What Is a Large Bird House Called: Aviary, Dovecote Nest Box

A large bird house goes by several names depending on its purpose: an aviary (an enclosed flight space for confined birds), a dovecote or pigeon loft (housing for doves or pigeons), a purple martin house or colony house (a multi-compartment structure for colonial nesters), or simply a large nest box or roost box (for solitary cavity nesters like owls, kestrels, and wood ducks). Which name applies depends almost entirely on the species you want to attract and what you need the structure to do.

Why the name actually matters

If you search for plans, lumber, or advice using the wrong term, you can end up with a structure that completely misses the mark. An aviary is built to keep birds inside; a martin house is designed to attract wild birds from the outside. A dovecote suits domestic pigeons but will sit empty if you want to attract barn owls. Getting the terminology right from the start means you buy the right materials, cut the right hole sizes, and mount the structure at the right height, and your backyard birds actually use it. It also matters legally: keeping certain wild bird species confined in an aviary requires permits in the US and Canada, while putting up a passive nest box for native cavity nesters does not.

The common names and what each one means

Aviary

An aviary is a large enclosure, anything from a walk-in wire cage to a purpose-built room or building, designed to house birds in a contained environment. The defining feature is confinement: birds live, fly, and often breed inside without leaving. Aviaries are used for exotic species, captive research populations, zoos, and the private keeping of non-native birds like parrots, finches, or softbills. Building or running one for native wild species in North America requires federal and state permits under the Migratory Bird Treaty Act.

Dovecote (also dovecot)

A dovecote is a structure specifically for housing domestic doves or pigeons. Historically, these were raised towers or cupolas with internal compartments for roosting and breeding. The classic design keeps birds semi-free: pigeons fly out and return on their own, but the cote provides nest cubbies, protection from predators, and a home base. A pigeon loft is the modern working version of the same concept, typically a shed-like building used by fanciers for breeding, showing, or racing pigeons.

Purple martin house (colony house)

A purple martin house, sometimes called a colony house, is a multi-compartment structure mounted on a tall pole, purpose-built for purple martins, which are highly colonial cavity nesters. Each compartment is a small room sized specifically for a martin pair. These structures are placed in very open areas with clear flight approaches, near human activity, on poles typically 12 to 20 feet high. They are not cages: martins are wild, free-flying birds that choose to nest in them.

Large nest box and roost box

A large nest box is simply an oversized single-compartment box built to the specifications of a larger cavity-nesting species: a barn owl, screech-owl, American kestrel, wood duck, or chimney swift tower. 'Roost box' refers to the same type of structure when used primarily for winter communal roosting rather than active nesting. Both are passive structures: you mount them and let wild birds find and use them on their own. These are the most practical option for most backyard birders and beginner DIYers.

When to use each type

How to choose the right structure for your situation

Work through these questions in order and you will land on the right structure almost every time.

1. Do you want to keep birds contained, or attract free-flying wild birds? If contained: build an aviary (and check permit requirements first). If free-flying: continue.
2. Are the birds domestic pigeons or doves? If yes: a dovecote or loft is the right structure. If no: continue.
3. Are you targeting purple martins in an open, sun-exposed yard at least 40 feet from trees? If yes: a multi-compartment martin house on a 12-to-20-foot telescoping pole is the answer. If no: continue.
4. Are you targeting a single large cavity-nesting species such as a barn owl, screech-owl, kestrel, or wood duck? If yes: build or buy a species-specific large nest box sized to that species' exact specifications (see the table below). If you want to support chimney swifts, build a chimney swift tower instead.
5. Still unsure? A large nest box is the lowest-cost, lowest-risk starting point for most backyard birders.

Which species use large bird houses, by region

Not every large cavity nester lives everywhere. Here is a practical regional breakdown to help you match your structure to birds that actually live near you.

Exact specs for each large-house species

These dimensions come from Cornell Lab's NestWatch, the Purple Martin Conservation Association, Ducks Unlimited, and Penn State Extension. Treat them as targets, not rough estimates: getting the entrance hole wrong by even a quarter inch can let in predators or exclude your target species entirely.

