Houses

Best Bluebird Houses and Nest Boxes for Eastern Bluebirds

By Beak & Branch Editorial · Published August 20, 2026

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Our picks below are research-based — built from manufacturer specs, long-term owner feedback and independent reviews. We buy and field-test top picks on a rolling basis and update each guide as hands-on results come in. How we work.

A bluebird house is mostly a hole with a box behind it. A round entrance of 1 9/16 inch (40 mm) or smaller excludes European starlings; go materially wider than that, or let a hole be gnawed or drilled out, and you have handed the box to them. That is why every serious nest box discussion starts at the hole and works outward. The rest of the spec sheet matters — but the hole decides who moves in.

The useful thing here is that the standard is public. Bluebirds are one of the most intensively managed cavity nesters in North America — purple martins east of the Rockies go further still, nesting almost exclusively in housing people put up for them — and the North American Bluebird Society (NABS) publishes recommendations that describe a box, not a brand.

The box standard, in numbers

Floor area. NABS notes that eastern bluebird boxes commonly run 4 x 4 or 5 x 5 inches inside. Most society and agency plan sets land on 5 x 5; some western and mountain plans go to 5.5 x 5.5 or 6 x 6. Sources genuinely disagree, and both ends fledge birds — the 4 x 4 boxes are simply tighter for a brood of five.

Depth below the hole. NABS puts the drop from the bottom of the entrance to the floor at commonly 4½ to 6 inches; some plan sets and species tables run to 10. Depth is not what stops a raccoon — NABS credits a 5-inch roof overhang above the entrance and a predator-resistant pole, and slot designs such as the Kentucky and Troyer boxes are deliberately shallow at 4 to 4½ inches to discourage house sparrows.

Ventilation and drainage. Gaps or upward-angled holes near the roof let heat out; holes or clipped corners in the floor let rain out. Both are cheap to build and conspicuously absent from decorative birdhouses.

No perch. A dowel under the hole is the clearest sign a box was designed for a gift shop. Bluebirds don’t need one, and a perch gives house sparrows and starlings somewhere to stand while they harass the nest.

Thick, bare walls. Three-quarter-inch stock is the usual recommendation: it resists warping and buffers cold spring nights and hot June afternoons alike. Metal boxes are an outright bad idea in sun.

It has to open. NABS treats monitoring access as essential, not optional — the buying feature most people underrate.

For the full build sheet, including species other than bluebirds, see our nest box dimensions reference.

The hole: 1½ inch, 1 9/16 inch, oval or slot

This is where precision earns its keep.

NABS’s current factsheets give eastern bluebirds a range — 1½ to 1 9/16 inch round — and 1 9/16 inch for western and mountain bluebirds. Its 2021 Getting Started factsheet goes further: ‘to simplify the entrance size advice, a 1 9/16” round hole or a 1 3/16” horizontal slot entrance is probably ideal for all three bluebird species.’ NABS’s own specification sheet and its nestbox recommendations factsheet both put western bluebirds at 1 9/16 inch; the Sialis entrance-hole discussion paraphrases NABS as 1½ inch for eastern and western. The disagreement is in the secondary summary, not in NABS’s published numbers. NABS also recommends the 1 9/16-inch hole anywhere mountain bluebirds occur, including where their range overlaps eastern or western populations — so across much of the interior West, the larger hole is the default rather than the exception.

Both accepted round sizes are starling-proof, and it is worth being precise about why. A round hole of 1 9/16 inch (40 mm) or smaller excludes European starlings, so 1½ inch and 1 9/16 inch both shut them out — the sixteenth of an inch between them is not what decides the box. Starlings get in through round holes materially larger than 1 9/16 inch, and through holes that have been enlarged, drilled out or gnawed wider.

NABS itself and long-running bluebird references argue 1 9/16 inch is the safer all-round choice: western bluebirds vary in size, and the larger hole is still inside the starling-proof range. Both of the facts usually cited here actually point the same way: starlings have been found dead wedged in 1 9/16-inch holes — they cannot pass it — and 1½-inch holes have been linked to worn shoulder feathers on mountain bluebirds squeezing through. The only argument against 1 9/16 is speculative: that southern starlings could over time become small enough to enter it. No wild starling has been documented entering an un-enlarged 1 9/16-inch hole. Match the hole to the species that actually breeds in your county, and in overlap country go with 1 9/16.

