Most birdhouses go unused. The entry hole is wrong, the box faces the wrong direction, or it is in a spot no bird would choose. Get the specs right for your target species, mount it correctly, and put it up before breeding season - birds will find it.
Entry Hole Size by Species
| Species | Entry hole | Box height | Mounting |
|---|---|---|---|
| Bluebirds | 3.8cm (1.5 in) | 1.5-2m | Post in open field |
| Chickadees | 2.9cm (1-1/8 in) | 1.5-3m | Tree trunk or post |
| House wrens | 3cm (1-1/4 in) | 1.5-3m | Small tree, edge of yard |
| Tree swallows | 3.8cm (1.5 in) | 1.5-3m | Post near open water |
| Purple martins | 5cm (2 in) | 3-6m | Multi-unit house on tall pole |
| Woodpeckers | 3.8-6.4cm (1.5-2.5 in) | 3-6m | Tree trunk |
| Screech owls | 7.6cm (3 in) | 3-6m | Tree trunk, shaded |
| Wood ducks | 10x7.6cm (4x3 in) | 1.5-3m | Near water |
| American kestrels | 7.6cm (3 in) | 3-6m | Tree or post, open area |
The wrong hole size is the most common reason birdhouses go empty. Too small and the bird cannot enter. Too large and predators or house sparrows move in.
Placement Rules
| Rule | Why it matters |
|---|---|
| Face the hole east or north | Avoids afternoon sun overheating the box |
| Shelter from wind and rain | Protects eggs and chicks from exposure |
| Away from feeders | Nesting birds want quiet, not feeder traffic |
| Near cover but not hidden | Birds need a clear flight path to the entrance |
| Mount on a pole with a baffle | Prevents snakes, raccoons, and cats climbing up |
| Space boxes 10-30m apart | Most species are territorial and will not nest too close |
When to Put Up Birdhouses
| Season | What to do |
|---|---|
| Late winter (Feb-Mar) | Install or clean boxes before breeding season |
| Spring | Monitor for nesting activity, do not disturb active nests |
| Summer | Clean out boxes after each brood fledges |
| Autumn | Leave boxes up for winter roosting shelter |
Nesting Materials
Leave natural materials near the box - dried grass, small twigs, animal fur, feathers. Some species excavate their own cavities and prefer wood shavings inside the box. Never stuff the box with material yourself - let the birds build.
Never provide synthetic fibres, dryer lint (contains chemicals), or string longer than 5cm (entanglement risk).
Birdhouse Maintenance
| Task | When |
|---|---|
| Clean out old nests | After each brood fledges, and again in late winter |
| Check for damage | Autumn - repair cracks, replace rotting wood |
| Remove wasp nests | Before breeding season |
| Scrub with hot water | Annual deep clean, no chemicals |
What NOT to Do
- Do not paint the interior - fumes are toxic to chicks
- Do not add a perch - predators use perches to reach inside
- Do not mount on a tree without a baffle - easy climbing for snakes
- Do not check the box constantly - disturbance causes nest abandonment
The right entry hole size for the right species, mounted in the right direction, put up before breeding season. That is 90% of what it takes to get birds nesting in a birdhouse. Everything else is a bonus.