I threw some plugs at those birds working the inflow, yesterday, and a couple of weeks ago.
I don't think you're doing anything wrong, I truly don't think there were any bass there, just tons of bait.
Always remember that the presence of birds and bait does not always indicate the presence of bass.
During the conclave, we had about five boats and ten rods throwing everything you could think of at a big school of noisy pogies, without a sinlge hook-up. I'm convinced that there were no bass amongst those fish either or somebody would have found one...
That's my story, and I'm sticking with it.
Jay