Nestboxes (Insulation /Ventilation- Heat/Cold)

Subj: Re: Ventilation (was Goldberg)
Date: 7/27/99 2:03:45 PM Central Daylight Time
From: birdsfly"at"innercite.com (Hatch Graham)
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Hatch here in hot California.
Hot air still rises. (No reference to you, Bruce. ;) My problem with an open screen bottom is that the hottest air is where the sun strikes bare ground (especially if it's dark-colored). The air in contact with the hot ground warms up and rises; right into your box, methinks, unless you have a breeze. You will also get convective rise from a powerpole or tree in the morning or afternoon depending on the aspect of your box. The side of the pole facing the sun is getting the sun's rays at closer to a 90° angle and will be hotter than the ambient air and "chimney" right up the pole.

I think you will want insulation on the floor as well as sides. Vents are essential but mainly to vent off the heat of the chicks when they get hotter than they should. I don't know what the answer is when the temperature (which is recorded in the shade) exceeds 105°. You can only hope the well insulated box is holding some cooler air from the previous evening. Opening the bottom would be a disaster because air rising from sun-heated ground would certainly exceed the "official" in-the-shade temperature.
Hatch

...
--
Hatch Graham, Editor, Bluebirds Fly! California Bluebird
Recovery Program
El Dorado County "at" 3100 ft, Lat 38°37'43"N, Long 120°37'47"W
-------------------------------------------------------------------------
for the encouragement and conservation of cavity nesters  -especially bluebirds- anywhere in the West

 

Subj: RE: Ventilation (was Goldberg)
Date: 7/27/99 7:42:09 PM Central Daylight Time
From: dusty"at"fsinc.com (Dusty Bleher)
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I don't think that's quite accurate Hatch. Yes, hot air does rise, and cool air sinks. But as soon as the air rising is out of the radiant heat infusion zone (where the contact heating gets done), it begins to lose heat (or at least, not gather a lot more heat). At that point, it's just the ambient temperature.

If it's hot out today, it'll be hot at that point too. But no hotter then the temp of the rest of the air. Sure, you'll probably get some localized heating, and some pipes and other such devices may well create some chimney effects. But in most cases, more than a few feet above the ground will probably be simply ambient temp.

The job of insulation is to prevent the movement of heat energy through a material surface junction. It works best when there's a means of adding or removing heat energy (keeping things hotter or cooler then ambient under the influence of a "heat pump"). When applied in a normal entropy environment, all it will really do is delay the onset and release of energy. It won't really change the amount of energy transferred.

While it's cool inside, insulation will keep the heat out. But, once the heat has "leaked" in, and it begins to get cooler outside, then that same insulation will keep the heat in. So I'd suspect that it's net effect in hot climates is probably near zero. In colder climates, it should help conserve the temperature increase caused by the birds body temp inside the structure.

Tough problem. No simple solutions.

Dusty
San Jose, Ca.

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Subj: Ventilation talk
Date: 7/27/99 8:46:39 PM Central Daylight Time
From: haleyapriest"at"hotmail.com (Haleya Priest)
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Haleya Priest Amherst, MA

Bruce, Hatch, Dusty, et al, Not that I have a handle on any of this ----  but, something I've been wondering about with this heat. First, keeping the sun off the box seems like the #1 priority. Then the box  can stay pretty close to ambient temp. Someone sent me plans for a huge  shade roof -overlapping the box by a good six inches. Will that keep every  little shred of sun off the box?? If not, WHAT WILL? That might be the  place to start - cuz no matter how much breeze you have blowing through a  box, if the sun is hitting it, it becomes hotter than the ambient air.

Second, what about having the screen on the TOP of the box, instead of a  regular roof. THEN, have a shade roof 2" or 3" above the screen roof, so that it would keep rain AND all the sun off the box. This could be a "summer roof" - maybe the box could be designed so that the  regular roof could be easily taken off and this summer "roof" and shade roof  would be put on once the weather heats up enough to warrant it. Having the screen on the bottom helps with the blowflies, but the very  nest itself creates an insulation layer - would it REALLY cool the box all  THAT much?? I get it that every little bit helps - but just wonder if there  isn't a more efficient way to deal with the heat. I don't know if the bb would accept a screen roof. I don't know if a  screen would be an invitation to other problems.......yadda, yadda. Whadda ya think. H

 

Subj: Other types of and/or sources for nestbox material
Date: 8/26/99 4:00:01 PM Central Daylight Time
From: Orbit352"at"aol.com
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Tom Heintzelman, Milton, Santa Rosa County, FL (western panhandle, inland) USA

