Bluebird and Small Cavity Nester Conservation
Sialis - Bluebirds and other small cavity nesters


Bluebird Nestbox Styles:
Pros and Cons

Need plan links for some. Need floor dimensions and hole-to-floor depth! More pictures/drawings would be good - but I don't have them for all styles, and it might make page load too slowly. ACCURACY IS VERY IMPORTANT and is being verified.

Ask a dozen people what their favorite nestbox style is, and you may get a dozen different answers. Probably the most commonly used are NABS, Peterson, Slot, and Gilbertson. If I bought ONE box for Eastern bluebirds, it would probably be a Gilwood (which they seem to prefer in my experience) or maybe a Troyer (a box used successfully by Bluebirds Across Nebraska - see info). If I had House Sparrow problems, I would go with a Gilbertson PVC nestbox. If I bought four boxes, I would probably get a Gilwood, Gilbertson, Peterson and NABS. But that's just me. Some box styles are shown below (move your cursor over each to see the name, and click to go to a description). See links to various plans. Also see REALLY useful website on with plans and recommended habitat, height and spacing.

nestbox styles

Generally Accepted Good Nestbox Design Specifications: Use a box designed specifically for bluebirds. The North American Bluebird Society (NABS) has specifications for nestbox designs. See Basics for more info. If I were looking for the ideal box, I would want:

  • a roof that will shed rain and provide shade. (A 2-5" overhang may deter predators. A shallow saw kerf (groove or drip edge) will help keep rain from soaking into box.)
  • no perch (gives House Sparrows an advantage)
  • a suitable size entrance hole that will keep out bigger birds, without rough edges (round 1.5" diameter hole for Eastern Bluebird [EABL], or 1.375" x 2.250" oval hole, or 1 3/16" high slot opening. Mountain and Western Bluebirds need a 1 9/16" hole, and EABL like that size too.) Larger holes or slots allow starlings to enter. Hole guards to make a 1 9/16" hole are hard to come by, but some suppliers do have them - e.g., (Use a Forstner bit instead of a spade/paddle bit or hole saw for a nice clean, perfect hole.)
  • ventilation to prevent overheating but not so much that it will get too cold or wet inside. (Note: some boxes in Wisconsin use no side ventilation due to black fly problems.) When drilling holes in the sides, aim the drill at an upward angle to prevent water from running inside the nestbox.)
  • drainage holes in the floor (wet nest preferred by blow fly?), recessed to prevent moisture entering via capillary action
  • designed to prevent water from getting inside the box (e.g., roof design, recessed floor placed inside of nestbox walls). Can also cover exterior with clear silicone caulk, with extra silicone on inside and outside seams
  • deep enough so predators can't reach in and get to eggs/nestlings, but not so deep that fledglings will have trouble exiting
  • a door that opens for cleaning and monitoring, but closes securely so predators can't enter
  • ability to mount (e.g., on a pole) or hang
  • usually made of wood (untreated, unpainted 3/4"-1" thickness is commonly used, or painted a LIGHT color on the exterior only), PVC, or hardiboard type material.
  • If rough wood is not used, add saw grooves or kerfs to the inside under the entrance hole to enable fledglings to climb out if Tree Swallows (TRES) nest in your area.

Other key criteria (predator protection, mounting, location, etc.) are discussed on the basics page.

Personal preference may be associated with:

