Based in El Paso County, Colorado, David Tønnessen likes to describe himself as a “life-long naturalist.” He is currently finishing a master’s research project focusing on bioacoustics monitoring and analyzing bird sounds, a field he plans to pursue beyond his degree. David guides part-time for Colorado Birding Guides, and his photographs can be found on the company’s website. He is also an eBird reviewer for Colorado and serves on the Colorado Bird Records Committee.—Teresa Connell

What is the aim of your research project?

The goal is to standardize a way to estimate populations of Montezuma Quail by detecting their calls on ARUs (recorders). There are so many ways to work with bird sounds, and the exciting part to me is that it is a poorly studied area with great potential for new discoveries and great potential to contribute to how we monitor birds and other wildlife. At the 2024 WFO Conference, I gave a talk at the science sessions, “Passive acoustic techniques to monitor a cryptic Galliform.” It was about a project, funded through Sul Ross State University with support from Cornell University, for monitoring Montezuma Quail populations, where I used BirdNET to go through audio data to answer questions about this secretive species.

How did you get interested in this area of research?

Nathan Pieplow has been a great inspiration. His expertise in bird sounds and using spectrograms as a tool of identification stoked my motivation to explore bird sounds more. We got to know each other well when I was an undergraduate at University of Colorado Boulder. We had a birding club with a few student members and Nathan as the club’s faculty advisor. While I’ve always considered myself a heavily auditory birder, he introduced me to the visual component of ear-birding, and how spectrograms can be useful even for someone as ear-centric as myself.

The moment that stuck with me most and opened my eyes to this fact was seeing the spectrogram of a Black-capped Chickadee. In the field I would just hear two notes, so the mnemonic “cheeseburger” never made sense to me because it has three syllables. The first note is obviously higher and more distinctly separated from the second note, but then there is a third note at the same pitch as the second note, only very subtly separated. After seeing the subtle break between these notes in a spectrogram, I started to hear it in the field, and now the three-syllable “cheeseburger” makes sense.

What this taught me is that using your visual sense can sometimes reveal the blind spots in your hearing, so to speak. But I will also say that this works the other way too: sometimes there are subtle qualitative differences in sound that I can’t easily pinpoint in any spectrogram. So, I think using multiple senses to analyze a sound can help you parse out slight subtleties that for whatever reason one of your senses might be overlooking in the messages sent to your brain.

How did your passion for birding start?

The moment I first looked at birds as a source of fascination was probably as a 7-year-old, when I saw a brilliant Northern Cardinal land on the feeders my parents had put out when we lived in Minnesota. After that, I was hooked on poring over my now very beaten-up Peterson Field Guide to Birds of North America, but it took me another few years until I actively started biking in pursuit of birds as an eager 13-year-old living in incredible San Mateo County, California. Since then, my family has lived in Colorado, where I was very lucky to spend most of my formative years with easy access to stunning open spaces and public lands that helped cultivate my interest in being a birder and naturalist.

Do you have favorite hotspots? Or favorite species that call to you?

These are classically tough questions, but I think my answer to the first would be whichever hotspot I’m currently birding for the first time. As a bigger generalization, hotspots that combine accessibility and species diversity are often the best. As for a favorite bird, people are sometimes surprised to find out I delight in many less flashy species because of certain past experiences and perhaps because of subtle marks in their plumage and behavior that aren’t generally appreciated enough. Black Swift, dippers (Cinclidae), Varied Thrush, and Black-billed Magpie are a few that come to mind. I’m a big Corvid fan.

There are so many things I enjoy about birding, and those things are constantly evolving. I most consistently find comfort in returning to my local CBCs here in Colorado: grinding for hours despite sometimes adverse conditions, and at the end of a long day sharing your efforts with a community of others who share your passion, and comparing how your collective observations measure up to other years. There is a similar appeal to, say, a big day, where despite what limits you might face in duration, area covered, and so on, you focus all your diverse skills and expertise to maximizing the output—the species—on that route.

Is there any advice you’d like to share with younger students?

To high school–age students who think they want to be involved in bird work in the future, I encourage two things: getting fieldwork experience and planning a college education. These do not necessarily need to be in that order. Beyond this, I recommend very careful consideration and research going into any potential graduate school choices.

Do you enjoy the WFO conferences? Is there anything WFO can do to improve them?

I’ve very much enjoyed the conferences, which I’ve been coming to whenever I’m able since 2016. I love that WFO has been proactive in including youth in the conferences, and I encourage expanding ways that WFO can be more inclusive.

Where do you see yourself in 10 years?

I’m trying to reach the right balance between field and lab work. I love guiding part-time, but I also want to continue to do meaningful science to promote bird and biodiversity conservation.

I would be perfectly happy at a research lab focusing on bird sounds, fine-tuning how we can use bird sounds, and using bird sounds to answer questions from a unique perspective. One way bird sounds have been traditionally overlooked until maybe recently is the role vocalizations serve in separating species. Speciation happens when you get some form of reproductive isolation, whether because two birds look different or they are located in different places, or they speak a different language (their sounds)—in other words, morphological or geographic differences, or differing vocalizations. Recent splits in species have come about because of new work looking at differences in their sounds; the recent split in Chihuahuan Meadowlark is a good example. I want to see where else bird vocalizations differ and how that can inform how we define and understand species.