How To Clean Out A Birdhouse Or Nest Box

Cleaning out a birdhouse or nest box is just one of those winter gardening chores we should do each season. In fact, depending on the situation you should do it at the end of each brood and nesting boxes is a good practice to try to minimize parasites, disease, and mites.

In this article I’m going to give you the process/procedure to clean and disinfect a birdhouse. The entire job should only take 10 minutes or so. Afterwards I will discuss in more detail the debate on whether cleaning out old nests is necessary, what kind of parasites/diseases can infest nest boxes and birdhouses, and some closing thoughts.

• How to clean out a birdhouse / nest box
  • Materials
  • Cleaning procedure
• When to clean out a birdhouse / nesting box
• Do bird houses / nest boxes need to be cleaned out?
• Diseases / parasites/ pests that can infest a birdhouse
• Benefits
• Final thoughts

How to clean out a birdhouse / nest box

Materials

The following materials should be gathered to clean out a birdhouse.

• Spray bottle
• Bleach
• Scrub brush
• Old tooth brush
• Hose or pump sprayer filled with tap water
• Tool to open birdhouse (screw driver, pliers)

Does a birdhouse need to be disinfected?

Looking at the materials list you are probably asking yourself if you really need to scrub the inside of a birdhouse. The answer to that will be determined by the conditions inside.

If you open the birdhouse and see fecal matter on the walls or evidence of spiders in the house (spider egg sacks) then you should consider giving it a scrub with a 1:10 bleach and water mixture. That will disinfect and kill any bacteria or mites that may be lying dormant.

If you open the nest box and it is just a plain nest, then you can simply toss it out and brush away any remaining nesting material. No bleach needed.

Process to clean out bird house or nest box

1 – Open the birdhouse

The first step is obviously to open the bird house. Depending on the style this may require loosening some screws or just pulling a nail to release a door. (My preferred opening style relies on just a single nail to secure the wall).

2 – Remove and inspect the nest

Examine the bird nest. Look for spider egg sacks, larvae, bird fecal matter or other debris. Depending on what you see you may wish to disinfect the walls of the house.

3 – Brush out the birdhouse / nest box

Use a wire brush and old toothbrush to remove any nesting materials. The toothbrush can be helpful for making sure any drain holes are cleared and unobstructed.

4 – Disinfect the walls and floor

If you found that the walls were soiled, or evidence of overwintering insects, you should disinfect the walls and floor of the birdhouse. Spray a 1:10 mixture of bleach and water onto the walls and scrub. This will disinfect and kill any bacteria or eggs that may be present.

5 – Rinse the walls and floor with water

Use a hose or pump sprayer to then rinse the walls and floor with water. This will remove any bleach or harmful fumes from the birdhouse/nesting box.

6 – Dry the birdhouse / nest box

Dry the birdhouse/nesting box for several days. It is best to do this in the sun. But you can leave the birdhouse mounted to dry if you can keep it open, ensuring lots of airflow.

For bluebird nesting boxes I can prop open the door by simply using a stick as shown below.

7 – Reassemble the birdhouse / nest box

Once the walls and floor are fully dry, you can reassemble and close up the nesting box.

RELATED – Overview of Nest box and birdhouse designs.

When to clean out a birdhouse or nesting box

You can clean out a nesting box as long as it is not being actively used. So, this can be done anytime before or after the active brooding season. Below you can find a table listing common species of bird who use birdhouses, nest boxes, or nesting platforms, when they nest and what time of year the birdhouse/nest box should be cleaned out.

Bird Species	Nesting Season	When to clean out birdhouse / nest box
American Robin	April – August	Remove nests from platforms or nesting shelves from September through March
Black-capped Chickadee	April-July	September through February
Carolina Chickadee	March-July	August through February
Carolina Wren	March – October	November through February
Eastern Bluebird	Febrary-September	October through January
House Wren	April – September	October and March
Mountain Bluebird	April-September	October to March
Tree Swallow	May-July	August and April
Tufted Titmouse	April-July	August through March

Do birdhouses really need to be cleaned out?

In nature birds that use nesting cavities such as hollowed out dead trees don’t empty them before starting a new nest. So, should we do this in birdhouses and nest boxes? This can be a complicated question, one that is still hotly debated in the birding community and within science.

Some research has found that Bluebirds will prefer to reuse old nesting materials by a large margin.[1] While others have found the exact opposite result![2] So what is the correct answer? Well, let’s take a look at the studies.

The study that found old nests [davis 1994] were preferred by Bluebirds hypothosized that the old nests may harbor larvae of a wasp, Nasonia vitripennis. The larvae from this wasp will actually kill and eat the blowfly larvae, and thus the researchers concluded that the Bluebirds are aware that old nesting sites should be better protected from blowfly larvae.

