Ultimate Guide & Checklist: Get Bluebirds to Use Your Nest Box

Top reasons why bluebirds aren’t nesting in your nest box:

Top reasons bluebirds aren’t nesting in your nest box include an insufficient hole size, insufficient box size, using a birdhouse rather than a bluebird nest box, location, location amenities and competing species that take up a nest box preventing bluebirds from nesting.

In this ultimate guide, we have combed through several peer-reviewed papers and sourced our own experience to give you the best resource to use in order to optimize your nest box placement and finally attract bluebirds to your area. At the end of this paper, we provide a helpful checklist to use in order to determine how to better optimize your bluebird house placement.

Before getting significantly into bluebirds and bluebird trails, we attempted to put up our first nest box up at our old house in hopes of attracting bluebirds. All we got were house sparrows (which were evicted). Upon moving, we tried again. And again, we got house sparrows, which were again evicted.

As new, hopeful landlords, getting bluebirds to nest in a nest box, it took us three years. This may seem alarming if you’re wanting to get started. So we’re providing a lot of tips gathered from experience as well as from peer-reviewed studies to increase your chances for success. At the end of the article, we’ll provide a check-off table you can use to improve your chances of not only getting bluebirds to take up your nest box, but also enabling them to have a successful nest.

Some of you may read this advice and think, “well I’ve set up a nest box in a not-so-ideal area and still got bluebirds.” This is true. Just because a location or box isn’t ideal, doesn’t mean bluebirds won’t nest in your nest box. Obviously, if you’re getting bluebirds to nest, this article isn’t for you. However, if you’re having trouble getting bluebirds to stay, changing a few things up based on this guidance may be exactly what you need.

Obvious reasons bluebirds aren’t using your nest box

Immediate things to check for if bluebirds are not using your nest box include entry hole size, box size, whether you’re using a bluebird nest box or decorative birdhouse, and if you’re located in a more urban area.

Appropriate nest box entry hole diameters for bluebirds

Nest box entry hole sizes for eastern and western bluebirds should be 1.5 inches in diameter. Mountain bluebirds need a slightly larger entry hole diameter of 1-9/16 inches.

All you have to do is get a ruler out and measure. If your entrance hole is larger than mentioned, this may not deter bluebirds. However, it may also increase the chances of predation. You can use hole guards or hole reducers in this situation to reduce the hole size of your nest box.

If the nest box entry hole is too small, bluebirds obviously will not be able to nest there. And in this case, you’ll want to consider purchasing a new box, modifying the current box, or just modifying the front panel of the box with the opening to be the correct size.

Appropriate nest box sizes for bluebirds

Use a 5-1/2” x 5-1/2” x 9” nest box size to give eastern bluebirds, western bluebirds, and mountain bluebirds enough space for them and their nestlings. Slightly smaller dimensions may not deter bluebirds. It’s when the dimensions are significantly different where you might run into problems.

You’ll want to check the dimensions of your existing box. Even if a box is a little smaller than the above mentioned dimensions, this might not entirely be a dealbreaker. These dimensions just allow ample room for a large clutch.

It’s when the dimensions are significantly smaller that bluebirds might become dissuaded to use the nest. For instance, a 3-3/4” xn3-3/4” x 6” nest box will likely be even too small for the momma bluebird to feel comfortable in.

Once again, if you’ve determined your nest box is too small, your best option is to replace it with something better suited for your bluebirds.

Our top recommended nest boxes:

*These links are affiliate links. They do not cost you anything extra. However purchases through these links gives Cavity Nesters a small kickback which helps support the content of this site.

Decorative birdhouses vs. bluebird nest boxes

Though charming and often beautiful, decorative birdhouses are actually dangerous to bluebirds and other native cavity nesting birds. If you have put one of these up hoping for a bluebird to take up residence, only to be disappointed, there are a number of reasons why. 

Even if you have had some success with these birdhouses in the past, birdhouses are not recommended because they do not allow proper monitoring, proper predator protection and optimal conditions for nestling success. 

If you have put up a birdhouse in your yard, even have spotted bluebirds in your area but have not had any settle into the birdhouse, it may likely be because bluebirds who have nested in birdhouses before had unsuccessful nests (meaning none or most of their offspring did not survive to fledge).

