You can use wood shavings or coarse sawdust from untreated timber or lumber. What I am using in my nest box is Cat Litter from plant fibre. Biodegradable and dust-free.
AlenAxp Answered question
You can use wood shavings or coarse sawdust from untreated timber or lumber. What I am using in my nest box is Cat Litter from plant fibre. Biodegradable and dust-free.