In a later study [Stanback et al, 2001] the researchers found a strong relationship of Bluebirds (and other species) avoiding nest boxes or areas that have a high parasite infestation. They found that their preferences changed over the years due to the amount of parasites present at nesting sites. So, while a bird may not be opposed to using a successful nest box again, it would avoid using one with a high number of parasites.

First, and I will come back to this point sort of as an ‘anchor’, ectoparasites such as blowfly larvae will harm nestlings. Nests with ‘heavy’ blowfly infestations result in fewer successful fledglings.[3] And no matter what you do, at some point your birdhouse or nestbox will likely become infested with blowfly larvae. [4]

Now, if one were managing many nest boxes across a large area, cleaning out each nest box could be quite a job. And one may consider only removing old nest material to save on labor, or perhaps only clean nest boxes out every other year. However if you have a regular suburban yard with 1-2 birdhouses, then a full sterilization at the start of the brooding season shouldn’t take more than 30 minutes of work.

What kind of parasites and diseases can infest birdhouses?

Blowfly larvae

Of particular concern to Bluebirds, blowfly larvae will attack baby birds and bite/suck their blood. Some surveys have found as much 80% nest boxes will be infested with parasites (Calliphoridae). Nest boxes that are not parasitized have more young survive to fledge the nest. [3][7]

The lifecycle of the Blowfly larvae is important to understand. In Spring, after nesting has begun Blowflies emerge. They have evolved to mate and lay eggs in birds nests. And thus their larvae will attach themselves to baby birds at night, and that is how they feed. For the species that attacks Bluebirds, they complete their larvae stage in 11-13 days, which is roughly the timespan of a baby Bluebird from hatching to fledgling.

Wasps

But the food chain doesn’t end with the blowfly larvae, as there is a wasp parasitic (Nasonia vitripennis) who will lay it’s eggs on blowfly larvae, thus killing them. If these wasps are present, they can significantly reduce the pressure on nestlings by killing the blowfly larvae. And, these wasps will overwinter in nest boxes. It has been suggested that removing nests in Fall or Winter will result in the death of these wasps, and therefore you should not remove old nests until very early Spring, prior to the breeding season. [1]

Mites

Feather and other mites have been found bluebirds, with some surveys finding more than 90% have some mites on their feathers. [5] Abundant infestations may harm fledglings whose feathers are not fully formed, reducing skill and ability in flying, which just adds risk to their already precarious existence.

Salmonella

Just like us, birds can become infected with Salmonella. Parents that pick up the disease from other birds near feeders or foraging insects may transfer it to their young. And, Salmonella is harbored in fecal matter.[6] While Bluebird parents tend to remove all fecal matter from the nestlings, as the babies grow often some will be missed. I often find bits of bird fecal matter on the interior walls when I clean them out and disinfect them.

Benefits of cleaning out a nest box

Keeping the nest lower in the box

Some birds who use nesting boxes will not reuse a nest, but build a nest directly on top of the old one. This raises the nest height closer to the hole, which can lead to some problems I will describe below. But this really does happen – I’ve seen it first hand when in 2022 I had a nest box used by Chickadees who successfully fledged 5 young. After they left, the nest box was taken over by House Wrens who proceeded to build a new nest of sticks on top of the Chickadee moss nest!

The lower the nest is inside the box, the longer the young will stay in the nesting box, which means stronger fledglings. Every day the nestlings stay inside, the more feathers they grow meaning the better they will be able to fly (which is a birds main defense). Also, the lower the nest is inside the box means it is harder for raccoons, opossums, and cats to reach in and grab the mother or babies. [8]

Now, if one really wants to avoid those predators the best method is probably a Noel Predator Guard. I have detailed instructions on how you can make you own.

Sterilizing

Sometimes birds who roost in nest boxes can be a bit messy. As the babies grow there is less room, and thus they aren’t as concerned with cleaning out fecal matter, resulting in a dirty nest box. A dirty nest box can easily harbor harmful diseases, mites or bacteria, and make for a more suitable home for future problems.

Final thoughts

Cleaning out a birdhouse or nest box in your yard is a small chore that has a real potential to reduce disease and parasites on Bluebirds. Whether you need to do this or not is still hotly debated, but the real answer I believe is for you to observe your nest boxes. If they are not being used, it may very well be due to a heavy infestation of parasites. If that is the case, then the answer is clear – you should clean and disinfect them.

Nonetheless I’ve not found any reason to ‘not’ clean them out, at least in early Spring. Doing so at this point should preserve any wasps that may be wintering in an old nest. And sterilizing any of the fecal matter seems like common sense. I have three bird houses on my 1/2 acre, and this job really doesn’t take much effort. The way I see it, birds have a tough existence as it is, and if I can do a little chore that raises their chances of successfully fledging a brood, then by all means I should do it.

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