Do I need to clean out my nest box and how often?

The best practice is to clean out any nest box that has been occupied after the breeding season. You simply remove the front, slide out the inner liner, dump it, and place more mulch inside. This will safely be done anywhere from September to November. However, since barn owls sometimes breed in the offseason, if you do encounter birds, eggs, or chicks at the time of cleaning, just put off cleaning until the next year.