How BIG should a bird house be
What size a bird house must be would depend on the species you intend to attract, but knowing that, it is still possible to attract species you would prefer to avoid.
How big should a bird house be would not only depend on the bird species, but the entire build is based around the floor size. Once you know that, its easy to know what birds you can attract to the box. No one size, universally accepted bird house size, but its important to be accurate to deter more invasive birds.
To build or buy a bird house, how big the bird house should be will begin with what size the floor is, then it all falls into place.
What makes a Bluebird house just that is a common 4 by 4 inch floor size, while the larger Kestrel uses a floor size of 8 by 8 inches.
Why you must know that is because all bird species require their own specific size, with depth and width inheriting the floors internal measurements.
Good bird houses you can buy will refer to a bird specific floor size, so there shouldn't be any surprises later on if you were to at least read the label.
Other than the depth, width and the most important dimensions of all, the floor size - how tall, or how high the bird house must be is a feature that must be accurate.
Height of bird houses are measured from the front panel, so while a bird house belonging to a Bluebird house has a 10 inch height, a more common 8-9 height applies to more species.
While the height of the box comes second to importance over the floor size, remember this is where the bird house entry hole is cut into, so room is needed for the hole.
Bird house size table
| Species: | Floor: | Height: | Width: | Depth: |
|---|---|---|---|---|
| American Kestrel | 8 x 8in | 16in | 8in | 8in |
| American Robin | 6 x 8in | 8in | 6in | 8in |
| Ash-Throated Flycatcher | 6 x 6in | 9in | 6in | 6in |
| Barn Owl | 36 x 23in | 24in | 36in | 23in |
| Barn Swallow | 6 x 6in | 6in | 6in | 6in |
| Barred Owl | 14 x 14in | 26in | 14in | 14in |
| Bewick's Wren | 4 x 4in | 7in | 4in | 4in |
| Black-Capped Chickadee | 4 x 4in | 9in | 4in | 4in |
| Carolina Chickadee | 4 x 4in | 9in | 4in | 4in |
| Carolina Wren | 4 x 4in | 7in | 4in | 4in |
| Chestnut-Backed Chickadee | 4 x 4in | 9in | 4in | 4in |
| Downy Woodpecker | 4 x 4in | 9in | 4in | 4in |
| Eastern Bluebird | 4 x 4in | 10in | 4in | 4in |
| Eastern Phoebe | 6 x 6in | 6in | 6in | 6in |
| Eastern Screech-Owl | 8 x 8in | 16in | 8in | 8in |
| Eurasian Tree Sparrow | 4 x 4in | 10in | 4in | 4in |
| European Starling | 6 x 6in | 16in | 6in | 6in |
| Great-Crested Flycatcher | 6 x 6in | 9in | 6in | 6in |
| Hairy-Headed Woodpecker | 6 x 6in | 12in | 6in | 6in |
| House Finch | 5 x 5in | 8in | 5in | 5in |
| House Sparrow | 4 x 4in | 10in | 4in | 4in |
| House Wren | 4 x 4in | 7in | 4in | 4in |
| Juniper Titmouse | 4 x 4in | 9in | 4in | 4in |
| Mountain Bluebird | 4 x 4in | 10in | 4in | 4in |
| Mountain Chickadee | 4 x 4in | 9in | 4in | 4in |
| Northern Flicker | 7 x 7in | 17in | 7in | 7in |
| Purple Martin | 6 x 6in | 6in | 6in | 6in |
| Red-Bellied Woodpecker | 7 x 9in | 17in | 7in | 9in |
| Red-Breasted Nuthatch | 4 x 4in | 9in | 4in | 4in |
| Red-Headed Woodpecker | 6 x 6in | 14in | 6in | 6in |
| Prothonotary Warbler | 5 x 5in | 6in | 5in | 5in |
| Tree Swallow | 5 x 5in | 7in | 5in | 5in |
| Tufted Titmouse | 4 x 4in | 9in | 4in | 4in |
| Violet-Green Swallow | 5 x 5in | 8in | 5in | 5in |
| Western Bluebird | 4 x 4in | 10in | 4in | 4in |
| Wood Duck | 12 x 12in | 22in | 12in | 12in |
| White-Breasted Nuthatch | 4 x 4in | 9in | 4in | 4in |
Floor size critical
Most important factor of a bird house build is how big the bird house must be. Example of that is a Bluebird house must be 4 by 4 inches, based on the floor size.
Floor size sets the foundation for what dimension the rest of the bird house would be. To get this wrong would result in a to big or too small bird house not acceptable for birds you intend to attract.
