Building a home for bluebirds only four standard components, but that doesn’t mean you won’t have any trouble luring the birds elsewhere.
The elements of a Bluebird home The entry hole of a bluebird house should be no smaller than 1-1/2 inches in diameter. The doorway, 8 inches from the bottom of the box’s interior, would be situated dead center. The minimum dimensions for the floor are 4 inches by 4 inches, and the minimum dimensions for the internal width and depth are also 4 inches by 4 inches. The minimum height for a bird house is 10 inches.
That this wooden box is fashioned in a manner that mimics the bluebirds’ native environment is crucial to an appreciation of what makes a Bluebird house a Bluebird house.
The bluebird has adapted to nesting in the hollow, or a hole of a specified size cut into the trunk of a large, old tree. I should mention that the hole was developed naturally and could have been used as a woodpecker’s nest in the past.
Bluebirds typically build their nests in trees between 2 and 20 feet off the ground, however they have been observed constructing nests as high as 50 feet in the air.
What this means is that you may make a bird home that is perfect for bluebirds without making something that only they can utilize.
The blueprints for the bluebird house call for four main components: a 1-1/2-inch wide entrance hole, a hole placed 8 inches in front of the house, a complete 10-inch height, and a roof overhang.
The floor of this bird home must measure in at least 4 inches by 4 inches.
An oval entry hole rather than a circular one is an example of a reasonable margin for error, as is a smaller hole to assist ward off pesky birds.
Most of these specifications for a Bluebird house apply to the more frequent Eastern Bluebird; slight modifications are necessary for the Western and Mountain Bluebird, although they are by no means mandatory.
It is generally agreed that Bluebirds prefer a tall box with a sloping roof, and that this box should be mounted on a tree trunk or a wooden post in vegetation.
Bluebird specific 1-1/2 entry hole
Though it may seem peculiar that Eastern, Western, and Mountain Bluebirds all prefer different sized holes when it comes to choosing a nesting site, manufactured bird houses have their own set of challenges.
According to studies, a hole larger than 1-and-a-half inches may seem too huge for Bluebirds to fit through, and a hole smaller than that may be too small for them to enter.
However, if you’re trying to keep non-native birds out, such starlings or house sparrows, a 1-1/2-inch entry hole for bluebirds might be too big.
Although a 1-1/2-inch diameter entrance hole is essential for Bluebird houses, the success of your nesting project cannot be guaranteed no matter how well you market your home.
It is important to know what species of bluebirds you have in your yard because the entry hole size of 1-1/2 inches is typically only relevant to Eastern bluebirds.
Although the Eastern Bluebird has better nesting success in a 1-1/2″ hole, the optimal size of a Bluebird house for the Mountain Bluebird and similarly for the Western Bluebird is between 1-9/16″ and 1-13/16″.
This comes from extensive interspecies research and may explain why the holes appear to be so large.
Hole position 8 inches up
Assuming you already know which species of Bluebirds inhabit your backyard and have the appropriate hole size ready to go, the location of the hole is the next most important consideration.
The hole in a bluebird house should be placed in the center and should be exactly 8 inches above the ground.
All three species are affected by the size of the entrance hole, but only the Eurasian Tree Sparrow can use a box with a hole large enough for its specialized nesting material.
Common as a Bluebird house may seem in appearance, is this unusual feature of an 8 inch high entrance hole location that is rare for sure – with inside measures taking into mind alone.
For a Bluebird house that tops out at 10 inches in height, this would seem like an entry hole that is 8 inches up but nearly 2 inches below the top front piece of the bird house.
The hole’s placement is going to be crucial to any bluebird house, since it can cause the hole to be too shallow or too deep.
Comfortable 4 x 4 floor size
The dimensions of the floor on which bluebirds must nest are the basis for the distinctiveness of a bluebird house.
How big a bird home should be for a Bluebird is 4 by 4 inches, its only then can the Bluebird house be made based on this not so distinctive floor size.
Bluebirds can be deterred by a too tiny bird home as they need the room to expand their wings within the box, but at the same time a too huge bird house catered to them can appear unsafe if it has a too vast interior.
Studies have found that a 4 by 4 inch floor space is optimal for all three species of bluebirds (Eastern, Mountain, and Western).
Wrens, chickadees, sparrows, titmice, nuthatches, and even Downy Woodpeckers all fit well in the same sized birdhouse, so Bluebirds don’t have anything on them.
If the floor is either small or too huge for bluebirds, the complete house won’t be correctly sized for them.
Full 10 inch house height
Although a Bluebird house can only be considered such if it has a floor area of 4 square inches, there is another important dimension to consider: the desired height of the Bluebird house as seen from the front.
The corresponding height for a bird house with a floor measuring 4 by 4 inches is 10 inches.
And while the exterior size may make it look overly enormous, the interior dimensions are what really matter. You might think it’s too little for Bluebirds to nest in now, but if they want to do so, they’ll be very content.
Full 10 inches is required, therefore even if the entry hole is set at the maximum height of 8 inches, it still only leaves a clearance of 1 to 1-1/2 inches at the very top.
The front can be made an inch or less more depending on where you bought it or if you make it yourself, thus these numbers don’t always equal up.
After learning that the floor of the Bluebird house is four inches by four inches and the front is ten inches in height, you would guess that the box is also four inches by four inches.
The front of a bluebird house might just need to be 10 inches, but the back will need to be 12 inches (or more) to allow for adequate slant on the roof for water to run off.
If you disregard how and where a bluebird house should be placed in your backyard, the physical characteristics boil down to just four.
There is some wiggle room in the number of required features to accommodate all Bluebirds.
As a starting point, there is a 1-1/2-inch entry hole designed for Bluebirds, which can be adjusted to a smaller size to dissuade non-native species of birds.
Positioning the hole in the middle is a necessary, however it must be elevated 8 inches above the interior floor to accommodate bluebirds.
The inside floor space must be at least 4 square inches, but the total size of the box is what distinguishes it as a “Bluebird house.” That would translate to an interior depth of 4 inches and a width of 4 inches.
The Bluebird box’s front-to-back height would be around 10 inches.
The additional height in the back panel makes the bird house 11 to 13 inches in height overall, which is necessary to produce the slant on the roof for rain water to run off.
And there you have it; the key distinction between a bluebird house and any other bird house is the size of the entrance hole.