ANY 4" PVC Tube Box (see photos at end of page)
Original NABS (4 x 4)
Carl Little (4x4)
Droll Yankee (4x3)
Flying Nun (3&3/8 x 6)
Fox Box (4x4)
Gilwood (3.5 x 4.25)
Huber Flip-Flop (3.75 x 4.5)
Hutchings PVC Tube (4" Round)
Lenker Box (4x4)
Kentucky Slot (4 x 4)
Loren Hughes Slot (3&3/8 x 3&3/4)
Mel Bolt (4 x 4.25 or smaller 3.75 x 4.5)
Ohiowood (4.5 x 4.5)
Peterson (3.5 x varies to nest height)
Troyer Slot (slant front) (3.5x4)
Rita Efta Slot Box
Simplest Slot (4x4)
Van Ert Slot (4x4)
Vince Bauldry Box (4 x 4)
House Sparrow Resistant:
BEFORE YOU DECIDE TO BUILD OR BUY a House Sparrow Resistant box, read the following discussion (Bluebird-L): Gilbertson Box Discussion The discussion has application to any small House Sparrow Resistant nestbox.
Whether bluebirds will nest in small boxes and fledge chicks is quite different from discussions of the space per bird that is required for optimum growth and survivability after the fledge. The only poster who consistently tries to bring back the discussion to after-fledge survivability is Keith Kridler. Pay close attention to the information and background he offers.
Photo shows a Gilwood (3.5" x 4.25" floor space) with a peanut butter jar inside to give perspective to the tiny size of the box.
Griffin Box (4x5.5)
Springer Chalet (4x5.5)
X-Box (4x5.5) (entry hole on long side)
A Note on Tree Swallows:
5" x 5" Floor
David Gwin (large Peterson 5x5 & 8" hole drop)
Herman Olson> (5x5)
Johnson (5.25 x 5.25)
Wings of an adult bluebird can partially open and it would appear that about four to five bluebird nestlings would be quite comfortable on a box floor of this size.
6" x 5" Floor or Larger
By comparison, I am now building oversized boxes with approximately 6" x 5" floors. Notice that even this 6" width does not allow the wings to extend.
2-Holed Mansions (6 x 5)
Long Point (Tree Swallow Project) (6 x 5.5)
Large Slot Box Plans (7 x 5.5)
If I did not have to hoist boxes into trees, I would be building larger floors of 6"x6" (see Bob Wilson's Plans below)
The 6" x 5" floor appears to fit the physical needs of Western Bluebirds. There is space to move about and exercise wings even with clutch sizes of six or seven chicks.
Betty Lovejoy of Yorba Linda, Calif., has had clutches of seven western bluebirds fledge from her box of this size for three straight years—the large floor area looks a lot different when it is filled with seven active chicks. These robust western bluebird nestlings still had more days of growing before they flew from the nestbox.
There are fecal deposits on the straw but, because of the extra space in the box, it is able to dry into a powdery texture which does not affect the nestlings' feathers.
Around the date of fledging, a layer of slime sometimes occurs even on the large floors but it is much thinner (less danger to nestlings) with the larger surface area.
Gilbertson (4" tube)
Navratil (4" tube)
Hutchings (4" tube)
The photo to the right is a Western Bluebird. The circle underneath it approximates the size of a Gilbertson PVC tube.
Obviously, that floor size is too small for western bluebirds. Yet, it is my understanding that Steve Gilbertson sold about 3,000 of these nesting tubes per year for over a decade. Cheap to make, cheap to ship. As of 2012, he's no longer making them but he leaves behind a legacy of incredibly small boxes that are promoted and sold by the North American Bluebird Society (NABS).
Below is a post by one of today's foremost bluebird authorities, Keith Kridler, in response to a question posted on Bluebird-L, a forum for bluebird discussions. It begins with discussions specific to PVC tubes but contains a superb range of nestbox considerations:
the young bluebirds inside the nestbox because they tend to be able to hop to the entrance hole well before they are ready to fly. Survival rates would have to be determined with radio controlled devices from different box styles (various floor sizes) and fledge dates to determine if one box style were better at fledging stronger young birds better able to keep up with the parents and more importantly able to avoid predators. I believe that larger floor area will allow more exercise and just because all 7 baby bird fledge from a 4" pipe box does not mean they are ready to start and fly a marathon when that predator gets them in their sights hours after they fledge! KK
You may contact me, Linda Violett
As of June 15, 2012