A few critical notes on the table above: wood duck boxes need the interior walls scored or fitted with a hardware cloth ladder below the entrance so ducklings can climb out. For exact construction details, see Ducks Unlimited’s Build a Wood Duck Box plan which lists the recommended oval entrance size, interior scoring for duckling toe‑holds, drainage hole count, and materials Ducks Unlimited's step‑by‑step wood duck box plan specifies a 4.5" × 3.5" oval entrance, recessed toe‑holds, five 1/2" drainage holes, and a cedar 1×10 (3/4") board in the materials list.. Screech-owl and kestrel boxes need the interior wall under the entrance grooved for the same reason. Barn owl boxes need a deep internal drop from the entrance to the floor, as the Barn Owl Trust recommends roughly 450 mm (about 18 inches) to prevent owlets from falling out prematurely. Purple martin compartments should never have an outside perch, which makes it easier for European starlings and house sparrows to stage an invasion.

Materials: what to build with and why

The safest, longest-lasting large nest boxes and martin houses are built from untreated, naturally rot-resistant wood with walls at least 3/4 inch thick. Thick walls buffer temperature extremes and add structural rigidity, both critical for large structures exposed to wind and weather. Never use treated lumber inside a box where birds will nest: the preservatives are toxic. Exterior hardware and fasteners should be rust-resistant to avoid staining and structural failure over time.

Avoid pressure-treated wood entirely inside any nest box or compartment. Avoid metal roofs without adequate ventilation beneath them: they turn boxes into ovens in summer. Never use particle board or MDF outdoors; they disintegrate quickly and can harbor mold. If you want the exterior of a large box to last longer in harsh climates, a coat of exterior latex on the outside only is a simple, safe solution.

Tools and workshop prep

You do not need a fully equipped shop to build a large nest box or even a multi-compartment martin house. A basic tool set covers most builds. Here is what is genuinely essential versus what just makes the job faster.

Essential tools

• Circular saw or hand saw: for cutting lumber to length and width
• Drill and drill bits (including a 3" and a 2-1/8" spade or Forstner bit for entrance holes): the entrance hole is the most critical cut you will make
• Jigsaw: for cutting oval entrance holes (wood duck) or irregular shapes
• Tape measure and pencil: measure twice, cut once, especially on large panels
• Square (combination or speed square): keeps box walls perpendicular so panels seat correctly
• Screwdriver or impact driver: for assembly with galvanized screws
• Clamps (at least two): holds panels while you drive screws solo
• Safety glasses and hearing protection: required any time you run power tools

Helpful but optional tools

• Miter saw: speeds up repetitive cross-cuts on martin house compartment dividers
• Router with roundover bit: smooths exterior edges for a cleaner look and better paint adhesion
• Band saw: safer and more precise for cutting entrance hole inserts and hardware cloth
• Workbench with vise: stabilizes large panels for drilling and cutting
• Tin snips: for cutting hardware cloth in aviary or predator-guard projects

Workshop and safety checklist before you start

1. Clear a flat, stable work surface at least 4 feet by 8 feet for large panel layouts.
2. Check that all blades and bits are sharp: dull bits tear wood fibers and cause grain blowout on entrance holes, which leaves rough edges that can trap birds.
3. Pre-drill pilot holes near edges of cedar and pine to prevent splitting, especially on pieces 3/4 inch thick.
4. Keep a fire extinguisher accessible and never run power tools near sawdust piles.
5. Sand any interior surfaces that will contact eggs or young birds: rough interior walls on the floor area can trap moisture and bacteria.
6. Wear a dust mask when cutting MDF, plywood, or any treated wood scraps in the same shop session, and dispose of offcuts from treated lumber separately.
7. Label all cut parts before assembly: martin house compartment dividers are easy to mix up once cut.

Predator-proofing and ventilation: do not skip these

Cornell Lab's NestWatch analysis found that nest boxes fitted with predator guards had roughly 6.7 percent higher nest success rates compared to unguarded boxes. For large boxes mounted on poles, a cone baffle or stovepipe baffle below the box is the single most effective addition you can make. Entrance-hole extenders (a wooden or metal block that extends the entrance tunnel by 1.5 to 3 inches) make it significantly harder for raccoons to reach inside with a paw. For boxes on trees or buildings, Noel guards (a wire cone over the entrance) are an effective option.

