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4.3. Rules for the six-letter code system

As with the Bird Banding Lab's four-letter codes, six-letter codes are derived by abbreviating the name of the bird. Names are not limited to standard AOU species names. Codes may be based on obsolete names (e.g., Short-billed Marsh Wren), subspecies names (Peale's Falcon), color morphs (Blue Goose), or even vague categories like “raptor” or “Empidonax sp.”

  1. Birds with one-word names are abbreviated by taking the initial letters of the name:

    CANVASCanvasback
    RUFFRuff
    MURRELmurrelet sp.
    EMPIDO Empidonax sp.
  2. For two-word names, take the first three letters of the first word and the first three letters of the last word. Hyphenated words are always treated as separate words:

    CEDWAXCedar Waxwing
    LARFALlarge falcon sp.
    STOPETstorm-petrel sp.
  3. For three-word names, take two letters from the first word, one from the second, and three from the third:

    BABWARBay-breasted Warbler
    GRPCHIGreater Prairie-Chicken
    DABSHEdark-backed shearwater sp.
  4. For four or more words, take one letter each from the first three words, then the first three letters of the last word:

    GBBGULGreat Black-backed Gull
    BCNHERBlack-crowned Night-Heron
    BTBWARBlack-throated Blue Warbler
  5. To reduce the number of conflicts, certain similar color names are abbreviated in standard ways:

    Color nameThree-letter formTwo-letter form
    greenGRNGN
    grayGRYGY
    blackBLKBK
    blueBLUBU
    brownBRNBN

    Examples:

    BLKPHOBlack Phoebe
    GRYJAYGray Jay
    GNWTEAGreen-winged Teal