Home Depot handles 3/4 inch thick, 70 inch long PVC fence boards in both 4 and 6 inch widths. This carrys the "U.S. Fence" label and goes for $1.98 and $2.33, respectively. Looks to be the same as or similar to the material Bob Wilson uses for his PVC NABS style nestboxes that can be viewed online at:
http://www.hometown.aol.com/jimmcl/bbbox/nestbox/bwbox.htm . At the beginning of 1999 one Jerry English (jerry"at"carolinavp.com) announced that a Carolina Vinyl Products http://www.carolinavp.com had designed a "proven bluebird house that is very cool ... works well in hot climates." Sorry folks, I didn't check this one. Terry Washburn from SW Arkansas uses 1/2 inch thick foam PVC, a flat sheet product made by Alucobond Technologies, Inc, of Benton, Kentucky, phone 800.626.3365. I understand the foam is "sandwiched" between two nonporous, very smooth "skins" making it exceptional for achieving accurate, close-tolerance nestbox parts. Terry has about twenty of these. A complete description with pictures may be viewed at http://www.cei.net/~twash/bluebirds.html

 

Subj: Box material, etc.
Date: 11/29/99 10:50:11 AM Central Standard Time
From: blueburd"at"srnet.com (Bruce Burdett)
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To the Constituency,
In response to recent questions about box material, I'll go briefly through my spiel on the subject, by now very familiar to many of you. Here in New Hampshire, I've been very happy with white pine, but I use stock which is 7/8" thick and planed on just ONE SIDE. I get it very reasonably from a local sawmill, air-dried in their own vast yard. The extra thickness (compared with 3/4") makes a sturdier and better-insulated house, and some of them have been up for 9 years now,
year-round, with no warping, checking or deterioration of any kind. Further, I always put the rough side IN on the front board, so that the chicks (and Tree Swallows, with their puny legs) can get a clawhold under the hole. Lately, I'll admit, I'm cutting some saw kerfs under the holes as well, just to provide a little more purchase for the swallows. I use 5- or 6-penny galvanized nails for fastenings, and caulk only the seam between the roof and the back-board. I build SIDE-opening boxes because I think they make monitoring easier. (and also photography) I secure the opening side with a brass round-headed screw. I just received a timely GIFT of ninety 1" galvanized poles, (!!) to which I attach the boxes with a couple of 1/4" bolts

That's my spiel. And remember, I'm in NH, - not CA or TX or FL.

Bruce Burdett, NH Bluebird Conspiracy, Sunapee NH

 

Subj: wood thickness
Date: 11/29/99 10:12:38 PM Central Standard Time
From: tater2"at"gateway.net (tater2)
Sender: owner-BLUEBIRD-L"at"cornell.edu
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Gary in E. TN - The reason I asked about the thickness was the fact that 1" wood compared to 5/8" or 1/2" is so much heavier. I was all thinking about putting some of the thin styrofoam on the inside for insulation from both the heat and the cold. Also the foam is a type of material that the young and the old can get a grip to climb out. What do you all think of that plan? I'd love to hear from those that have been at this for a while. Also what affect would "Thompsons Water seal" have on the birds if any, works great on our decks. Now that I have all of the house decorated for the season I now have time for the birds and can't wait to get some roost boxes made.

 

Subj: Re: nestbox/roostbox thickness
Date: 11/30/99 7:10:07 AM Central Standard Time
From: dmccue"at"usit.net (Dan McCue)
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Greetings all! Just a thought from the midsouth of TN. I think the greatest disadvantage is the added weight of the box, since the box(roost) is larger. I really doubt that even up north that the addional thickness will make much difference in cluster of bluebirds huddled on the floor of the roost box. What think ye? If it is sealed reasonably tight, you still have the hole(s) open on the entrance face. Ya'll have any other ideas to Haleya's questions? Regards and happy holidays to all bluebirders on the post. Dan McCue, Camden, TN, 70 miles due west of Nashville where it is 30 degrees this morning!

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Subj: Styrofoam and wood thickness;
Date: 12/1/99 9:58:53 PM Central Standard Time
From: hubertrap"at"webtv.net (Joe Huber)
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Hi all, Thee has been some discussion on using Styrofoam in roost boxes to help keep the birds warm. There is a way to use it and that would be in the floor. Place a piece about 1/4" thick on the bottom floor then add 1/4" plywood on top of it. This is where all the birds are anyway. They need not be in contact with the Styrofoam. It is full of tiny air pockets and stops the transfer of heat or cold. Could make a large difference in body temperature of birds.

All the discussion about wood thickness may be confusing to those who don't work with wood. When you go to the lumber yard to buy a 1" thick board It is really only about 3/4" thick if it is lumber that has been planed smooth. The standard on this was lowered again several years ago and some of this 1" stuff may be under 3/4". At one time this lumber had to be 7/8" thick. Many of you are getting rough cut lumber at a mill where you can actually get it 1" thick. I used cedar that was planed on one side and it was 3/4" thick. I know a little about wood and have been able to determine what real thickness everyone is talking about. Many others may have not understood what the true thickness is in some posts. Guess if they don't work with wood it doesn't matter. Maybe if I keep
going it will sound like Wendell. Don't worry Wendell I'll never be able to keep up with you. Joe Huber in Venice Fl where we actually need a jacket tonight. Be glad when this 2 day cold snap is over.

 

Subj: Re: wood thickness
Date: 12/1/99 10:02:59 PM Central Standard Time
From: springer"at"alltel.net (Gary Springer)
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Hello Gary in E.TN and all,

I too believed that a roost box would be more comfortable for Bluebirds if it was constructed of thicker wood. Accordingly, I built one using 2"X10" lumber and insulated it with foam insulation board as well. It weighs about 17 pounds.

