Bird codes and banding codes are four-letter nicknames for birds.
This is the most common type of bird code. When the name is two words, the code is uses the first two letters of each one.
When the name is one word, the code is simply the first four letters.
When the name is three words, the code is the first letter of the first two words, and the first two letters of the third.
A hyphen is treated like a space if it occurs at the beginning, but having one at the end flips the order.
When the name is four words, the code is the first letter of each one regardless of hyphens.