In these cases, two names abbreviate to the same code under the rules, but since one of the colliding names is so much more common than the others, the commoner name is allowed to use the collision form and the rarer name is assigned an alternate. The author feels that this practice is highly unsafe.
1. BAGO Barrow's Goldeneye BRNG Barnacle Goose 2. BBWA Bay-breasted Warbler BWAG Black-backed Wagtail 3. BRSP Brewer's Sparrow BANP Band-rumped Storm-Petrel 4. BRWA Brewster's Warbler BRWX Black-rumped Waxbill 5. CAGO Canada Goose CACG Cackling Goose 6. GCWA Golden-cheeked Warbler GOLW Golden-crowned Warbler 7. GRFL Gray Flycatcher GREF Greater Flamingo 8. GRWA Grace's Warbler GRAW Gray Wagtail 9. OCWA Orange-crowned Warbler ORAW Orange-cheeked Waxbill 10. RTHU Ruby-throated Hummingbird RUFH Rufous-tailed Hummingbird 11. SOSP Song Sparrow SOOP Sooty Storm-Petrel 12. SPSA Spotted Sandpiper SPOS Spoonbill Sandpiper 13. STFL Scissor-tailed Flycatcher STOF Stolid Flycatcher 14. STSA Stilt Sandpiper SHAS Sharp-tailed Sandpiper 15. WCPI White-crowned Pigeon WHIP White-cheeked Pintail 16. WHSW Whistling Swan WHOS Whooper Swan