Replace these boxes with actual bluebird boxes. We have some recommendations here.

If you have decorative birdhouses, and still would like to put these in your hard, plug up the holes. We cannot emphasize enough how dangerous these types of birdhouses are to native cavity nesters.

Additionally, do not let invasive cavity nesting birds take up residence in any birdhouse or bluebird nest box. Invasive cavity nesters such as the European Starling and House Sparrow kill native cavity nesters for nest boxes. They will even kill birds when plenty of nest holes are available. 

Location: Urban vs. residential and rural

While some may have success attracting bluebirds to a more urban, busy area, this will not likely be the case. When given the choice, bluebirds will be more likely to select nesting sites in quieter, residential and rural locations before choosing a nesting site on a busy street, in a commercial area or in a very urbanized area.

Our advice, if you’re in a busy area (off a main road, near large stores, in a city block), don’t get your hopes too high. Again, it’s possible you might attract bluebirds, but the chances are very low.

Troubleshooting other reasons bluebirds aren’t nesting in your nest box

Aside from the obvious entrance hole size and nest box size, there are some other important factors to consider when trying to attract bluebirds to your nest box.

Bluebirds may not be nesting in your nest box due to the distance the box is from a tree line, the distance the box is from a large tree, the availability of water, the availability of food, the number of competing bird species, nest box type, whether old nesting material is present, and the distance between other nesting bluebirds.

Nest Box Distance From a Tree Line

Years ago, when we first began attracting bluebirds to our home we had no success at our first house. Looking back, this is because we had a few strikes against us:

• Our house was off a main road
• There was a high invasive house sparrow, eurasian tree sparrow and starling population
• Our backyard had numerous large trees.

Bluebirds particularly like to nest in open areas with a few trees nearby. They are less likely to nest in heavily wooded areas. 

An older study that observed more than 1100 nest sites of mountain bluebirds, eastern bluebirds, house wrens, tree swallows and house sparrows found that the location of the nest site was very important in determining whether a bird would take up a nest site or not. The study found that both mountain bluebirds and eastern bluebirds selected artificial (nest box) sites that were in more remote areas such as pastures with the presence of a few trees (Munro & Rounds, 1985).

We have noticed this from our own experience monitoring trais and putting up our own residential nest boxes.

For instance, when monitoring trails initially established by Eagle Scout troops, we discovered that boxes put up at the edges of tree lines and forests were mostly taken up by house wrens and house sparrows (evicted). So far, we have never observed bluebirds occupying those nest sites.

In a residential setting, we have also observed bluebirds taking an interest in a birdhouse near a tree line. However they would not settle in this box. Instead, house wrens would.

Bluebird houses placed in more open areas with large trees no closer than 15 to 20 feet were taken by both bluebirds and chickadees.

Therefore our suggestion is to experiment with your bluebird house’s location. If you’ve set it at the edge of a tree line, you might want to locate a more open space in your yard. 

Additionally, take a look at the canopy. Since bluebirds like more open areas, you may want to try to put your box at least 30 – 40 feet away from the canopy, and experiment from there.

During the experimental process, give each location a week. Your best bet, is to start your experiment in the most open area of your yard as possible, and go from there.

We will acknowledge that many people have had success mounting bluebird houses to trees (something we do not recommend as it increases predator potential). Again, the tips from this article are things to try when you’re not having any luck. So if your house is mounted to a tree, purchase a pole system, and experiment with other areas.

If your yard is heavily shaded by large trees, again, you can try and experiment. But this might be one of the reasons you’re not having any luck. But chin up. It could be that there are multiple other reasons you’ve discovered besides the location of your box as to why you might not be having as much success. Try optimizing as much as possible, and you might still be able to attract bluebirds to your next box, even if you’re in a more wooded area.

Nest box distance from large trees

A theme might be starting to show up when it comes to nest box location. Bluebirds prefer open, grassy spaces as nest sites with a few trees in the area, to optimize nest box placement, try making sure your nest box is no closer than 16 feet (4.8 meters) from a large tree (greater than or equal to 8 inches  in diameter and/or 25 feet or taller). 

Researchers David Horn, Mary Benninger-Truax and Donald Ulaszewski of the department of biology at Hiram college found a relationship between nest box distance from taller trees, shorter trees and bluebird preference as well as nesting success rate.

