It really just depends on where you are huntin. If hunting small lakes, then you could get away with 1-2 doz, but when hunting large lakes, and bays, the ducks really like numbers. Sure the painted mallards will work, I got about a doz in my spread, but when looking out at your spread on an early morning, what do ya see???? a bunch of black silos. I think the ducks focus more on the shape, then anything else. Like matt said, divers have a sloping back, and they ride real low in the water, unlike puddlers.