Go ahead and put the wood shavings in now. Not more than 2 or 3 inches or some eggs will get lost in the shavings. A predator guard is a must. Also, the area inside below the opening must have a rough surface or 1/4" wire mesh attached for the ducklings to climb out. I just cut shallow slits with a skill saw. I do the same on the outside so the hen can grip on and look inside is the wood is smooth. They only do this when first investigating the house, once they are nesting they will fly right in. I'm always amazed they don't bust right out of the back of the house when coming in at full speed. I have 13 house now and I call them time share units as Screech Owls will use them in the winter. I always use cedar shavings, I've been told that cedar deters insects.
