You got all kinds of sub-lethal options aside from taking down the bird feeder.
Spray the cat with water. A spray bottle or garden hose should do it. Add a drop of lemon juice or vinegar if you want to really impress the animal.
Throw rocks. Got aim? Lob a small rock at the torso or rear end. Almost hitting the cat counts and will deter them from coming back.
Air gun pellets. I have used this method on one particularly obnoxious, aggressive neighbourhood cat who would cut up our females. Aimed for and hit the rear half of the animal. Molly stayed away for a very long time after that.
She was fine and continued to prowl the neighbourhood -- everywhere except our place.
Have any bear spray on hand? A whiff should deter. Just check the wind before you let fly. Full on in the face exposure at close range could maim or kill the cat. Probably not necessary unless the cat attacks people.