To Clean Or Not To Clean Your Nest Box?

Photo © Steven Liffmann

By Anita Tendler, Cornell Class of 2019

Prior to the breeding season, we make sure that our nest boxes are ready for their future occupants. As the season progresses, we watch the naked hatchlings grow and develop into fully-feathered fledglings. Once the breeding season comes to a close, our nest boxes are abandoned and the leftover nesting material remains, which leaves the question, “What should be done with old nests?”

Nest boxes vs natural cavities

Eastern Bluebirds In A Tree Cavity
Eastern Bluebirds In A Tree Cavity

In natural cavities, birds often must deal with old nesting material that is already present.

Nest selection of natural cavities is quite different in comparison to our handy nest boxes. With a finite number of natural cavities to choose from, most birds can’t afford to be too picky. Birds often choose to reuse successful natural cavities because constructing a nest from scratch requires critical and limited time and energy. However, the threat of ectoparasites (e.g. mites, blowfly larvae) from the old nesting material can also act as a strong deterrent for cavity selection. With most birds not having the option to be choosy with their nest site selection, birds like the Eastern Bluebird simply build atop old nesting material if alternative cavities aren’t available.

Nest boxes provide cavity-nesting species the option to choose among several nest sites. As well-constructed as some nest boxes might be, they are not immune to ectoparasites, the presence of which can deter some birds from occupying a nest box.

Does removing old nests mean fewer ectoparasites?

Some birds have adapted to cope with ectoparasites, so cleaning out your nest box may not have any impact on whether they occupy it. Male House Wrens, for example, clean out the old nesting material between clutches, essentially doing the job for you.

House Wren Readying The Nest
House Wren Readying The Nest

Male House Wrens remove old nesting material between clutches.

To measure whether human intervention was helpful, researchers in Illinois removed old nesting material from some nest boxes that they knew successfully reared fledglings in the prior breeding season (Pacejka and Thompson 1996). With the other boxes left for the House Wrens to clean, the researchers conducted a mite count to determine if there was a perceptible difference. They found that there was no real difference, so regardless of who, or what, cleans out your nest box, mites will still be there.

Not all birds clean house

Bluebirds do not remove old nesting material, rather they simply build over an existing nest. If you do not clean out your nest box, it may become filled to the brim with old nesting material. This can potentially leave the new nest dangerously close to the entrance hole, where predators can easily reach it.

Eastern Bluebird Eggs
Eastern Bluebird Eggs

Some bluebirds prefer a clean nest box, but it depends on location.

To learn whether removing old nests influenced Eastern Bluebird nest box occupancy, a team of researchers in North Carolina erected 100 nest boxes. After a successful first clutch, they cleaned out half and left the others as is. When the bluebirds were left to make a choice to re-nest in a box with a positive association or to avoid ectoparasites, a whopping 71% of them them chose to move to a clean nest box (Stanback and Dervan 2001).

So that means you should clean your nest boxes, right? As compelling as these results are, it’s important to remember that this is situation-dependent. Interestingly, opposite conclusions were reached in a Kentucky study that found that Eastern Bluebirds in that state preferred nest boxes with old nests in them (Davis et al. 1994). There, parasitic wasps kill blowfly pupae over the winter; therefore, removing old nesting material may actually compromise this natural process.

To clean or not to clean? It depends…

Cleaning out your nest box is your choice, as nest site selection varies among cavity-nesting species. When making your decision, feel free to weigh the pros and cons, taking into consideration individual species preference and ectoparasite abundance. If you’re hoping to attract House Wrens to your nest box, don’t worry, they’ve got it covered. But, Eastern Bluebirds are a bit tricky. Depending on where you are, cleaning out your nest box may either invite or deter them.

A Mouse's House
A Mouse's House

Whether you decide to clean out your nest box at the end of the breeding season or not, don’t forget that leftover nesting materials make the perfect home for small mammals. If mice occupy nest boxes, you should definitely clean the boxes in the spring by removing nest material and washing with a soapy solution. Take precaution and wear gloves and a mask when removing rodent nests; they are far less fastidious than birds.


