Nest boxes should be cleaned before and after each nesting season. Nests can harbor harmful bacteria and parasites, and throughout winter birds may use your houses to shelter from cold nights so you need to make sure they're been cleaned out before the next nesting season begins. 

First, put on some disposable gloves (some people also like to use a face covering for extra protection). Then you'll need to open up each box and remove all nesting material and scrape out any feces that may have accumulated on the walls or floor. Dirty nesting boxes can attract rodents, mites and bacteria that can be hazardous to birds. Any nesting material and other debris needs to be properly discarded to keep pets and other critters from getting to it. 

Next, scrub or soak each box with a solution made up of one part chlorine bleach and nine parts hot water and allow to sit for a few minutes (you can also use a 1:1 water to vinegar solution). Once clean, rinse the boxes with hot water to make sure all the solution is completely removed.

Before you put the boxes back up, let them dry thoroughly in the sun to ensure that no mold grows on the inside of the box.

Now your boxes are ready to provide safe housing for this spring and summer's baby birds!