No nestbox or birdhouse is perfect, however, there are researched designs that are typically approved due to a design that promotes a safe nesting cycle for its residents.
Building a birdhouse is a great activity for a cold, rainy, or snowy weekend. Here are some basic plans for a bluebird house that is approved by the North American Bluebird Society!
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Bluebird house location
Place each nest box 300 feet apart
Place in an open area on a pole, not on a tree trunk
This prevents climbing predators from easily accessing the nest
The entrance hole needs to be at least 5 feet above the ground
Place in a location that is easily accessed by humans
Regular maintenance is necessary
Regular monitoring is necessary to prevent invasive species from using the box
Face the entry of the nestbox to the south or the east to prevent afternoon overheating
Face the entry away from prevailing winds (during the breeding season)
Bluebird house materials
Solid wood between 3/4 and 1 inch in thickness can be used
Use a hardwood that does not have or require a chemical treatment
Do NOT use:
One board 1" x 6" x 4' long
This will supply the floor, side, front, and back pieces
One board 1" x 10" x 12"
20 - 1⅝ inch deck screws
3 - 1¾ inch galvanized nails for the pivot points
A post of varied material (metal, wood, etc)
Bluebird house dimensions
4 x 5½ inches (Eastern Bluebirds) to
5½ x 5½ inches (Western and Mountain Bluebirds)
5½ x 10 inches
5½ x 12 inches
If you make it longer than 12 inches, you will have an excess lip above or below your box for attaching to a post or pole
Side size (two)
Front length - 10 inches
Back length - 12 inches
Width - 5½ inches
Length - 12 inches
Width - 10 inches
Bluebird house assembly
Follow these steps, in order, to assemble the bluebird nestbox:
Wear your eye and respiratory protection devices!
Bluebird house drainage
Cut a small amount of the corners off the floor to allow for drainage
Bluebird house hole size
Cut a 1-9/16 inch entry hole in the front section for the bluebird house to accommodate for all bluebird species.
If you only have Eastern Bluebirds, you can use a 1½ inch hole
The hole needs to be 5½ inches from the bottom of the front board
Smooth the edges of the hole with sandpaper
Saw cuts (called kerfs) into the backside of the front board to make a ladder for the babies to fledge
Build the bluebird nestbox
Connect the bottom to the front, back, and ONE side
Recess the bottom board ¾ inch
Predrill the attachment points for the deck screws
Attach the second side to the front and back boards using the two galvanized nails
Predrill the slots in the front and back boards and into the 1-inch side of the sideboard. Insert the nails. These nails act as your pivots.
Use the third nail to act as the latch by drilling a hole in the front or back board and the 1-inch side of the side board.
Insert the nail to prevent the pivot until box maintenance is performed.
Drill ½ inch vent holes at an upward angle
If you are in a colder climate, do not add vent holes
Attach the roof
There should be a 2-inch overhang on each side, a small overhang of 2 inches, or less, over the back, and the remainder should be over the front board
Attach your box to a firm location
Some bluebird lovers place them on large fence posts, T-posts, or metal conduit
Regardless of material, the post needs to be firm against the strongest of winds
Want to see diagrams for this project? Check out the updated bluebird nestbox recommendations from NABS! You can also check out the plans offered by NestWatch from Cornell Lab of Ornithology.
Bluebird house hole sizes
Eastern Bluebird hole size
For Eastern Bluebirds, use a 1½ inch round hole
If you get multiple bluebird species, use the larger opening (see below)
Western Bluebird & Mountain Bluebird hole sizes
For Western Bluebirds and Mountain Bluebirds, use a 1-9/16 inch opening
If you get multiple bluebird species, use the larger opening
How to protect a bluebird house
There are multiple ways to deter climbing and other predators from a bluebird box:
Do not use a perch
This deters House Sparrows and other birds
Install a slick or unstable baffle
Wax the pole (if metal)
Use a cone
You can remove the nests and eggs of invasive species like House Sparrows. However, disturbing the nest of a native species, even if it is not what you want in the birdhouse, is a violation of the Migratory Bird Treaty Act and could subject you to fines. Brown-headed Cowbirds are a native species and removing an egg from that species is still a violation.
Bluebird house maintenance
Here are some helpful tips to for continuing a good condition of your bluebird nestbox:
Clean the nestbox after EACH brood has left
Check for water leaks
Repair or replace rotted wood
Check the entrance hole to ensure the size has not changed
Want to purchase a bluebird house?
Purchasing a bluebird house can be a tricky situation. Most bluebird nestboxes are made to accommodate Eastern Bluebirds, so if you experience a different species, it will not be conducive to those species. Also, cheap wood and screws are often used. If you decide to go the purchasing route, try to find a box that fits the recommendations above. "Predator guards" and "extra features" are a waste of money. Do not fall for those sales tricks.
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Remember there are no perfect boxes, but here is a seller on Amazon that will adjust your house to your specifications: Cedarnest Bluebird Houses.