  • material:
    • the most common are wood, PVC and occasionally poly (which is not the same as PVC), which vary in weight (and thus usefulness for tree hanging), durability, ease of cutting, heat retention, warping, the look, etc.
    • Some choose not to use aromatic (red) cedar. White pine and white spruce hold up pretty well.
    • Screws are preferred over nails (or glue) because they are easier to tighten, remove and replace. Use galvanized stainless screws which won't rust.
  • ease of construction (for DIYers - see links to suppliers for the not-so-handy)
  • ease of mounting or hanging
  • ease of monitoring (need ability to see even tall nests without door obstructing view)
  • durability (ability to withstand weather, predators, vandals, horses/cows, etc.)
  • where it opens (note: you can make a box that opens in multiple places - you can make an inexpensive hinge for the roof with a tire innertube strip and staples)
    • front - easier to clean and remove blow flies or see inside and to install inbox trap. May be a problem with wren guard or monofilament installed. With hinge on top, can be hard to see paper wasps building on roof or to treat roof - bottom hinge is better for this. Also during monitoring, bird only has one exit choice (front that is being opened), so be careful not to squish an escaping bird.
    • side - easier to clean and remove blow flies or see inside; easier to see paper wasps building on roof and to treat roof (e.g., with vaseline or soap); easier to install wren guard and monofilament to deter HOSP; allows startled incubating female to exit the front entrance when monitor opens side; may be harder to install inbox trap.
    • top may be good for fotos, nestcam mounting, paper wasp control or monitoring (easy to count) on horseback or HOSP trapping and preventing premature fledging, and for banding. Hard to adjust nest height or remove blow flies from under nest, may be a problem with sparrow spooker installed, if large wasp nest is attached, may be hard for short people to monitor.
    • I do NOT recommend boxes that open from the bottom - nests could fall apart, eggs roll out, premature fledging likely
    • some have multiple choices.
  • closure (e.g., must unscrew door - good for vandals but slows monitoring. Doubleheaded nail [or one on each side, angled down] keeps it from getting lost in a hole. Hinge from top or bottom affects visibility, cleaning and risk of eggs/nestlings falling out. In areas with raccoons, need a mechanism they can't open) (Note: A small block of wood as a "door stop" will help you close it just right.)
  • floor size (Western Bluebirds [WEBL] may require a larger box. Eastern [EABL] may prefer smaller boxes - Raymond Marr reported almost twice as many 4x4" boxes were used as 5x5" boxes in RI [Sialia, Spring 1993]). A larger floor size offers birds opportunity to place the nest cup in the back which helps deter some predators. I TRY to note finished (post-construction) interior floor size in the table below, but sometimes plans or suppliers provide the total floor dimension.
  • floor drainage (to keep inside and nesting material dry), recessed or not
  • toeholds for adults (kerfs on the OUTSIDE of the box below the entrance hole.) Note perches are NOT recommended as they offer an advantage to House Sparrows.
  • utility for trapping or banding
  • total interior volume (A Year 2000 TBN study indicated floor size had no effect on bluebird clutch size),
  • size and weight of box (especially for large trails or hanging boxs)
  • depth (overall, and depth from the bottom of the entrance hole to the floor)
  • cost (to build or purchase)
  • whether or not it is preferred by House Sparrows. Note that despite any claims you may read, HOSP can and may use or enter any box suitable for bluebirds. IMO, the only box with any (limited) HOSP deterrent effect is the Gilberston.
  • ease of inbox trapping - is it easy to install a Van Ert or Huber style inbox trap (difficult on narrow, side-opening boxes, Troyers. Slot boxes can leave room for escape.)
  • roof size (overhang for shade/shedding rain), style, single/double roof (for insulation)
  • slant of roof (flat, forward tilt [which may drench birds at entrance], backward tilt, rounded, slanted to side) and rain grooves
  • entrance hole size and shape
  • ventilation (and ability to cover/plug holes for roosting/cold weather - the Texas Bluebird Society box performs very well in heat)
  • insulation (heat and cold)
  • ease of cleaning
  • predator deterrence
  • location of box (weather and predator factors. E.g., rat snakes are not a concern in CT but may be a primary predator in FL)
  • old vs. new (it's not clear whether bluebirds prefer "used" boxes)
  • finish (sealed, exterior painted, exterior stained or treated with linseed oil, coated with one coat of Thompson's Water Seal or clear silicone etc.) Tom Comfort likes Shingle Saver (dries clear in less than an hour, clean up with plain water) to protect roofs from weathering - DAP clear silicone also works.
  • number of boxes needed (e.g., cost or ease of construction is a big factor for a trail with hundreds of boxes)
  • species of birds (e.g., a box that appeals to a Prothonotary warbler [PROW] may be different than one that appeals to an Eastern Bluebird)
  • demonstrated performance (and whether it has been adequately tested)
  • cavity nester preference (probably more dependent on the location of the box than the box style), and
  • cavity nester productivity (number of eggs, clutches and fledglings).

Many bluebirders (who tend to be creative, committed people) modify boxes based on experience or for experimental purposes.

This webpage doesn't address other variables like orientation, height,mounting method, hole guards, predator guards, toe holds, lumber thickness, variations for roost boxes, etc., which in themselves often trigger spirited debates.

Here are some pros and cons associated with boxes designed for bluebirds, which may also be used by secondary cavity nesters such as chickadees, Tree Swallows, House Wrens (HOWR), House Sparrows (HOSP), tufted titmice, etc. Many are my personal opinion, and none are intended as endorsements. See references for more information on formal nestbox comparison studies, etc. There is probably no "best box" that works best in all areas, under all conditions, for all species.

Links to plans or makers are listed where I could find them. Also see list of nestbox suppliers. Commonly available boxes are shown with a yellow background. If I wanted bluebirds, and got one box it would be a Gilwood. If I had House Sparrow problems, I would use a Gilberston PVC box. On my trail, I offer a variety of styles to the birds.

The bottom line? Offering a variety of boxes in good locations, coupled with responsible monitoring and maintenance will probably produce the best results. In reality, cavity nesters may not be as fussy as we are. They have even been known to use a box that flipped upsidedown. They just need to be able to get inside the box to build a nest, lay eggs and feed young, and end up with strong, healthy nestlings that fledge successfully.