What they found was a greater number of unused nest boxes that were positioned closer to taller trees. The mean distance of used nest boxes was 4.8 meters (~15.7 feet) from the nearest tall tree, with there being observed preference for nest boxes further from large trees (Horn, Benninger-Truax, Ulaszewski, 1991).

Additionally, they discovered a positive relationship when nest boxes were placed closer to smaller trees, which makes sense when you consider the perching needs of a bluebird who will be searching for bugs and grub.

The takeaway from this is if your nest box is pretty close to a large tree, experiment by putting it out further. If your nest box is in a more open area, but you happen to have a nearby bush, experiment by putting the nest box about 10 feet from the bush. 

When experimenting, allow about a week. Oftentimes what will happen is bluebirds will come and inspect the nest box and make a decision. If in a week, they’ve looked in but haven’t settled, try a different location.

Availability of food and water

If you have tried everything and bluebirds are still not using your nest box, make sure you have a good water source with running water. Furthermore, food should be nearby, but not too close to the nest box.

A water bath is very helpful for attracting bluebirds to a nest box. What might attract them even more is a running water source. There are plenty of solar powered water fountains that you can add to the water bath to help attract bluebirds.

Our favorite combination to use is this water bath that sits on the ground along with a solar powered water fountain that is very inexpensive.

Traditional stand waterbaths require a little bit more maintenance and need to have a good amount of weight to them, which makes cleaning it a little more of a pain. The ground version is a little more natural for birds, with a lot less fuss.

Food is the next thing to think about, and there are two factors here. First, food can help attract bluebirds to a nesting site. Second, however, is that you do not want the food to be right next to the nest. One of the best quotes we heard regarding the second concept is 

“No one wants to live next to a McDonalds.”

It’s true. Having a feeder next to a nest box will invite other bird species and give bluebirds less privacy. Therefore, when arranging your nest box, and feeder, place your feeder at least 30 – 40 feet from the nest box.

You may also want to consider taking other feeders down that could potentially attract harmful birds like starlings and house sparrows or eurasian tree sparrows.

As for what food to provide, most often bluebird landlords will provide dry or live mealworm. Live mealworm is especially important when nestlings are present because they are a source of water (never give a bluebird nestling water).

However, having only one food source can be detrimental to bluebirds. Mealworm, particularly, are not a good source of calcium for egg-laying mothers. The results of a calcium deficiency could lead to fragile eggs or the mother bird becoming egg-bound. 

Egg bound is a situation where an egg is stuck or lodged and has not been laid (Joy & Divya, 2014). For a mother bluebird, this could likely be fatal. Calcium deficiencies are one of many reasons this could happen. 

One way bluebirders supplement calcium is by adding pulverized chicken eggshells to the mealworm feed. 

However, some bluebirders encourage planting native plant gardens. Native plants help promote the presence of native insects in the area, which provides a better banquet for your bluebirds.

Competing species in the area may deter bluebird nesting

If you have house sparrows, Eurasian tree sparrows, European starlings or house wrens in your area, bluebirds may be more reluctant to occupy your nest box. These four particular competing species can be very destructive to bluebird nesting success.

House Wrens

House wrens are native cavity birds in the US. And even if they have their own nest box, a male may be interested in building dummy nests in other boxes. 

Unfortunately, house wrens (not to be confused with Carolina wrens) will invade bluebird nests, poke eggs and throw them out of the nest, even throw very young nestlings out of the nests.

Because they are native in the US, you cannot trap them or interfere with an active nest. However, there are a few precautions you can take.

The first is to keep your nest box in a more open area, away from a tree line. The further from a treeline, the less interested a wren will be in the nest because they do not like meadows and open fields. In our experience, 50 feet away from a tree line is still not far enough, especially if there are tall trees between the tree line and where the nest box is located. You are better off trying to keep your nest box at least 75 – 100 feet away from a tree line. And again, that may not stop a house wren, but it should hopefully minimize chances of invasion.

Your next precaution to take is to install a wren guard after the first egg is laid. You want to ensure that your bluebirds can still get into the nest. Sometimes they struggle.

When installing the wren guard, the hood or awning should just barely hide the hole. 

We have an incredible resource on what a wren guard is, how to make one, how to install them and everything else.

