This time of year I sprout wheat seeds for them. Sometimes I feed them as sprouts, sometimes I let them green up a little - the ducks seem to appreciate leafy green things this time of year. Lettuce cores are appreciated also (but make sure you don't have any doofus ducks that choke on things - I have watched mine numerous times and they seem to be able to handle lettuce cores responsibly).
It seems to me a little less expensive to sprout things for the ducks - but I still do purchase greens for them sometimes when I am feeling flush.
Not joking. Really. This is how I think….
I've never heard of sprouting wheat seeds. I'll have to look up how to do it. This morning they gave me 1 egg again and got pineapple that was getting too soft in the fridge for my tastes. We'll see if they like pineapple.