Variation of Pros Cons Floor
Comments Plan
Aromatic Cedar     Inexpensive, so might be useful as a HOSP trapping nestbox. Made of (thin) aromatic cedar, which some bluebirders think is not healthy for nesting birds. ? A-style roof. 7 x 8 x 16" overall, comes with rope for hanging. Perky Pet
Baffle Dick Purvis Tree Branch
See Tree Branch. May resist raccoons, less awkward to mount than Tree Branch. Designed to prevent nesting in front of baffle. Side pivots up for monitoring. See Tree Branch. Takes more material than a conventional box. Bigger and more difficult to mount than other styles, awkward to hang. 6x6" nesting area 1 9/16" entrance at each end (front and back). 4 1/8" baffles inside, 2" in front of each entry hole. Plan
BAN EABL Nebraska Game & Parks Commission NABS One standard 8' 1" x 6" board makes 2 boxes.   4x4"
6 13/16" hole to floor depth.
Slanted roof, side slot vents. Side door pivots from top. Recessed floor. Roof 9 1/4 x 10 1/2" Plan
Vince Bauldry

and Hill Lake

May not be preferred by HOSP Screened top allows water and cold air to enter and potentially cause fatal hypothermia to nestlings. Not endorsed by NABS. Some users add additional ventilation to sides, and cover opening after first egg and install sparrow spooker. Bluebirds may not like Plexi. 4x4"
10" deep.
1" thick guard around entry hole. Saw kerfs on interior wall.
Original has a 3" hole in the top covered by screen. Can be covered by plastic in some designs. Plastic may overheat eggs/nestlings resulting in death. Purchase - NOT RECOMMENDED. BRAW recommended screen top version. Plan on p.11
Bermudez Barry A. Bermudez (see 2002 issue of Bluebird) Purple Martin style Experimental box that may deter starlings/HOSP. Mount 4.5-5.5 ft. high. Allows entrance by predators - owls, cats, raccoons. 5X5"
Hole 8.5" above floor
2.75" entrance hole. As soon as native species is confirmed, you MUST back hole down with a reducer or use a Noel Guard or a wobbling baffle.  


  1/2 gallon
milk jug size See milk carton.
Inexpensive, easy to put together. Paper wasps don't build on wax. Usually lasts only one season. Carton can be easily torn apart by mammals. Can get so hot the wax melts. Bottom can fall out along with nest. Access for monitoring? Flat roof does not shed water.   No longer marketed? May be acceptable for one time use with removal at the end of nesting season.  
Bittner or B201 Ron Bittner   Two slot entrances. Deep. May not be preferred by TRES?     Bird enters by walking over a block. Entryway is located up under the eaves on the sides of the box.  
Bluebird Love   NABS Well made, large roof overhang, velcro ventilation covers for roosting, can purchase wren guard Pricey, heavy, large     Purchase - OUT OF BUSINESS?
Bo Villa Gourd S&K Manufacturing Plastic gourd Plastic, 4" clean out hole can be used for nestcams. Easy to monitor and clean. Lightweight, easy to mount on T-post. Difficult to clean? Bluebirds may not prefer, HOSP may. 8.5x11" floor. 4" hole-to-floor depth Plastic sideways gourd with a platform. Starling Resistant Entrance hole can be used. Suggest spray painting interoior with dark Krylon. Purchase (difficult website to navigate). Regular gourd has 2" entrance, request bluebird version with faceplate and non-slip floor insert.
Bolt (Mel)
Tilt Front
Mel Bolt NABS     4x4.25 or 3.75x4.5" Two sizes - larger requires more cutting. Plan
Carl Little Carl Little NABS Vents on side and front
Sloped roof sheds rain
Full swing down door
  4 x 4"
NABS approved
(Slant Box)
Paul Carrier   Entrance on bottom resists weather.
Simple to build?
Does NOT deter HOSP. Impossible to trap. Nest and eggs can fall out. Not preferred by EABL. 4x7" Horizontal box, slanted bottom with entrance hole on bottom. Top comes off for monitoring. Plan

(e.g., Schwegler woodcrete or wood-crete)

  Also called Wood-crete Durable. Waterproof. Schwegler website claims attracts 2x occupants compared to wooden boxes. 25 year warranty. (Surprisingly?) approved by NABS. Sliding front panel door with kerfs. May be preferred by titmice. No ventilation. May overheat in direct sun resulting in high nestling mortality, esp. dark brown box. Use only in full shade. Entrance hole smaller than 1.5". May be used by hornets. Weighs 5 lbs. No way to attach a spooker, wren guard, Van Ert/Huber traps.   Cylinder with peaked roof and molded ring for hanging. Some are painted a dark color, others are gray concrete. Comes with different door panels (32 mm, 26 mm, oval 29 x 55) Purchase - (not recommended)
Ceramic       Many do not have adequate ventilation/provide access for monitoring/
    Purchase - NOT RECOMMENDED. Use for decoration only (plug hole)
Gary Springer


Improved ventilation and shading. Attractive gable roof. Quick pole mount design. May be difficult to monitor a tall nest due to roof design. May have excess ventilation for cold areas. Rain can enter on each side of roof hinge. Very heavy. May not be attractive to EABL. Need to remove roof and back to install screws for Van Ert trap. 4x5.5" Top is hinged.


