Jesse, The four-letter codes were originally created as shorthand for banders. There's a couple of different systems in use, but here's a good source that lists the basic rules you can use to figure out the code for probably 99% of species: https://www.carolinabirdclub.org/bandcodes.html And as for deciphering them, here's a handy alphabetical list: http://www.birdpop.org/DownloadDocuments/Alpha_codes_eng.pdf Hope this helps, Matt Smith Sent from my iPhone > On Jan 5, 2015, at 2:29 PM, "Jesse Yancy" <jlyancy@xxxxxxxxxxx> wrote: > > This might sound simplistic, but I’m often confused by the new abbreviations > that are often used in this forum (TRKI for tropical kingbird, for instance) > and I was wondering if there is some sort of guide to these or are they just > ones birders use as shorthand. > Jesse Yancy >