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Bluebirds are one of the most desirable birds to attract to your backyard. Their beauty, song, and the fact that they only eat insects are just some of the benefits Bluebirds bring. And adding a nest box is one of the best ways to attract them. A male Bluebird bringing breakfast to his babies But if you've googled Bluebird Houses, you can quickly get overwhelmed! There have been so many different designs and styles to choose from. From what is commercially available to what you can build yourself, it can get a bit confusing. A baby Bluebird taking it's first steps! Well, in this article I'm going to go through everything you need to know about Bluebird Houses. We are going to go step by step through the different styles, the pros and cons, how hard they are to make/buy, install, and maintain. By the end of this article you should be able to confidently select the correct Bluebird House design for your situation, and have a full understanding of what needs to be done successfully attract bluebirds to your yard. In this article: Where do Bluebirds like to nest?What is a Bluebird House / nestbox?Different styles of Bluebird HousesPros and Cons of different Bluebird HousesWhere & how to install bluebird housesHow to protect bluebird houses from predatorsMaintenance of bluebird houses Where Bluebirds build nests in the wild Bluebirds are cavity nesters. Meaning that in the wild they excavate nest cavities inside dead, rotting trees. Many birds do this from chickadees to woodpeckers. In fact if you are hiking in the woods sometime and notice a dead tree, look up and examine the trunk. It is likely you will see some large holes that are in fact nesting cavities from various species of birds. Hungry! How birds excavate nests in the wild When a tree dies, over time fungus will infect and consume the wood. But it doesn't happen in a linear fashion, the fungus will spread throughout the wood and sort of slowly dissolve it. This makes the wood 'punky' and easy for a bird to peck away at it, eventually making a cavity. Nesting cavities visible in a dead tree Why the bluebird population declined The population of Bluebirds declined over the years due to habitat loss and competition with House Sparrows or European Starlings. In regards to habitat loss, this is primarily due to a lack of suitable nesting areas. Bluebirds like to nest in cavities of dead trees on the edge of a forest that borders some grasslands, in which they will hunt for insects. [1] The decline of suitable nesting sites for Bluebirds makes complete sense when we consider the development of property and suburbia in America. The development of towns, suburbs, and farmland has reduced the number of standing dead trees, which means fewer nesting locations. Luckily through massive conservation efforts by the public and various Bluebird Societies, the population is rebounding. Bluebird House / Nest Boxes Ok, so what is a Bluebird House? Well, there are many different styles and variants. In fact there are so many small design differences, each with their own purported benefits that it can be very confusing. So, I'm going to simplify this down to four different styles and compare and contrast each of them. Different styles of Bluebird Houses So, Bluebirds need a nest box of some kind which fulfills the same role as a cavity that was excavated from a dead tree. Ok, so we need a box. And, a box with a roof and hole is perfectly fine. In fact, in the most simple sense, that is all we need. Just make sure you incorporate other necessary features like ventilation and drainage. Any variation that meets the basic box dimension requirements below would be sufficient. FeatureDimensionFloor size4"x5.5"Height9"Entrance Hole diameter1.5"Distance from top of house to hole1"Roof overhang4-5" I've attracted Bluebirds for years using variations of the above simple box. So, know that 'simple' works! But, there are many variations that exist, each with various degrees of success. They are quite different, and their different features can offer various advantages. The traditional Bluebird House / Nestbox A traditional Bluebird House is just a box with an overhang roof. It will open so that the nestbox can be monitored, either from the front or the side. This basic design has been in use for decades with lots of success. The design is simple, easy for anyone to DIY, and will serve Bluebirds well as long as the opening is protected. A simple nest box with a flat roof. A nestbox with a sloped roof A simple and effective innovation to the traditional flat nestbox is the addition of a sloped roof to shed water. Depending on how it is constructed, it can also reduce predator attacks, as the longer roof overhand makes it more difficult for a raccoon or cat to reach into the entrance hole. It is still simple to construct or purchase, and installation is the same as other styles of nestbox. Sloped roofs allow water to drain off the