No longer sold by Springer

Chalet, Meadowood John
Chalet Ridged roof to keep moisture out. Good ventilation. Well crafted. Quick mount. Redwood. See Chalet, Springer.
Expensive to purchase.
5x5 or 6x8 (Chateau)
side opening. Dept to floor 6"
DANDR Douglas DesPain Slot See Slot. Double roof with 8.25 x 8.5" durable Hardiplank overlay, removable tray for cleaning. Relatively easy to build. See Slot. No side ventilation but holes can be drilled. Floor 3 3/4 x 4". Slot is 5 1/2" above pullout tray.   Plan and Photos. NABS approved.
Decorative Various     Generally not appropriate for bluebirds - often too deep, do not open, no kerfs, inadequate ventilation, painted dark colors etc.   Can be a death trap for nestlings NOT RECOMMENDED. Use for decoration only - plug hole.
Duncan William Duncan NABS See NABS. 5x5 floor suits MOBL and WEBL. Simple to build. See NABS. No roof side overhang, rain can enter through vent slots. Back does extend above top (affects mounting.) 4.5 or 5x5" NABS box predecessor. Slanted roof (variation backward tilt) Top?Side? opening. Drainage holes in floor.  
Droll Yankees Bob Benson Tapered Chalet style Large overhang and rain resistant. Fairly deep. NABS approved. Unusual hole configuration may be preferred by bluebirds. Expensive. Complicated to assemble. DO NOT USE plastic predator guard that came with earlier models- too small for bluebirds! Would require a special metal hole guard to prevent chewing.Door on older boxes may open inward - drill a hole and put a screw in. Floor 4 x 3 1/16", similar to Peterson. 4.25" to from bottom of entrance hole to bottom of box.
Benson is also experimenting with slot style, shallower box for HOSP.
Odd entrance (upside down egg shape/tear drop 1.5"x1.25") Pine. Side door opens down. One seller
Emad Fawzi Emad NABS
Top or front opening. Large roof, less likely to leak. Easy to make (1 piece of wood), easy to mount trap. Light.     Has "drip" grooves on front underside of overhanging roof. Plan
Flying Nun Bill Devin Gilwood style hole - roomier interior Durable curved PVC roof sheds rain/snow;
Gilwood style hole; attractive;
1" thick wood,
pre-fittted for bottom mount; good ventilation; removable plexi to prevent premature fledging; light, strong wood.
HOSP may be attracted to domed roof. Will birds miss ability to perch on top for defense? ( due to curved roof?) Tricky to install wren guard? Remove plexi to trap HOSP or to see inside nest cup. See Gilwood hole issues. Floor - 3 3/8" x 6".
6.75" hole to floor.

Curved roof, tapering body, plexiglas viewing/clean out side opening door. Also available with hanger

Will HOWR avoid?

Website purchase
Fox Box         4x4"    
Garden Design       Roof access only   Long cylinder shape with pointy roof Purchase
Gilbertson Steve Gilbertson   Considerable roof overhang. PVC lasts long term - strong and durable. Not PREFERRED by HOSP, may be preferred by EABL and chickadees. Cheap and easy to build or buy. Lightweight so can be mounted on thinner pipe (into hole in roof overhang). Easy to bring down to show nest to a child. Easy to dump out old nests. Weather resistant. Easy to photograph in from above. Small interior - too small for WEBL? Use two hands when removing or box can be dropped. Difficult to check for/remove blow flies/do nest change. When mounted on pole may swing around (use a little duct tape to prevent). No commercially available metal hole protector. 1/16" walls slightly less heat resistant than Schedule 40 PVC. Very difficult to mount nestcam. Can't use Vanert inbox trap. HOSP may utilize/attack users. 4" tube (PVC sewer and drain pipe), 4 5/8 to 4.5" hole-to-floor. Often painted to look like birch, interior brown to darken. Cedar roof. Squeeze box to match up the pins in the holes to reattach to roof. Use universal trap (hangs on hole). To avoid overheating, use large roof or place where shaded in the heat of the day.


Purchase Gilbertson box on Amazon

Gilwood Steve Gilbertson   Considerable roof overhang. Easy to make. Recessed front panel and larger U-shape entrance protect from wind, rain, sun.
Adjustable bar. Very attractive to EABL in my experience.
Small interior. Door sometimes sticks badly. Roof is not slanted. No commercially available metal hole protector. Starling have been observed entering but are unlikely to nest due to small interior volume. Must use Van Ert trap style for this hole. In hot climate may need addtl 3/8" vent gap.


5" hole-to-floor

Hole is 2.25" diameter, 1.25 - 1&3/8" from bar to bottom of hole (adjustable)

Entrance hole ~4" area. Steel wire prevents starling entry. Gilbertson made comes with kerfs inside door. Use universal trap (hangs on hole).



Gourd (Natural)     Free. If it does not have access panel, impossible to adequately monitor or remove nesting material. HOWR may prefer. Thin, fragile, short life.    

Also see Supergourd


Griffin Sherman Griffin Duncan Side and top opening. Hole 6" from floor. Removable top sometimes gets stuck. 4x5.5"    
Grivich   NABS?   Shape limits types of inbox traps to Gilberston/Van Ert PVC box style.   Small at top, large at bottom - resembles woodpecker cavity.  
Hanging Boxes (also see Two-hole mansion)             - Two-holed hanging mansion (L. Violett)
- San Diego - standard
- California Bluebird Recovery Project
Southern California
Herman Olson Herman Olson NABS     10" deep total, 4x4 floor 7.25 x 9" roof slands backwards, side opening. Kerfs under wood block around entrance hole. Plan on p.14
Hill Lake Andrew Nelson NABS Deep box designed to deter predators, with 2x4" predator guard over entrance. Roof overhangs by 2.5". Relatively easy to construct.

