The author has written a computer program to analyze the Bird Banding Lab code system. This program forms the codes according to the rules, and then produces a report showing all the cases where there were collisions (two or more names abbreviating to the same code) or for some other reason the BBL code is not the one expected by the rules.
Collisions involving birds found in the AOU Check-List but absent from the ABA Checklist have been omitted.
A total of 102 names were involved in collisions. Usually, substitute codes are given to both forms involved in a collision. When one of the forms is fairly rare, however, the BBL has allowed the common form to use the collision code---which I consider a very dangerous practice.