The Hermit Thrush Sings in the Harmonic Series

There is a small brown bird on the lookout deck at Oaks Bottom that almost everybody walks past.

She is worth stopping for, and not only because she is beautiful. She may be the most musically interesting animal in the refuge.

Brown above, heavily spotted below, with a white eye-ring and a rust-red tail. About the size of a sparrow, and about as loud as one until she opens her mouth.

She Was Looking At Me

We read a tilted head as curiosity because that is what we do when we are curious. Birds tilt for a different reason entirely: their eyes sit on the sides of the skull, and the sharp part of the retina points sideways. To examine something closely, a bird has to turn and aim.

So the gesture is anatomy, not expression. But the meaning we read into it happens to be correct — she turned her head because she was studying me. We get the right answer for the wrong reason.

How You Know It Is Her

There is a bird that looks almost exactly like her — the Swainson’s Thrush — and one mark separates them. The Hermit Thrush has a rust-red tail that contrasts with a browner back. The Swainson’s is the same olive-brown from head to tail, no contrast anywhere.

In this frame the sun is behind her, the tail is fanned, and the red is unmistakable. Front-lit it would read as warm brown. Backlit, the feathers go translucent and the color saturates.

Two other things help. Her eye-ring is white and bold; a Swainson’s wears buffy spectacles. And she has a habit the Swainson’s does not: she raises her tail and lowers it again slowly, almost a pump, often with a flick of the wings. Once you have seen it you can name her from behind, at distance, with no color at all.

There is also the calendar, which settles it before you raise the binoculars. Swainson’s Thrushes breed here in summer and are gone by the end of September. Hermit Thrushes are the ones that stay for our winter. A spotted thrush at Oaks Bottom in October is almost certainly this one.

The Part That Stops Me

I write music. So this is the bird I think about most.

The Hermit Thrush has a song people have been trying to describe for two hundred years — flute-like, spiralling, unhurried, each phrase starting on a different pitch. Thoreau and Whitman both wrote about it. If you have heard it in a forest at dusk you do not forget it.

In 2014 a group of researchers did something nobody had quite done before: they took hundreds of recorded Hermit Thrush songs and analyzed the pitches mathematically. What they found is that the notes she chooses are drawn, far more often than chance allows, from the harmonic series — the same stack of overtones that sits underneath human musical scales, underneath a bugle call, underneath the open strings of a cello.

She is not imitating us. The harmonic series is physics; it falls out of how any vibrating column of air behaves. We built our music on it because we were listening to the same universe she is. But of all the birds that have been studied, she is one of the very few shown to favor it.

Which means this small brown bird on a deck rail in Southeast Portland is working in the same tuning system I use when I sit down to write.

And She Is Only Passing Through Her Own Year

A songbird’s wing is folded away almost all of the time, and when it is open the bird is usually moving too fast to see. Here it is held still and lit from behind, so the feathers go translucent and you can count them.

Look at the shape. Those are long wings for a bird that spends its life hopping through leaf litter, and that is not an accident. Hermit Thrushes migrate, many of them at night, navigating alone. The bird on this rail flew here in the dark from somewhere further north, and will do it again in the spring.

She will not sing much while she is with us. The full song belongs to the breeding grounds, and what we mostly get in winter is a low chup from the undergrowth. But she is carrying it.

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The lookout deck is a good place to stand still. Most of what passes through Oaks Bottom does it quietly, at the edges, in brown.

I photographed a Hermit Thrush here a year ago almost to the week. I do not know whether this is the same bird. I would like it to be.