Like everyone else has said, depends on the size of the chicken. My mom's Silkie was killed by a neighborhood cat, but the is no way they could take out my 10 lbs Wyandotte. Non-lethal adverse techniques would work great. The water is good, but you could get an air soft gun, my brother and his friends shoot each other with these, it will leave a bruise, but won't hurt the cat seriously. You could set a live trap and catch them, make the short stay scary with loud noises, water, anything that cats hate, and then release the cat. I would not want to come back.