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Meet the Birder: Tom Stephenson

APRIL 7, 2022

Artist Profile: Greg Kozatec

JUNE 7, 2021

We caught up with Tom Stephenson, expert birder and co-author of The Warbler Guide. Tom has lectured and written on subjects ranging from bird vocalizations to photography and has guided trips on multiple continents. A musician, he worked with several Grammy and Academy Award winning artists throughout his career, and was the Director of Technology at Roland Corporation.

How did you get into birding?

I'm a birder – as is my brother and his son – because [my brother’s] fourth grade teacher had her students learn some bird species. And my brother and one other kid in the class liked it enough that she started taking them birding. And then I went along, and we just kept it going. For me, birding is a lifelong learning pursuit. That's why I also like art, architecture, poetry, music. They’re similar – you explore and can always learn more. You have this sense of focus.

Eventually we moved to Ithaca, where the Cornell Lab of Ornithology was just getting started. And Arthur Allen and Paul Kellogg [professors of ornithology at Cornell] took us under their wings. They had meetings and talks at the lab, and I remember seeing my first spectrogram. They had a machine that looked like a lie detector, with a big cylinder going around with a pen on it, and they played a Winter Wren song and it was all over the map. They also had a bird list up, and if you got the first of year sighting for a bird, you got your initials on the board. My brother and I decided one year we were going to get as many warbler species as we could. Every day we would bike to this park, bird, and then go to school. I think we got something like 40% that year. It was a challenge, and as a kid that can really motivate you.

How do you continue to learn as a birder? How have things changed?

I've always been interested in tools and technology. What’s going on now? One thing is the use of cameras in the field. Almost all field guides were by people who were in the field much of their lives – some all day long, every day for like 40 years. That kind of experience gives you access to a personal database of what things look like and how they behave.

But now, I can go on the Macaulay Library [scientific archive] and look at 200, 300, 400 photos of Pacific Loons or Franklin Gulls. I have access to more field data than anybody who’s ever written field guides before. I can measure things. And I've found that some ID points in field guides are not consistently true. And that's one of the reasons people get confused by birds in the field. They look at their field guide and it goes: the Lesser Yellowlegs’ bill is the same length as the width of the head. And the Greater’s is larger than the width of the head. Well, it turns out there's about a 30% overlap in that statistic. Even though the Greater Yellowlegs’ [bill] is a lot bigger than the Lesser’s in absolute value – if side by side, you would not mistake the two – using the bill length and the head width is not necessarily a great way of making that identification. If you use the eye as a metric, which you could easily do with a photograph, then you can separate them quite easily because the eyes are not as different from each other as the bills or the head widths are.

You’re also a great bird photographer. Have you always been into photography? Did that come about with birding or is that a separate passion that just met a happy medium with birding?

Earlier, I never took pictures as a birder, in part because of the expense. Then photography became digital, and when I began leading foreign trips and having opportunities to give talks on them, I said, well, I better start collecting some pictures. When I did The Warbler Guide, I needed pictures for that too. I brought Scott Whittle into The Warbler Guide project because he was a photographer with a discerning eye. I wanted to be sure that the photographs scanned easily as a similar thing. If you scan drawings by the same artist, it's easy to look from one to the other; your eye doesn't go through any cognitive dissonance about the backgrounds or anything. I wanted that to be true for the Warble Guide photos, and we shot almost all those with flash so the light would be consistent. I’ve had pictures published and in books and different places, but I don't think of myself as a photographer particularly. I think the camera's an incredibly great tool for birders. You can look at things that are hard to parse from a binocular view….not necessarily because you can't see them. You're just not used to studying them because they're not that well depicted in field guides.

Wilson's Wabler. All bird photos by Tom Stephenson.

Yellow Warbler.

How did The Warbler Guide come about? 

I wrote the book I wish I had. It was not available. Jon Dunn and Kimball Garrett did the Peterson Warbler Guide, which is very rich in detail. But there are like 10 pages of plates and 600 pages of text. In order to get through what they have in the book, you have to be dedicated to reading it. And if you’re in the field, that’s not the way your brain is working. If you’re in a visual mode, you want to look and figure out what’s going on.

I had a few rules. Number one: show the bird how you see it in the field. What I wanted was to show all the birds in all the plumages consistently: from below, from the side, from 45 [degree view]. The other rule was to make sure that any species that you could confuse that bird with were shown right with that bird. That’s the only way to have a confident ID – to say, well I think it's this, but if I look at everything that is similar, then I'll know for sure.

In fact, one of the motivators for this book was a trip I led where we saw Wilson's Warbler above us. And people were like, oh maybe that's a Wilson's Warbler…but I won't know until I see the cap. And in the Peterson Guide, there’s an arrow pointing to the cap. But the undertail pattern of a Wilson's Warbler is easier to use as a way of distinguishing it, because the undertail of the Wilson's is dark and long, and the undertail of a Yellow Warbler is wide and yellow. They're totally different. But people weren't looking for that because they were used to looking for those ID points with the arrows.

You also write a lot about vocalizations in the Warbler Guide. Tell us about the tools and techniques for learning bird sounds.

Yes – the other thing were the vocalizations, which are the hardest thing for most birders. I think one reason for this is that every single field guide in the U.S. since 1895 with one exception says, “the bird sounds like” and then it tries to transliterate the sound: tweet, tweet, tweet, or seet, seet, seet, or whatever. And that is incredibly subjective. It might help you if you're the one that came up with it, but it's not going to help me because a seet to you might be a peet or a tseets to me. There's no objectivity to it.

This makes translating from a field guide to what you're hearing in the field basically useless. Using spectrograms was important to me, as was developing objective terminology that would mean the same thing to everybody. I had several terms for qualities of the song: a phrase was the repetition of two or more elements in a row. A section was when something changes drastically – pitch, speed, texture (it’s clear then it becomes buzzy).

When you look at a spectrogram and understand the structure of a song, you hear everything better. You know what to listen for. I'll give you an example. The Yellow Warbler, Magnolia, and American Redstart sound somewhat similar. Their primary songs are all clear, have three sections, and are fairly similar in speed. But there's a difference. In the second section, the Yellow Warbler always sings two or more elements or phrases, never just one. The Redstart and the Magnolia Warblers both always sing only one. So just by knowing that – and being able to count, I guess – you can separate those quickly. And Redstarts, especially on territory, sing a three-section mate attraction song and alternate that with a one-section song. And Magnolia Warblers never do that. This alternation of the song forms is unique to the Redstart.

Top and bottom: Magnolia Warbler and American Redstart.

There’s so much to learn about birds, and I love how you earlier described birding as a lifelong learning pursuit. Birding isn’t just knowing the name of the bird, but knowing the bird itself: its behavior, life cycle, habitat, song. What’s next for you and birds? 

I’m working on a number of projects, but one I’ll tell you about is a book and an app about U.S. bird songs. I’m going to apply the same general structural and timbral analysis for all the other bird species. It'll be organized by comparison and types of songs. Warblers have a fairly narrow range of vocalization types. All warbler songs have a beginning and an end. Some other species’ don't, like Red-eyed Vireo. You can't say what's the Red-eyed Vireo’s song – who knows, because it just sings for eight hours straight. Thrashers are mimics, so you can't learn a Thrasher song because the individual birds have different element types. That’s the book, and I’m also working on a recording app, which is a companion to the songbook because it will allow you to look at the spectrograms of songs you record. You can play them back at half speed or less, and study the structure of the song, looking at the spectrogram.

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