BluebirdersBauldry Nestbox Not Recommended

Bauldry Nestbox Not Recommended

open top nestbox photo sold by CovesideThe following is an excellent summary of research and results of the Bauldry/Open Topped Box Design by Diane Barbin of Harrisburg, PA,  originally posted on the mailing list Bluebird-L 3/25/99.  Personally, I do NOT recommend use of this box because it unnecessarily exposes nestbox contents to the elements, and has not been proven to deter House Sparrows, which are happy to nest in gutters and exposed signs on buildings.


The fence post sites which the open top design is intended to mimic were last resort sites which Bluebirds had been driven to by the invading Starlings and House Sparrows. Kevin Berner and Robin Clark support this view.

Fence post sites and open top box designs are inherently inferior to the NABS, Slot Box, Peterson and Gilbertson designs. This view is supported by all listed below and by all known books in print on Bluebirds including those of Zeleny, Scriven, Toops, Grooms & Peterson, Stokes and Troyer.

Weather is a significant factor in nesting success, and the Bauldry box design is intuitively and empirically proven to be the least protective of Bluebirds from weather. Each year nest box reports document the dramatic effect of weather variations across the country on nesting success (see e.g. Black, 1997 Nesting Box Report, 20 Sialia 88 (Summer 1998)(Paragraph 2, noting effect of the unusually cool wet springs in several states including northern Pennsylvania). The MDC study of the Bauldry Box confirmed its weakness in this respect.

The open top box has not been shown to deter House Sparrows or House Wrens.  This view is supported by Mr. Berner and the MDC, Mr. Berner notes, and the current research supports a conclusion, that the Gilbertson box is the most House Sparrow deterrent design currently available.

The box has been in existence long enough that further testing is not warranted. This is not a new design. It has been in existence for more than 20 years and has not proven its worth, like its competitors. There is no productive purpose in endangering Bluebirds to prove what is both evident and well established, while birds may nest in and fledge from such boxes, the boxes are inferior to several other designs which have demonstrated their superior characteristics.

We cannot support any effort to test the Bauldry Box in Pennsylvania. Putting out nestboxes in Pennsylvania that have no roof, in prime Bluebird habitat, given our variable spring weather, is not responsible. There is too much potential for harm to the Bluebirds, and too little likelihood of any productive results. Reinventing the wheel at the expense of our local bluebirds is not responsible. Perhaps we are thinking too hard. If neither Bluebirds nor House Sparrows will chose an open top box unless there is no alternative, perhaps all that proves is that even a bird brain knows to come in out of the rain, if it can….

Having said all that, if there are those out there who still feel that this box should be tested, then my suggestion to you is to do so in prime House Sparrow habitat, that is NOT also a prime Bluebird habitat. Such a study may reveal whether or not they are House Sparrow resistant, without also jeopardizing the lives of the Bluebirds who we are working so hard to help.  This is the model used by Berner who went further and made the hole smaller so that wrens could, but Bluebirds could not, use the test boxes. See Berner, House Wrens and Open topped nest boxes, 21 Bluebird 12 (Winter 1999).


All dedicated Bluebirders are in search of the perfect nestbox, one that will allow for the Bluebirds to have the greatest success against all odds.  Sometimes debates on narrow issues can take away from more productive work on behalf of Bluebirds. While a healthy debate can lead to productive innovation, uninformed experimentation usually leads to avoidable deaths for those we are trying to assist. I cannot sit silent when the very real risk of such avoidable deaths is present.

Dorene Scriven has written, “While it is true that Bluebirds will nest in old boots, bottles, mailboxes, tin cans, and badly designed boxes if they are in a good location, when we deliberately attempt to attract Bluebirds, we should feel obligated to use a box built to best advantage.” Scriven, Bluebird Trails: A Guide to Success, 40 (1993). It is from a sense of obligation to the Bluebirds we are trying to assist, that I continue this dialogue on the Bauldry/Open Topped Box design.

