Use them or not. To each his own. If you are a bander, you are required
to use the four-letter alpha code and the AOU number when preparing a
banding schedule (report) for submission to the Bird Banding Laboratory.
The Lab issues a bander the alpha code and AOU number for all birds
banded in the U.S.. Plus codes for ages, sex, etc..

To a birder, it's a matter of choice. I favor using the full name.

Gene Kridler
Y.O B.D.B. (Five-letter alpha code for Ye Olde Broken Down Biologist)
ekridler at olympus.net
Squirm, WA