Tree Swallow nest box
Published dimensions, a cut list for 1×10 (9 1/4 in.), and the placement rules that decide whether the brood survives. The entrance is 1 3/8–1 1/2 in. — cut it to the smaller figure if the range gives you a choice, because a hole bored oversize cannot be made smaller and lets European Starlings in.
Tree Swallow
- Entrance hole 1 3/8–1 1/2 in.35–38 mm
- Hole above floor 5 in.127 mm
- Floor 5 × 6 in.127 × 152 mm
- Cavity depth 5–6 in.127–152 mm
- Mounting height 5–12 ft1.5–3.7 m
Habitat and placement: Open ground near water — marsh edges, ponds, wet meadows, and fields within a few hundred yards of insect-rich water.
Spacing between boxes: Pairs of boxes 5–20 ft apart, with pairs 100+ yd from the next pair. That pattern lets one swallow pair and one bluebird pair coexist.
Predator guard: Baffle on a smooth pole; swallows are otherwise easy prey for raccoons that can reach the entrance.
When to install: March through April, ahead of the first swallows returning to your area.
Notes: Feathers are the currency — swallows line the nest cup with them. Drop a few white feathers near the box in spring and watch birds catch them mid-air.
Dimensions from: NABS box design notes; sialis.org spec compilation
No perch. Ever. A perch gives predators and House Sparrows a grip — cavity nesters do not need one.
Cut list
Every board you need, sized so the assembled box matches the published interior above. Pick your stock — the list updates.
1×10 (9 1/4 in.) · about 6 linear feet including waste
| Qty | Piece | Size | Notes |
|---|---|---|---|
| 1 | Floor | 5 × 6 in. | Trim about 1/4 in. off each corner for drainage. |
| 2 | Side | 6 × 8 1/4 in. | Bevel the top edge: 6 3/4 in. at the front rising to 8 1/4 in. at the back. |
| 1 | Back | 6 1/2 × 16 1/4 in. | Runs 4 in. above and 4 in. below the box for mounting screws. |
| 1 | Front | 6 1/2 × 6 3/4 in. | Bore a 1 3/8 in. hole, centred side to side, with its centre 5 3/4 in. up from the bottom edge. |
| 1 | Roof | 10 1/2 × 8 1/2 in. | Overhangs 3 in. at the front and 1 in. each side; butts against the back board. |
Note: Published figures put the hole within 5/16 in. of the ceiling. That is what the sources say for this species — build the deeper end of the range if you have the choice.
Before you cut
- Untreated wood, 3/4 in. thick. Cedar, cypress, or pine. Never pressure-treated, and never paint or stain the interior.
- Score the inside face below the entrance so nestlings can climb out. Smooth plywood traps them.
- Drainage and ventilation. Trim the floor corners; leave gaps or drill holes near the top.
- Make one side or the front open so you can monitor and clean between broods.
- Baffle on a smooth metal pole. This matters more than height, orientation, or anything else on this page.
When and where to put up a nest box — timing by region, habitat matching, orientation, and predator guards that actually work.
Other species
- White-breasted Nuthatch 1 1/4–1 3/8 in.
- Tufted Titmouse 1 1/4–1 1/2 in.
- Downy Woodpecker 1 1/4–1 1/2 in.