I've been out of town most of the time since I mounted it 14 feet up on a telescoping pole so I'm not sure if Bluebirds have roosted in it as yet.

However, I do believe there have been some excellent posts providing good arguements and evidence that the extra thickness may not be necessary.

It will take quite a bit of experimentation to determine whether or not the extra thickness and/or insulation provide more desirable roosting for Bluebirds.

Gary Springer in N.E. Georgia

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Subj: Re: NABS 1" wood
Date: 12/1/99 10:36:34 PM Central Standard Time
From: springer"at"alltel.net (Gary Springer)
Sender: owner-BLUEBIRD-L"at"cornell.edu
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To: bjohnso3"at"midsouth.rr.com
CC: springer"at"alltel.net (Gary Springer), BLUEBIRD-L"at"cornell.edu (BLUEBIRD-L)

Dear Bruce,

I've been itching to jump in about cedar since the first posts about finishes and sealers on nest boxes. I can't resist your 'invitation'.

I believe I know more about the properties of cedar and wood preservatives than the Bluebirds.

Knowing what I do, if I were a bird and was to select a box to raise my nestlings in, I'd choose the coated box over the cedar one every time and cite health concerns as the reason.

Gary Springer

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Subj: More on heat resistant boxes
Date: 1/4/00 7:16:42 AM Central Standard Time
From: kridler"at"1starnet.com (Keith & Sandy Kridler)
Sender: owner-BLUEBIRD-L"at"cornell.edu
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Keith Kridler

Materials: The "blue" Styrofoam mentioned sandwiched between a PVC sheet and thin plywood will probably be an excellent material for nestboxes. "blue"
styrofoam is normally a closed cell foam designed for use underground or underwater and should not absorb water thus losing it's R-value or resistance to heat transfer. Since it is closed cell, very few manufacturing gasses should be released.

Steve Gilbertson PVC: Several issues of THE BLUEBIRD & before it SIALIA (quarterly journal of the North American Bluebird Society) have letters or
articles questioning the use of this material due to losses of birds to heat or excess heat gain compared to 3/4" wood boxes. I have had good success with Schedule 40 PVC boxes used in East Texas (since 1976) Very detailed heat tests done by Robert Patterson in the early 80's (published in Sialia) showed that even without ventilation holes PVC boxes (the sparrow resistant experimental model EX. #3) made from schedule 40 PVC were as good or better at repelling heat than nearly any other type box tested. I went and measured S&D (sewer and drain) pipe (this is what Steve G. uses) at various dealers and then schedule 40 pipe. S&D pipe is UNDER 1/16" (.060")while schedule 40 is around 1/4" (.245".258") or four times thicker. Comparing S&D PVC to Schedule 40 is like comparing an 1/8" thick wood box to a 3/4" thick wood box. For areas with high heat in summer the PVC boxes should be made from schedule 40 material and left white.

The recent heat test done in THE BLUEBIRD (PVC vs. Wood vs. aluminum) only tests the boxes to midday. Harry Krueger's heat tests of various boxes
monitored at 30 minute intervals in East Texas showed that even the Peterson box with a roof thickness of 2&1/4" and a back thickness of 1&1/2" when the
entrance faced square into the rising sun actually reached the highest temperature (during late summer) at 6PM (when a tree line gave shade to the test boxes) The Peterson nest box heat gain was about double at 6 PM what it was at noon! (Heat gain is the inside box temperature over a controlled ambient air thermometer located in full shade.) Due to the design of the Peterson box with no overhang at the rear of the box and the steep angle of the roof, the sun can strike the entire length of the back board and if the box is slightly turned can also heat up an entire side from about 2PM until dark. If you use this box you should test with a high/low thermometer to see if facing east or another direction might not actually be cooler than the "Face all boxes EAST" rule of thumb. I have only used the Peterson box as an example as to what sunshine on the side of any nestbox can do to inside temperatures since it has the thickest roof and
back in commercially made nestboxes available over the counter.

The best wood nestboxes (lowest heat gain) in the 3/4" thick wood division of the 1980's heat tests were hexagon and octagon shaped boxes. Probably
because they had less square inches of flat wall to absorb the sun's late afternoon rays. The angles would help bounce off the rays rather than absorbing them.

I got sidetracked with the holidays and will work up a heat resistant design for extreme heat areas that I think would work well. KK

 

Subj: Opps correction
Date: 1/4/00 7:35:31 AM Central Standard Time
From: kridler"at"1starnet.com (Keith & Sandy Kridler)
Sender: owner-BLUEBIRD-L"at"cornell.edu
Reply-to: kridler"at"1starnet.com
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KK I meant to say that maybe facing the Peterson box WEST might be cooler and that you should test various directions with ALL nestboxes you use. Also
experiment with roof overhang. KK

Subj: Re: More on heat resistant boxes
Date: 1/4/00 9:05:47 AM Central Standard Time
From: RWil2654"at"aol.com
Sender: owner-BLUEBIRD-L"at"cornell.edu
Reply-to: RWil2654"at"aol.com
To: kridler"at"1starnet.com, BLUEBIRD-L"at"cornell.edu

Hi Keith & All;
Keith I will send you one of my boxes so you will stop playing around with futile attempts to cut heat in PVC Pipe boxes. Without air spaces that act as vent to carry the heat out the top you will never be able to cut the temp inside the nesting box. Send me you address and I will send you a box. All other take a look at my web site. I am now build some boxes to hang in trees on the golf course here that has all three species of bluebirds. They are still around as of yesterday.