Ventilation is equally non-negotiable in large boxes. Drill at least two 5/8-inch holes on each side near the top of the box, and cut drainage holes (at least four, 3/8 to 1/2 inch) in the floor or recess the floor 1/4 inch above the base to keep it dry. A sloped, overhanging roof protects the entrance from rain and direct sun. These are not optional extras: a box without drainage and ventilation will lose eggs to overheating and fungal growth.

Mounting, placement, and timing

Placement is where most large nest box projects succeed or fail. Get the height and habitat right and birds find the box within a season or two. Get them wrong and you can have a well-built box sit empty for years. Purple martin houses must go up on a telescoping pole in very open areas, 40 to 60 or more feet from trees, and within about 100 feet of human activity. Wood duck boxes need to be within a reasonable flight distance from water and ideally face an open clearing or the water itself. The US Forest Service species review for Aix sponsa (wood duck) recommends entrance holes larger than 3.5 inches and mounting boxes roughly 6 feet or more above the water or ground to accommodate ducklings and compensate for scarce natural cavities Aix sponsa (wood duck) — US Forest Service species review. Screech-owl and kestrel boxes do best on poles or lone trees at the edge of open land, not deep inside a woodland.

Timing matters too. Put up owl boxes in late fall or winter before the January-to-February start of barn owl courtship, and before screech-owls start scouting cavities in February or March. Wood duck boxes should be in place by early February in the southern US and by March in northern states and Canada. Purple martin houses should go up in late winter (late January to February in the deep south, late March to early April in the northeast and midwest) to catch the first scouts returning from South America. A telescoping pole lets you lower the house for cleaning and adjustments, which is essential for martin houses.

Sanitation and seasonal maintenance

Every large nest box and martin house needs to be cleaned at least once a year, and active martin houses benefit from checks every one to two weeks during the nesting season to monitor for invasive species like European starlings and house sparrows. After each nesting season ends, remove old nesting material completely, scrub the interior with a stiff brush and a 10 percent bleach solution (one part bleach to nine parts water), rinse well, and let the box dry fully in the sun before storing or closing it up for winter. This step prevents mite, parasite, and bacterial loads from carrying over into the next season.

For wood duck boxes specifically, add 3 to 4 inches of dry wood shavings (not sawdust, which compacts and holds moisture) each spring before the nesting season. Do not use hay or straw, which introduce mites. For barn owl boxes, leave the old nest material unless it is heavily parasitized: barn owls often reuse the same box for multiple years and the compacted material provides a stable egg cup.

Legal and conservation notes

In the United States and Canada, all native migratory birds are protected under the Migratory Bird Treaty Act and equivalent Canadian legislation. This means you cannot legally keep a native wild bird in an aviary without specific federal and state or provincial permits, regardless of the size of the structure. Putting up a passive nest box or martin house to attract free-flying native birds requires no permit and is actively encouraged by conservation organizations. If you’re wondering what are bird houses for, they provide nesting and roosting sites for cavity-nesting species, offer protection from predators and weather, and support local bird conservation when properly sited and maintained. If you want to keep non-native species (such as exotic parrots or domestic pigeons) in an aviary, check your local zoning rules as well, since some municipalities restrict aviary structures by size or proximity to property lines.

From a conservation standpoint, every correctly placed and maintained large nest box genuinely helps. American kestrel populations have declined sharply across much of North America as old-growth trees and farm buildings with natural cavities disappear. Chimney swift towers are actively helping a species that lost its primary nesting habitat when old brick chimneys were capped or demolished. Purple martins east of the Rocky Mountains are now almost entirely dependent on human-provided housing. Building and maintaining these structures is one of the most direct, measurable contributions a backyard birder can make to local bird conservation. For more on the wider benefits of bird houses for wildlife and people, see our guide to the benefits of bird houses. Learn more about why are bird houses important and how proper nest-box placement and maintenance directly support native bird populations and local biodiversity.