Because of the current debate, my husband Andy and I have done some additional research regarding the Bauldry Box design. The results have convinced us that any research efforts by the Bluebird Society of Pennsylvania would be better spent on other designs and other issues, and that any testing of the Bauldry Box design should be confined to limited tests by qualified professionals in controlled conditions, such as the study recently completed by Kevin Berner regarding the raised topped variation of the open topped box design. We thought we should share this summary of the results of our research:

  1. NABS does not endorse this nestbox design. With an intercontinental membership of distinguished bluebirders, the rejection of this design by NABS is important evidence which should not be ignored, especially in light of the endorsement by NABS of the NABS Box, Slot Box, Peterson Box, and Gilbertson Box designs along with many variations of each. NABS has no reason to withhold approval of proven box designs, and no history of doing so.
  2. BRAW, the Bluebird Restoration Association of Wisconsin, does not endorse this box design. Vince Bauldry was from Wisconsin. The rejection of the Bauldry box design by his home state’s respected Bluebird organization is also strong evidence against the design. It is reasonable to assume that this style box was tried more extensively in Wisconsin than in any other area; just as the Peterson Box was tried more widely in Minnesota the state of its designer, Dick Peterson. Peterson boxes have proven themselves well beyond the borders of Minnesota as time has passed. Bauldry Boxes have not, this too is strong evidence against the design.
  3. BBRP, Bluebird Recovery Program of Minnesota, does not support this box design. BBRP long ago established itself as an organization worthy of respect for its work on behalf of Bluebirds. They are widely respected for their work evaluating box designs and predator guards. BBRP’s rejection of the Bauldry Box design is strong evidence against the box. Dorene Scriven the long time chair of BBRP has observed, “There is a considerable difference between a dry warm bluebird nest and a cold wet one.” Scriven, Bluebird Trails: A Guide to Success, 44 (1993).
  4. Kevin Berner, does not endorse this box design. Kevin is a Wildlife Biologist from SUNY, the NABS Research Chair, and has done a study of a variation of the open top design, the raised top design. The following are excerpts from recent email from Mr. Berner on this subject: “I’m not convinced that open topped rotten fence posts where ever that important as a ‘natural’ nest site. I’ve been reluctant to lure bluebirds to open-topped boxes for the very reasons you expressed, so I have never used them.” With respect to his test use of a raised roof variation of the open top design, Mr. Berner reported, “I have never used true open-topped boxes. I have used limited numbers of open-topped boxes with a roof raised around three inches above the open roof. I tested their ability to deter house wrens by reducing the hole size below what a bluebird could use and placing them in prime wren territory.  They were used by wrens a lot so that species isn’t deterred. I haven’t used them to deter house sparrows. I usually only have one or two sparrow nests in 100-150 nest boxes each year. I too am skeptical about a totally exposed box.  Vince Bauldry in Wisconsin has had great success with them for years, but few others have really supported their use. If you want to deter house sparrows, my research indicates that Gilbertson’s PVC boxes are the best choice. Mr. Berner’s study results were summarized in Berner, House Wrens and Open topped nest boxes, Bluebird, Vol.21, No.1 p.12 (Winter 1999), (Berner concluded the boxes did not deter House Wrens).
  5. Missouri Department of Conservation (MDC) does not endorse this box design.  Although plans for the box are available on their web site, along with NABS box plans, Ken Drenon of the Missouri Department of Conservation responded to an email inquiry regarding MDC’s experience with the Bauldry open top box design as follows:” MDC researched the Bauldry box and found a higher nest failure, however, unusual weather conditions during the research may have affected the finding. Also, MDC found the box did not deter sparrows.”  Unusual weather is exactly what can reasonably be expected in a normal weather cycle. If we fail to account for the worst weather of a cycle, general use of a flawed design could lead to the decimation of the Bluebird population.  Moreover, house sparrow and/or house wren deterrence was the only justification for the use of the box over other designs, and the studies indicate that it does not provide that advantage.
  6. Grooms and Peterson, noted authors and Bluebirder, have written, “Some matters are not controversial. A good box must offer protection against the elements. It should be insulated so that the female can keep eggs and nestling warm with her body heat. Drafty houses won’t allow Bluebirds to keep the eggs warm during early spring cold snaps.” Grooms & Peterson, Symbol of Hope: Bluebirds, p.101 (1991). Not surprisingly, the Bauldry Box Design is not included in their collection of recommended designs, though the NABS design, the Huber Flip-Flop which compete with the Peterson Box are recommended and the Slot Box and PVC Boxes are mentioned favorably.
  7. Lawrence Zeleny, a founder of the Bluebird restoration movement, emphasized that protection from weather was an essential design criteria for a good box.  Zeleny wrote, “Nesting boxes for Bluebirds have been used with varying degrees of success for many years, and numerous conflicting opinions have arisen in regard to proper construction of the boxes. Fortunately, Bluebirds are not at all particular and seem quite willing to use almost any kind of box that they can enter, provided it is in the right kind of location and is not already occupied. It is important, however, to adhere to certain basic requirements in order to … offer the greatest possible protection to the Bluebirds from their enemies and from adverse weather.” Zeleny, The Bluebird, p.51 (1976).  Zeleny specifically promoted boxes with roofs which overhung the entrance hole “to minimize the chance that rain would be blown in to the entrance hole.”

