I'm sorry, that's... not actually what Alpha Codes are.
Alpha codes have to do with birding. And like... field notebooks.
Er, yes. Let's get on with it, then.
Alpha codes are 4-letter or 6-letter sequences that represent specific bird species. These codes were created for the use of bird banders, who catch, document, and then release wild birds. These banders have to work quickly. Writing out the entire species name is a waste of time. So, they have shorthand alpha codes.
A bit of history! The first nationally recognized alpha codes were distributed by the U.S. Bird Banding Laboratory. These codes were used for a very long time. However, they didn't account for bird species found in Mexico and Central America. So, in 2003, Peter Pyle and David Desante created a new set of codes that did cover those species. These codes come in two flavors for each bird: one 4-letter code based on the species' common name, and one 6-letter code based on its scientific name. These codes can be found here. All species found in North and Central America, plus the Caribbean, have two assigned codes. (The historical information came from here, the Institute for Bird Populations.)
Yes, that's a really long list, but don't worry! You can use the Find feature (control+F) to find the species that you need. And once you've looked up a particular bird a few times, you'll memorize its code. They're pretty intuitive. If a bird's name is one word, its 4-letter code is just the first four letters, like Gadwall becomes "GADW." If a bird has two words in its name, the 4-letter code is usually the first two letters of its first name and the first two letters of its last name. For example, House Sparrow is "HOSP." If a bird has three words in its name, the code is usually the first letter of the first name, the first letter of the second name, and the first two letters of the last. Great Blue Heron --> "GBHE," or Red-winged Blackbird --> "RWBL." These tricks don't always work! Sometimes two species have similar names, like Barn Swallow and Bank Swallow. They can't both have the code BASW. So, they get special names, like Barn Swallow --> BARS and Bank Swallow --> BANS. These codes can be tricky, but with a bit of patience, you'll figure them out.
Now, you have a cool language to scribble into your notebook! It's quick and easy. Non-birders won't have a clue but birders will get it immediately. Join the clique. This is what my notebook looked like after my birding trip this morning. If you want you can try to figure out what birds I found! Just so you know, my notes are a bit silly. (oh also the *'s mean 100 birds each)