I can't believe that you actually killed a flying bird with a little old 20ga
Next thing you know you'll be looking for a DH 20 and be taking up Grouse and Woodcock, maybe even Mallards over decoys in flooded timber with the 20. Back in the days of my waterfowling adventures I shot a lot of ducks useing a 20ga Rem 1100 with a skt choke in the timber. Try it you'll like it.