References:

  • Davis, W. H., P. J. Kalisz, and R. J. Wells. 1994. Eastern bluebirds prefer boxes containing old nests (Preferencia en Sialia sialis por cajas que contienen nidos viejos). Journal of Field Ornithology 65(2):250–253. Link
  • Pacejka, A. J., and C. F. Thompson. 1996. Does removal of old nests from nestboxes by researchers affect mite populations in subsequent nests of house wrens? Journal of Field Ornithology 67(4):558–64. Link
  • Stanback, M. T., and A. A. Dervan. 2001. Within-season nest-site fidelity in eastern bluebirds: disentangling effects of nest success and parasite avoidance. The Auk 118(3):743. DOI: 10.2307/4089937

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45 Comments

  1. Kevin Holladay says:

    In northern New Mexico we are close to the epicenter of the country’s hotspot for hanta virus. Deer mice, Peromyscus, are the main vector for this virus….great reason to clean out nest boxes every year for Western and Mountain Bluebirds.

  2. Barbara Walker says:

    I’ve been told other knowledgeable Bluebird enthusiasts that it’s important to remove the old nest because if a new nest is built on top of the old one the babies and parents become vulnerable to predators, being closer to the access hole.

    Also it’s easier to see what sort of bird is rebuilding if you start with a clean box.

  3. bpsperry says:

    Just what does cleaning out a nest box mean? Merely emptying it of nesting material or is there a need to “wash” it?

  4. Kevin Corwin says:

    I monitor a line of nestboxes about 30 miles south of Denver, they get Mountain Bluebirds and Tree Swallows. I check them weekly, and when a bluebird nest fledges the female quickly builds a new cup (not an entirely new nest structure) on top of the old flattened one and has already started laying the second set of eggs before my next weekly monitoring trip. The Tree Swallows nest much later than the bluebirds and only once each season.

  5. Janet K says:

    Thank you for this article. I’ve wondered if blue blue birds would re-use their nests. We get blue birds and chickadees in our 8 nest boxes. They make very different kinds of nests. I’ve assumed that a bluebird would not move into a box with an existing chickadee nest. I’ve always cleaned them out so that all boxes are equal in the spring. I usually leave the nests until late January in case someone wants to use it for cold weather shelter. So far we’ve not had any issues with mice moving in.

  6. George Kaye says:

    Interesting blogs about cleaning out nestboxes and predator guard effectiveness!
    I monitor about 75 nest boxes in Franklin NC, most of which are near the Little Tennessee River. A serious “predator” problem I deal with is ants. They love to move into the boxes with their own eggs. I believe I have no choice but to get rid of the nests when nesting season is over. Even during nesting season, when the birds have fledged, I get rid of the nest so the next bird will not have to build a new nest on an ant colony.
    I obtained some diatomaceous earth to sprinkle on the nestbox floor nest spring to see if this helps. Anyone have any experience with diatomaceous earth?

    • Robyn Bailey says:

      Hi George, we hear you about the ants! Fire ants, especially, can prey on nestlings. NestWatcher Tara T. in Florida shares her ant-proofing tips in this years’ annual report: “In the Southeast, fire ants
      can be a serious problem. We have caulked the small space between the predator guards and the posts, and just before our birds begin laying, we go out and spray a few inches of the post just under the guard with ant spray. The caulk keeps rain from washing it away and it has proven to be effective at saving the nestlings from the ants.”

    • Yes, we use diatomaceous earth (diatoms) in our chicken coop to control mites. Works great and is safe for foul and even earthworms in the soil.

  7. Annie and David says:

    Hi Fellow NestWatchers,
    We have had a Western Bluebird box with guard for a few years and every year the first clutch is successful. However, the second clutch never has survived. We go to clean the box out and for tree years in a row there are desiccated babies left in the box. Does anyone know what is wrong? Should we shut up the box after the first clutch has fledged?

  8. Rich says:

    Annie & David, I also have nest boxes for Western Bluebird, and my experience for achieving a second clutch is cleaning the next box out after the first clutch. The bluebirds are quick to rebuild a second nest. Not sure if cleaning out the nest box is the primary reason for a successful second clutch, but you may want to test it. Also consider that the weather temp. during the second clutch maybe higher. Good ventilation is important. As a side note I’ve noticed the offsprings from the first clutch help to feed the young of the second clutch.

