At the risk of further beating a dead horse, here are the rules used by the U.S. Geological Survey's Bird Banding Laboratory (BBL) for constructing 4-character species codes ("alpha codes") from the common names of North American birds. After unsuccessfully searching the BBL web site, I obtained this material from http://infohost.nmt.edu/~shipman/z/nom/bblrules.html.
Perhaps more than you wanted to know, but a few folks had expressed interest in the "rules." ---Ron Refsnider ========================== *The BBL code system: Rules for forming the codes* The US FWS Bird Banding Lab codes were introduced in: Klimkiewicz, Kathleen, and Chandler S. Robbins. Standard abbreviations for common names of birds. North American Bird Bander 1978, 3:16-25. Codes are formed using these rules: 1. If the name consists of only one word, the code is taken from the initial letters, up to four: DUNL Dunlin DOVE Dovekie OU Ou GADW Gadwall 2. If there are two words in the name, the code is made from the first two letters of each word: AMWI American Wigeon EAME Eastern Meadowlark 3. For three-word names where only the last two words are hyphenated, the code uses two letters from the first word and one each from the last two: EASO Eastern Screech-Owl WEWP Western Wood-Pewee 4. For other names with three words, the code takes one letter each from the first two words and two from the last word: RTHA Red-tailed Hawk WWCR White-winged Crossbill WPWI Whip-poor-will 5. For four-word names, the code takes one letter from each word: BCNH Black-crowned Night-Heron ASTK American Swallow-tailed Kite NSWO Northern Saw-whet Owl A /collision/ is a situation where two or more names would abbreviate to the same code using these rules. The Bird Banding Lab decides what code to use in these cases. If one name is far more common than the other name or names involved, typically the common species gets to use the name. In most cases (e.g., Lark Bunting and Lazuli Bunting) when both birds are common, the collision code is not used, and unambiguous substitutes are provided for both forms.