Design Your Own Bluebird Box . . .
This page has information and links to help you design your own bluebird nestbox and/or make the best choices for nestbox purchases.
If you are interested in building basic boxes (rather than your own unique design), click on Nestbox Builder for detailed plans and then on "Tutorials" for building guidance.
The biggest mistake most nestbox designers make is to limit the nestbox size to what can be cut from a single fence board rather than building to the ideal size required by nesting bluebirds.
Do not concern yourself with the size of a fence board. Figure out your ideal box dimensions and the pieces you will need to build it. Then pick through scraps at a lumber yard to get what you need to build one box for next to nothing. If you are building multiple boxes, purchase a few boards in the various sizes you'll need. A little extra lumber (waste) gives you the option to work your layout around knotholes and board flaws.
How large do you want the floor? Floor Space
It is estimated that each bluebird-sized chick should have approximately 4 sq. inches of space for optimum survivability after the fledge. Make your calculations based on the largest clutch expected.
How deep (safe) do you want the box? Depth of Box
Note: Deeper boxes should have at least 5"x5" floors so birds have sufficient "flutter space" for easy exit. If you plan on building/buying a box with less than 5"x5" floor, skip this option and use the standard 6.5" drop. Most nests are about 2" high so there is only 4.5" drop from the holes to the top of the nest in a standard box (too risky for my trail, especially when safer boxes can easily be built).
On my own trail, missing chicks/eggs (avian predation) did not stop until the drop (hole-to-floor) was increased to 8.5". If you are seeing crows or jays around boxes and/or missing eggs/chicks, consider building deeper boxes (along with at least a 5x5 floor).
If you build a deep box and later decide you don't want or need an extra inch or two, no problem, just add a block of wood to the inside to bring the "floor" closer to the holes.
However, if you build a box too shallow and decide afterwards that you need extra depth protection, there's no quick fix.
3. Escape Route
Do you want to provide an escape for birds if the box comes under attack?
If so, then here are some box designs to study:
Kinney ; you would need to make one of the feeding portals larger to allow passage
Or build a 3-holer designed by Sherryl of central Oklahoma
ALL box designs can be altered. No measurements are set in stone. The above box styles can be used as springboards because they have sufficient floor space and can be built or modified to allow adults an avenue of escape through either a slot or an extra hole.
Some monitors argue against adding an escape route because, even though adults will have a good chance of escaping the attack, they say it does nothing for the eggs and chicks.OK, Monitors who prefer to lose everything all at once (adults along with eggs and chicks) should NOT add an escape route.
Monitors who choose a box design with an escape route (slot or second hole) for the adults will also have a very good chance of the parents surviving for continued defense of eggs/chicks. If defense of eggs/chicks is not possible (let's say a raccoon raiding the box), the surviving parents may stick around for a second nesting while you figure out how to add a baffle for ground predators.
The above box design topics should be considered from the standpoint of optimum protection, comfort and survivability of the nesting birds you expect to have in the box.
House Sparrow Resistant Boxes: "House Sparrow Resistant" means something substandard was built into the box design on purpose so that House Sparrows will avoid (resist) the box. Those intentional built-in "flaws" are usually tiny interior box space or shallow hole-to-floor drops.Here is a link to a huge list of boxes, including House Sparrow Resistant Styles: Other Box Plans
Keys to Success
Monitors with House Sparrow problems do not have to settle for HOSP Resistant boxes. See
4. Research — And Use Critical Thinking Skills
Try to locate actual tests of how each box style or mounting system performs. What are the compromises? For example, Bauldry boxes with an open hole in the roof might be House Sparrow Resistant (House Sparrows avoid using them for good reason), but Bluebirds would also be at risk from hypothermia in cold/wet weather and possible sunburn (through the hole in the roof) during hot summers.
Beware of Bluebird "Preference" or "Productivity" Reports
Quite a few studies are able to scientifically prove that bluebirds "prefer" a certain box style or that shallow boxes are "more productive". Same thing was done with the Open Top box. Here is a 27-year study by Wisconsin that "proved" Open Top boxes had less House Sparrow problems, less House Wren problems and were more productive than standard boxes with solid roofs. Almost everyone today knows not to use Open Topped (Bauldry) designs but here is that scientific report that supports the use of Open Topped boxes: Breeding Success of Eastern Bluebirds
Now Wisconsin has done more recent studies that "prove" shallow boxes are more productive than deeper boxes. And that information is included in Wisconsin's Informational Packet (scroll down about a quarter of the web page to "What kind of Nest Box Should I Use For a Bluebird Trail?" where they state 4" to 5" drops with 4"x4" floors work best.
Wisconsin's shallow box study may go the same route as their ill-fated Open-Top study.