  9. Kelly says:

    My bluebirds stay in the box all year round. I have never cleaned it out because I am afraid to disrupt their home. It has been many years. Not sure what to do

  10. Deb Collette says:

    I clean out my Gilbertson boxes after each brood and drop them in a 10% bleach solution for about ten minutes. Then I rinse them very well and let them dry overnight. I’ve never had any parasites and the birds begin building their second nest within days of my putting the houses back up. I leave the boxes out all winter for the birds to use to roost in if they need cover. I’m in Toledo, Ohio.

  11. Sharen Arnold says:

    This question is a little off topic, but I hope you can help. Last summer, a pair of Eastern Bluebirds had a clutch in a gourd house I had hung from a tree. I saw the parents bringing food and carrying away fecal sacs. Then one day there was no activity. No sightings of any birds at all. At the end of the season, I checked the gourd and found a perfect nest with no signs of eggshells. I don’t know if the clutch fledged or if a snake might have gotten in and eaten the babies so the parents abandoned the nest. I don’t know how old the babies were. If the babies fledged, would it be abrupt? Wouldn’t the family be near the nest for a few days until the babies could fly well? I appreciate any info you can share. I’ve informed myself better and put up houses with baffles this year, but wonder about those babies from last year.

  12. Darcy says:

    i live in south western Ohio. At what time of the year should you clean out old nests if you are going to do it? Thank you.

    • Holly Faulkner says:

      Hi Darcy,
      If you choose to, you should clean out nest boxes after the breeding season is over in fall. As mentioned in the article above, some birds and small mammals may use the nest boxes to roost over the cold months, so you may decide to wait until early spring. However, if you wait, it would be a good idea to check out our Common Nesting Birds and Right Bird, Right House tools (found under the “Learn” tab at the top of the page) to investigate the species in question and view the months where it is actively breeding, so you can avoid clearing the nest box then.
      -Holly Faulkner, Project Assistant

  13. Karen says:

    I live in Pawling ny & I saw the bluebirds return to the house they used last season but I did not clean it out yet should I do it now before they move in?

  14. Sunni says:

    I’ve watched a pair of bluebirds drive established tree swallows out of a box nest, then carry all the contents out, dropping it along their flight path. When they were satisfied they had done enough, they found their own new material to carry in.

  15. Deirdre says:

    The Bewick’s Wrens in a nest box on our porch fledged yesterday. This has been a successful box each spring for several years. Sometimes there is a second brood and just now, the adults seem to be starting over with courtship behavior – not removing nesting material.

    Should I clean out the box between broods in the same year? Same question applies to Black-crested titmouse nests in boxes.

    I usually clean out the boxes in the late summer or fall and put some pine straw to provide roosting protection. – in central Texas
    Thanks.

  16. Holly Faulkner says:

    Hi Deirdre, During the breeding season, you should leave the nesting material in the box – the parents will likely need it for another brood. At the end of the season, you can remove the nesting material and scrub the inside with a mild detergent and water.
    -Holly Faulkner, Project Assistant

  17. Chip C. says:

    I installed a new nest box here in west/central florida recently. About two weeks ago I began seeing a female eastern bluebird in and out of the box. She had completed a fine nest within 4 or 5 days. Now, 7 to 10 days after nest completion, I see both her and a male ‘hunting’ from a nearby power line but still no eggs in the box as of today … 4/25/18. Is it likely the nest will still be used and that I simply need to be patient? Thanks!

  18. Holly Faulkner says:

    Hi Chip,
    Birds will sometimes make multiple nests, and it’s common for some to start building a nest and then stop. It’s possible these bluebirds decided not to finish the nest, or that they have another nearby. That being said, even if they don’t decide to use this nest, they or another pair may decide to use the box for their (second) brood.
    Let us know if you have further questions at NestWatch@cornell.edu.
    -Holly Faulkner, Project Assistant

  19. Rose says:

    My birds are doing spring cleaning right now. 😀 yay

  20. Jackie says:

    Central Florida here……we have had Eastern bluebirds nesting in our two boxes for several years. Generally have 2 to 4 Broods each season and I usually clean out the nesting box after they fledge . We always seem to miss when the babies fledge…. Is there a time of day that they usually fledge out? We sit about 12 ft away on our deck, and they are used to seeing us but we’ve never seen the babies leave. We usually do see them later, but would love to see their first flight. We keep mealworms available almost all the time for them so they keep coming back…. Which we love. We have their second brood this season apparently getting ready to fledge, but other than sitting here 24 hours a day I think we’ll miss them again. But still love having them nearby.

