It's not cedar, just regular. I have noticed them eating at it and wondered that as well. I know the bantams seemed to have their poop, for lack of better words, stuck and I tried to clean it off of their bottoms. The reds are having no problems going. I even heard one squirt it out tonight...
I just got my first chicks ever on March 17th, I got 6 red pullets and 4 bantams from the local Tractor Supply Co. I put them in a 40 gall rubbermaid hard plastic water tub for horses. I put a mixture of sawdust and shavings on the bottom, a 1 gallon waterer, and a 24% Dumor chick starter feed...