Birdhouses are an excellent way to help our feathered friends with shelter to raise their brood, but these houses need to be cleaned every year, since parasites and illness-causing bacteria can live inside. Wearing rubber gloves, remove the old nest from inside the birdhouse; you can leave it in the grass to decompose naturally. Then use a mixture of 1 part bleach to 9 parts hot water and spray the birdhouse to disinfect it. Scrub it with a sponge. Place the birdhouse in a sunny spot to dry out. Once you reinstall it, new birds will quickly make it their home.