How do I get rid of annoying chickens?

Okay long story short my mom put cat food out in our backyard for the cats that live outside, but a few weeks later we had 3 hens and a rooster show up and they've started eating all the cat food. I've hit them w/ a broom, rocks, sticks, poles, you name it and I've either thrown or hit them w/ it and they still insist on coming around. I'm at my wits end w/ these stupid chickens, can anyone tell me how to get rid of them w/o taking away the cat food and water or killing the chickens themselves? I don't know who they belong to either.