An oval hole of 1 3/8 x 2¼ inches is the third accepted option, and it is the Peterson-style entrance, not a slot. Cut it to that dimension exactly: NABS warns that smaller starlings may be able to enter oval holes, especially ovals that were not cut precisely to size, so a home-cut oval that drifts wide is the failure mode to avoid. The fourth option is a horizontal slot, 1 1/8 to 1 3/16 inch high and running the width of the box, used on the Kentucky, Hughes and Troyer slot designs. NABS gives the slot as 1 1/8 to 1 3/16 inch for eastern bluebirds and 1 3/16 inch for western and mountain bluebirds; its 2021 factsheet calls a 1 3/16-inch slot probably ideal for all three. The bare 1 1/8-inch figure survives only on the older specification sheet that described the approval programme NABS retired in 2012. If you see “2¼ inches” quoted for a bluebird box, that is the long axis of an oval — a 2¼-inch round hole is a starling door.

One buying note: NABS ran a nestbox approval programme, lending its seal to commercial boxes that met its minimum specifications, but discontinued it in February 2012. NABS now publishes specifications only, so a current “NABS approved” badge is a seller’s claim against a retired standard — read the numbers.

Cedar, pine or recycled plastic

Cedar is the default for good reason: rot- and insect-resistant, stable outdoors, weathers to grey without maintenance, and used by most of the well-specified mass-market boxes.

Eastern white pine, cut thick, is the traditional trail-box material and insulates better than thin cedar because there is more of it. It wants a light exterior finish or shade in hot regions, and lasts less long untreated.

Recycled poly-lumber never rots, splits or fades, which makes it the low-maintenance answer in wet coastal and freeze-thaw climates. Two caveats. Colour is a genuine welfare variable — box interiors are reported to run well above ambient air temperature, and bluebird eggs and nestlings do not survive sustained temperatures around 107°F, so a dark poly box in full sun is a worse buy than a light one. And thin plastics regulate temperature poorly; the 5/8-inch poly-lumber in the better recycled boxes does not.

Whatever the material, interior walls are generally left bare — NABS allows a non-toxic product if you use one, but nothing that seals or smooths the front wall, which is what fledglings grip on the climb to the hole. Pressure-treated wood is out entirely. On the outside, light colours are preferred because they reflect heat.

Monitoring access is a buying feature

A box you cannot open is a box you cannot manage — and unmanaged bluebird boxes are how house sparrows get free housing and blowfly larvae go unnoticed under a nest.

• Front-opening boxes are easiest to clean and inspect; the trade-off is that a sitting female has one exit route, past your hand.
• Side-opening boxes let the female slip out the entrance while you work, and make it easier to spot paper wasps under the roof.
• Top-opening boxes are excellent for photos and quick counts, and awkward for the two jobs you do most: adjusting nest height and clearing blowflies from underneath.

Any of the three beats a sealed box. Our predator guards guide covers the hardware side, and bluebird house placement covers the height, facing and spacing decisions that matter as much as the box.

Best overall: Woodlink NABB Audubon Cedar Bluebird House

The NABB is the closest thing to the published standard sold at mass-market prices: a 5 x 5-inch floor with the entrance centred about 6 inches above it, a ventilation gap at the top, a drain hole at the base, no perch, and a front panel that slides down for inspection and cleaning. It is kiln-dried inland red cedar around three-quarters of an inch thick.

Its hole is 1 9/16 inch, which Woodlink presents as correct for eastern, western and mountain bluebirds. That matches NABS’s advice for overlap country, and it is starling-proof like the smaller size. Cedar greys within a season or two — normal, not a defect.

Best for parasite management: Nature’s Way CWH3 Cedar Bluebird Box House

The CWH3 is the box for people who intend to actually manage a nest: a clean-out door, wall and floor vents, and an elevated mesh floor that lets blowfly larvae drop away from the nest cup instead of feeding on nestlings overnight. Kerfs below the entrance give fledglings grip on the way out. The entrance ships at 1½ inch — inside NABS’s eastern-bluebird range — but a second 1 9/16-inch predator guard is included in the box, so it can be converted for western- or mountain-bluebird range without buying anything extra. Both guard sizes are starling-proof.

Two honest caveats from owner feedback. The compact exterior puts the interior floor at the small end of the accepted range rather than a full 5 x 5: fine for most broods, tight for a large one. And a recurring complaint is the lack of pre-drilled mounting holes, plus occasional shipping damage.

