I see Jon has created a Bands observed field, so I have added that as an option when adding observations to this project.

You can go back and add that field to observations already added to the project. No strict format, but for birds generally note colours and metal bands, left leg first, in a format like "metal/yellow, red/white/dark green"

(click on the journal's title (above) to see the discussion/comments section for this project)