Bob Wilson
2654 Sperber Lane
Grand Junction, CO 81506 ...

I believe Evelyn's personal observations are accurate.
I know here in Ontario, that the person with the largest Bluebird Trail in the province, no longer puts any vent holes in the sides of his modified NABS, modified Peterson, & Modified Gilwood nest boxes.
His reason to me was that the temperatures her in southern Ontario never get too hot, and he felt that it was more important to keep the nestbox as dry and warm as possible.

So, what I'm now experimenting with is using removable tapered Plastic Plug caps that can be inserted in the vent hole(s) on each side of a nestbox.
They can all be left in place in early Spring & Summer to keep the inside of the nestbox as warm as possible. And IF the temperatures get excessively hot for a period of time, individual plastic plugs can be removed from one side only or both sides to allow cooling air flow to lower the inside nest box temperatures.
This arrangement also allows for keeping the Plastic vent hole plugs in place on prevailing winds / rain sides, thus keeping the box warmer and Dry.

I'm trying to standardize on the same size vent holes for all my Bluebird nestboxes, so I can place my order for the tapered plastic plugs, from the company in the States.
Since I will be getting several thousand plastic plugs in this order, I will have them available to sell if anyone is interested.
All you have to do is to drill the correct size vent hole with either a small Forstner Bit or a good Brad Point Drill bit, in the sides of the nest box, then insert the Plastic Plugs.
I'm thinking of using 1/2" or 5/8" vent holes.
Any comments?

Regards,
Larry A Broadbent
Chatham, ON

Keith Kridler Mt. Pleasant, Texas
See there never is a simple answer to any question:-)) Yes it is very good to be able to add and subtract ventilation in some areas but it is ultimately up to the adults and their ability to generate heat for their survival and their young during the cold temperatures.

Experiment: Take a warm cup of water pour 1/4 cup of warm water into four zip lock baggies. Wrap one baggie tightly up into a warm dish cloth. Place one baggie into a cardboard shoe box with a lid. Place one baggie into a shoe box without a lid. Place one baggie inside an insulated water jug or a vacuum thermos jug. Place all four containers into your freezer. Check them in four hours, eight hours and 12 hours. (You can substitute your nestboxes sealed or unsealed if you like instead of shoe boxes.)

In winter in the far north it is dark for more than 12 hours a day. A nestbox or container is totally dependant at night on the outside temperatures. Even without an entrance hole and totally sealed it will remain almost the same as ambient air temperature.

The ability of bluebird eggs to survive going down to just below freezing to just below 105*F is incredible. Any temperature above about 78*F and the fertilized egg begins slowly forming. Maximum healthy formation of the chick is at about 99.5*F. Air temperature in the south during the middle of the nesting period causes the eggs to warm and develop with or without the female sitting. This happens with open nesting species as well as species who nest in cavities.

Bluebirds winter coats often have them surviving winters with temperatures way below freezing for weeks at a time. They even bath in melting ice puddles. They may or may not ever enter a nesting box a night preferring to roost in trees.

Most female birds can keep their eggs and young warm in open nests in early spring even when it rains everyday and their nests are continuously soaked.
The color of the nestbox and the placement of the nestbox in regard to direct sunshine has more effect on the temperature inside the nestbox than does ventilation. If the female birds incubate their eggs in extreme heat the female can actually keep the temperature of her eggs at safe temperatures even with air temperature way above lethal temperatures. KK

I agree that the female is in charge of generating the heat for their survival.

But, in case of severe cold if the female should be gone quite a long time looking for food to survive, would not a warmer nestbox be an advantage to the eggs?

The same is my thoughts when I place the solar screen on nestboxes that are in the sun all day to keep the temps from soaring inside it. I just feel we can do a little something to help the cavity nesters in the man made cavities we provide.

Evelyn Cooper
Delhi, LA

Birds can survive most cold if they have food.

However, isn't it strange that you find them all huddled together when they roost? Is it because they just love each other or is it to keep a little warmer? How are we to know?

Evelyn Cooper
Louisiana Bayou Bluebird Society
Delhi, LA

I just talked to my husband about Keith's experiment of putting baggies or nestboxes in a freezer with and without ventilation.

He says that is a completely different scenario than having warm bodied birds either nesting or roosting in a closed up nestbox that generate heat and make the nestbox warmer with heat that is continued to be generated from their bodies. If the birds have enough fat and fuel in their bodies, they will continue to generate heat. He also says that if that nestbox has vent holes on each side, that cold air coming in will take some of the warmth of the birds away.

Sorry, Keith, he disagrees with having vent holes open on each side in very cold weather for nesting or roosting birds!

