In order to keep birds returning to your houses year after year, it's important to clean them out anually. All my bird houses have some sort of clean out access. See your specific model for instructions. If you have a bird house that cannot be cleaned out, consider replacing it with one that can.

Once there is no more activity in and around your bird houses (usually in late summer or autumn) remove any old nesting material and debris. This can be composted and will often have components such as guanno that can help build better soil.

This is also a good time to do any other maintenance such as painting or minor repairs. When repainting, please remember that most birds prefer natural-looking colors and will generally not nest in brightly colored houses. Good options are always shades of brown or dark green.