From my bird book:
Diet - insects, oily seeds, sometimes berries. So for seeds, anything which can make oil, such as flax, rapeseed, peanuts etc, but not cereals.
It's very annoying when the birds flick perfectly good and nutritious seeds onto the ground. There are plenty of birds which prefer to eat from the ground, but if you're wanting to attract birds such as tits and gold finches, those nuthatches must be driving you crazy.