Evelyn Cooper
Delhi, LA

Interesting discussion. I do not believe ambient air temperature is the only consideration in heat loss or heat stress in the birds in the nestbox.
If it were, building a nestbox out of a milk jug would be perfectly acceptable. If it were, vent holes would not be an issue, but I believe they are.

To quote NASA's wind chill website, "Any warm object, like a human being, will lose heat when it is exposed to cold air. The greater the wind speed, the faster the object will lose heat. The difference between people and inanimate objects is that we feel or sense the heat loss. A temperature we feel is called a sensible temperature. Maybe you've noticed that some days feel colder than others when there is a strong wind blowing, even if the temperatures are the same!"

Good cross ventilation on a hot summer's day can cool the birds off a little even though the temperature in the nestbox may remain the same as the
outside temperature. Now transfer this logic to a cold spring day. A good
cross ventilation is going to suck the heat out of the birds quicker than in a nestbox that is sealed up tight.

I learned (or think I learned) a lot from Lois and Clark's first nesting this past spring. For those of you who haven't heard the story, Lois and Clark were the "super" bluebirds who built six partial and complete nests in boxes I have mounted on the bank of a farm pond on my trail. Maybe I should have called the female Goldilocks instead because she finally chose the box that was "just right". I wondered why, with the other five nest starts, they finally chose this particular box. The conclusion I came to was that the vent slots (at roof line) of their box were much narrower than the other five. All the boxes were constructed identically otherwise, but the others had more standard 1/2" vent slots. The box they chose had slots about half that width.

Lois began laying her clutch on April 2 and I learned something more about the amazing ability of eggs to hatch regardless of some very cold night temperatures. The lows for the nights were (in degrees Fahrenheit):
4/2=22; 4/3=31; 4/4=30; 4/5=22; 4/6= 29; 4/7= 42. Mom of course was not
incubating her eggs yet on these nights and I wondered if any of them would make it. Five out of six eggs hatched.

At about a week old, a field check indicated that all five nestlings were doing fine. Five days later, they were all dead. Field notes indicated rainy and cold weather with daytime temperatures in the 40's between these two observations. Mom may have been off the nest a little too long or the nest may have gotten damp if some rain made its way in. Either way, hypothermia seemed the most likely cause, but I am still not certain.

I plan to block vent slots in any box chosen early in the spring next year.
I will remove the blocking material when temperatures are consistently warmer. This may be after the first clutch. The birds teach me a lot and you all teach me more.

Paula Z
Powell (Central) Ohio

Paula,
Excellent post! Your personal observations and note keeping of the temperatures during the early April nesting of your Bluebirds adds weight and validity to your comments.

Paula wrote>"I plan to block vent slots in any box chosen early in the spring next year. I will remove the blocking material when temperatures are consistently warmer. This may be after the first clutch."

I agree with your observations 100%. This is excellent advice for Bluebirders especially in the northern States and for Canada.

This is precisely why I feel it make 100% sense to be able to block vent slots or vent holes in early Spring when the temperatures are still very cool and at times cold. Then be able to remove the vent hole plug(s) when and IF the temperatures become very warm or hot.

If you'd like to see my concept of removable plastic plugs for vent holes in nestboxes, I'll be glad to send you 2 pictures and a brief description.
I'm thinking of using 5/8" diameter Vent Holes with the removable tapered plastic pugs.

Regards,
Larry A Broadbent
Chatham, ON

Keith Kridler Mt. Pleasant, Texas a warm sunny 40*F morning

Young Eastern Bluebirds when they fledge often roost shoulder to shoulder as soon as they get better at flying in about a week. In Montana the late Art Aylesworth said that in their tree less expanses of prairie grass that Mountain Bluebirds when they fledged would sometimes gather the young birds together just before dark and you could find the whole brood of just fledged young gathered into a group sitting tail to tail very similar to their seating arrangement which they had sitting in the nestbox. He said that sometimes the young birds needed a day or two flying in short flights to reach the first real tree or thick bush to roost in off the ground at night.

Bluebirds tend to roost as a family and the famous pictures taken by Michael Smith in Maryland in the late 1970's of the Mad Bluebird and the hollowed out log stuffed with bluebirds shows about 7 adult bluebirds while in total there were 13 adults (two parents and 11 young from the previous summer) piled on top of each other with 6 buried underneath the others. They roosted most really cold nights in the same nestbox they fledged from. There are reports of so many bluebirds entering small nesting boxes that people feared that the dead birds they sometimes found actually suffocated. Without an autopsy they might have and probably did die of other causes. If they did suffocate then small drain holes in the bottom might benefit the birds under the pile.

Fawzi Emad and others have used larger floored, specially made roost boxes and without cameras we really don't know if the bluebirds will spread out on the floor or pile up in a corner. Are they using the nestboxes as a wind break or as shelter from Owls and other night raiding predators? It is interesting to find out that one of the two most common cavity nesting birds to nest in large nestboxes for owls and wood ducks is actually the Eastern Bluebird!

I am sure that since bluebirds have a coat that they can fluff up to protect them at -30*F wind chill (about the temp of the Mad Bluebird photo) or that they can adjust by flattening their feathers to hold less heat that these birds can and do pile up if they are in danger of freezing to death.

