What makes a Bluebird house, a Bluebird house
Bluebird houses are not so unique as others, but four major features are indeed needed if you were to ever attract Bluebirds to nest.
What makes a Bluebird house a Bluebird house relies heavily on the entry hole in a 1-1/2 inch size. Entry hole would be located in the center of the box measuring 8 inches up from the inner base. Floor size must be 4 by 4 inches with an internal 4 inch width and depth - with the bird house being 10 inches tall.
What's important to know when understanding what makes a Bluebird house a Bluebird house, is how this wooden box replicates their natural habitat.
Bluebirds have evolved to nest in the cavity, or a hole in a certain size within the trunk of a large, mature tree. Naturally formed hole I might add that indeed could of been previously used as a woodpecker nest.
Nests within trees would be located in the median range of 2-20 ft. off the ground, but it is possible Bluebirds will nest up to 50 ft. or more, if their natural environment allows it.
How this translates to what would be - not so much a unique to the Bluebird species - but a bird house that is suited to their needs for sure.
Build of the Bluebird house would be divided up in to four major features: it would have a 1-1/2 entry hole; hole positioned 8 inches up in front; with a full 10 inch house height.
More importantly than all that, this bird house would need a floor size of 4 by 4 inches.
Error of margin is possible within reason, with an oval entry hole shape over a rounded one possible, or a smaller hole to help deter nuisance birds.
Most of these requirements for a Bluebird house is in relation to the common Eastern Bluebird - with a few changes required for the Western and Mountain Bluebird, but not a must I might add.
What kind of bird houses do Bluebirds like is universally accepted as a tall box that uses a slanted roof, where it must be fixed on a tree trunk or on a wooden post in vegetation.
Bluebird specific 1-1/2 entry hole
Strange as it is for Bluebirds of the Eastern, Western or Mountain variety to nest in the cavity of a tree with varied hole sizes, its not so easy with an artificial bird house.
Research as shown that Bluebirds require an entrance hole of 1-1/2 inches, or else it can appear to be too big for their needs, or too small to enter.
Having said that, a Bluebird entry hole of 1-1/2 inches can be reduced a little, if anything to deter invasive species of the Starling or House Sparrow kind.
Safe entry hole of 1-1/2 is what truly makes a Bluebird house, with a house specifically designed to attract Bluebirds to nest only, but that is not a guarantee.
Identifying what Bluebirds are in your yard should be prioritized because as it happens, the recommended 1-1/2 inch entry hole - can mostly relate to Eastern Bluebirds only.
Its been shown that while a Eastern Bluebird sees more success nesting in a 1-1/2 hole, how big a Bluebird house should be for the Mountain and so too the Western would be, is anywhere between 1-9/16" to 1-13/16."
Big as these holes may seem, this comes out of long research between the species.
Hole position 8 inches up
Once you've identified which of the Bluebirds are present in your backyard, with the correct hole size ready to go, the position of the hole is a vital one.
Where to put the hole in the bird house of a Bluebird would of course be in the center, but it must be exactly 8 inches up.
Height of the Bluebird entry hole relates to all three species, but can be present on a box for the Eurasian Tree Sparrow only, and no other bird species.
Common as a Bluebird house may seem in appearance, its this unique feature of a 8 inch high entrance hole position that is rare for sure - with internal measurements taking into consideration only.
How this would appear on the front of the bird house would be the 1-1/2 in entry hole 8 inches up, but a near 2 inches below the top front section for a Bluebird house that is 10 inches tall maximum.
What is going to be a vital part of any Bluebird house would be the placement of the hole, as it can lead to being too shallow or to deep for their needs.
Comfortable 4 x 4 floor size
What would set the foundation for the uniqueness of a Bluebird house, is the size of the floor where Bluebirds must nest on top.
How big a bird house should be for a Bluebird is 4 by 4 inches, its only then can the Bluebird house be built based on this not so unique floor size.
Bluebirds can be deterred by a too small bird house as they need the room to spread their wings within the box, but at the same time a too big bird house catered to them can appear unsafe if it uses a too large interior.
Once again, research as shown that a 4 by 4 inch floor size to see more success with all Bluebirds, including Eastern, Mountain and Western.
Not a unique size so much too the Bluebirds as Wren's, Chickadees, Sparrows, Titmice, Nuthatches and Downy Woodpeckers share a similar floor size bird house.
Remember, the Bluebird floor size sets the foundation for the entire house build, so if its a little smaller or larger, this puts the whole sizing out of order - thus resulting in a house that is not setup for Bluebirds properly.
Full 10 inch house height
While a Bluebird house can only be classed as such with a 4 by 4 inch floor size, one more vital dimension is how tall should the Bluebird house be, as measured at the front.
With a bird house that uses a 4 by 4 inch floor size, this would then correspond to a bird house that is 10 inches tall.
And while it can appear too big, its important to know these measurements apply to the internal dimensions only. Now it feels the opposite as you may think its too small, but in fact its just the right size for all Bluebirds to happily nest in, if they do.
Full 10 inches is a must, so with an entry hole positioned up to 8 inches high, that would leave a clearing of only 1 to 1-1/2 from the top.
These measurements don't always add up, but that's only because the front can be built an inch or less more depending on where you bought it, or if you make it yourself.
Now that you know the Bluebird house to have a 4 by 4 inch floor size, with a 10 inch front - you probably would of guest by now the box is 4 inches in width, 4 inches in depth.
Bluebirds houses might need a 10 inch front, but 12 inches - more or less - is needed in the rear, to create an angle on the roof for rain water to drain away.
To summarize
If you ignore the crucial placement of a Bluebird house in your backyard, the physical attributes is concentrated on four features only.
Few features are vital to accommodate all Bluebirds, with room for a margin of error.
First up is a Bluebird specific 1-1/2 entry hole that can be made slightly smaller to help deter invasive birds.
Hole position is in the center of course but it must be set 8 inches high based on the internal flooring, to please the needs of Bluebirds.
What truly makes a Bluebird house a Bluebird house is the overall sizing of the box, with a 4 by 4 internal floor size a must. In turn that would correlate with a 4 inch depth, along with a 4 inch width internally.
Height of the Bluebird box would be in the 10 inch range, as measured at the front.
The bird house would be 11 to 13 inches tall in total as this extra height sitting in the back panel helps create the much needed slant on the roof for rain water to run off.
And there you have it, what is so unique about a Bluebird house is its entry hole size, with all its other but not so unique features preferred by similar size backyard birds.
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