Best for monitoring: Coveside 2-Side Open Bluebird House

Coveside’s two-sided box solves the monitoring problem structurally: one side carries a clear viewing panel for a look inside without opening anything, the other swings open for post-season cleaning. It is handcrafted in Maine from 1-inch eastern white pine, thicker than almost anything else in the category, with a solid wood predator block extending the entrance tunnel, a rough interior for fledgling grip, ventilation and drainage, and a 1½-inch entrance.

It is the heaviest and priciest of these picks, and that weight wants a proper pole rather than a fence-post nail. Acrylic viewing panels scratch and cloud over the years — expect the window to age faster than the box.

Best in harsh weather: Birds Choice Recycled Bluebird House

Built from 5/8-inch poly-lumber made from recycled plastic, with stainless hardware, this one is aimed at climates that destroy wooden boxes — driving rain, salt air, repeated freeze-thaw. It will not crack, split, rot or fade, the entrance is a starling-proof 1½ inch, and the design includes a side door for cleaning, an overhanging roof, vents and drainage, plus an interior front screen so chicks can climb to the hole. The predator resistance comes from the overhanging roof and from how you mount the box, not from the hole diameter — NABS is explicit that wooden guards over the entrance do not stop raccoons (although a wooden guard or metal plate can prevent squirrels or woodpeckers from enlarging the entry hole). The step-up “Ultimate” version opens on both sides, one for cleaning and one for viewing.

The caveats are colour and weight. Choose the lightest shade offered, not the handsome dark one — poly in full sun is exactly where the overheating risk lives. And a minority of bluebird landlords report lower uptake on plastic than on wood.

The specialist pick: the Gilbertson PVC nest box

If house sparrows are your actual problem, the Gilbertson deserves a look: a small-diameter PVC cylinder under a wooden roof with a deep overhang, with an unusually strong reputation among bluebird landlords for sparrow resistance while staying attractive to bluebirds. It will not rot, and the hole cannot be gnawed larger.

The trade-offs are real. Blowfly checks are harder; the walls are around a sixteenth of an inch thick and less insulating than wood; and some landlords consider the interior cramped for a large brood. It sells mainly through bluebird societies and specialist retailers, not the big marketplaces.

Frequently asked questions

What size hole does a bluebird house need? 1½ to 1 9/16 inch round for eastern bluebirds; 1 9/16 inch for western and mountain bluebirds, and NABS’s 2021 factsheet calls a 1 9/16-inch round hole probably ideal for all three species. Both round sizes exclude European starlings, which cannot pass a round hole of 1 9/16 inch or smaller. A precisely cut 1 3/8 x 2¼ inch oval and a horizontal slot 1 1/8 to 1 3/16 inch high are the accepted alternatives. Round holes materially larger than 1 9/16 inch, and any hole enlarged or gnawed wider, let starlings in.

Should a bluebird house have a perch? No. Bluebirds land at the hole without one, and a perch mainly helps sparrows and starlings harass the nest.

Can I paint a bluebird house? Outside, light colours are best — pale exteriors reflect heat, and box interiors can run far hotter than the surrounding air. Interior walls are generally left bare — NABS allows a non-toxic product if you use one — and never seal the interior walls that fledglings need to climb.

Do I need to open the box during nesting season? Managed boxes do better than ignored ones: checks let you catch blowfly infestations and clear out house sparrow and European starling nests, and bluebirds tolerate brief, calm inspections well. Identify the occupant before you touch anything. House sparrows and European starlings are non-native and are not protected by the Migratory Bird Treaty Act, so their nests and eggs may be removed; every native cavity nester you will actually find in a box — tree swallow, chickadee, titmouse, house wren, nuthatch — is federally protected, and removing an active native nest is illegal. State and local rules can add further restrictions. Stop opening the box once nestlings are 12 to 13 days old — do not open it from day 13 onward — or, if you don’t know the hatch date, once they are fully feathered and alert, which is when a disturbed nestling jumps instead of crouching.

Will a nest box on its own bring bluebirds? Not usually. Bluebirds hunt insects over short grass, so open ground matters more than hardware — and a box within sight of a mealworm offering or a purpose-built bluebird feeder tends to get found faster than one standing alone.

Dimensions and hole sizes here are drawn from published North American Bluebird Society recommendations, Cornell NestWatch guidance and long-running state bluebird society references; where those sources differ, the disagreement is stated rather than resolved. Product specifications reflect manufacturer and retailer listings at publish time. We plan to buy top picks for hands-on yard testing; this guide will be updated with our own photos as results come in. See how we test.