How to attract Eastern Bluebirds to a nest box

Field notes

Eastern Bluebirds are the bird most people want in a nest box, and for good reason. They're startling to look at, they're devoted parents, and they were nearly wiped out of much of their range before nest box programmes brought them back. They also can't excavate their own cavities, which means a well-sited box is genuinely useful to them rather than just decorative.

Here's what matters, roughly in order of how much difference it makes.

Mealworms, first

Nothing else comes close. A shallow open dish of live mealworms placed fifteen to twenty feet from the box, in clear line of sight from the entrance, is the fastest way to get a pair interested. They find the food, then they investigate what's next door.

Live works better than dried at the start — the movement catches their eye. Once a pair is visiting reliably you can taper off, and they'll generally stay for the box.

The feeder needs to be an open dish or tray, low to the ground. Bluebirds won't use a tube feeder and are wary of anything too enclosed.

The box itself

• A 1.5-inch entrance hole. Large enough for bluebirds and Tree Swallows, too small for starlings.
• Roughly a four-by-four-inch interior floor.
• No perch below the hole. Bluebirds don't need one, and it mainly helps House Sparrows.
• Unpainted, untreated wood. Cedar or pine.
• Leave it bare inside. They build their own nest and don't want yours.

Where it goes

Four to six feet up, on a smooth metal pole rather than a tree or a fence post. Trees and buildings give predators a route up, and they're also where House Sparrows prefer to nest.

Face the entrance east or south-east so it catches morning sun. Put it in full or mostly full sun — bluebirds avoid shade.

Keep it at least ten to fifteen feet clear of any tree or structure. A raccoon can jump four or five feet horizontally from a trunk, and a squirrel further.

Fifty feet or more from dense brush and buildings discourages sparrows. Fifty to a hundred feet from a tree line is the sweet spot — close enough for shelter, open enough for the way bluebirds hunt, which is to perch low and drop onto insects in short grass.

A predator baffle is not optional

A cone or cylinder baffle on the pole below the box keeps raccoons, snakes and cats out. Bluebirds won't commit to a box that doesn't feel safe, so the baffle earns its place twice — it protects the nest and it makes the site attractive in the first place.

Timing

In Michigan, bluebirds start scouting boxes from late February through March, before nesting begins in earnest. Getting a box up in autumn or winter is not too early — it gives the wood time to weather and means it's already there when the scouts come through.

Clean out any old nest material and leave it empty.

If sparrows show up first

House Sparrows are non-native, aggressive, and will evict bluebirds and destroy eggs. If you see them investigating the box early, watch it closely. Most serious nest box keepers remove House Sparrow nests to protect native species. It's a decision worth reading about properly before you need to make it.

Our box is mounted, baffled, and facing east. It's still empty — nesting season doesn't start here until March. The interior camera is live in the meantime, and you can get a note the day something claims it.