newbie question: how much do ducklings eat?

[JStark]

Having raised ducklings now for 10 days, I can attest to the fact that they eat a LOT. Quite a lot. And yes, contrary to physics and biology, they poop far more than they eat.

However, I don't know how much they eat, yet, because they also poop into their food quite a bit, so I'm constantly throwing out the wasted food...