Dimensions Unseen

What does it mean if most of what is remains beyond the ability of humans to comprehend?

A Masked Tityra Source: Tim Lenz eBird S23198902 Macaulay Library ML 35572591

Our birding guide Desmond pointed to a tree in the distance, but my focus stayed on the throbbing pain behind my eyes. It’d been years since we’d birded, and my ability to quickly shift my attention from scanning tree tops for movement to focusing on any flashes of color I saw, to then sighting that same flash in my binoculars was painfully limited. But knowing that pain is temporary, but a great bird is forever, I lifted my binoculars in search of the masked tityra perched above. Desmond and Allie, binoculars up, marveled at the orange ring around his eye, his two-toned beak, and black mask. I sighed, closed my left eye, and tried to focus in on the finer details with my right eye. But before I could focus, he flew to another branch, and the process of finding him began again. Thankfully, he was having a leisurely morning, and paused on the next branch long enough for me to get a good look at him.

At least I thought I got a good look at him. But it turns out that I may have been missing his most spectacular characteristics — not because I wasn’t looking hard enough, but because my eyes aren’t able to see them.

I recently finished An Immense World by Ed Yong, a masterful account of how animals perceive the world that left me in awe of the animal senses he describes and his ability to convey complex topics in fun, approachable prose.¹ Each animal experiences the world differently. To describe these differences, Yong uses the term Umwelt, which was coined by Jakob von Uexküll in 1909 to describe the perceptual world that each animal can sense and experience.

It turns out that birds have a very different Umwelt than humans. Their ability to sense the Earth’s magnetic field and use it to orient and navigate, magnetoreception, is well-known, though scientists aren’t exactly sure how the sense works. While birds can hear across approximately the same frequency range as humans — some animals like elephants can hear at much lower frequencies — they hear on a faster timescale. They sing and hear notes that are too close together for us to comprehend. The Masked Tityra sounds like a rubber ducky, so my inability to hear the nuance of its song doesn’t upset me, though I’m sure that I miss much of the magic in the trill of a Wood Thrush’s song.

What blew my mind — and what I needed to reread several times to believe — is that birds can see hundreds of million more colors than we can. Some animals like dogs and horses are dichromats with blue and green cones; they see the world in shades of grey, blue, and green. Most humans are trichomats with a third red cone. Birds are tetrachromats; they have a fourth type of cone cell that perceives violet or UV light. Here’s how Yong describes the difference between human and bird vision:

Picture trichromatic human vision as a triangle, with three corners representing our red, green, and blue cones. Every color we see is a mix of those three, and can be plotted as a point within that triangular space. By comparison, a bird’s color vision is a pyramid, with four corners representing each of its four cones. Our entire color space is just one face of that pyramid, whose specious interior represents colors inaccessible to most of us.

Non-spectral colors like purple don’t exist on the rainbow but can be seen by stimulating our red and blue cones together. Because birds have a fourth cone for UV light, they can see a multitude of color combinations that are inaccessible to use, including UV-red, UV-green, UV-yellow, and likely UV-purple. Interestingly, many bird feathers that appear white to us trichomats reflect UV light, and may not look white to birds. In other words, the seemingly plain white masked tityra I was straining to see may have been strutting his amazing, UV reflective feathers for all tetrachromats to see. A month later, and this fact still boggles my mind.

My point isn’t that we should be sad that we’re missing out on some avian splendor (though that pains me) but rather to highlight that are view of the universe is limited and shaped be our Umwelt. We focus on what we can measure and understand, yet most of what exists is beyond our perceptions. Birds see millions of colors we can’t see, dolphins use echolocation to deduce what’s inside opaque objects in ways we don’t understand, and knifefish use electrolocation to perceive and understand their environments. At a higher level, 95% of the universe is made up of dark energy and dark matter that doesn’t seem to interact with the visible universe in a way that we can measure. My guess is that those interactions do occur, but that our Umwelt limits our ability to figure out, perceive, or measure exactly how those interactions occur.

This leaves me with a deep sense of awe and wonder at the creativity of life and diversity of ways that animals successfully navigate the world. It makes me want to do more to preserve natural spaces and environments, because there is both so much we don’t understand, so much we can’t understand, and more importantly, so much that we don’t need to understand to know that it’s worth protecting.

On my third successive day of birding, I was struck by how many of my old skills had returned. I wasn’t at my peak, but I could scan the horizon and sight birds in my binoculars without feeling the strain behind my eyes and associated exhaustion of using a part of my brain that had long been dormant.

Now I can appreciate how birding expands my Umwelt. I’ll never be a tetrachromat, but by stretching my brain in ways I haven’t, I can expand my ability to perceive the world. Enhancing the senses adds richness and color to our lives in a way that cannot — and does not need to be — quantified to be appreciated.

Awe, wonder, an acceptance that much is beyond my perceptive abilities, and a belief that working to expand my Umwelt is a noble goal unto itself. That’s what I’m trying to focus on today, though I do still feel an urge to know what the masked titrya, and all the other “white” birds out there, look like to birds.

1. He footnotes damn near every page with an amazing aside and integrates an apt Insane Clown Posse quote into a scientific book. Deep respect.