Prum’s Plumes

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You could call Richard Prum a birdbrain if you’d like, but only if you meant it in the strictly literal sense. It’s an appropriate term for someone who started birdwatching at the age of 10. The Yale professor of ornithology, awarded the MacArthur “genius grant” in 2009 for his theory on the evolution of feather structure, was cited by the MacArthur Foundation for work that intertwines “developmental biology, optical physics, molecular genetics, phylogenetics, paleontology, and behavior ecology to address central questions about bird development, evolution, and behavior.” WEEKEND’s Jennifer Gersten sat down with the professor to talk pets, paint and plumage before he flew off to his next class.

Prum is looking hip.

Kathryn Crandall
Prum is looking hip.

Q. I read that you’re thinking about developing a novel type of blue paint. Why the color blue?

A. Blue pigments are really rare in animals, and nonexistent in vertebrate animals. That means that every time you see blue in the skin of an animal, you’re looking at a structural color, which is produced by the optical interactions of light waves with the material of the skin or feathers. These colors are made by nanostructures, and we’ve discovered that birds develop structural colors by using self-assembly — they create the physical conditions that allow the nanostructures to grow themselves.

Blue birds make little tiny air bubbles that create their blue color. These bubbles selectively reflect blue light: You could make greens or reds or yellows using pigments or structures, but blue can only be created by structural colors in vertebrates. The color is then made through a process called phase separation, which is the same process that produces bubbles in a lava lamp, or bubbles in beer. That raises the prospect of a structural blue paint that would phase-separate like blue feathers and create a color that wouldn’t fade because, unlike a molecular pigment, it would be permanent and durable.

Q. You’ve become well-known for your studies of feather coloration, and in 2010 you became the first to construct the full-feathered plumage of a dinosaur. Are there any colors you wouldn’t expect to see in dinosaur feathers?

A. Our window into the color of dinosaur feathers was accidentally provided by the fact that some of their pigments fossilized well, so we’ve been able to construct well the colors that are produced by melanin. But we can’t really identify a lot of the other types of colorants, whether they’re structural colors or other pigments, so our window into that time is a little sketchy. What we do know is that the beautiful reds and blues and greens, even among living birds, appear to be of rather new evolutionary origin. So it’s quite possible that dinosaurs and early fossil birds hadn’t yet evolved those types of colors.

There are definitely colors that are really hard for them to make. Hot pink turns out to be a very rare color, but there are birds that actually make it in a complicated way.

Q. You’ve mentioned that it’s highly likely that dinosaur skin was colored prior to the evolution of feathers. What, then, would explain the need for colored feathers?

A. For most of the century, we thought we knew exactly why feathers evolved. And the answer was, “for flight.” We only made progress on what happened by not asking that question. Only by ignoring the possibility of a functional solution did we make any progress at all in how feathers evolved. There are still lots of questions about what adaptive advantage feathers might have had, and coloration is one of them.

Q. Do you eat birds?

A. I’m pretty much a fish-itarian. But when Thanksgiving comes along, I’ve been known to eat a bird part or two, though I don’t eat most meat.

When I was an undergrad I read “Diet for a Small Planet” by Frances Moore Lappe, and I became a political vegetarian from the idea that if we eat lower on the food chain, we can lower both hunger and our ecological impact on the planet. And then I found out that I rather preferred the diet, although I still think that all those things are still true.

Q. Have you ever been attacked by a bird?

A. On nesting colonies of terns, sure. The terns near the nest, they do not like anybody around. They swoop at you and try to peck your head. … Usually they peck the tallest person. Sometimes, I’ve also been not the tallest person in the group, so in that case I haven’t had to worry.

Q. What can we learn about ourselves by studying birds?

A. My work in evolutionary aesthetics proposes that we will learn a lot more about the nature of aesthetics as a discipline by studying nonhuman species, which evolve preferences and have subjective experiences that have real consequences.

