Later this morning someone got hungry or brave. When my husband went to check on them, the whole run was covered in foot prints.
Yeah!
Thanks all for pointers.
After researching, my husband got sand to lay on floor of the chicken run. We got it all ready while the chickens were romping in the yard before bedtime. When it came time to go inside, they were afraid to walk on the sand. They would not go in at first, then when they did, kept smashing...