American Kestrel nest box
Published dimensions, a cut list for 3/4 in. exterior plywood, and the placement rules that decide whether the brood survives. The entrance is 3 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.
American Kestrel
- Entrance hole 3 in.76 mm
- Hole above floor 13–15 in.330–381 mm
- Floor 8 × 8 in.203 × 203 mm
- Cavity depth 16–18 in.406–457 mm
- Mounting height 10–30 ft3–9.1 m
Habitat and placement: Open country with hunting perches — farmland, grassland with fence lines, highway margins, and orchards. Needs an unobstructed approach to the entrance.
Spacing between boxes: Half a mile between boxes on most landscapes; closer where prey is unusually abundant.
Predator guard: Baffle on a smooth pole. Boxes on buildings or utility poles need a guard too, since raccoons climb both.
When to install: Winter, ideally by February — kestrels start scouting cavities well before eggs.
Notes: Put 2–3 in. of wood chips in the bottom. Kestrel numbers have fallen across much of North America, so a box on open farmland is one of the higher-value boxes you can put up.
Dimensions from: 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.
3/4 in. exterior plywood · about 11 linear feet including waste
| Qty | Piece | Size | Notes |
|---|---|---|---|
| 1 | Floor | 8 × 8 in. | Trim about 1/4 in. off each corner for drainage. |
| 2 | Side | 8 × 20 1/4 in. | Bevel the top edge: 18 3/4 in. at the front rising to 20 1/4 in. at the back. |
| 1 | Back | 9 1/2 × 28 1/4 in. | Runs 4 in. above and 4 in. below the box for mounting screws. |
| 1 | Front | 9 1/2 × 18 3/4 in. | Bore a 3 in. hole, centred side to side, with its centre 15 3/4 in. up from the bottom edge. |
| 1 | Roof | 12 1/2 × 11 1/2 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
- Prothonotary Warbler 1 1/8–1 1/4 in.
- Purple Martin 2–2 1/2 in.
- American Robin open front