Western Bluebird 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 9/16 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.
Western Bluebird
- Entrance hole 1 9/16 in.40 mm
- Hole above floor 7 in.178 mm
- Floor 5 1/2 × 5 1/2 in.140 × 140 mm
- Cavity depth 9 in.229 mm
- Mounting height 4–10 ft1.2–3 m
Habitat and placement: Open woodland edge, oak savanna, burns, orchards, and pine country with grassy openings. Wants scattered trees for hunting perches rather than unbroken lawn.
Spacing between boxes: About 100 yd between boxes; pair boxes 5–20 ft apart where Tree or Violet-green Swallows compete heavily.
Predator guard: Baffle on a smooth pole. Where cats or ground squirrels are common, mounting height matters less than the baffle does.
When to install: February to mid-March through most of the range; earlier at low elevations in California and Arizona.
Notes: The 1 9/16 in. hole is the accepted size for Western and Mountain Bluebird — a 1½ in. hole cut for Eastern Bluebird can be tight for a female carrying nest material.
Dimensions from: NABS nestbox recommendations; 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 7 linear feet including waste
| Qty | Piece | Size | Notes |
|---|---|---|---|
| 1 | Floor | 5 1/2 × 5 1/2 in. | Trim about 1/4 in. off each corner for drainage. |
| 2 | Side | 5 1/2 × 11 1/4 in. | Bevel the top edge: 9 3/4 in. at the front rising to 11 1/4 in. at the back. |
| 1 | Back | 7 × 19 1/4 in. | Runs 4 in. above and 4 in. below the box for mounting screws. |
| 1 | Front | 7 × 9 3/4 in. | Bore a 1 9/16 in. hole, centred side to side, with its centre 7 3/4 in. up from the bottom edge. |
| 1 | Roof | 10 × 9 in. | Overhangs 3 in. at the front and 1 in. each side; butts against the back board. |
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
- Mountain Bluebird 1 9/16 in.
- Black-capped Chickadee 1 1/8–1 3/8 in.
- Carolina Chickadee 1 1/8–1 3/8 in.