5. Filter out Group Bias
Only a few years ago, high-profile experienced monitors were advising that box exteriors should not be sealed because birds "preferred" natural aging wood. It took decades of birds dying from hypothermia before the tradition of "natural" boxes was abandoned. People are STILL building box styles based on the old theory that extra light in nest boxes will deter House Sparrows.
The Gilwood box was being touted as House Sparrow Resistant, in part, because of extra light via the large mousehole. Extra light in the box doesn't matter to House Sparrows. I have tried putting Plexiglas roofs on some boxes in ADDITION to the 2 holes. House Sparrows may be wary of box changeups at first and then readily use boxes with Plexiglas roofs.
Keep in mind that "expert" viewpoints are opinions and perceptions based on yesterday's information.
6. Use your OWN common sense
If you have a clear idea of what you want, STOP right here. Don't read any further. You are better off getting your supplies and heading straight to the workshop based only on the basic information provided above.
Then come back and read about the add-ons or to fine-tune your design. Here is a good place to start on nestbox information (grab a cup of coffee first): Bluebird Box (by the Omaha Bluebird Society).
Chances are that you won't have to concern yourself with box add-ons if you built a box with good basic dimensions.
Front, top or side opening. Keep in mind that if all your holes, vents and openings are on one side of the box, you can slant the box face slightly downward toward the ground so the box doesn't take in water during rainstorms. Choose your style accordingly. Rain
Roof Style & Considerations (see above link)
Water sealing, drip edges; (see tips below)
Drain holes (some recommend them, some don't )
Hole Shape/Size: NABS Box Specs
Sun - Heat Shields
FLOOR DRAIN HOLES:
The vast majority of Bluebird monitors cut drainage holes in their box floors. If boxes are completely sealed with a waterproof "skin" of silicone caulk on the outside, water problems can be virtually eliminated. That goes hand-in-hand with having all openings on one side of the box that can be turned away from prevailing wind and tilted slightly toward the ground. I do not add drainage holes.
The logical solution is to completely waterproof boxes (silicone caulk is effective) instead of drilling holes in the floor. If you have a top-opening box and water is getting into the box, then yes, you will need to add floor drain holes until you can build a replacement box.
Attention to Details
Make sure the box
tilts slightly toward the ground (not as drastic as the Peterson
Box face angle, but same principle).
Give both the
inside and outside box seams an extra layer of waterproof
Screw in the box
floors so they are slightly higher in the back; any water that
gets inside the box should flow toward the front door and leak
out from the gaps at the front side seams at the door face. Be
sure to face your boxes away from wind/water.
Add a length of
wood trim to the front edge of the box—spaced so it sticks a
little above the roof edge to divert water to the sides of the
box and a little below and/or form a drip edge.
kerfs (toeholds) on the inside front under the holes.
Bet Zimmerman has listed a huge amount of box styles into one chart, listing them alphabetically and providing a brief synopsis of each style (about fifty boxes shown) on this chart: Box Pros and Cons (Sialis.org) . Most of them are basically the same thing with some minor modification.
Sorting it out by a logical sequence:
At some point (I think we are already there) it will become necessary to replace box names with box ID's according to dimensions and other basics just as we do with numbers on a fertilizer bag. For example, a Gilwood would look something like the following:
5.5" Hole-to-floor "Drop"
Here's an interesting circle of nestbox names and styles . . . . . .
The Tuttle box design is a standard front-opening box. The "Gilwood" box (pictured above) is a smaller version of the Tuttle style with a mousehole entry. Bernie Daniels took the small Gilwood, made it standard size again with a round hole (basically a Tuttle again) but gave it a new name, the "Ohiowood".
There are way too many named boxes to sort through. So it is easiest to concentrate on the basic dimensions and then think about add-ons.
Box "designs" are simply a combination of ideas and features from other boxes, other monitors and additional observations.
A special thanks is given to Andrew Plaza of Pennsylvania who supplied me with a photo (above) of a box he built with a second "escape" hole after an incubating female was killed in his 1-holed box.
In his letter, he stated, "If you do use the 2 holes and see evidence of the Bluebirds using the additional hole as an escape route, please let me know."
The answer is a resounding YES, Bluebirds do use the escape hole.
PAIRING BOXES Is sometimes done to see which boxes are preferred. See the letter from Dick Peterson which is included on Steve Gilbertson's web site.
Most often, pairing is done as a House Sparrow control. When boxes are paired on my trail in HOSP problem areas, House Sparrows end up with two boxes instead of just one.
Pairing for Tree Swallows:But if you are pairing to accommodate both Tree Swallows and Bluebirds, see: Pairing for Tree Swallows
You may also want to keep an eye on Shari Katner's 2-holed box test site that was intended for House Sparrow/bluebird battles but she had Tree Swallows take the 2-holer during the 2012 season: Kastner 2-holed Box Test This is only one test site with HOSP/TRES competition; NO assumptions can be made from this single test site. Just something to follow for those that have Tree Swallows.
And, just for fun, moonwalking birds.