Since screech owls start nesting in cold weather, then a bluebird family roosting in their potential nesting site would be a welcome snack for small owls or kestrels! As long as high energy food is available bluebirds should be able to survive many sub zero nights without actually freezing to death.

The dynamics of wind chill and winter conditions for nestboxes used for roost boxes and specially designed roost boxes themselves are totally different than nestboxes with eggs or young during an unusual cold snap in spring. A hard rain over night turning to sub zero temperatures before dawn can be lethal for birds roosting where they get very wet.

In winter all the adult bluebirds should have a full winter coat and they only are in the boxes for extended times during the night. They spend the day hunting and searching out potential cavities possibly for roosting that very night or possibly for future nesting sites.

In spring a nest cup filled with eggs or young bluebirds less than 7 days old are all as cold blooded as a baggie filled with warm water. As soon as the female leaves the nest they begin to rapidly lose heat. This is where wind chill and being wet or cold can and does really affect young birds and the hatching of eggs.

Bird feathers are very efficient at holding heat. If you install a Temperature data logger (the size of five dimes stacked together, looks like a watch battery) only an inch from the breast of the female bluebird it will read almost NO heat gain over the inside of the nestbox temperature control data logger. Place it in contact with the eggs and the readings jump to 99*F or so. So even if you add four adult bluebirds to the nestbox on a cold winter night I don't think you will see much heat rise inside any nestbox with a open entrance hole.

There are fairly cheap remote temperature receivers on the market today that you can buy, install in your nestboxes near your house and read the outside temperature from the comfort of your warm home!

In spring time as soon as the first egg is laid then the amount of ventilation, location of the nestbox and color and style of the nestbox begin to have a tremendous effect on the inside the nestbox temperatures due to heat gain from sunshine. Smaller trails and backyard monitors can easily adjust ventilation and adding double roofs, in the heat of summer. The better solar reflecting shade roofs should be able to save a lot of eggs and very young birds that would get lost without "micro managing". Human nature in this hobby makes us all want to save EVERY egg that is laid in our nestboxes.

Changing weather makes changes in nestbox designs throughout the year necessary to maintain ideal nesting and roosting conditions. KK

Here is another observation I have made on my trail in the winter. The Bluebirds do not roost in the nestboxes unless the temperatures get below 15* and stay very low during the day and remain that way for several days.
That tells me they are seeking better shelter than trees and other places they roost when the conditions get like this. I have seen bunches of them fly out from under some old vehicles early in the morning where I presumed they roosted when it was not that cold.

We are talking about vent holes causing a DRAFT, not just the entry hole. We use the "echo roof" to create an air flow and the vent holes can create an air flow inside the nestbox. I believe they are seeking shelter against the cold, harsh wind too.

I wonder how many people will stop putting something in the vent holes because of this? I say stop them up and feed, feed, feed any birds you see hanging around!!! The ones that decided to stay with me are eating raisins and the chunky peanut butter ball like crazy on these very cold mornings!

I think Larry's idea of plugging them with the plastic plugs is great! I think I can put some of the plastic plugs for irrigation pipe into use that we have.

Evelyn Cooper
Delhi, LA

One of the advantages of being a small trail or backyard landlord is that we can do things like the solar screen and other things that would be just too expensive for the larger trails.

However, thicker wood for nestboxes on these trails can provide much better insulation and when monitors are doing their fall cleaning, it is not much trouble to stuff a little foam rubber in the vent holes for winter.

We took all this into consideration when LBBS nestbox builders made the nestboxes for the Kleinpeter Farm Dairy Trail (our newest trail). One of our workers secured Cypress lumber 3/4" from a saw mill and we made all the roofs with 2" or better overhang all the way around. Kenny tells me that even with the extra weight, they are holding up fine on the barbed wire fence. He got the plan to put them on the wire from Keith. You can go to www.nabluebirdsociety.org, click on Affiliates in the left-hand corner, then when that page comes up, click on Affiliate News and read about the trail.
This is the biggest trail for LBBS' involvement. I know Kenny and his love for the bluebirds and cavity nesters and I know they will be in GOOD hands!!!

I have had to replace some of the older nestboxes on my trail and I am using the thicker wood and larger roofs.

I just checked part of my trail and there were no birds roosting so far. Our temps have dipped into the upper 20's.

I did find a very small ring of grass where they had started a little nest during all this extremely warm weather we've had until the last week. I find one nearly every year in late fall.

Evelyn Cooper
Delhi, LA
Louisiana Bayou Bluebird Society

Out here in Sonoma County it doesn't get really cold (at least, not very often), even at night. This time of year we have light frost, but during the day it usually reaches the upper 50's to 60's. At night temperatures rarely drop below freezing. Some years we have had unusual freezes where it stays below freezing for several days, and our birds really suffer then...they aren't used to that kind of cold.

