Nest Box Spec Finder
Published dimensions for 19 cavity nesters, in inches and millimetres — hole size, floor, depth, mounting height, spacing, and the predator guard you actually need. Print the card and take it to the saw.
- Untreated wood, ¾ in. thick or more. Cedar, cypress, or pine. No pressure-treated lumber, no interior paint or stain.
- Rough or grooved interior below the hole so nestlings can climb out. This is not optional — smooth plywood traps young birds.
- Drainage and ventilation. Corner holes in the floor, gaps or holes near the top.
- An opening side or front so you can monitor and clean between broods.
- A predator baffle on a smooth metal pole. The single most consequential decision you'll make — more than height, more than orientation.
When and where to put up a nest box — timing by region, orientation, habitat, and predator guards that actually work.
Questions
Why no perch?
Cavity nesters cling to the entrance — they have never needed a perch. What a perch does provide is a seat for House Sparrows harassing the occupants and a brace for a raccoon reaching inside. Boxes come with perches because perches sell boxes.
What size hole for bluebirds?
1½ in. for Eastern Bluebird; 1 9/16 in. for Western and Mountain. Cut it bigger and you have built a starling box. Cut it with a sharp spade or Forstner bit and sand the edge smooth.
How high should the box go?
Species-dependent — 4–6 ft for Eastern Bluebird, 10–20 ft for woodpeckers and screech-owls, 10–30 ft for kestrels. But height is not your predator defense. A baffled box at 5 ft outlasts an unbaffled box at 15 ft every season.
When should I put it up?
Four to six weeks before first eggs — February to March for most songbirds, earlier in the South. Woodpeckers and owls want boxes in fall or winter, since they roost in cavities all cold season and settle in months before nesting.
Which direction should the entrance face?
Away from prevailing wind and driving rain, and away from hot afternoon sun in southern heat. In much of North America that means facing east or northeast. If you can point it at a shrub or fence 25–100 ft off, fledglings get a landing target on the first flight.
Should I clean the box between broods?
Yes. Pull the old nest once the brood fledges — it encourages a second attempt and cuts parasite loads. Do a final clean before or after the season, and buy or build only boxes that open for monitoring.
Something else moved in. Now what?
House Sparrows and European Starlings are nonnative and unprotected, so their nests may legally be removed in the US — and left alone, they will kill native occupants. Every native species, including wrens and squirrels, is protected once eggs are present: leave it, and note what you learned for next season.