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Choosing the Right Bluebird Nesting Box

Choosing the Right Bluebird Nesting Box

Posted by JCs Wildlife on 26th May 2023

Bluebirds are one of the most endeared and desired backyard neighbors. These birds are not only beautiful to look at, but they also have strong family values. Their family values are unparalleled in the bird world.

All of these things make them one of the most interesting species to watch and welcome into your neighborhood.

There are 3 species of bluebirds that inhabit the US. The Eastern, Western and Mountain Bluebirds.

The Eastern Bluebird is the most common to take up year-round residency. They are present in almost ⅔ of the US. With that in mind, most of the information we discuss here will center around the Eastern Bluebird.

Attracting these wonderful creatures to your backyard can sometimes be quick and simple. However, in some cases it can take years.

Simply having a bird house does not guarantee the presence of bluebirds. The "build it and they will come" scenario does not always work.

But on a positive note, once they do find a house they like, they are likely to return year after year. This is provided that the surrounding area remains the same and the house is well-maintained.

Let’s address a quick housekeeping item. A bird house, or birdhouse, can also be referred to as a nest box or nesting box. When those terms are used here, please treat them as the same thing - a house for a bird to build a nest in.

Bluebirds are cavity nesters. This means they will build their nest inside a cavity, or hole.

The American Robin for instance is not a cavity nester. Like the Northern Cardinal and many other birds, they will build a nest in a tree, in a shrub or even on a ledge.

Given that bluebirds are cavity nesters, offering them a birdhouse where they can construct a nest is a good first step in enticing them to hang out with you in the backyard.

We will address five different topics when talking about successfully attracting bluebirds to take up residence in your backyard.

  • Types of bluebird houses and their characteristics
  • Mounting or placing your house
  • Bluebirds 101
  • Predators
  • Human neighbor responsibilities

Types of Bluebird Houses and Their Characteristics

There are many different types of bluebird nesting boxes out there on the market. For our purposes here, we are going to address the “basic house” and one other offshoot which we find very intriguing.

No matter what type of house you choose, there are a few basic essentials to keep in mind.

First of all, dimensions. The typical bluebird house is 4” to 5” square on the bottom. This provides an ideal space for the nest to be built.

The base should be about 5” to 6” below the hole. This allows ample room for the birds to get in and out and enough distance between the hole and the nest to prevent predators from reaching the eggs or young.

The entry hole should be 1-½” in diameter for the Eastern & Western Bluebirds, 1-9/16” for the Mountain Bluebird. If the hole is any smaller, the bluebirds will not be able to go in and out. If it were any bigger, larger “bully birds” or predators would have easier access.

The basic bluebird house is often referred to as a NABS house. NABS stands for North American Bluebird Society.

These houses will closely adhere to the guidelines mentioned above and are considered to be the standard in nesting boxes.

They can be made from different materials, but rough, untreated wood is common. Cedar is probably the most used type of wood, along with exterior grade plywood.

Cedar weathers very well without any type of sealers or paint. It resists cracking, splitting and warping. It is also a natural insect repellent and is simply an attractive wood to look at.

It is very important not to use treated wood for bluebird houses. Something very plain and natural is desired. If you do wish to protect your bluebird house, a natural option like linseed oil is recommended.

Some people like to paint their wooden bluebird houses. While this is okay, you should never paint the inside, only the outside.

Another common material used for constructing bluebird houses is poly lumber. Poly lumber, or “poly”, is a man-made recycled plastic product.

Poly is environmentally friendly, as it is made from recycled materials like milk jugs and other discarded plastic containers. It is completely safe for birds and provides a safe, secure and durable place for bluebirds to nest.

Poly is very easy to clean, it doesn’t stain and it will last forever. You will pay a bit more for a house made of poly, and these houses will be heavier than the cedar wood versions. But when you consider the lifespan of the house and the other benefits of the poly material, it becomes a very economical and smart choice.

Other things to look for are proper ventilation openings and drainage.

It is very important for the birds to have good air circulation inside the house. Most houses will have gaps at the top under the roof to allow for proper air flow.

You should also check for drain holes in the bottom of the box. If water gets inside during a storm or heavy rain, it needs somewhere to drain. This ensures the nest will stay dry.

Perches are a no-no. A good bluebird house will have no perches.

Bluebirds don’t need to perch. They will fly right in and out of the entry hole with no problem. Perches would also provide a place for unwanted birds to hang out and access the box.

Another must-have is a clean out access.

Most houses will have a hinged front or side that can be opened to allow access for cleaning. For some of the lesser-valued houses, you may have to remove a panel by removing screws.

The bottom line is there needs to be a way of accessing the interior of the house for clean-out purposes. Houses that are desirable use stainless steel or galvanized screws. These screws won't rust in the elements.

We can’t talk about bluebird nest boxes without mentioning the available options, or “add-ons”, if you will. While none of these are a necessity, they can help the bluebirds and the human “looky-loos”.

Here is a list:

  • Predator Guard - I would personally view this one as more of a necessity than an option. A predator guard is an “extension” that is placed around the entry hole and sticks out about ½” to ¾” from the hole. Just like the name suggests, a predator guard is used to deter unwanted visitors who may want to make bluebird eggs or young their next meal. The predator guard lengthens the distance between the entry hole and the nest inside the box. They work great for varmints such as raccoons or squirrels.
  • Kerfs - These are simply grooves cut into the wood or poly on the inside of the nest box, directly underneath the entry hole. The kerfs provide a gripping surface for the birds when they exit the nest.
  • Floor Riser - A floor riser is typically a wire stand that sits in the bottom of the birdhouse. The nest is built on top of this riser, leaving a space between the bottom of the nest and the box bottom. This helps with both air circulation and drainage. It makes the inside of the house more healthy for the birds.

  • View Door - Here’s a people-friendly option. We talked earlier about the clean-out door. The view door would be a similar hinged door that when opened, allows you to view the nest through a plexiglass window. Some bluebird boxes are made so that both sides will hinge open. One side is the clean-out, while the other side is for safe viewing.

We want to look at one more specialized option before moving on to discuss the placement of your bluebird house. That is the Peterson Bluebird House.

The Peterson nest box was developed by Dick Peterson of Brooklyn, MN. His somewhat unique design has been modified over the years and has become increasingly popular.

Think of a cheese wedge turned bluebird house! A large downward-swinging front door allows easy access to clean or monitor the box.

This design also allows for the door to be open without disturbing the nest. The tilted nest shelf creates an ideal base on which the adult birds can construct their nest. It also has holes drilled in it to help with drainage.

The box has several openings. The bottom has a large slot opening. The sides have small openings. The roof and sides have front and rear gaps to promote airflow.