Throw scraps off your deck and after a while they'll start to associate the deck is the magical place where all food comes from. Especially the good stuff like bits of t-bone steaks and red cabbage.
(Yeah, that's what I thought too).
So anyway, in the process of going on explores looking for food on my deck, they have a tendancy to crap there. It makes going in and out the door interesting - kind of like a treasure hunt.
Or walking off a plank.
Gene finally discovered the one thing that will keep the crap off the deck.