My parents don't have cats on their acreage (on account of all the vehicles), but my dad uses homemade traps that work very well. Take a 5 gallon pail and put grain or birdseed in the bottom, enough to cover the bottom. Then put a stick up the side of the pail. They run up, fall in, and then can't get back out. Then you deal with them or they'll get hungry and dry up. If you have a cat or dog they enjoy playing with the prisoners before they dispose of them.
