Black bird with white bill is most likely a coot. Especially if it is pointed. If you want to shoot them, go ahead, nothing wrong with eating a few.
If there is plenty of cover for you to sneak around the edge and through the marsh, then you should do fine jump shooting them. Otherwise, unless you are sitting on the "x", or in a flight path, chances are slim of getting very many within shooting range.
"Sticks and Stones may break my bones, but political correctness is killing me."