The USF&W 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:
DUNL Dunlin DOVE Dovekie OU Ou GADW Gadwall
AMWI American Wigeon EAME Eastern Meadowlark
EASO Eastern Screech-Owl WEWP Western Wood-Pewee
RTHA Red-tailed Hawk WWCR White-winged Crossbill WPWI Whip-poor-will
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.