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PVC vs. Wood Nestboxes
From: "Gary Springer" springer"at"alltel.net
I've been thinking about making nest boxes for cavity nesting birds that are a bit larger than the bluebird. I computed the floor space of some of the natural cavities these birds use and was quite surprised by the difference in floor space between round and square cavities. Maybe all of you have thought about the following but I never had: A "sparrow resistant" Gilbertson nest box made from 4 inch diameter pvc has about 75 percent less floor space than the 4" X 5.5" NABS and Chalet nest boxes illustrated in the Bluebird Monitor's Guide. (12.5 square inches vs. 22 square inches) The floor space of even a 5 inch diameter pvc nest box is still a full 40 percent smaller than the rectangular nest box with dimensions of 4" X 5.5". (15.7 square inches vs 22 square inches) It seems the most noticeable differences a creature would encounter when deciding to live in a pvc box or a wood box is interior floor space. The pvc box is about half the size of the 4 X 5.5 rectangular box. If we made wooden boxes with the same floor space as the Gilbertson box, the floor would be only 3.5" X 3.5". If we also reduced the distance from the floor to the hole from 6.5 or 7 inches to 4.5 inches to match the Gilbertson box, maybe a house sparrow would shun this excessively small wood box the same way the house sparrow shuns the excessively small PVC box. Just a thought. Gary Springer From: "Keith & Sandy Kridler" kridler"at"1starnet.com
Keith Kridler Mt. Pleasant, Texas where 5" of wet snow has terrified north Texas drivers! Dr. Wayne Davis from Kentucky actually did a study using small nestboxes with a 3&1/2"X4" bottom and only 5" total interior depth and I built and placed 50 of these along my trail in the early 1980's where House Sparrows were common. Just like the 4" diameter shallow PVC nestboxes, if a house sparrow wanted this location they did not mind nesting in the shallow, cramped quarters of these wood boxes. Small shallow boxes may be the least desirable nestbox for house sparrows but this does not mean that either style will NOT have sparrows nesting in them! Results of these "sparrow resistant" boxes varied from region to region and even across the street! We have to understand that house sparrows when they cannot find a nestbox will wedge their nests into the tiniest of cavities! There has been a male house sparrow carrying nesting material into the end of a horizontal 2" steel pipe used for the top bar of a soccer goal post just 150 feet from three of my nestboxes! Has this sparrow learned that the women across the street will not allow him to nest in their boxes? Does he prefer a tiny shallow cavity? Birds are as individual as birders themselves. The more different styles and sizes of nestboxes, the more different mounting heights, the more different sized entrance holes you have along your trail the more species of birds you will have using boxes. You will also find that bluebirds will sometimes prefer wood duck or barn owl boxes to nest in and Screech owls and wood ducks will sometimes prefer small Flicker nestboxes even when the "correctly" sized nestbox is right there available in the next tree or right under the other box! KK Date: Wed, 06 Feb 2002 11:31:17 -0800 Gary Springer wrote: One additional thought I have, Gary, since I've used the PVC boxes successfully for 2 seasons now (four-nestlings for 2 broods each season), is that the round shape makes the very small space more usable. There are no "wasted" corners. In other words, while the floor space is REALLY small, compared to square or rectangular boxes, since there are no hard-to-use corners, the birds can utilize the rounded space more easily. After all, the nests are round-shaped. That would, I think, mitigate against making the square boxes very much smaller in floor space, but I'm not an expert at all on the subject. VMS From: "Gary Springer" springer"at"alltel.net
Hi vm, An adult bird can sit diagonally from corner to corner in a square box. So the extra floor space in a 4" X 5.5" wooden box gives the 7" long Eastern Bluebird 6.5 inches to sit in instead of 4 inches as in the pvc box. So for the adult, the bird that decides which box to use, the extra space might be preferred and does not seem wasted. When there are 4,5, or 6 birds in the box, again, I don't see how any space could be wasted. To squeeze the nest site selecting female into the same small space provided by a 4" round pvc box, the square wooden box would have to be reduced all the way down to 2.5" X 2.5" because the distance from corner to corner in this very small square box is still 4". Based on what Keith wrote, in the right circumstances a house sparrow would still use this small box. But, I have no doubt the house sparrows when presented with the option of nesting in the 2" diameter goal post pipe or a 4 inch diameter pvc box, it would have selected the 4" round pvc box. If healthy bluebirds are fledging from the tight confines of 4" pvc boxes that are only 4.5" deep, maybe they can also fledge from similar 2.5" X 2.5" wooden boxes that are much deeper with thicker fronts, and, maybe these smaller boxes would be "sparrow resistant" as well, and, could be built in a manner that provides them with much more protection from cold weather and predation. Any ideas about why NABS recommends a box with a floor space nearly double that of the 4" pvc box? Gary Springer ----- Original Message ----- ... Date: Wed, 06 Feb 2002 15:33:41 -0800 Gary Springer wrote: Nope, except that when I bought my PVCs, it said that the builder studied the situation and found that sparrows didn't like the design. Perhaps they simply deduced that for the round design, with its different approach, it worked, to some extent, but the square design needed more depth. I don't know. I'd rather the round PVC had more depth, but perhaps it would be too hard for the fledglings to climb up the smooth sides, even though they are sort of roughed up near the hole. VMS From: "susan"at"changeswithin.com" changes"at"sunlink.net
