City bird, country bird

As cities continue to expand, their impact on wildlife grows too. Western Washington University Assistant Professor of Biology Chris Templeton and his graduate students are working with black-capped chickadees and zebra finches to better understand the impact of urbanization on antipredator behavior and cognition. 

Black-capped chickadees and zebra finches are well-studied birds whose vocalizations, stress responses, memory and problem-solving can offer us valuable insights into how birds adapt or struggle in urban environments.

Chances are, if you’ve spent any time in the PNW, you’ve witnessed antipredator mobbing behavior in birds. For example, you might have seen a group of crows chasing an eagle or smaller birds chasing a hawk. This is a common defense tactic among small birds.

Grace Nugent is a WWU biology grad student who studies predator perception and antipredator behavior in black-capped chickadees. Nugent got her bachelor’s degree in wildlife ecology from University of Wisconsin, Madison and was working as a wildlife biologist for the Wisconsin Department of Natural Resources when she came across Templeton’s research on the highly sophisticated vocalization system of chickadees.

Nugent wanted to know more, so she left her girlfriend and Australian shepherd behind (temporarily) in Wisconsin last year and moved to Bellingham to work with Templeton on his research.

“Leaving my family in Wisconsin was tough, but I knew this was a rare opportunity to pursue research I’m passionate about,” said Nugent.

Black-capped chickadees have predators of various types and sizes, including raptors and cats. So, predator-specific escape plans are crucial to chickadee survival. But how do chickadees know what escape plan to use? 

Templeton’s own research as a graduate student established our current understanding of the way black-capped chickadees communicate details about predators to one another through vocalization. 

“Chickadee calls encode information about the size of the predator and whether it is flyover or perched. And chickadees can change the fine-scale acoustic structure of their calls to signal degree of risk,” Templeton said.

Templeton’s research has shown that when chickadees see a flyover raptor like a hawk, falcon or owl, the chickadees produce a soft “seet” call. For a perched predator, chickadees recruit each other and members of other species as mobbers to gang up on a predator with a loud “chicka-dee-dee-dee” call, adding more “dees” to the end as the risk increases.

A small raptor, like the pygmy-owl, is a greater threat than a larger owl or hawk because of their increased speed and agility in a forested area. A dangerous predator like a pygmy-owl, a weasel or a neighbor’s cat might demand a noticeable 10 or 15 “dees” at the end of a chickadee call. But Templeton’s research showed, in the case of one particular pygmy-owl encounter, that highly threatening predators can elicit as many as 23 “dees.” 

In the forest, chickadee vocalizations are a high-stakes commodity, not only because their communication system protects their own species, but because more than 50 different species are known to respond to chickadee vocalizations.

Urbanization and black-capped chickadees

For black-capped chickadees, how do predator perception and antipredator behavior change in the context of light and noise pollution and habitat fragmentation? This is the question Nugent wants to answer.

For her study, Nugent chose 15 urban sites and 15 remote sites where she’s observing black-capped chickadee behavior in response to three predators: Cooper’s hawks, northern pygmy-owls and feral cats. 

To ensure she has a significant population of black-capped chickadees to observe, Nugent led the birds to the selected sites with seeds for a couple weeks. Then she placed lifelike, animatronic taxidermy raptors and a stuffed cat (all of which she engineered and programmed herself) in the area.

In the presence of these predators, Nugent records black-capped chickadee alarm calls and monitors other stress responses like wing flicking, foraging and mobbing behavior.

“If a black-capped chickadee is foraging, it means they aren’t as stressed. But wing flicking is a very social, high-stress behavior. And we’ll monitor mobbing behavior, where they collectively harass a predator — I’m really hoping we’ll get to see that behavior,” Nugent said.

Characterizing these behaviors across various urban and remote research sites should help Nugent inch closer to a better understanding of how urbanization impacts the way these little birds perceive predators. 

Templeton says we don’t have to speculate — the animals can “speak” for themselves.