  21. Laura T says:

    We have 6 boxes up and 1 has a blue bird and 4 have tree swallows. The last has what we call a hoarder – filled right up to the top with sticks and pine needles. Has anyone ever seen or heard of a bird doing that? We were wondering if it was the bluebird being territorial otherwise as it is closest to theirs. Anyway, when do we clean out the boxes for tree swallows and bluebirds? I’ve heard with bluebirds after their first brood so they can nest again, but having trouble finding info on tree swallows. What about barn swallows as well? Thank you! We are in St. Croix Falls, WI.

  22. Holly Faulkner says:

    Hi Laura,
    You shouldn’t need to clean out the boxes for any of these species as all have been known to re-use nests (unless of course there are parasites/infestations that need taking care of). However, if you do decide to clean out a nest box, it may require some precise timing: you’ll need to wait until you’re sure all of the nestlings have fledged and yet also when there is no signs yet that a bird is attempting to lay a second clutch. Our best advice is to clean them in autumn, and again in very early spring, even February, if they are being used as a roost over the winter.
    -Holly Faulkner, Project Assistant

  23. John H Matthews says:

    I have a bird house hanging from the corner of the carport roof. In the past 12 months I have had Carolina Wrens living there and they have had 3 sets of offspring. the last group just left the nest. I inspected the interior and they had used the previous nest and just added to it. I have started building houses for the birds in my back yard which include American Restart (RARE), Titmouse, Black Caped Chickadees, Carolina Wrens, Speckeled Woodpeckers, Blue Jays, Doves, Finch, Thrush,and Blue Birds flying thru.
    I do not think it is necessary to clean out the houses. THe birds make do.

  24. Katie says:

    We live in northern West Virginia and we had five bluebird eggs in one of our nesting boxes, and gradually one by one the bluebirds threw the eggs out of the nest. When there were just three eggs left, we noticed ants crawling all over a couple of them. My question is whether we should clean that nest out, now that there aren’t any eggs left due to a potential ant infestation.

    Thank you in advance for your assistance!

  25. Holly Faulkner says:

    Hi Katie,
    If there are no eggs in the nest and you’re sure the bluebirds are not getting ready to lay a second clutch of eggs in that box, you can clear the nest/ants out. If there are still eggs in the nest, we recommend waiting one month from the date they were laid, or when you first saw them in the nest, to ensure it is not an active nest.
    If you have further questions, please email us at nestwatch@cornell.edu
    -Holly Faulkner, Project Assistant

  26. Terri says:

    I have 2 birdhouses that chickadees originally made nests in. The wrens came and drove the chickadees away. The wrens set up their nest in one of the houses and now the second house, which clearly has a nest in it has been abandoned by both the wrens and chickadees. Do you think it will be utilized at all this season? Should we clean it or wait until the end of the season? Thanks.

  27. Holly Faulkner says:

    Hi Terri,
    House Wrens sometimes make a couple of “dummy nests” before deciding on one in which to lay their eggs. You can check the wren nest cup to see if it is lined with grass and feathers – this may indicate the adults is about to begin laying eggs. In any case, we recommend waiting at least a few weeks from the last time you saw an adult near the nest, to be sure the nest is not active. If the nest is not active, then yes, you can clear it out of the box, however if you are not absolutely sure, it’s best to wait until the end of the season.
    -Holly Faulkner, Project Assistant

  28. François Villeneuve says:

    Hi, I have a chikadee birdhouse in Rimouski, Quebec, Canada. As for my tree swallows, I clean it every spring. But it seems that chikadee does not like it. For the second time in 3 years, they do not use it this spring.

