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Tree swallow birdhouse plans give you everything needed to build a simple nest box that tree swallows will readily accept: a 1-1/2 inch thick cedar or pine box, a 1-1/2 inch entry hole, a floor of about 4 by 5 inches, and a mounting height of 5 to 10 feet in an open area near water or a field. This guide walks through the dimensions, the cut list, the assembly order, and the placement details that make the difference between a box that sits empty and one that fills with a pair of swallows in spring.
Why Tree Swallows Need a Specific Box Design
Tree swallows are cavity nesters that favor open country near water, such as marsh edges, pastures, orchards and farm ponds. Unlike bluebirds, they do not need a box tucked deep in the woods. They do, however, need a box that is dry, well ventilated, and sized correctly, because they line their nests with feathers and will abandon a box that overheats or lets rain in. Many failed attempts at attracting them come down to a box that is too small inside, has no drainage, or sits too close to trees where predators can climb.
When you start from proven dimensions rather than improvising, you avoid most of those problems. The plans below follow the general guidance published by North American nest box monitoring programs, which recommend an interior floor of roughly 4 x 4 inches up to 5 x 5 inches and a 1-1/2 inch entry hole to exclude larger competitors like European starlings.
Materials and Tools Checklist
Before you cut anything, gather the following. Untreated cedar, cypress or rough-sawn pine work well because they resist rot without paint or stains that could be harmful to birds.
- One 1 x 6 board, 6 feet long, at true 3/4 inch thickness (nominal) or a 1×6 cedar board, or enough 3/4 inch material to yield the pieces in the cut list
- Exterior wood screws, 1-1/4 inch, stainless or galvanized
- Wood glue suitable for exterior use
- A table saw, miter saw or circular saw with a guide
- A 1-1/2 inch Forstner bit or hole saw for the entry hole
- A 1/4 inch drill bit for drainage and ventilation holes
- A drill/driver, clamps, tape measure, square and sandpaper (120 grit)
Cut List and Dimensions
Most tree swallow box plans use 3/4 inch nominal lumber for walls and a slightly thicker floor, but the key measurements are interior dimensions. The table below gives a standard configuration.
| Part | Quantity | Dimensions (inches) | Notes |
|---|---|---|---|
| Front | 1 | 10 x 5-1/2 | Cut entry hole about 1-1/4 in. from top |
| Back | 1 | 12 x 5-1/2 | Extends above roof for mounting |
| Sides | 2 | 8 x 5-1/2 | Angled top edge to match roof slope |
| Floor | 1 | 5 x 5 | Drill four 1/4 in. drainage holes |
| Roof | 1 | 7 x 7 | Overhang 1 in. on front and sides |
Cut the front and back wider than the sides so the roof and mounting surface line up. A slight roof overhang keeps rain from running down the front wall.
Step-by-Step Assembly
Cut and Mark the Entry Hole
Mark the center of the front panel about 1-1/4 inches below the top edge of the front board, which places the hole high enough to keep the nest dry and to make it harder for predators to reach in. Drill a 1-1/2 inch hole with a Forstner bit, clamping the board to a scrap piece so the back does not splinter.
Assemble the Walls and Floor
- Dry-fit the sides between the front and back. Check that the interior is at least 5 inches square.
- Apply glue to the edges and attach the sides to the front with 1-1/4 inch screws, pre-drilling to prevent splitting.
- Attach the floor so it sits about 1/2 inch above the bottom edge of the walls. This recessed floor lets water drain out through the gap and makes cleaning easier.
- Drill four 1/4 inch drainage holes in the floor.
Attach the Roof and Mounting Hardware
Center the roof so it overhangs evenly, then screw it down from inside through the top of the sides. Leave the roof attached with screws rather than glue so you can open the box for annual cleaning. Drill two ventilation holes near the top of each side wall, about 1/4 inch in diameter, to keep the interior from overheating in summer.
Finish and Mount
Sand the exterior smooth, round over sharp corners, and leave the wood unfinished on the inside. A light coat of exterior-safe sealer on the outside is acceptable, but avoid paint and stains on the interior. Mount the box on a pole or fence post with a predator guard, typically 5 to 10 feet above ground in a clear area.
Placement and Mounting Tips
Where you put the box matters as much as how you build it. Tree swallows prefer open fields, pastures and pond edges where they can hunt flying insects. Face the entry away from prevailing winds, and place the box at least 15 to 20 feet from dense trees or shrubs that give predators cover. Two boxes spaced 15 to 20 feet apart often attract pairs, since tree swallows tend to nest in loose colonies when the habitat allows.
Wait until spring to install the box, ideally before the birds begin scouting in late March or April in most of the US. Clean out old nesting material each fall, which removes parasites and prepares the box for the next season.
Common Mistakes
- Interior too small. A box under about 4 inches square can be too cramped for a full clutch of eggs.
- Entry hole too large. Holes bigger than 1-1/2 inches invite starlings and house sparrows, which will evict swallows.
- No drainage or ventilation. Trapped moisture and heat cause nest failure.
- Painted or treated interiors. Chemicals can harm nestlings, so keep the inside bare.
- Mounted too close to cover. Trees and brush give cats and snakes easy access.
- Using a perch. Tree swallows do not need a perch, and a perch can help predators and competing species.
Tips for Better Results
- Mount the box before spring and check it weekly once birds start visiting.
- Use a predator guard or baffle on the pole to block climbing mammals.
- Monitor the box and record nesting activity, since many local wildlife groups welcome that data.
- Clean the box after the nesting season ends, but never during active nesting.
Recommended gear
A Forstner bit is the most useful tool for this project because it drills a clean, flat-bottomed 1-1/2 inch entry hole without tearing the wood on the exit side. A flat or hole-saw style bit works too, but a Forstner gives the cleanest result on thin cedar. View on Amazon
A predator guard, usually a stovepipe or cone-shaped baffle, is essential for keeping raccoons and snakes away from the nest. Choose one sized for a 1-1/4 to 2 inch pole. View on Amazon
A stainless steel exterior screw kit keeps the box from rusting over several seasons and avoids staining the cedar. View on Amazon
FAQ
What size hole do tree swallows need?
A 1-1/2 inch entry hole is the standard for tree swallows. It is large enough for them to enter and small enough to keep out European starlings.
How high should I mount a tree swallow box?
Most guidance recommends mounting between 5 and 10 feet above ground, in an open area with a clear flight path.
Do tree swallows use a perch on the box?
No. Tree swallows do not require a perch, and omitting one is often recommended to reduce access by predators and competitors.
Should I paint the inside of the box?
No. Leave the interior bare. Paints and stains can release fumes or residues that may harm nestlings.
What kind of wood is best for tree swallow birdhouse plans?
Untreated cedar, cypress and rough-sawn pine are common choices because they resist rot and are safe for birds without finishes.
When should I clean out the nest box?
Clean the box after the nesting season ends, typically in late summer or fall, and never while birds are actively nesting.
How many eggs does a tree swallow lay?
Tree swallows typically lay between four and seven eggs per clutch, though clutch size varies with location and food supply.
Conclusion
With the right interior size, a 1-1/2 inch entry hole, proper drainage and a careful mounting location, these tree swallow birdhouse plans produce a box that birds will actually use. Build it from untreated wood, keep the interior bare, and mount it in an open area near water or a field. Check on it through the season and clean it each fall, and you will have a dependable home for these insect-eating swallows year after year.