Tree Swallows

Tree swallows are native and can compete with bluebirds. This is the case when one box is available or a flock is in the area.

But these beautiful birds can also pair well with bluebirds. And the pairing can be mutually beneficial.

Some bluebirders mount two boxes to a pole facing opposite directions, with one being for the bluebird and the other being for the tree swallow.

More eyes on the nest is really helpful in defending territory.

Eurasian Tree Sparrows

Eurasian tree sparrows are nonnative cousins of the house sparrow. They are mostly found in St. Louis, Missouri. However, they have been spotted in Illinois, Indiana, Wisconsin – even as far north as Canada.

They are not federally protected. However, you will need to verify with your state about whether they are protected.

If you are in an area that is full of these sparrows there are a few immediate actions to take:

1. Check the food you’re putting out. If it contains white millet, milo and wheat – take it down. Eurasian tree sparrows will also eat nyjer (finch seed). So during nesting season, you may want to take down your finch feeders or move them very far away.
2. Make sure you have no holes or cavities in your siding, gutter, or anywhere on your house. Be especially careful of your dryer vent.
3. If they are not protected in your state, the best way to manage these sparrows is to trap and dispatch (a kinder way of saying to euthanize).
4. You can install a sparrow spooker on your nest box after the first egg is laid. However, these will not always work. Especially if you have a lot of Eurasian tree sparrows in your yard.
5. Monofilament, which is fishing line, is another option. We have a detailed article about what sizes to install on your nest box, and how to install it. 

Eurasian tree sparrows are less aggressive and less persistent compared to house sparrows. But when they do get into a nest box with eggs or nestlings, they will kill them. We do not have confirmation on whether Eurasian tree sparrows will kill adult birds.

If you do happen upon a nest, and they are not protected in your state, destroy it. The sparrows will continue to rebuild, and that is fine. If they’re busy, they aren’t busy with another nest. If any eggs are laid, you boil them or oil them so they are no longer viable. Then place them back in the nest to keep the bird occupied. These methods should only be used when they are not protected in your state, and if you do not have the nerve to dispatch them.

House Sparrows

House sparrows are another invasive and extremely destructive bird to native cavity birds in the United States. 

So many times, bluebird trail managers have done a nest check, only to find a mother bird pecked to death in her nest. This is a quick sign to bluebird trail managers that she was killed by a house sparrow. 

Many times, the sparrow will pin the adult bird down, killing it. What’s worse, they don’t discard anything. They just build their own nest over the remains. And we’re not dramatizing or sensationalizing this either. It happens all too often, which is why bluebirders are serious about managing house sparrow populations – trapping, dispatching and discouraging them from trail locations.

If you have house sparrows in your area, it’s not even a good idea to try to attract nesting bluebirds. And often, if the house sparrow population is pretty large (they’re there every day, not once in a while), bluebirds will not settle in a nest box.

Unfortunately, due to how aggressive house sparrows are, it is not enough to deter them. Deterring house sparrows can buy time – sometimes it works, but when competition is high, monofilament and sparrow spookers only buy time.

Ultimately, if you want to bring bluebirds to your nest box, in this situation, you must trap and dispatch house sparrows regularly.

If you’re nervous about the idea of dispatch, there really aren’t a lot of options. Never relocate a house sparrow. Relocating house sparrows only create problems in other areas, leads to bird deaths there. 

Some people will clip flight wings. Some sites say to clip just the first four, but they can still be pretty good flyers in this situation. 5-6 can still let them fly short distances for food and water, but limits their maneuverability.

There are some drawbacks to wing clipping:

1. It may draw more predators to an area where they’re released (and they should never be relocated, even if their wings are clipped). This is not a good situation because it could end up causing problems for your nesting bluebirds or other native cavity nesters.
2. It takes time, and if you have a big sparrow problem, that’s a lot of time and energy spent trying to clip wings.
3. If you do it wrong and clip a blood feather, it can cause a lot of blood loss to the bird.
4. The wing feathers grow back. If they are still around after the wing clipping, and the feathers grow back, the sparrow is back to its dirty business.

Different types of nest boxes may not appeal to your bluebirds

Between a traditional wooden box and a recycled plastic box, bluebirds in our experience have preferred the wooden box. We have had very little success appealing to bluebirds when using plastic boxes. 

