The birdhouse on its pole against a clear blue sky, black resin tiles on one wall and carved blocks on the other

Avian Habitat

A house for the Eastern Bluebird that says when it is too hot.

Heat is the quiet danger in a nest box. A first-time host has no way to see it.

So one wall of the house turns white to say so.

The sky is blue,
so the house wears the sea.

A calm sea is dark. When the heat builds, the cast wave pales to white, like whitecaps before a storm.

The birdhouse seen from below against deep blue sky: resin tiles step out on the left like breaking waves, carved blocks on the right, the roof floating above on its posts

An Eastern Bluebird clinging to the carved entrance of the house

Built to one bird's measure.

The door: 1.5 in
Its head: 1.0 to 1.25 in
Its body, across: 2.0 to 2.5 in
Its height: 5.0 to 6.0 in
Beak to tail: 6.3 to 8.3 in

It stands on a pole: Eastern Bluebirds need a very stable nest, and a pole keeps predators away.

The birdhouse from the front: tiles on dowels to the left, carved blocks to the right, the hook latch at the foot

Two walls, two waves.
One cast in resin. One carved in wood.
Cool, the tiles are black.
Epoxy resin and a heat-sensitive pigment, cast, cured and cut into six tiles.
Too hot, they turn white.
No gauge and no app. Anyone can read it from across the yard and give the nest some shade.
The other wall is carved.
Six wooden blocks, cut by hand like the surface of the sea.
The roof never touches the box.
Its fins shed the sun. The gap under it lets the heat out.
Unhook. Lift. Clean.
A farm-gate hook holds the box on its floor. Lift its tip out of the eye in the wall and the box comes off for cleaning.

A warning you can read without knowing anything about birds.

The resin wall with all six tiles black — Cool

The same wall with the tiles clouding to grey — Warming

The same wall with all six tiles turned white — Too hot

Heat, made visible.

A schlieren view shows warm air as light and shade. As the house warms, the air climbs its walls and leaves over the roof, and the tiles pale from black to white. As it cools, they darken again.

Simulated airflow, with time compressed.

On a hot afternoon the house stands on its pole against a blue sky, its resin tiles turned white

1Roof One board, kerf-cut into fins and bent. The fins shed the sun.
2Posts They hold the roof clear of the box. Heat leaves through the gap.
3Box Stained hardwood, sized to the Eastern Bluebird.
4Door 3.8 cm, 1.5 in. The recess is carved in three levels.
5Tiles Epoxy resin with a thermochromic pigment, cast, cured and cut. Six, on two dowels each.
6Blocks Six wooden blocks, carved by hand.
7Base and floor The box sits over a raised floor and lifts off it.
8Hook and eye Zinc. Opens from the top.