ENVIRONMENT

Common Indiana songbird under threat from climate change

Rachel Smith
An Acadian Flycatcher, a common Indiana songbird, sits in a nest. Researchers predict that these abundant songbirds could be seriously threatened by the warming temperatures that come with climate change.

“Piz-za! Piz-za!”

Yes, it’s the catchphrase of a popular pizza franchise. But if you’re deep in an Indiana forest and hear this distinctive refrain, you probably aren’t hearing an order for a 12” pepperoni pie. Rather, you’re likely in the presence of a male Acadian flycatcher.

These inconspicuous, olive green birds may be hard to spot, but they’re common summertime visitors to Indiana. In fact, an estimated five million Acadian flycatchers migrate to the eastern United States from the Neotropics each summer to breed.

Although the flycatchers’ explosive “piz-za” song resounds throughout Midwestern forests today, researchers predict that these abundant songbirds could be seriously threatened by the warming temperatures that come with climate change.

Frank Thompson, a wildlife biologist with the U.S. Forest Service, has been studying Acadian flycatchers in the Midwest for more than two decades. Over this time, his team has monitored thousands of flycatcher nests and accumulated a robust dataset on flycatcher breeding productivity — that is, the number of young produced per female bird.

Thompson’s group also collects data about environmental factors that could affect the birds, including habitat aspects, such as forest cover, and climate variables, such as temperature.

“We started monitoring nests, not with the idea of climate change in mind at all,” Thompson said. “It was really around the question of habitat fragmentation.”

Baby Acadian Flycatchers, common Indiana songbirds, sit in a nest. Researchers predict that these abundant songbirds could be seriously threatened by the warming temperatures that come with climate change.

And yet, when Thompson’s team looked at relationships between these environmental factors and the flycatchers’ breeding, they saw that higher temperatures were linked to reduced flycatcher breeding success. In other words, fewer baby flycatchers successfully hatched and left the nest when temperatures were warmer.

The strength of this relationship raised a red flag for the researchers. They began to wonder what would happen to the flycatchers under climate change. Could they use the relationship between temperature and breeding to predict how different climate change scenarios would affect the large populations of flycatchers that breed in the Midwest’s central hardwood forests?

“To really inform policymakers or managers or conservation agencies, we knew we had to translate that potential effect all of the way to a population level impact,” said Thomas Bonnot, an assistant professor at the University of Missouri and lead author on the project. “That’s where we really start to understand the severity of the potential threats that are out there.”

Bonnet used sophisticated modeling techniques to predict how the breeding of Midwest Acadian flycatcher populations would respond to climate warming over the next 80 years. He ran various climate change scenarios that ranged from mild to severe temperature warming.

Flycatcher population losses with climate change

The results were concerning: Bonnot’s team predicts that Acadian flycatcher populations will decline substantially under the most extreme climate scenario, which reflects a continuation of current climate policies and greenhouse gas emissions. With severe warming, these abundant populations are at risk of becoming locally extinct from the Central Hardwoods region, with potential losses of about 3.7 million birds in less than a century.

“(Acadian flycatchers are) not on anyone’s climate threatened list, and yet…by 2100, this species could be having severe population crashes in large portions of its range,” said Morgan Tingley, an ornithologist from the University of Connecticut who was not associated with the study. “What does that mean for other species, particularly for ones that are less common and abundant?”

Bonnot hopes that this result, recently published in Nature Climate Change, will act as a wakeup call.

“Common species that we don’t worry about right now could be at risk. We need to be ready and vigilant in monitoring those situations,” he said. “We have confidence in our results and predictions, but at the same time, I hope they don’t come true.”

Baby Acadian Flycatchers, common Indiana songbirds, sit in a nest. Researchers predict that these abundant songbirds could be seriously threatened by the warming temperatures that come with climate change.

This work also illustrates the importance of curtailing the carbon emissions that lead to climate warming. Bonnot’s team found that Acadian flycatcher populations remained stable through the end of the century under milder climate scenarios.

“Simply addressing climate change and limiting the degree of warming that happens has a profound positive impact on reducing that risk to flycatchers,” Bonnot said.

Although the predictions of the most severe climate models are dire, there are additional factors that could alter the outcomes. For example, the Acadian flycatchers could adapt to warmer temperatures by altering their behavior, breeding earlier in the season or shifting their distribution northward to cooler regions.

Making changes to save flycatchers

The researchers’ predictions inform the conservation and management of both Acadian flycatchers and other birds, including species that are rare or have less data available.

For the Acadian flycatcher, these models suggest that limiting the amount of climate warming is an effective way to conserve this species. Still, this work can also help find alternate ways to reduce harm to this species, given higher temperatures.

“The good news is that (with) the same methods that we use to estimate this risk to the population, we can turn around and use those same methods to play out some ‘what if’ scenarios about what would be best to conserve these populations under these threats,” Bonnot said. “If climate change is going to play out like the models suggest, then we need to be prepared with approaches to save these species.”

Baby Acadian Flycatchers, common Indiana songbirds, sit in a nest. Researchers predict that these abundant songbirds could be seriously threatened by the warming temperatures that come with climate change.

For example, they can use their model to assess whether different management actions will improve flycatcher survival or reproduction.

Future iterations of the model can also incorporate other environmental changes that will happen alongside climate change.

“More is changing in the environment than just temperature,” Thompson said. “One of the biggest threats to songbird populations in the east has been habitat fragmentation.”

Tingley agrees that incorporating habitat changes into the models are the next step.

“We often focus on climate change because it’s this huge thing that’s coming down in the future," he said, "but often times, we’re imperiling more species in the short term just by eliminating their habitat."

The researchers hope that this work will increase public awareness of both songbird conservation and the complicated role that climate change plays in the decline of species populations.

“The easiest thing is to pay attention to birds — join a local Audubon society, go bird watching and teach your children to appreciate birds,” said David Flaspohler, an ornithologist at Michigan Technological University who was not associated with the study. “That doesn’t take much work at all and it will always give back to you more than you put into it.”

Other ways to help local songbirds are to protect and restore local habitats, for example, by removing invasive species. Or, you can become involved in citizen science efforts, such as Project Nestwatch, a nationwide effort to collect data on bird breeding success.

“I don’t think we can sit back and say these birds are going to be just fine,” Flaspohler said. “If that tapestry of evolutionary history is going to be unraveling in the next hundred years, I think that deserves attention and I think people should be concerned…we’d like to see healthy populations and we’d like for our grandchildren to enjoy that same biological heritage.”

An Acadian Flycatcher, a common Indiana songbird, sits in a nest. Researchers predict that these abundant songbirds could be seriously threatened by the warming temperatures that come with climate change.

Rachel Smith is a 2018 American Association for the Advancement of Science Mass Media and Science Engineering Fellow. She is being hosted by IndyStar and working collaboratively with its environmental reporting team that is made possible through the generous support of the non-profit Nina Mason Pulliam Charitable Trust.

Reach Rachel at sarah.bowman@indystar.com or emily.hopkins@indystar.com.