However, the bluebirds that nest in my yard have always roosted in the nestboxes at night during the cooler weather. Once it starts getting dark early in the evening, they sit on my fence, or in the trees, waiting for the right moment to slip into the box till morning. I have seen seven of them come out at sunrise, one after the other, like blue beads on a string! I have two nestboxes and birds are roosting in both of them, even though I never have two pair nesting at the same time during breeding season.

I have two birdbaths, and some mornings there is a thin crust of ice on them when I get up. I break the ice, so the birds can drink, and I did see a male WEBL bathing one morning recently! Gave me chills. He splashed around quite a bit, and then flew to the fence to dry off in the sun. It didn't seem to chill him at all, so those feathers must be amazing insulation.

This year we are feeding a banquet of chunky peanut butter, oatmeal, cornmeal and raisins and it seems to be a big hit with the crowned sparrows and woodpeckers. So far I haven't caught a bluebird eating it though. I still put out niger thistle seed, as the goldfinches haven't left yet. They usually leave this month and return in early February. I always have black oil sunflower seed available, too, and the nuthatches and TUTIs enjoy it. I offer more raisins when the weather gets worse, and dried cherries sometimes too.

Happy holidays to everyone!

Barbara in Cloverdale, CA

This has nothing really to do with the conversation at hand about ventilation, etc, but have you guys had a chance to get a good look at a female bluebird's brood patch? You have to blow the feathers apart (which takes a bit of experimenting) to see the abdomen.

On a female who's incubating, the brood patch is a featherless area (about the size of 2 or 3 quarters) that's pretty soft & very warm. It's essentially a hot water bottle that she rests on top of the eggs or small nestlings.

Even more interesting is the male's cloacal protruberance, the temporary swelling which serves as external genitalia. We do breeding season banding for MAPS (the Monitoring Avian Production & Survivorship project), & i've seen some that are so swollen, they look downright painful. (Mostly on Song Sparrows & Gray Catbirds, oddly enough, but that may just be because they're the most numerous breeding birds at the site.)

Possibly even more interesting is the male Tree Swallow, who develops a partial brood patch. Perhaps it's because he does so much box guarding. (During the egg & young nestling period, the pair will often just switch places. One will leave the box just as the other is flying in. It's very neat to watch.) I mean, as long as they're in there, they might as well do some work, right? :-)

Both the brood patch & the cloacal protruberance disappear after breeding ends, & the internal parts shrink down. Which makes sense -- If you need to be light to fly, why waste grams (or tenths of grams) on full-sized ovaries or testes during the winter?

Birds are darned neat. If you get the chance this spring, check this stuff out.

=====
Torrey Moss
Kalamazoo Nature Center

From: danhan7 "at"sbcglobal.net [mailto:danhan7 "at"sbcglobal.net]
Sent: Monday, December 20, 2004 1:29 AM
Subject: Re: Vent holes

Dan  Hanan
35 miles SE of Austin, TX

My Texas Bluebird nestboxes are currently being built with three ventilation slots: two upper and one in the floor. The upper slots measure approximately 5/8” x 5 ½” and are located above the drop down front opening door and in upper part of the back wall. To winterize the boxes, a block, whose thickness is greater than 5/8”, is cut to fit inside width of the box and to be as long as needed to fit completely through the vent slots (from the outside back, through box inside, and the front door). The front and back parts of the block, which fit into the slots, are cut down to slightly less than the 5/8” slot dimension; this cut-down will also hold the block in place. The block is then inserted into the slots while the door is open and when the door is closed, the upper slots are also closed. Thus, the box is winterized by the block.

For additional ventilation and for water drainage, my boxes have a 3/8” floor slot just behind the front door. This is used instead of drain holes or notched floor corners. The slot also has the additional function of providing clearance for opening the door. Additional winterization can be achieved by filling the floor vent with waded up paper, cloth, or whatever.

Ventilation slots work better for me than drilled holes as they provide greater ventilation of the Texas heat and also, the black fuzzy spiders don't fill them up with their nests and thereby stop the ventilation

From: Kenny Kleinpeter [mailto:kpkmajk "at"cox.net]
Sent: Monday, December 20, 2004 8:01 AM
Subject: RE: Birds huddling together for warmth or companionship

Keith, it doesn't do our cause (we are still trying to save the bluebird, right?) any good to call the most involved of us, “micro-managers .”  That 's a negative term that implies “over-manag ement ” and suggests that we have nothing better to do than try to say a few birds.   Also, by stating that 90% of nestboxes don't have predator guards and leaving it at that, you give the impression that it's normal or acceptable.  It's offensive to say that bluebirders who use predator guards and worry about things like ventilation and temperature to improve clutch-rates are bad.  Quite frankly, I think promoting or, at least tolerating unprotected boxes (more aptly described as death traps) is not doing this list or the effort to save the bluebird any good at all.  People who “micro-manage” boxes discover efficient and effective ways to improve the bluebird species.  We should all be grateful for such “bad people.”   Why do I get the impression that you have sublim in al purposes in your story-telling posts to justify little or no management of your boxes??

