Research

 


November 28, 2016

Lessons in Listening

UNC researchers capture the songs and study the behavior of canyon and rock wrens

By Debbie Pitner Moors

It’s a gray fall morning at Bobcat Ridge Natural Area just west of Loveland. UNC biology professor Lauryn Benedict, doctoral student Nadje Najar and master’s student TJ Hathcock walk along a high path, then stop as Hathcock lifts his binoculars and looks toward a rocky outcropping.     

Somehow, amidst the myriad natural sounds drifting over the landscape, he’s picked out the sound of a rock wren, like a miner sifting for gold. His hearing is tuned to the musical notes of this small, brown bird, and Benedict and Najar hear it too, lifting their own binoculars.

This is a bird species that all three of the scientists know well. Benedict has been studying the rock wren and its cousin, the canyon wren, for six years. Najar has just returned to Greeley after a summer-long study of rock wrens that traversed from Texas to Montana, and Hathcock has spent the last two summers scaling rocky outcroppings to play rock and canyon wren recordings and capture their sounds.

The iconic song of the canyon wren is arguably the soundtrack of the American West, lifting and curling and cascading along canyons, boulder fields and cliffs that range from central Mexico to just south of the U.S./Canadian border. The song of the rock wren is less well known, but is also part of the acoustic fabric of rocky western habitats.

While Benedict, Najar and Hathcock each focus on different questions about canyon wrens and rock wrens, their research interconnects as they study social behavior and communication, as well as habitat use, in these cliff-associated wren species.

The songs of canyon and rock wrens haven’t been studied much, so the team’s work at UNC is an important foray into new areas. They’re looking at how habitat may affect song, the differences in vocalization of males and females, how they communicate, how birdsong has evolved and how the birds respond to intruders.

“Animals do things differently,” says Najar, pointing out that rock wrens she studies react to intruders in different ways. “Some don’t give themselves away at first. Others charge in. You get extremes of aggression versus non-confrontation.”

Although canyon wrens and rock wrens are closely related, a curious and significant difference between the two species has to do with the number of songs in their repertoires. While a single canyon wren sings about five different song types, a rock wren far surpasses that, with a loquacious 120 songs. Why have two closely related species evolved so differently from a communication standpoint? That’s a question that could bring insight into how bird behavior and communication are shaped by factors like social context, habitat and population density.

To investigate these issues, Benedict and her team record birdsong in the field, then use technology to translate sound into a visual representation of song pitch, duration and changes that are often too subtle for the human ear. The resulting spectograms paint a picture that’s helping sort out small differences in communication from one wren to the next.

Individual birds of the same species all sing songs that recognizably belong to that species, much the same way that people speaking a single language all use the same words and phrases. Nevertheless, there are differences between individuals in terms of the particular song types they use and the way they sing them.

As among humans, these differences can arise from geography — populations that are distant from each other often have different “dialects” or “accents” — or they can arise from individual differences. Benedict, Najar and Hathcock are all working to understand some of the individual level differences that cause the songs of each bird in a neighborhood to sound unique.

Studying how and why these little brown wrens communicate can be an exercise in patience. Describing a typical day in the field, Hathcock says he’s often awake at 4 a.m., spends about an hour driving to the field, then hikes in (loaded with recording equipment, binoculars and a backpack), and sets up and waits (sometimes for hours) for the show’s star to appear. But it’s work that he loves. And it’s a love for science that he hopes to share once he finishes his master’s degree in Biology by becoming a high school teacher. “My generation is so tech-oriented,” he says. “We’re really trying to get kids out of the classroom.”

Sparking an interest in the natural world may just be one of the benefits of studying bird communication and behavior. Scientists are also looking at the effects of birdsong on humans — from lowering anxiety to improving study skills and concentration.

Along the rocky shoulders of Colorado’s Bobcat Ridge, distanced from the noise and pervasive technology of everyday life, it’s not hard to imagine the therapeutic benefits of birdsong. It’s a lesson in listening and connecting — in being immersed in the landscape rather than passing through it, finding the current of music that slips through the natural world.