To add to Gary's questions ... What *is* the average size of totally natural cavities out there in the wild that seem to be preferred by the blues? What is the average thickness of the walls? Personally speaking ... I like lots of room to breathe and lots of padding /insulation. Then of course, I'm only one 'wild thing' among millions;-) Thanks for any input from anyone! Date: Wed, 06 Feb 2002 16:08:44 -0600 At 02:18 AM 2/6/02 -0500, Gary Springer wrote: ... Although I have not tried Gilbertson or other PVC nestboxes to discourage sparrows, what I have read on the list indicates that they are not fool-proof. If they are all that is available, house sparrows will use them. If they have a choice, they will choose the roomier boxes and by default the bluebirds will get the smaller nestbox. Another factor to consider is that a larger interior may be more comfortable for the birds, less stuffy in extreme heat. There has even been some speculation that a larger nestbox may allow birds to use their wings to assist in exiting the box, which might benefit tree swallows under some conditions. Kate Oschwald Date: Wed, 06 Feb 2002 18:43:46 -0400 Haleya Priest Amherst MA However, I do want to add that part of the "HOSP resistant" Gilbertson is that the PVC is thin-walled and HOSP tend (I say that lightly because there are exceptions) towards prefering a thick walled home better. However, KK is right, watch the really incredible places these guys nest - OUTRAGEOUS places they'll nest - this is part of their "success" story here in USA/Canada. :-) H From: "Gary Springer" springer"at"alltel.net
First of all I want to say that my posts on this thread on wood vs. pvc are written for the purpose of creating a dialogue to see if we can come up with something new about house sparrow nesting preferences, not to advocate anything It is possible that we have missed something in the design of the Gilbertson box that for some people has been used by sparrows less frequently than some wood boxes. We're working with a lot of variables here. Haleya brings another of the often cited reasons some designs of pvc boxes are "house sparrow resistant"; that being that "the house sparrow has a preference for thicker boxes" I believe even this remains only a hypothesis. I've seen plenty of house sparrow nests in aluminum downspouts. Has anyone ever built and tested several 4" inside diameter, one inch thick pvc nest boxes to see if sparrows preferred it over the thin walled pvc boxes? Until that has been done, the "thick wall theory" will remain a theory, no matter how many tests are cited in which wooden nest boxes of varying thickness were the subject. And, does the "thick wall theory" state that the house sparrow prefers nest boxes with thick walls, or that it does not like the lack of protection from predators provided by a thin wall at the entrance hole? As a means of predator prevention to increase the safety of these thin shallow boxes, has anyone ever increased the thickness of a pvc box at the entrance hole by placing a one inch thick block of wood on the inside of the box? If so, have sparrows suddenly become attached to a pvc box so designed? If not, it might be a good idea. Gary Springer ----- Original Message ----- ... Date: Wed, 06 Feb 2002 23:03:09 -0400 Haleya Priest Amherst MA The only problem I foresee is that you don't have HOSP on your land!!!! You'll have to get others to put up your experimental boxes. I'd be a guinea pig for one box. In any case, I don't think we'll ever come up with the perfect "sparrow proof" box because these guys WILL nest anywhere and in anything.... I do know that Steve Gilbertson has tried using 6" PVC boxes with the result being the HOSP did use them more often than the 4". :-) H Gary Springer wrote: First of all I want to say that my posts on this thread on wood vs. pvc are ... From: "Jim McLochlin" bluebirdbox"at"cox.net
I will weigh in on this one as well. As many of you know I use passive house sparrow control and a major part of that control is the use of Gilbertson style PVC boxes. I use these in conjunction with a few NABS style and Peterson Boxes. Invariably "on my trail" the sparrows will select the more traditional wooden NABS style and Peterson Boxes. I do "believe" that Keith hit the nail on the head with his post that when the traditional wooden boxes are present that the sparrows will select the wooden ones first. I have also noticed that the bluebirds will do the same. The preference seems by both species seems to be for the wooden boxes. However the sparrows, being the defender they are, will claim and retain that box. The bluebirds move to without a fight for the less desirable, but available, Gilbertson style boxes. Why are Gilbertson less desirable than those constructed of wood? We could all go to great length to state why we believe the Gilbertson is less desirable but on my site is a reprint of what Steve Gilbertson had to say on the subject. See - http://audubon-omaha.org/bbbox/nestbox/gilstory.htm As I have said before, and Keith just stated again, by keeping a variety of boxes on your trail (even if you have a dominant box style) will allow all the desirable species a place to nest. I know I need to add more variety to my trail, but when I set up a trail or add a multitude of boxes in sparrow dominated habitat a sparrow resistant box only makes sense. Whether that box be a Gilbertson or a Troyer is important, I'm not sure. I have had success with Gilbertson boxes and thus they will continue to be my box of preference. I also know that when house sparrows are so dominant that passive controls won't work, then maybe the habitat isn't right for me and my passive methods. I then leave that area to others who don't mind using the active sparrow controls. There is another factor that goes into setting up a trail in my area, nest box weight. The typical trail that I walk, set up, or reconstruct is a trail that must be walked. It is typically anywhere from 1 mile to 2 miles long, through hilly un-maintained grounds (high weeds and brush). I can, and have, carried up to six boxes with poles (including rebar) at a time. When I carry this many I usually have a helper (my wife, or the trail owner) carrying my Van Ert (by the way the Van Ert web site has move to - http://www.vanerttraps.com/ ) rebar driver or a sledge hammer. The point is, how many of the heavier wooden boxes would I be able to carry on the same trip? Two is pretty typical for me. So what happens is when I set up a new trail I place Gilbertson style boxes out. Then over time as I update, add a box or two, and many even replace a box I use a box constructed of wood. This allows me to set up a trail in a short period of time and then add boxes and variety to my trail over time. Jim McLochlin The Audubon Society of Omaha = http://audubon-omaha.org/
-----Original Message----- ... From: "Keith & Sandy Kridler" kridler"at"1starnet.com Keith Kridler Mt. Pleasant, Texas A bird's nest size is only part of the reason for determining "recommended" nestbox sizes. What would happen if all robins were to lay 12 eggs in their normal sized nests this year? Would there be 3 times the number of young robins fledge or would 7 out of 12 get crowded out of the nest and fall to the ground as the young birds grew? Bluebirds can and do live in very cramped quarters sometimes but would you trap House sparrows and then keep them for weeks in a box where some had to stand on the backs of others? Try placing 7 House Sparrows in a 4" round or 3.5" square box with a clear side and observe them for a couple of hours. Remember 14 day old bluebirds are heavier and larger than full grown House Sparrows! I have built many sizes of wood boxes in the past and glued various colors of Formica to the fronts on the outside and inside to see if slickness or plastic smells were a deterrent to sparrows with varying results. I have also built PVC pipe boxes and glued in sections of 1&1/2" diameter PVC pipe to create "tube" entrances of 3/4" length to 2" length for these boxes and still had varying results with all species of birds using or not using the nestboxes. I would bet that I could get House sparrows to nest in a Campbell's soup can with a wall thickness of .025 sometime this summer if I put up enough of these cans! :-)) KK From: "Gary Springer" springer"at"alltel.net Hi Kate, You wrote to list several days ago: "Another factor to consider is that a larger interior may be more comfortable for the birds, less stuffy in extreme heat. There has even been some speculation that a larger nestbox may allow birds to use their wings to assist in exiting the box, which might benefit tree swallows under some conditions." I believe you brought up a very important point. In my opinion birds fledging from square boxes with 22 square inches of floor space and 9" tall (instead of 4" diameter pvc boxes with 12" square inches of floor space and 6" tall) will have an advantage after they fledge. Because there is about twice as much air space in the larger box, it seems each breath inhaled by the nestlings will contain less air which has been exhaled by other nestlings and contain far less contaminants created by all types of secretion of the nestlings and adults which become air borne by evaporation and during exercise by the nestlings as they flap their wings vigorously inside the box so they can develop the muscles needed for flight. Not only does it seem cleaner air would promote better general health and stronger lungs which are extremely important in flight, but also, the far greater space enables them to spread their wings wider, exercise more and develop into stronger birds before being exposed to the outside world where their ability to fly is their lifeline. But, if the smaller boxes are effective in deterring house sparrows, their use has an important application in some areas. Gary Springer From: "Gary Springer" springer"at"alltel.net Keith so rarely writes anything with which I disagree that I don't pass the opportunity to debate when he does. I also agree with most of his post below. Except: Even though the air inside the nest box may be very near the outside temperatures because the entrance hole is like an open door, I believe the temperature in the nest beneath the incubating female will be warmer in a nest box constructed from thick wood with drainage holes blocked because the movement of heat from the nest and nestlings beneath the female through the walls and bottom of a well insulated box will be much