Depth typically puts nest cup out of reach of predators, but some bluebirds defeat by building tall nests, in which case it can be lowered. Impact of narrow width relative to depth?
BRAW monitors found birds preferred smaller volume interior. Low bluebird productivity? Depth may favor TRES but they may have difficulty exiting.

9 to 12" from hole to floor, typical depth
11 1/8"

Flat top, side opening. 5.5 x 5/8" slot vents on both sides.


or Plan on p.12

Hill Lake, Modified     BRAW study showed it produced more bluebirds than original Hill Lake. See Hill Lake. Hill Lake floor is raised (or a new floor is secured) at about 3-5" from the bottom of the entrance hole.    
Flip Flop
Joe Huber NABS
Built in sparrow trap   3.75x4.5"   Plan
Horizontal see Frank Zuern            
K-Box Terry Glanzman, BRAW Slot with upsidedown mouse hole Shallow box may deter HOSP. Backdward tilting roof. Small floor. No ventilation. Shallow box may facilitate avian predation.
4x4" floor, 4" from bottom of hole to floor Experimental. U-shape vertical slot for entry. Top opening. No ventilation holes for gnats. 3/4" wood.

PDF version of plan

Kinney (4 hole) Tree Swallow Henry E. Kinney of MA Multi-hole One entrance hole + 3 smaller holes allow faster feeding, prevent hole hogging, improve ventilation. T-perch and cleat on roof. Perch may facilitate use by HOSP. Difficult to monitor from rear door. May wish to increase side and rear overhangs and add side ventilation holes. 10&3/4 x 7& 3/8 floor.
6.25" from hole to bottom
Modified plan for standard wood by Berger
Little Bird House Steve Garr Chalet style For Carolina Wrens, Prothonotory Warblers and Chickadees      


for sale at Birds-I-View

Log Lawrence Sawyer   Natural look attractive to humans. Special lathe or 4 5/" Forschner bit needed to bore hole. Dangerous if bit hits nail/knot hole while drilling. 4" diameter Tulip poplar will retain bark about 20 years. Logs cut in winter will retain bark longest - can staple on.

Can use tree tops with woodpecker cavities.

see 1917 plans


Log, Original Nest Log© Morning Star Ranch   Natural look. Oversized (13.5x18") double roof. Good cross ventilation (1/2" gap) by roof. Recessed floor. Kerfs. Drip guards. See-through guard by door. Thick walls for insulation. Deep to deter avian predators. Expected to last 20 years. Heavy (3 lbs. when cured). Not suitable for hanging. Expensive ($129). Only Gilbertson trap will fit, would be hard to put bag over to remove trapped bird. Needs flexible hole guard. Thick hole may result in wear and tear and make feeding more difficult. 7" from hole to floor,
5 1/4" diameter.
Logs without bark. Roof of Western Red Cedar, body of Eastern Red Cedar. Side opening. Need 1.5" conduit for mounting. Purchase
Lowe's (hardware store) Made in China NABS Deep. Window screen to help fledglings exit. Inexpensive. Very small floor area, no ventilation. Front of box pivots up to open but no latch. Glued or tiny brad nails. 3/8" wood.   Ones sold in TX are made in China.  
Meadowood See Chalet            
Metamucil Container
Andy Fondrk and Dan Best   PROW actually seem to prefer these over natural cavities. Free.   7" deep, 3.5" diameter Painted (gray, tan or green enamel) with 1" plastic screened side vents, and a 0.25" screened drain hole.  

Milk Carton (Waxed Cardboard)

  1/2 gallon Free, thus may be useful for short-term research. Paper wasps don't build on wax. May be preferred by PROW over wooden boxes. Usually last only one season. Carton can be easily torn apart by mammals. Can get so hot the wax melts. Bottom can fall out along with nest. No access for monitoring. Flat roof does not shed water.   Entrance and ventilation holes added. NOT RECOMMENDED EXCEPT FOR TEMPORARY RESEARCH.
Milk Jug
  1/2 gallon Free. May overheat if not painted? Access for monitoring?   Entrance and ventilation holes added.  
NABS - Bluebirds Across America   NABS See NABS. See NABS.     Plan
NABS - Double (Echo) Roof Bruce Burdett, Fawzi Emad   Insulation from heat/cold. See NABS. See NABS.     Plan
NABS - Jack Finch Jack Finch NABS Easy to monitor. Metal hole protector. Double roof covered w/ brown aluminum. Metal strap for mounting. Cardboard flowerpot inside for cleaning/ monitoring. Now made of solid wood.   4x5.5" Plastic coated 12 guage wire run through front and side to fasten. Sometimes painted brown to protect. Purchase
NABS - Kentucky Four Seasons William Freels NABS Rounded white fiberglass roof for heat and rain protection. Plexiglass vent covers (adjustable). 1" thick all over. Designed to mount on a T-post so additional holes through back needed for other mounting methods. No kerfs inside door. 4x5.5"
4.5" inches from hole to floor
NABS - Lenker   NABS See NABS. See NABS. 4x4" Side opening Plan
NABS - Olson Herman Olson NABS See NABS. See NABS. 5x5" entrance hole 6-7/8" from the bottom, a slightly slopping roof  
NABS - Original adapted from T.E. Musselman NABS Tested by time, oft used by EABL. Easy and quick to make with little lumber waste. Lightweight for wooden box. Removable top. Some do not have adequate roof overhang for rain deflection. Roof/back joint can leak if not caulked. Bit more difficult to build than Duncan. Top may be torn loose by livestock. Back does extend above top (affects mounting.) 4x4" or 4x5.5. Hold depth 5 1/8". Many variations since approved by NABS, including larger floor and more roof overhang. In hot climates, consider increasing vent gap to 1/2" Plan
NABS - Stokes D and L Stokes NABS See NABS. See NABS. 4x5.5" (minus lumber thickness)   See book
NABS - Tuttle Dick Tuttle NABS See NABS. Cheaply and easily built with handsaw and drill. 3 boxes from 1x10 board. Rain grooves on roof underside. See NABS. Door pivots wear/fail. 5x5" Designed so schoolchildren can build. Flat roof. Side or top opening.  
NABS - Robert Wilson PVC Robert "Bluebird Bob" Wilson   See NABS. Free material, doesn't warp or rot and hole can't be enlarged. 15-20 degrees cooler than wooden box. See NABS. Need a table saw or mitre saw.   Jigs help with construction. Plan
NABS - Zeleny Larry Zeleny NABS
See NABS. See NABS. 5x5" Side opening Plan
Nature House ? ? Top flips for cleaning. Drip ledge on roof.

