The author checked the six-letter system for collisions by writing a computer program that applies the rules mechanically to each name, and then running the program on a file of all the species names from the current AOU Check-List.
Only nine two-way collisions were found. There were no three-way collisions. Here is a list of the collisions and their resolutions. For safety's sake, both species involved in a collision are given substitute codes.
Wrong Right Name
------ ------ ----
BAROWL BRDOWL Barred Owl
BRNOWL Barn Owl
BLAWAR BKBWAR Blackburnian Warbler
BKPWAR Blackpoll Warbler
BLUGRO BLUGRB Blue Grosbeak
BLUGRS Blue Grouse
BRSPET BRIPET British Storm-Petrel
BARPET Band-rumped Storm-Petrel
BTGWAR BTNWAR Black-throated Green Warbler
BTYWAR Black-throated Gray Warbler
GOCWAR GCHWAR Golden-cheeked Warbler
GCRWAR Golden-crowned Warbler
LESPET LCSPET Leach's Storm-Petrel
LSSPET Least Storm-Petrel
RUTHUM RTHHUM Ruby-throated Hummingbird
RTLHUM Rufous-tailed Hummingbird
SPOSAN SPBSAN Spoonbill Sandpiper
SPTSAN Spotted Sandpiper
Using the six-letter system with names other than standard species names leads to more collisions. Some involve obsolete names, or forms that have never been accepted on the standard checklists. These are included to allow handling of older names and names from rejected or hypothetical records.
Here is the list of all the additional collisions encountered after using this code system for over ten years of work with CBC and other field records of all kinds.
Wrong: Right:
------ ------
BELSPA BLDSPA "Belding's" (Savannah) Sparrow
BLLSPA "Bell's" (Sage) Sparrow
BUFBOO MASBOO "Blue-faced" [=Masked] Booby
BFOBOO Blue-footed Booby
CATHAR CATHAC Catharacta sp.
CATHUS Catharus sp.
COLUMB COLBA Columba sp.
COLBID columbid sp.
COLBIN Columbina sp.
DENDRO DENCYG Dendrocygna sp.
DENICA Dendroica sp.
FRINGI FRINLA Fringilla sp.
FRINID fringillid sp.
FRININ fringilline sp.
HARHAW HRLHAW "Harlan's" (Red-tailed) Hawk
HRSHAW Harris' Hawk
INHMYN COMMYN Indian House [=Common] Myna
HILMYN Indian Hill [=Hill] Myna
PASSER PASR Passer sp.
PASINA Passerina sp.
PASINE passerine sp.
PROCEL PROCID procellariid sp.
PROCIF procellariiform sp.
WILWAR WLSWAR Wilson's Warbler
WLWWAR Willow Warbler
YELLOW YELLEG yellowlegs sp.
YELTHR yellowthroat sp.
Note: Names starting with "Mc" or "Mac" are
treated as one word. Code MAGWAR would otherwise
be a collision between MacGillivray's and Magnolia warblers.