Quiet doesn't solve the visual problem. The pigeons are in the front of the house. I can't go out there with a pistol and hope that no one see me and calls 911. There is no window that I can shoot out of and ping the pigeons. I need other solutions. SL suggested a few - I'll keep working on it. I did ping them with my pellet pistol, and I think I might have wounded one enough that it died later, but it's not reliably lethal.
OK. Feed them. Mix in metal shavings from a local machine shop.
It takes a few days for them to die, which they will do elsewhere, one by one.
No pesky dead birds laying around your house to alarm the neighbors...