Heat issues?

4x4", 6.5" from hole to floor. Double walled metal (24 gauge aluminum). Has drainage holes. Purchase: Nature House Inc. P.O. Box 390, Griggsville, IL. 62340-0390
Navratil Bluebird Buoy Frank Navratil Gilbertson

Low maintenance. Sliding front-opening door allows access to entire cavity. Can use spare door with variable hole size. 12" plywood roof covered in aluminum shades. Must use hanging inbox trap. 4" sewer & drain pipe, 10" long Long section of pipe below entrance acts as predator guard, and slides over mounting pipe. Plan
Navratil Hanging PVC Frank Navratil


Roof designed for ease of hanging.   4" tube   Plan
Ohiowood Bernie Daniel Gilwood Simpler door etc. making it easier to construct than Gilwood, larger floor size        
Olson, H. Herman Olson NABS? BRAW noted it produced more bluebirds than TRES.   5x5" Roof slants towards back. Door pivots open from top. Plan


(oval entrance

Dick Peterson.   Small floor size may expedite nest completion. Birds may prefer larger body-shaped opening. Several comparison studies indicate higher numbers of bluebirds fledged per box (1, 2). May produce more bluebirds than TRES. Steeply sloping roof shields hole from rain and sun, deters predators (like cats.) Good insulation for areas with cold spring weather. Sloped floor facilitates blow fly removal. Box is top-heavy (2x4 stock) and may tilt if not securely mounted. Narrow (3.5" wide). When door is opened eggs/nestlings may tumble out if nest and box are tilted or when box is crowded (e.g., 6 nestlings) as they may lean against the front. More expensive and complicated (need table saw and miter), can be expensive to purchase. Some have problems with starling access. Not all inbox traps work. Paper wasps like to nest in gap under floor. 5" hole depth when properly built - some are 5.75". The result of 20 years of research by Peterson. 1.375" x 2.250" oval entrance hole. Front opens from top down. Because of size and weight, try T-post mount, or use conduit (3/4") strap on top back, and even two pressure-treated 2x4x10" clamped to bottom of pipe on ground. If starlings in your area can enter, place wooden block with drilled round hole over oval hole.


BRAW has unvented version

Peterson - alternate   Peterson See Peterson. See Peterson.     Plan
Peterson, modified Fawzi Emad Peterson See Peterson. Circular hole to deter starlings. Not as heavy as original Peterson (3/4" wood), wider (4.5" wide). Drip grooves on roof. See Peterson.     Plan
Peterson, modified for width and depth David Gwin Peterson

See Peterson. Deeper entrance may discourage avian predators. Larger box suits flycatchers and woopeckers. Can be hung from trees to deter predators.

See Peterson. 5x5" floor, 8" drop from bottom of hole to floor 2" added to each of exterior dimensions. All other cuts are as per original Peterson design. Use 2x6s instead of 2x4s. Picture
Plain   NABS Easy to build, lightweight. Bottom recessed to prevent door from pinching. Plain looking. 4x5.5"? Side opening. Well suited for Gilbertson conduit/rebar mount off roof. Plan
Prescott Prescott Bluebird Recovery Project NABS Front or side opening. Drip kerf under sloped roof. No side ventilation. 5x5".
7" drop from hole to floor.
For WEBLs. 3/4" plywood CDX or cedar. Roof and sides have 10 degree slope. Plan
PVC fencing Bob Wilson NABS esp. Tuttle Panels can be glued (PVC cement) or screwed. Dead air inside plank insulates. Scraps can be obtained from fencing contractors.     Made from white, hollow 1x6" planks. Front opening.  
PVC tube- Hutchings Don Hutchings Also see Gilbertson Uses factory made PVC end cap for top and bottom. Shallow boxes may deter HOSP, deeper boxes cooler and deter predators. Compact. Monitor by removing bottom cap. Added interior toeholds (e.g. horizontal caulk beads) recommended for TRES. 4" PVC pipe that is 8-11" long (min 4.5" from hole to floor) and 1/4" thick (Schedule 40 PVC ppe) Single screw used to remove bottom cap. Has drain holes in bottom cap and 3/4" vent holes near top of pipe. Square PVC board or wood roof attached to top end cap.  
PVC-tube Chickadee Daniel Mennill Also see Gilbertson See PVC tube-Hutchings See PVC tube-Hutchings 3" diameter, 35 cm long, 27 cm from hole to floor   Instructions
Raised Roof - Orthwein Bob Orthwein


