I just got in from cleaning the boxes my daughters and I put up 2 yrs ago for a winter project. Last year they wern't used(I think I got them in a little too late the spring before). This year all three were used.
. I saw the crews out the other day cleaning boxes onn game lands in my area. Try and find out who does them in your area and see if you could volunteer to help sometime. I am sure they would love the help.
all of the ones i ever did we put a nesting material like woods chips in them ,,be carefull with sawdust it tends to hold too much moisture ,, also make sure the boxes have some small vent holes about 3/8 or 1/2 inch .we put a couple holes at the level of the eggs and a couple towards top of the box