I may not be an expert on chickens, but if there's one thing I know it is cats. I have a similar problem, with my dear kitty Ralphie, who insists on napping on top of my warm fish tank. He has caused no harm, and I am a big softy, so I allow him To continue, however I shouldn't. Anyway, it is very easy to keep cats off of things. Just buy a bottle that has a squirting top, like the windex bottles, except NEVER use bottles that have ever contained any type of chemical. You can buy these at a dollar store for like a dollar or so. Fill it with plain tap water, not super hot and not freezing, no matter how much you want revenge on your cat, and squirt him/her whenever they do something bad. DONT just squirt them until there soaking wet, as this can cause bad behavior problems. Also, NEVER squirt them in the face. A neat squirt in the rump is enough to deter most cats. Also, be aware that if you squirt them while in top of the incubator, they will likely launch themselves off and it may tip it over, so you must be prepared for this the first few times. With luck, and patience, you will have a well behaved cat who leaves the tempting warmth of the incubator alone.
Also, if you want further protection, you could get a little heat pad for you kitty, however a nice lap is usually a good source of warmth.
I hope this helps!