“Alarm calls give us insights into how an animal perceives its world — I’ve always been interested in trying to understand from that perspective. You can try to guess, but the animal can actually tell you by how it classifies a predator. When you bring in urban and noise pollution, this gives us the opportunity to understand the less solid, less obvious effects that we are having on these animals,” Templeton said. 

Lainey Bee is a WWU biology grad student who studies urbanization’s impact on problem-solving skills, impulse control and behavioral flexibility in zebra finches. 

Bee earned her bachelor’s degree in biology from Virginia Commonwealth University, then worked for four years as a seasonal field technician collecting data on birds and bird populations for a variety of nonprofits and universities. Her work as a field technician ignited her passion for studying how human activity interferes with animal behavior. This led her to Chris Templeton’s research on bird behavior.

“I’ve loved grad school. I took years off school to do other things. I was still in science, but it’s very different than being around great scientists. I just love working with Chris — he’s been so available and so patient. Being surrounded by a community of scientists every day has been so valuable for my own education,” Bee said. 

In zebra finches, traffic noise is known to reduce cognitive function and development, and light pollution is known to alter brain plasticity. Templeton said that the cognitive effects from highway noise alone is extreme. 

Bee explores urbanization’s impact on cognitive function in zebra finches by exposing the birds to a series of treatments and observing their behavior afterward. 

“Past studies have generally focused on the impact of a single pollutant on bird behavior,” Bee said. “But in a human-built environment, animals are never exposed to only one pollutant at a time — it’s always lots of things at once. And taken together, effects of multiple pollutants can exacerbate each other, so I wanted to merge studying multiple sensory pollutants.”

In the lab, Bee exposes the zebra finches to a highway-noise pollution treatment for five days, a light-pollution treatment for five days, a combination treatment for five days, then an ambient light and noise treatment (control) for five days. After each five-day treatment, Bee observes the birds and their behavior around food in a variety of situations. 

Finches are not food-storing birds, but they can learn spatial memory tasks like how to repeatedly locate the one baited feeder in a maze full of empty feeders. So, to test pollution’s impact on spatial memory, Bee gives the birds a little grid of covered holes with a food item placed under one covering. Then she observes how well the birds are able to memorize the food location under each five-day treatment. 

Bee also tests pollutant impact on the finches’ inhibitory control, or their ability to suppress an attempt to solve a problem in favor of a more successful attempt. For example, if a zebra finch is given a clear cylinder with a meal worm in it, a bird without inhibitory control will peck at the side of the tube where the worm is located. A bird with good inhibitory control will go to the end of the tube to retrieve the worm through the opening. 

Bee hypothesizes that the combined noise and light pollution will work together to reduce cognitive function and development more than a single pollutant on its own. 

Anyone can learn to be a scientist

This fall, Nugent and Bee entered their second year as Templeton’s grad students, and they're spending the year analyzing their data. 

Western’s Biology Department is known for prioritizing mentorship and collaboration, and both Nugent and Bee said they’ve been impressed with the program. Nugent said that, in particular, she appreciates the sense of community and support in the Biology Department at Western.

“I have a chronic disability that’s been a barrier, but everyone has been really accommodating. Chris has been nothing short of amazing — so helpful in guiding me and helping me create a research question and build my own project. He lets me do my own thing but is a helping hand if I need it,” Nugent says. “The biggest thing at Western in the bio department is that sense of community, and without it I would be struggling.”

Bee said during her time at Western, she has learned so much about what it means to be a scientist — and that anyone can do it! 

“I thought it was an innate ability to be a scientist and ask the important questions. But after working with various researchers in different stages of their careers at Western, I understand now that it’s a learned skill,” said Bee. “Being at a university like Western that really cares about students and developing scientists has inspired me.”

Learn more about Western’s master’s program in biology here.  

Allie Spikes covers the WWU Graduate School and Fairhaven College of Interdisciplinary Studies for University Communications. Reach out to her with story ideas at spikesa@wwu.edu.