Size of the floor for most common backyard birds is based on a 1:1 ratio; meaning if the floor size measures 4 inches wide, it would also be 4 inches deep.
And that would be your floor size that applies to all but three of the bird house requirements as outlined in my table above.
How big should a bird house truly be must be set out on floor size dimensions only, as a too big house can attract more invasive or unintended occupants, while a too small bird house can indeed deter all of them
Set out the bird house build, or if you were to buy a bird house using the floor size, as this can be referenced to my table to make sure you have the correct bird house in mind.
Front Height exactly
Once you've figured out how big the bird house should be based on its floor size, the second most important factor is how tall should the bird house be.
Its vital this section is accurate at the front as it will include the rounded bird house entry hole, depending on the bird species you wish to attract.
The bird house front will determine the overall height of the box, thus the width and depth of the box will inherit this measurement, if it follows an exact 1:1 ratio.
Example is a Bluebird house must be made with a 4 by 4 floor size with a 10 inch front; thus the width and depth would also be 10 inches.
Height of the bird house is vital to get exactly to, or close too the dimensions listed.
Extra height can be included only on the back end, as its here where the slope is needed to allow rain water to cascade off the roof - so therefore an extra inch or two is needed to create this much needed angle.
Width to floor size
To attract America's favorite bird house birds to nest in your box can be easy if getting the size outlined for the birds you intend to bring to it.
In terms of the width these dimensions will basically follow the width of the floor size, while using the vital internal measurements only.
While a Bluebird house would measure 4 by 4 inches internally, so would the outer panel of bird house sides.
Unlike the side panels, the bird house front and back panel can be aligned with the flooring, so would see the side panels inheriting the width, and so to what thickness of the Cedar.
To demonstrate that, once again a Bluebird floor size would be 4 by 4, and so to would the front panel have a 4 inch width, along with the vital 10 inch height.
Width cut for the rear panel is exactly that too, but extra length is needed to use as an area to screw, or indeed to mount to a tree in a more environmentally friendly manner.
Depth still applies
To refer to a different type of bird house this time, the one belonging to the House Finch uses a 5 by 5 inch floor size.
Again, you need to know this because the internal dimensions inherits the floor size for the width and depth of the internal box.
To go along the lines of the 5 by 5 floor size, of course the depth would be 5 inches.
Depth measures a little differently in that the outer dimensions are wider, as the side panels that creates the depth need to take the thickness of the Cedar into consideration.
What that would do is allow the side panels to align up with the front and rear panel, as the front/back panel is flush with the floor size, while the side panels are not.
Depth of bird houses applies to most birds who will use a box to nest in, only not surprising the Barn Owl uses more width than it does depth.
Error of margin acceptable
What truly makes a good bird house is one specifically built to attract a certain type of bird species, depending on where you live in the States.
I must say the floor size, height, width and depth all are important factors when sizing up how big a bird house should be overall.
However, you will be pleased to know there is some room for error of margin. What that means is, if the box is slightly to small or too big, it can still attract the bird you intend to attract to it, and then some.
What isn't good is attracting birds to nest in your bird house you really wished to avoid, such as Starlings and House Sparrows - so there can be negatives for sure.
Instead, error in sizing a bird house can be contributed mostly to the floor size, as it would set you up with many issues to come.
Get the floor size correct with a margin of error of less than 1/2 inch (half inch) only, then the width and depth can vary slightly if need be.
Height of the bird house really needs to be accurate so do refer to the table outlining this important data - you'll notice many species share the same height - so the bird house can attract many species to it.
Summarize it all up
What size should a bird house be can depend mostly on the type of bird species you wish to nest in the box.
How big said bird house would be would begin with the floor size. To get this correct if bought or built yourself - the rest of the dimensions will follow suite.
To have a bird house that attracts Bluebirds uses a 4 by 4 inch floor size, and therefore the width and depth would also be 4 inches across with 4 inches deep.
Height of the bird house is important as birds may only nest in a bird house that is tall, as measured in the front.
Extra height is required in the rear as the support back panel is used to mount, as well as to secure the back section of the bird house of course. But an angle is needed on the roof so this is where a taller back panel comes into play.
Bird houses must be built to a specific size internally as small birds can find a box to be too big, while a larger bird has no room to spread its wings.
Handmade bird houses basically inherit the size of what cavities birds use in the wild, so while height is an important factor, width and depth is a little less so.
Get the floor size exactly right, then everything else will fall in to place, size wise.
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