May deter HOWR nesting . Improved ventilation for hot climates. HOSP will use.   HOWR may still enter to destroy eggs of others. Plan
Rubicon   NABS Plastic lasts forever. Easy door opening. Pricey. May not be preferred by cavity nesters? Front door panel slides down for monitoring, nest may catch on it, might increase likelihood of premature fledging.     Purchase
Shantz Bryan Shantz     Used for Mountain Bluebirds?      
Simple Joe O’Halloran Peterson Small nest-volume box, preferably with a Peterson-oval portal, designed for easy, and economical shop production.   3x4" unfinished
Slanted roof and front. Two slots across rear underside of roof keep water from dripping on back of box. Plan
Simple Joe O'Halloran NABS Large overhanging roof to deter mammalian predators. Easy to mount. No vents, designed to deter black flies (Wisconsin - BRAW)   Small nest cavity. Front drop down opening. Plan - Lafayette
Plan - BRAW
Slant - see Carrier              
Slippin' Silo D Michael Worley Gilbertson Nest container pulled out through bottom to monitor. 2 models available. One has vent covers, can also cover hole during monitoring to prevent premature fledging. Diameter?
6" long thin wall PVC tube?
Flat or sloped roof. Unusual nest-insert (plastic) with screen. Does not deter HOSP. Purchase
Slot (basic) See below   May not be preferred by HOSP. Large slot provides good ventilation. MAY be easier for bird to escape HOSP attack. Easy to build, no entrance hole drill needed. If roof warps, slot can widen to allow starlings, or narrow to prevent bluebird entry. Preferred by HOWR? Mixed results on HOSP deterrence. Other birds (bluebird, TRES) may not prefer. Shallow box may promote premature fledging. Stuchbury trap works, width of opening may allow escape with a Van Ert inbox trap.   Small and shallow. 1 3/16" slot. Deeper, larger variations may need 1 1/8" slot to deter starlings. To prevent roof warping, use 3/4", 5 or 7 ply exterior grade plywood.  
Slot - Efta Rita Efta Slot, Duncan and Tuttle
See Slot. Slightly sloping roof. See Slot 4x4", 6" hole-to-floor depth 1 3/16"slot. See note. Plan
Slot - Johnson   Slot See Slot See Slot 5.25x5.25" See note. Plan
Slot - Kentucky Wayne Davis Slot See Slot. Can add block to reduce depth to 3.5" See Slot. 5" deep. 4x4" See note. Plan
Slot - Loren Hughes Loren Hughes Slot and Peterson
See Slot. Cup for nest inspection and cleaninng. See Slot. 3 3/8x3 3/4"
4.5" hole depth
Angled roof and front. See note. Plan
Slot, Simplest

? used by Jack Bartholmai

See Slot. Low productivity? 4x4x4"
1 1/8" slot.
1 3/16" to 1 1/4" slot, NOT 1 1/8" as some plans show!  
Slot - Troyer
Slant Front
Andy Troyer Slot Large roof overhang. Lightwieght (can use 1/2" conduit). May be preferred by bluebirds. Not preferred by HOSP. Small interior. Trapping is harder with slot boxes using a Van Ert. The angle of the front can make it difficult to install a Van Ert trap, which hits the roof when it trips. Slot 4.5" above floor. Rectangular with a 1 1/4" or 1 3/16" slot entrance at the top of a downward-slanting front with bottom pivot. Shallow interior. Optional pull-out tray. See note.


BAN Sales

Slot, Van Ert Floyd Van Ert Slot See Slot See Slot 4x4" See note.  
Songbird Shake Shingle   NABS Cottage look with shingled roof that also provides ventilation. Stapled together? Depth will not prevent avian predation. 4.5x5" floor, 4.75" from hole to floor 3/4" Western Red Cedar. Front opening (hinged at bottom)  
Supergourd             Purchase
TB (Texas Blues) -1 Keith Kridler, Texas Bluebird Society   Best performance in Shiels heat tests. Excellent ventilation. Large roof overhang and floor size. Good style for a nestcam.   4 3/4" x 4 3/4" floor. 7.5" from hole to recessed floor. TB-1 is from 1x12 cedar/pine, table saw required. TB-1A is 1x6, 1x8 and 1x10 lumber with largest floor area (32 square inches), for species that need more space.
TB-1B is 1x6 and 1x10 lumber. TB-1C is built from 1x6 lumber.
Tree Branch - see Zuern and Baffle         Interior stain may attract birds to darker interior  
Triton Tom Comfort Gilfort/Gilwood/Peterson Durable waterproof PVC white roof and LP siding, Gilwood entrance appeals to bluebirds, easy Gilbertson conduit/rebar mount, turns in wind Pricey     Plans
See Slot - Troyer              
Two-Hole Mansion Linda Violett, with Andrew Plaza's 2-hole concept NABS (esp. Tuttle) Dual holes improve ventilation and may allow bluebirds to escape HOSP/predators. Face guard and depth may prevent predation, esp. avian. Roof gutter. Heavy. One hole must be closed off for trapping (use rubber plug). Larger two-holers may attract honeybees, harder to contain bees when lowering a hanging box. More ventilation an issue in cold temperatures? 5x6", 8.5" hole-to-floor depth