top. We've got our own plans on how to make this style from a single cedar fence picket. This is very low cost, as you can typically by a cedar picket for less than $4. Then you just need some nails and construction adhesive. You can find our guide to make this style here. The sloped/slanted Peterson Style nest box The Peterson style nestbox was developed by Dick Peterson of Brooklyn Center, Minnesota back in 1992. It was refined over the years to it's current form. This box is innovative in that it has a more extreme downward slope and irregular opening. Instead of a traditional 1-1/2" hole diameter it has two overlapping 1-3/8" holes to form an oval. The more dramatic slope sheds rainwater better, and also makes it more difficult for predators. It also can be easy to monitor with the opening hatch. And certain reports indicate that it is a more popular nestbox with bluebirds than the traditional flat boxes. The only drawback is the larger hole may allow Starlings and other birds to enter the bluebird house and harm the babies. PVC Bluebird Nestbox The PVC (Gilbertson) nestbox is a unique design. It is made by using 4" PVC drain pipe, a wooden floor with a drainage hole, and then mounted underneath a roof on a pole. It offers a decent amount of protection from the elements, can be economical to make multiple boxes (you could make a lot of nest boxes from one pipe), and is easy to monitor the status of the birds. Comparison Bluebird House StyleCostBuild DifficultyRain ProtectionPredator ProtectionLink to PlansTraditional BoxLowEasyLowLowPDFSloped-roof BoxLowEasyMediumLowPDFPeterson Style LowMediumHighImprovedPDFPVC Pipe (Gilbertson)MediumMediumLowImprovedPDF When all considerations are weighed, the Peterson style or sloped version of the traditional nest box is the best type of Bluebird House to make or buy. They both offer protection from rain, and are more difficult for a cat, squirrel, or raccoon to reach into. But- if you already have a traditional or round PVC house on hand, you should by all means use them. So, once you have selected a design. Now, how should we obtain a box? Well, if you have a bit of DIY ethos you can construct your own. Or, many of these designs we've reviewed are available for purchase. If you are working on your own backyard alone, and only interested in bluebirds, then building a single sloped or Peterson style box would be the most economical. Installation of Bluebird Houses Direction Bluebird houses should be placed so that the opening faces AWAY from prevailing winds. If you are in North America, this likely means that the opening hole of your bluebird house should be facing East. Height Bluebird houses should be mounted 4-6' off the ground. Location Bluebirds prefer to nest within, or on the edge of grasslands. So, you need to have a location that you can mount your nest box. Regular residential lawns are good locations for Bluebird Houses, as long as there is enough open grassland to support them. Nest boxes can be mounted on poles, fence posts, and even trees. But you need to take good care to protect the nestbox from predators. To mount a nestbox to a pole, then you can use a 4' section of 1/2" rebar pounded into the ground 2' deep. Then slipping a 5' section of EMT conduit over the rebar makes a secure base to attach the bluebird house. Utilize strap clamps and screws to secure the nest box. Two strap clamps attached to the EMT conduit will be sufficient to secure the nestbox to the pole. Additionally, you can purchase t-posts and attach directly to them. They provide a strong, sturdy way to mount the bluebird house. Bluebird house mounted to a T-Post with strap clamps. This was part of a local Bluebird Trail, or series of nest boxes spaced at least 300' apart Protecting Bluebird Houses from predators Like most nest boxes, Bluebirds are susceptible to predators. How best to protect against them depends on the predator. So, you need to be aware of the potential bluebird predators that are in your area. BearsRaccoonsSquirrelsCatsHouse SparrowsSnakes Note that even with the best protection, sometimes animals are able to defeat the predator guards. So, we do our best, and try to protect the birdhouses based on what is in your area. Bears To protect nest boxes from bears, hang them very high (10') on wooden walls of a barn or shed. As bears cannot climb flat wooden walls. Other alternatives is to mount it on a very strong metal pole 8-10' off the ground, or even suspend the bluebird box between two tall objects on a wire. Cats, Squirrels, and Raccoons The easiest way to protect a bluebird house from a cat, squirrel or raccoon is to install a Noel guard around the mounting hole. This effectively prevents them from reaching inside of the hole. It is very effective for most nest boxes. We have a guide on how to fabricate your own Noel Guard from hardware cloth here. If the house is mounted on a solitary pole, you can also consider protecting it with an 8" stove pipe baffle