It’s the same process through which human beings gained a greater knowledge of the universe and their place in it. We used to think that everything revolved around us. Then we realized, “Oh wait, we’re actually orbiting around this star in the backwater of the cosmos.” We gained a greater appreciation of our own specialness because we realized we come from such an arbitrary and seemingly unspecial place. I think that the same contextual understanding of humanness is expanded by studying other aspects of biodiversity, especially in a realm like aesthetics where we seem to think we’re the entire story.

Q. Your work posits that birds might pick mates based on traits they find aesthetically appealing in the opposite sex, not merely indicators of physical fitness. Do you think birds might be as superficial as humans when it comes to good looks?

A. A lot of my work right now focuses on aesthetic evolution, which is the evolution of the aspects of organisms that function through the perceptions of other individuals. Often those perceptions are characterized by sensory evaluations and choice. Essentially, aesthetic choice: Do they like something?

We know birds have specific preferences — the diversity of avian color and communication systems is actually a consequence of evolution. Every species of bird on the planet has a distinct courtship display, and every single species has a different concept of what it finds beautiful in a potential mate. [For example], bowerbird males create a home seduction theater where they collect items — beetles, fruit, butterflies — and display them for the female. They do this full time. One-hundred percent of male bowerbirds invest a huge amount of their waking lives to the production of these aesthetic ornaments.

Q. You’ve been interested in birdsongs from an early age. Have you heard of the work of Olivier Messiaen?
[Note: The 20th century composer and ornithologist Olivier Messiaen used birdsongs in a number of his compositions. His “Oiseaux Exotiques” incorporates no less than 40 distinct birdsongs in what has been characterized as an “avian fantasy.”]

A. I’ve done a little scholarship, never published, on Messiaen’s use of birdsong. As you know, Messiaen was a brilliant composer and creative person, and he was fascinated by birdsong. He used to go around with staff paper and notate pitches of birds from the wild, and since he had perfect pitch it was credible. I was interested in whether he was capable of transcribing the actual complexity of birdsong.

Birds can actually sing two songs at the same time. They shape the quality of their notes, the timbre, with very complex, rapid modulations of two voices that we can detect by slowing down birdsong to a tenth of its current speed. The question for me was if Messiaen actually knew this. What I found was that although he used chords to color sound, he didn’t modulate sound independently in time as the birds actually do to shape the notes that they make. So it turns out that no, he didn’t anticipate this aspect of ornithological science in his composition.

Q. Did you see any other creatures while you were studying birds in South America?

A. I’ve had encounters with toxic snakes. … Luckily, I wasn’t bitten. When you’re a birdwatcher, you have to keep your eyes on the trees, and you cannot spend all your time looking at your ankles, or you’ll never get anything done. You just have to have faith that your number isn’t going to come up.

Q. What is the strangest bird you’ve studied?

A. I haven’t actually studied it, but the strangest bird I’ve experienced is the oilbird, which is a nocturnal frugivore. It eats fruit, flies around at night, nests in caves and has echolocation. It’s called the oilbird because it eats mostly palm fruits and avocados that are very high in fats. The young oilbirds are basically big lardballs, and early colonists would collect them and render them down to scoop off their oil for lard for use in cooking. The birds expel the seeds of the plants they consume in their poop. In their caves, you’ll see little knee-high avocado and palm fruit trees that are entirely white growing in bird guano.

Q. Have you ever kept birds as pets?
A. No, I haven’t, and that’s kind of odd. We actually house-sat some parrots recently and got a chance to experience birds in the house — two small parakeets that flew around the house. I thought they were charming, I actually could have gone for them — but they ended up pooping all over the house, and because they really loved to fly, we didn’t have the heart to keep them in the cage all day. These birds needed to fly to be happy, but they needed to be happy in someone else’s house — that was my wife’s conclusion.

Q. I hope you’ve never been accused of being a birdbrain.
A. I think in elementary school, that was actually pretty common. … ”Ranger Rick,” you know, and all. When I was a kid, the hippie thing was still around, so everybody associated birdwatching with back-to-the-land hippiness. … I got a lot of ribbing when I was a kid.

Q. I think you turned out okay.
A. Yes, I think I did.

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