
      RTHU Ruby-throated Hummingbird
      RTHA Red-tailed Hawk
   

   Hyphenated word last:

      EASO Eastern Screech-Owl
      EAWP Eastern Wood-Pewee
   

   There are a very few bird names where the first word contains two capital letters. Such words are treated like a hyphenated word:

      LCSP LeConte's Sparrow
      MGWA MacGillivray's Warbler
   

5. If the name has four parts, either separate words or hyphenated parts, the code is the first letter of each part

      BCNH Black-crowned Night Heron
      NRWS Northern Rough-winged Swallow
      BBWD Black-bellied Whistling-Duck
   

Note that it should go without saying that in order to use these rules, you MUST know exactly what the bird's name is. You MUST know that it's American Robin, not just Robin. You MUST know that it's Tricolored Heron, not Tri-colored Heron.

There are no published rules for resolving collisions in the BBL system, but I have observed the patterns below. First, note that the basic rules for two- or three-word names divide the name into a “first name” and “last name”, or specific name and group name, and the specific name always gets two letters and the group name two letters. Most of the ad hoc cases deviate from this equal division between specific name and group name.

• The most common way of resolving a collision is to take three letters from the specific name and only one letter from the group name. For example, Carolina Wren, Cactus Wren, and Canyon Wren all reduce to CAWR, so unique codes were obtained by taking three letters from the specific name and only the W from Wren: CARW, CACW, and CANW.
• When the above rule still does not provide unique codes, then the code may be made by using only one letter from the specific name and three letters from the group name. For example, Northern Shoveler and Northern Shrike both reduce to NOSH by the basic rules, or NORS by the above rule, so the actual codes are NSHO and NSHR.
• If both of the above rules still fail to create unique codes, another possibility is to use the first and last letters of the specific name instead of the first two letters. Thus, the codes for Barred Owl and Barn Owl are BDOW and BNOW (in the BBL system. The IBP codes are the much less intuitive BADO and BANO, and unfortunately eBird uses these).
• The “last letter” approach is also used in some four-word names. For example, Black-throated Green Warbler is BTNW and Black-throated Gray Warbler is BTYW, using the last letter of the distinguishing word.
• There are some cases that don't fit any of these rules, for example BRNG for Barnacle Goose and BAGO for Barrow's Goldeneye.

When codes collide, usually all of the involved species take ad hoc codes. But in some cases where one species is rare or has a limited distribution, and the other is commoner or more widely distributed, the ad hoc code may be only used for the less common species. This is illustrated by the last example above, where Barrow's Goldeneye keeps the basic code BAGO even though it could be confused with Barnacle Goose, which gets an ad hoc code.

Some specific problems with the BBL codes relate to their primary purpose for banding. For some species, no official code is provided. For example, the BBL does not oversee banding of gallinaceous birds, so it provides no code for them. Also, they tend to retain established codes rather than update them as nomenclature changes. For example, they retain CAGO for Canada Goose even though Cackling Goose is now recognized as a species. And sometimes they provide only specific codes for recognizable forms rather than an over-all code for a species. For example, they have several codes for various forms of Snow Goose, but SNGO is not an official code for the species. The codes from the IBP address these problems.

As you can see, there are many reasons not to use these codes. The foremost reason is that they are a barrier to communication with people who do not know the codes. Another reason is that you are likely to make mistakes, and years later when you refer back to your notes you may find yourself unsure which species you actually meant. Nevertheless, you can't stop people from using the codes so it's best to try to learn them. I suggest that the most appropriate use of the codes is for quick taking of field notes that you will transcribe before you forget what you meant (and will not use to communicate with others). If you are already a user of the codes, I predict that if you study the table carefully, you will discover at least a couple of species for which you've been using the wrong codes.

The table below lists a suggested code for each species that might be recorded in the Carolinas. This code is either the BBL code; or if none is provided, the IBP code. If the code is an ad hoc code rather than one that comes from application of the basic rules, there is an asterisk in the Exception column. If the IBP ad hoc code differs from the one from BBL, it is listed in the Alt. code column. For ad hoc codes, the reason that the basic code cannot be used is explained in the Conflict with column. The code for the conflicting species is also given there.

Both BBL and IBP list numerous codes for recognizable forms other than species. A few of these are listed in a second table; see the original sources for others.

The table below lists a sample of codes that are defined for forms that are not species. See the original sources for others.