Front opening. Suitable for hanging. Need to provide adequate overhang over each entrance.



Two-Hole Mansion, EABL Modified for EABL by Fawzi Emad and Barry Whitney NABS See Two Hole. Tilted roof. See Two Hole. 4.5x6" Modified for EABL Plan
Ugly Gary Gaard of BRAW Flyguard and NABS? Deters TRES (perhaps due to recessed entrance hole). Sub-roof for strength, and restricted headspace designed to discourage HOSP. Funnelshape
moisture wick (15 degree cut, space the width of a carpenter pencil) to keep the nest dry to prevent blow fly.
  1-1/2” X 2 vertical oval hole. Experimental. Entrance hole recessed by extending the sides of flyguard house. No side ventilation (black fly deterrence). Large front roof overhang. Plan
Ultimate Bluebird House   NABS both sides open to plexiglas partition to allow for safe observation of the nest. Aluminum screen attached above floor may discourage blow flies. Expensive. Inadequate ventilation?     Purchase
Van Ert Floyd Van Ert Gilbertson

Considerable roof overhang. Roof firmly attached to pole with bracket and screw, then box slides down a track to be checked.


Have to put a nail in the track at a 45 degree angle to secure box so it doesn't slide down and out by itself.     Purchase
Wal-Mart Cedar Works /Nature's Niche NABS Plastic toggle to hold door closed. Inexpensive. Thin cedar, roof has insufficient overhang to ensure dry nest in severe storm. THESE BOXES DO NOT MEET NABS SPECS DESPITE LABEL.   Fledge quite a few bluebirds and PROW for some.  
Y-box Fred Yeager PVC Experimental     Shaped like an upsidedown Y with long entrance area Contact
X-box Dan Sparks, Tom Comfort et al NABS Experimental       Plans - Version 7
Zabel Z-50 and Z-50 PG Duane Zabel of BRAW            
Zuern (Horizontal)
Tree Branch
Frank Zuern   Reduces ability of predators (including owls) to access nest IF it is built behind baffle. Purports to minimize HOSP fatalities because the sparrow can't "mount" the bluebird and attack from behind. Babies can walk out when fledging. Prevents sun from entering box (con in cold weather.) Titmice may prefer. May prevent losses from heat compared to vertical box. Usually not preferred by bluebirds. May be more work for parents to enter past baffle, parents may not be able to view all gaping mouths to feed equally. Heavy, it is hard to mount. Side opening difficult to monitor. Does not deter HOSP nesting. May not deter mammalian predators as birds may nest in front of baffle. Lack of ventilation may result in overheating. HOWR may prefer. Uses more wood to build.   Horizontal box simulates a hollow tree branch. Over 90% nest near the back of the box, behind a vertical baffle. If they don't, move nest behind baffle after 1st egg is laid.Some have removable baffle for cleaning. Side opening. Designed to be mounted on 4x4 post. Some say its hard to build, some say very easy.


Also see Baffle Box

NOT NABS approved.

Other boxes I'm trying to get info on are V. Olson, Zabel Z-50 and Z-50 PG and Sommer (mentioned on BRAW website).

Acknowlegements: Thanks to:

  • *Designers are listed because they are usually the ones who did the fiddling, found out what works best and what the problems are, have access to plans, and have real world experience with that style, or "popularized" the style. Some of the designers did not name the boxes after themselves, but the naming has become a convention as a reference. Perhaps a naming system that is more informative (e.g. indicating basic style, floor size and depth to hole) would be more useful. A unique name does help people identify and discuss a box.
  • Linda Violett for floor sizes and information
  • Many comments from Bluebird_Listserv participants and archives
  • The Bluebird Monitors Guide, 2001
  • The Bluebird Box for posting plans online and Jim McLoughlin for his input
  • Wendell Long for Gilbertson photo with blue

More Information and References:

On this website (

Other wonderful resources:

Standard NABs box.  Sorry, I forget who took this picture! Slot box Carrier/Slant box. DOES NOT DETER HOSP. Zuern/Tree branch Two-hole Gilwood box, side view. Gilbertson box, photo by Wendell Long Standard Peterson box Loren Hughes slot box modified to let light in an attempt to deter HOSP.  Photo by Loren Hughes.

The very reasons some liked and swore by one kind of box turned out to be a disaster on my trail!
- Haleya Priest, 2001

It is NOT the box style but the monitoring style that determines whether you have bluebirds or not
- Keith Kridler, 2004

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