    Is it possible that chikadee prefers to keep the old nest from last year unlike the swallows?

    François Villeneuve

  29. Holly Faulkner says:

    Hi François,
    It may be good to look over the recommendations for placement to make sure that your box is in the ideal position for attracting Black-capped Chickadees (scroll down on this page: https://nestwatch.org/learn/all-about-birdhouses/birds/black-capped-chickadee/ ). Ideally, even if you clean out the old nest, the chickadees will be more likely to nest again in the box if a layer of wood shavings are placed at the bottom. If you have more questions, please email nestwatch@cornell.edu
    -Holly Faulkner, Project Assistant

  30. Karen Catallozzi says:

    Hello –
    I have a bluebird house in central Massachusetts that was being used by bluebirds up until a week ago. It looked like they were feeding babies for a few days. I went out of town shortly after that and when I returned, there was no activity and didn’t get to see if the babies left the nest or not. After no activity around the nest for a week, I checked the nest and there are 2 eggs left. Should I wait longer before cleaning out the box or is it OK to clean it now?

  31. Marion says:

    I purchased a second blue bird box recently which has a space of about 2 cms. at the lower front of the box . I asked the gentleman from whom I purchased the box why it was constructed that way and he said it was in order to let any rain run out. The other box is not constructed that way and I’m wondering which is the better of the two . Also is it possible that the new box will be used this late in the spring ?Thanks

  32. Marion says:

    My goodness I can’t believe it , I just checked the new bird box this a.m. and there is a nest in it . I think the bird building the nest is a house wren . Terrific !

  33. John Ruff says:

    Our bluebirds just fledged – today and yesterday. The last one flew out this morning. Bluebirds clean their nests so you will find no shells or fecal matter- just a nest. Last year the nest contained a baby that did not make it but that is a first for our house. Just because the nest is clean does not mean a snake or some other predator intervened. Bluebirds are very good parents.

  34. Judy Cobern says:

    I clean out the nest box after the family leaves the nest..The first time I didn’t … chipmunks took over the box! I don’t have a great love for chipmunks since they dig in my flowerpots & make a mess!

  35. jack says:

    As an amateur Blue watcher (southern California) i believe we successfully fledged one or two, although Not really sure, has anyone experimented with a camera inside the box ?
    Your thoughts are welcome , Thank you

  36. Holly Faulkner says:

    Hi Jack,
    Nest box cams are a great way to keep tabs on a nest. We have a handy page devoted to information on nest box cams here: https://nestwatch.org/learn/all-about-birdhouses/installing-a-nest-box-camera/
    -Holly Faulkner, Project Assistant

  37. Louise says:

    To the Franklin, NC native: You live in a beautiful part of North Carolina. My grandparents lived there for a few years and I loved visiting that area of my state. I live in Caldwell County and have a beautiful view of the Brushy Mountains from my back yard. Right now, I have dozens of hummingbirds and have finches, wrens, titmice, Cardinals, and other birds coming to my feeders. Nature provides us with much beauty and wonderful music from our native birds. I also have many rabbits this year and have seen the golden eagle on my power lines. This week, I saw a herd of deer, and once I saw a doe with twin fawns.

  38. stuart says:

    Kelly, I live in Northern Virginia, we also have blue birds in a nest box that live there year round so we never clean. The young stay in the box over the winter, but then disappear. They’ve lived there 10+ years. I don’t know if it is the original pair or not. Occasionally a second pair will take up residence in one of our other boxes box they don’t last for whatever reason – once it was a snake but we’ve fixed that.

  39. Dave Potter says:

    A box nearly full of coarse sticks is just about for sure the work of wrens. Several species of wrens [the male] makes several nests from which the female chooses. Cleaning out between nesting [if no eggs or new nest materials] Or in the next spring gets rid of pests of many kinds including squirrels, wasps, bees, snakes, ants etc. Make an effort not to breathe in the “dust” from a used nest…can’t be healthy. Starlings and house sparrows should not be tolerated. Checking wood duck nests in Oregon one spring I found several recently killed song birds [as well as other boxes in use by screetch owls.] I read that these owls cache prey [song birds] in nest boxes and their nesting season tends to coincide with song bird migrations.

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