Hi, all: I'm brand new to this: I've ordered 15 Buff Orpington pullets and 6 Rouen ducklings which should be arriving in the next few weeks. I'm about to begin constructing my brooder(s) and I need to know how much space per chick I should plan on. How much space does each baby chick need in the brooder? Does this change as the chicks get older? Thanks!