Waterfowl bands have a special place in waterfowl hunting. They're not ducks playing music, waterfowl bands are part of a long-running project where wildlife managers trap waterfowl, usually during late summer, and place small metal bands on the legs of ducks and geese to track migrations and populations.
As those banded birds migrate, they are frequently shot by hunters or eventually found dead from other causes, and the information on the band is relayed back to the U.S. Geological Survey and entered into a database. If you've shot a duck or goose with a band, you should report it by going to reportband.gov. After reporting, you will receive a certificate of appreciation that includes where the bird was banded and how old it was at the time of banding.
If you're curious where ducks and geese are banded in Idaho, and where banded birds are shot or otherwise found, go to https://idfg.idaho.gov/hunt/rules/migratory and scroll to the bottom of the page and click on the link.
The map on the website is interactive, so you can click on the location of the individual birds and tell where and when the birds were shot or found. The map also shows the location of where birds are banded, and the database goes all the way back to 1914. For example, you can see a mallard banded in September, 1914 at Utah's Salt Lake was recovered (presumably by a hunter) near Lava Hot Springs in January 1915. You can also sort the database by bird species.
The information bands provide has been used in North America from present through the early 1900s, but bird banding dates back to the late 1500s in Europe.