That’s not to say that bluebirds won’t use them. Plastic and PVC boxes have some advantages, and bluebirds will sometimes select these. But if you have a recycled plastic box, and you’re wondering why a bluebird isn’t nesting in your nest box, it might be worth buying a wooden box and putting it out in your yard. You may be surprised at the sudden success you have.

Leaving old nesting material in a nest box may be why bluebirds aren’t nesting

If you haven’t cleaned out the nest box, this may be a reason bluebirds are not wanting to nest in your bluebird box. Clean it out with a mix of soap, water and vinegar, then hose it out really, let it dry and then reset it.

As we’ve mentioned in all of the other sections, bluebirds will sometimes nest despite old nesting material being in the box. For instance, if you had chickadees in the nest box before, a bluebird might decide to build her nest over the old chickadee material. 

However, if you have a box up, and you’re not getting any bluebird takers, it’s not a bad idea to scrub out the nest. Cleaning the nest box also is a good health measure for your bluebirds.

Another thing we’ll add is if the bird previously nesting in the nest box was a house wren, and the box was not cleared out of sticks and debris, a bluebird isn’t even going to really be able to maneuver well enough to build her nest.

We do have a resource about how to clean out a nest box. Some things to think about when cleaning the nest box is what cleaning product to use. Soap and water is usually fine, but bleach is going to really disinfect. Vinegar mixed into a soapy solution is also really useful. In either case, you want to make sure you spray out the nest box really good so no chemical vapors are released in the heat.

Check if you have a wasp nest – bluebirds will not touch a nest with wasps.

If you’ve put a bluebird nest box out in your yard, and they aren’t nesting, carefully check it for paper wasps. If there is a paper wasp in the nest box, this will completely deter bluebirds from nesting in your bird box.

If you have found a wasp nest in your bluebird house, carefully remove it. Then scrub out your nest box. Wasps leave pheromones in the box where they’ve built a nest and this encourages other wasps to build. Deep cleaning the nest should remove or minimize the pheromone.

Furthermore, you can prevent paper wasps by rubbing bar soap around the top insides of your nest box. You want to rub the soap on the roof, around the insides of the box from the top to at least 1 inches down. And then rub soap on the outside under any wooden overhangs.

Unscented ivory soap is the best option to use.

Even if you’re using a plastic box, you’ll want to check for wasps. Wasps have built nests on vinyl and plastic before.

Download the bluebird nesting optimization checklist

We’ve provided a resource that summarizes this article. You can download and print this checklist or just go through it with a notebook. Use it to audit your nest box situation. This might give you a better understanding of why bluebirds aren’t using your nest box. And using the information in this article, you can look up some quick solutions on how to fix it.

Keep in mind, there are some deal breakers like having too small of a hole, or too small of a nest box. Or if you live in a tree-dense area, you may have less luck attracting bluebirds. The same goes if you live in a busy location, such as on a main road. In these cases, you can still try, but you may end up disappointed. We advise you not to invest a lot of money when attracting bluebirds. You can always buy accessories such as a baffle or nest camera once you’ve gotten bluebirds to nest.

References

Horn, D. J., Benninger-Truax, M., & Ulaszewski, D. W. (1996). Brief Note: The Influence of Habitat Characteristics on Nestbox Selection by Eastern Bluebirds (Sialia sialis) and Four Competitors.

Joy, B., & Divya, T. R. (2014). Egg bound and vent prolapse in chicken-A review of two cases. Bangladesh Journal of Veterinary Medicine, 12(1), 91-92.

Kleist, N. J., Guralnick, R. P., Cruz, A., & Francis, C. D. (2017). Sound settlement: noise surpasses land cover in explaining breeding habitat selection of secondary cavity‐nesting birds. Ecological Applications, 27(1), 260-273.

Munro, H. L., & Rounds, R. C. (1985). Selection of artificial nest sites by five sympatric passerines. The Journal of wildlife management, 264-276.

Nest Watch. (2019, August 27). Mountain Bluebird. Mountain Bluebird NEST BOX PLAN AND INFORMATION. https://nestwatch.org/learn/all-about-birdhouses/birds/mountain-bluebird/. 

Pinkowski, B. C. (1979). Nest site selection in Eastern Bluebirds. The Condor, 81(4), 435-436.