I've eaten several ruddy ducks. I like to soak them in brine over night, then give 'em a nice olive oil sprinkle.... then salt, pepper, and garlic powder. If you're just doing breasts, then you can fry then in olive oil, or grill 'em. If you're doing them whole, then I would cut them in half and grill them. Put the fat side down, and let that cook until the skin and fat are nice and crispy, then flip over the no more than 2 minutes.