slower. And, a couple degrees can make a difference, especially while the female can still cover the chicks. But, the Cornell study about to be conducted may show little difference in wood vs. pvc because the female's body covers the nest more completely in a 12 square inch pvc box than a 22 square inch wooden box. Therefore, in the smaller box, less cold air will pass through the entrance hole, down between the female and the sides of the box and on into the nest below her. But, if the female uses a generous portion of tightly woven nest material in both boxes, this benefit of a smaller pvc box may be lost. I think that a small thick wooden box will make it possible for the female to keep the eggs and newly hatched chicks much warmer on cold nights. But, if there is little difference in nest temperatures on cold nights in various types of boxes, it may be that the nests they build inside the nest box are more effective than we think. However, after the chicks are too large for the female to cover, I believe the regular size wooden box will be more effective against hypothermia for the reasons given. It seems a bird that periodically turns her eggs would also move her young birds around occasionally to share her limited warmth. It also seems that on a bitter cold night, a chick very close to, or, in contact with a thin single wall pvc nest box side will lose heat more rapidly than a chick against a wooden nest box wall. So many variables! Gary Springer PS If the bluebirds are able to nest in the "winterized"
boxes I referred to in my previous post, please ignore that
post. When these young birds become chilled (or over heated) to the point they cannot raise their heads for food they will perish. The young with experienced parents that nest after most cold spells are over and before high heat begins killing will have more offspring or natural selection will favor parents who are better at brooding their young or eggs. We must remember that closing all vents on a nestbox and building the box out of thick lumber DOES NOT increase the temperature inside of the box at night or if the box is in 100% shade! If you build an outhouse or an ice fishing shack like a nestbox with 6 inches of high grade insulation and have NO heat source inside this outhouse it will still be the same temperature as outside since you need a 3 foot X 3 foot window hole left open! Just like birds in frigid conditions in order for you to be comfortable you will need winter clothes. IF you take off enough clothes to allow body heat to actually warm up this open air outhouse (birdhouse) in sub-zero temperatures and spend the night in there you will probably die! By cramming several people in this shack you can reduce the effects of wind chill and conserve body heat by having a warm body on one or more of your sides but you still will not warm up the air temperature inside to any significant extent. This is one of those issues that Cornell's temperature/timer devices can show and is one of the reasons why I would like to be involved in this research! I believe it will show that there is very little reason to worry about heating our nestboxes for these birds are hardy or building super insulated nestboxes as in the end it will show that these boxes are just as cold at night as the outside temperature. KK Date: Mon, 18 Feb 2002 06:02:32 -0800 (PST) Snip We must remember that closing all vents on a nestbox and building
the box out of thick lumber DOES NOT increase the temperature
inside of the box at night or if the box is in 100% shade. Hello Gang - Of course Keith is right. Without a heat source eventually the temperature will equalize, even in a Thermos bottle. All the insulation installed in your house does is to slow the transfer of heat. The transfer of heat through a PVC surface is must faster than it is in wood. The thicker the wood, the slower the transfer. I remember having breakfast one bitter cold and very windy morning on the top floor of a tall building. The restaurant had large glass walls all around. The area near the wall was so cold that everyone was seated as near the center of the facility as possible. The glass walls were pulling the heat out near the walls faster than the heating system could replace it. The same principle of physics apply to nesting boxes of wood vs PVC. Pourous wood does not transfer heat as fast as a more dense wood due to the air spaces in the wood fibers, that comes in lesson 102. ;-) Best regards, Bruce Johnson From: Evelyn Cooper [mailto:emcooper"at"bayou.com] Sent: Tuesday, April 19, 2005 8:46 AM Subject: RE: On Avian Toxicity and Ignorance--Blue Porch Ceilings Bernie wrote to me: "If you support the use of construction grade PVC pipe as material for I've mentioned that inconsistency in your reasoning three times and you have yet to address the matter.> Bernie, I am sorry I failed to address the PVC pipe as a material to use. I I am TOTALLY opposed to using PVC for nestboxes. I have e-mails saved that You just do not see any PVC nestboxes in my state and the one person that So, now, I have made myself clear on that. :<)) Evelyn From: Bernie Daniel [mailto:bdaniel"at"cinci.rr.com] Sent: Tuesday, April 19, 2005 10:36 AM Subject: Re: On Avian Toxicity and Ignorance--Blue Porch Ceilings OK Evelyn. I may disagree with you but I give you an "A" for consistency!! I do not like 4 inch PVC pipe box either -- but not because I think it But I'm against the Gilbertson PVC box because I think the floor area (12.6 Bernie |
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