I tried placing on wood, didn't work. My little buggers have made it their daily challenge. I am no longer filling it halfway. If anything I just pour a cup full into the dish instead of unscrewinf the jar and filling it. I'll try hanging it and see if that helps.
I use a small, heavy square plastic, slope sided dog dish, the type they sell at Publix and such. I've found that they don't try to scratch in a small bowl and the wideness of the base makes it harder to tip. The bowl is on hardware cloth in the coop and whatever they spill out gets eaten by the birds hanging out underneath.