or squirrel baffle. An 8" stove pipe baffle is fairly easy to fabricate and low cost (~$15). As an added bonus a stove pipe baffle can be effective at stopping snakes. A squirrel trying to figure out how to defeat my stove-pipe baffle Snakes To protect the bluebird house against snakes, there are two primary methods. The first (and most effective) method is to mount the bluebird house in a mowed field, at least 10-15 yards away from any wooded or tall grassy area where a snake may live. This is effective as snakes can often become prey themselves out in the open. The second method is to use some sort of conical squirrel baffle to deter snakes. These can be purchased up to 23" diameter, and can be installed even after a birdhouse is put up. They are effective at stopping snakes that are roughly 4' or less. Also, stove pipe baffles have been reported to be somewhat effective at stopping snakes. But they must be at least 8" diameter. Coating the baffle with wax can also help increase the effectiveness of these guards. Snake protection on trees Snakes can climb trees. Yes, they slither right up the bark! So, we need to either use a tree that is isolated from snake habitat, or add some protection. Luckily a new solution has been discovered. Black Rat Snake climbing a tree A new study compared tree mounted nest boxes with, and without this acetate sheet wrapped around the trunk. The results were significant. Of the unprotected trees, 15% of the nests were raided by snakes. But for the protected birdhouses, only 1 (2%) was successfully raided. [2] For bluebird houses mounted on trees, you should use acetate sheets (thin, clear plastic sheet) to stop snakes. You just need to secure the sheet with duct tape. The sheet must be 32" tall and wide enough to be fully wrapped around the trunk. House Sparrows House Sparrows are an invasive bird species that has now become established all over the world. And they are very territorial and will attack nestboxes occupied by other birds to claim them for themselves or just to keep food competition down. They frequently kill other birds and evict them from their nest boxes and cavities. A house sparrow attacking a Chickadee nest box. The hole for a Chickadee nest box is too small for the sparrow There are several methods that have been shown to be effective at keeping house sparrows away. The most effective method though is to install a sparrow spooker after the first egg has been laid. They are available for purchase (no affiliation), or you can make your own. You can fabricate your own by using dowels, and small sticks overhanging the top of the box. Then, simply attach some shiny pieces of foil, mylar, or even cut-up aluminum cans. The light reflection scares the house sparrows away, and they should leave the nest alone. Once the nesting season is complete, you should remove the sparrow spooker, lest the sparrows become used to it. Choosing your predator protection based on the mounting style I've compiled the information below to help you best protect against predators. It should serve as a good starting point for most residential areas. But - if you know certain predators could be a problem, such as a large raccoon population, you may want to add additional protection. Bluebird House mounted on a pole Locate the pole at least 10-15 yards away from any tall grassland or forest. This will help dissuade snakes. Additionally you should add a conical squirrel baffle, and a noel guard. Bluebird house mounted on a wooden fencepost Locate the birdhouse at least 10-15 yards away from tall grasslands and forest edges. A noel guard is necessary as it is likely that many predators will be able to climb the fence. Tree-mounted Bird Houses Nest boxes can be mounted directly to trees. But, these trees should be isolated from other structures or trees that may allow a snake to get to the nest box. You should use the large acetate sheets around the trunks to dissuade snakes. In addition to the acetate sheets, you should install a Noel Predator Guard around the entrance hole to make it difficult (if not impossible) for a raccoon or squirrel to raid the nest. How to maintain Bluebird houses If your bluebird house is made from cedarwood or PVC, there will not be much (if any) maintenance. But for boxes made of pine or some other material, you will need to paint the exterior yearly to protect them from the elements. But you should inspect your nest boxes each Winter and determine if they need to be replaced or repaired. This is the last year of this birdhouse. I'm replacing it in 2022. Additionally, at the end of each nesting season, you should empty out the nest and brush out any material that is present. You may wish to take down the nest box at this time, as sometimes mice may build their own nest in the box. Also, if desired, there are disinfectants available for use on birdhouses that will not harm the birds but sterilize the wood. 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