Might want to try airguns instead of shotguns. I doubt it will be legal to discharge firearms anywhere near Brooklyn shores.

Them birds are smart, though. It only takes a couple of plinkings for them learn to fear the sight of a gun. The trouble is: they also learn quick that a gun sitting idle on a table is no threat at all - until somebody goes to use it. They will go about their business as usual as long as nobody makes a move toward the gun...