Really, if the direct approach with the owners in hopes of educating them on the pitfalls of free roaming cats isn't feasible for some reason (hey, sometimes you have a Hatfields and McCoys scenario brewing), or has failed, release the hounds on sight of the fangy feline and let them chase it away. You do have dogs I trust. So your dogs will get their exercise and it fulfills their chase instinct. They love it! Repeat this often enough in a short enuff time frame and the cat will find another hunting territory where it meets no resistance or fears its own predatation. I have employed this more than once. No harm has come to any cat since they are too agile and can climb anything. Of course this outcome is not quite guaranteed; but wild, protected songbirds ought not to be victimized by domestic cats, period. Refer back to the aforementioned "chat" on that score.
Of course there's always fireworks....you got yer bottle rockets, the dreaded sparklers, and some others but those are illegal within most municipalities and as such I wouldn't know anything about this sort of tactic.