I wonder w ho you think is better - a person who puts up 100 birdhouses on fence posts, trees or whatever is convenient or , a person that puts up 10 nestboxes according to NABS standards.   Factors like time, energy, and cost go into the final result: number of nesting attempts , along with clutch and fledge rates . I shudder to think of what goes on in unmonitored boxes.  Since such boxes ARE unmonitored , there is no data available on failure rates due to predation, competition , and infestation .  If an unmonitored box does prove acceptable, it fills with nests in one season making it useless.

I am assembling a 175-box trail that I am committed to monitoring every Monday from February t hrough July for as long as the boxes are up.  When I can no longer commit the time and energy to this project, the boxes will come down.  That's my commitment to the LB BS that provided the nestboxes, NABS that set the standards and, most of all, the bluebirds that will depend on them to survive.  Are you telling me that what I am doing is a joke?!  Calling me a micro-manager is quite discouraging and I would really appreciate you discussing some of these issues directly instead of inserting them indirectly into long "story-telling" posts about "the good-old days" or what-not.

Please share with this group of largely "micro-managers" just how many bluebird boxes you have erected in your lifetime and how many you manage ( that is, at least once a week).   I would have assumed that "standards " would mean what is professed in the hallowed "Bluebird Bird Monitor's Guide" that you allowed your name to go on but recently, you've stated that you disagree with some of the content of that book.   Are you in or are you out?!

Kenny Kleinpeter ...

Linda Violett - Yorba Linda, Calif.

Larry, since you are planning to use small vent holes (1/2" to 5/8" per your post), disposable earplugs are a cheap and easy way to plug up those small vents during the winter.

As a beginning monitor (1-holed boxes and small vents) I'd winterize the boxes by putting washers over the vents and securing them with a bolt and nut. Easy to add and remove but foam earplugs are even easier to plug small round vents.

Since I add an extra entrance hole to my boxes and increased the floor space, vents are obsolete . . . haven't used them for years.

Do you have enough cold to plug up any of the holes you use? I was wondering if you could close at least one off of the two-holed mansions for anyone having to consider severe cold weather?

I think the plastic irrigation plugs will work fine for me and we have hundreds of them.

Evelyn

Keith Kridler Mt. Pleasant, Texas
Dang! I never thought of "Micro Managing" Bluebirds as being derogatory! I meant it as a step up from "Nestbox Monitor" kind of like "Sanitation Engineer" instead of garbage collector:-))

Seriously now the ONLY way to really increase wildlife numbers or save a species is by "micro managing" every aspect of their life. Read the current articles in the news on California Condors and Whooping Cranes to see what it takes to save a species from the "brink" of extinction. In the USA only 7 out of 1,300 species that have been placed on the Endangered Species list have every increased to where they were removed from the list.

Eastern Bluebirds according to the latest issue from Cornell place their numbers at 20 million. That does NOT mean they are doing well in every state and they are probably very rare in many counties where predator proof nestboxes are seldom used and monitors consist of people nailing a box up in their yards and cleaning it once a year if then! The time to study and save a species is actually when they are doing very well and expanding their territory!

Checking a nestbox once a week is good for data collection but checking twice a week is far better for collecting data. Harry Krueger checked his 60 nestboxes EVERYDAY and he seldom EVER actually saved any birds from predators or death. Dr. Shirl Brunnell in Texarkana (Author of I Hear
Bluebirds) watched her bluebirds outside her office window almost constantly and failed to stop a lethal House Sparrow attack.

We ALL need to check our nestboxes as often as is possible and use the best guards available to protect against our local predators. By frequent monitoring you know when a small problem develops. Ask questions and very often someone offers a quick and easy fix like "ear plugs".

When we see nestboxes placed incorrectly in our areas we should all have some printed data handy to offer these "newbie's" or "Wanna be" nestbox monitors how to graduate up to "Nestbox Monitor". When or if they have problems then we teach them how to "Micro Manage" each problem to solve them one at a time....When you get REALLY good like Kenny then you get to graduate to professor and educate other "students" that happen along and want to learn about other species.

Just because I mention "90 percent" of nestboxes are placed without guards does NOT mean I like what I see, it only means we are NOT getting the Message out or that people are not understanding what we tell them. KK

Keith, I am glad you cleared this up. Since your sentence with the words micro-management had the words "solar screen" in it to, I thought you were talking about me! I found out later others felt the same way. I didn't get upset, just made me more determined to put out MORE solar screen! :<))

You know, in the past, those words WERE used in a derogatory manner and implied that we "smothered" our birds and the words meant "over managing".
We had quite a few LIVELY discussions then too. I think it would be wise in the future to make clear when there is doubt the way it is intended.

It is great to have many different knowledgeable people on this list and for each to lend their wealth of opinions and experiences. We are blessed!

It is also wonderful to have the "newbies" that ask such good questions. We need to be sure they understand the "best" way to take care of the cavity nesters and for them to know that things work different in every part of the country. Sometimes when we post, we forget that.

Evelyn Cooper
Delhi, LA

You wrote:

"in a woodpecker hole in a tree the sun wouldn't be able to heat the interior of the cavity the way it can with a nestbox."

I have read this many, many times, but it was refutted a couple of weeks ago. Do you know if any tests were ever done? It just seems to me that the tree would be a better insulator.

Evelyn
Evelyn, Dehli, LA