As Harry said, it is easy and quick to use the 4-letter banding codes when note taking in the field, but for reporting birds it is normally better to use common names, for the benefit of those who don't know the codes (probably most folks).

FYI, here is the link for all the 4-letter alph codes.  These are used by bird banders, which is regulated in the U.S. by the USGS Bird Banding Lab:   http://www.pwrc.usgs.gov/bbl/MANUAL/sname.htm

Jeff Shenot
Croom MD