Others also responded against the design:

  1. Jim McLochlin of Omaha, NE who maintains the The Bluebird Box web site responded, “The Bauldry nestbox and all of it’s derivations have been largely discounted in all but the driest of climates for the very reason you mention.  The latest design trends evolving from this box design are the raised roof designs. I would certainly not recommend an open top design to anyone.”
  2. Robin Clark owner of a Wildbird Market store and an experienced birder responded: “We have been in this business for a number of years and have had the opportunity to speak to lots of birders and wild bird market store owners, as well as some research people. The design in question was developed probably 20 years or more ago. It is supposed to simulate the top of old fence posts that have rotted out leaving a depression large enough to nest in. When this box was designed, the Bluebird was in major decline having had their natural habitat all but completely taken over by the English import sparrow. The Bluebird, for lack of other habitat, would use the tops of old fence posts and, consequently, this (then) new design. Sparrows did not need nor want to use an open top design. Fast forward to the present, with thousands of man-made boxes and a vast increase in Bluebird population. Given the choice between a home with a roof or one without, the Bluebird will choose the roof design (all other things being equal ). Why? Because they are cavity dwellers not cliff dwellers! While the design may well have helped in recovering the Bluebird population, its usefulness has long past and is now a curiosity rather than being beneficial to the species.”

The evidence in support of the design is questionable at best:

  1. The only research to supports the Bauldry box was done by Bauldry himself. If anyone has a copy of the report, we would appreciate a copy. We are informed that it involved only his box design and had no test controls to indicate whether greater success would have been achieved with more recognized designs. The cornerstone of the scientific method is confirmation by independent replication. We are aware of no studies which replicate the results of Bauldry’s self study. Considering the length of time that the open-topped box design has been around, by now there should be a larger number of supporting studies of this design if it was truly as successful as Mr. Bauldry had claimed.
  2. Last year’s article in Birder’s World was about a man who intended to try the Bauldry Box design in the coming season; not about a man who had done so successfully previously. It provides no evidence in support of its use and relies entirely on Bauldry’s self study to support its sweeping endorsement and unfounded claims of Sparrow deterrence. Moreover, there was no suggestion that the use in the coming year was in any way to be considered a study of the box, or that any controls were to be in place to establish scientific validity to the “test” use.
  3. None of the persons contacted by Internet had anything good to say about the design. All shared concern regarding the premise of the open top design, and none would recommend it.

More Information:

Good design is all about making other designers feel like idiots because that idea wasn’t theirs.
– Frank Chimero


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