Climate & Environment

Zero-emission vehicle adoption reduces air pollution, climate impact from transportation

Megan Maneval — Fri, 11 Apr 2025 19:58:29 +0000

Zero-emission vehicle adoption reduces air pollution, climate impact from transportation Megan Maneval Fri, 04/11/2025 - 13:58

CIRES

California’s “going zero” policy, which strives for 100% zero-emission passenger vehicle sales by 2035, will reduce ozone pollution and carbon dioxide emissions in Los Angeles, according to recent CIRES-led work.

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When helping can hurt: How efforts to adapt to climate change can backfire for vulnerable populations

Yvaine Ye — Fri, 11 Apr 2025 15:05:14 +0000

When helping can hurt: How efforts to adapt to climate change can backfire for vulnerable populations Yvaine Ye Fri, 04/11/2025 - 09:05

Yvaine Ye

When Hurricane Helene made landfall in the southeastern U.S. last September, it brought record-breaking rainfall to states including North Carolina, dumping as much as 2 feet of water in some rural communities.

It was the deadliest hurricane to strike the U.S. mainland since 2005, killing more than 200 people. Despite authorities’ efforts to evacuate residents in the region, many people had no choice but to stay put, some due to a lack of resources or unwillingness to leave their homes or pets behind.

“Not everyone can respond the same to climate change,” said Karen Bailey, assistant professor in the Department of Environmental Studies. “There’s been a growing recognition that climate change disproportionally impacts marginalized communities, but our current strategies for adapting and mitigating risk from hazards could potentially exacerbate inequity.”

Bailey, who studies how climate change, and efforts to adapt to it, impact different populations, sat down with ��ý�Ļ��Ʒ Today to share her insights.

Karen Bailey

How do different populations adapt differently to climate change?

People’s ability to adapt depends on many factors, from where they live to the resources available to them.

Low-income families, for example, may not be able to install ventilation systems to improve air quality after wildfires. In fire-prone areas, the ability to remove trees around a home depends on how much money the residents have or whether they own that property.

On a global scale, people in wealthy countries contribute the most to emissions that drive climate change, but those in low-income countries experience the worst consequences. For example, extreme heat has led to many deaths in South Asia, and the problem is worsened because of limited access to cooling devices.

You recently did a case study on a flood mitigation program in a rural community in the state of New York. What did you find?

In the Catskills region of southwestern New York, the government runs a flood mitigation program that buys out properties at high risk for flood damage. While the intent is to protect people and their property and reduce the risk of water pollution from flood-damaged structures, some community members who participated in the program told us they struggled to find affordable housing elsewhere. The buyout program also impacted the essential services the community had provided by potentially shutting down their local health clinic and putting the local grocery store at risk of relocation.

For this program, the primary metric of success that the authorities were using was how much land was bought up. They weren't really thinking about other potential benefits or harms associated with buying out property.

How do decision-makers balance the urgent need to prevent harm from natural disasters while considering the needs of different groups?

There's no easy answer to this question. Federal, state, and municipal authorities need to work quickly and provide resources to get people out of harm's way when emergencies like fires or hurricanes strike. But before, during, and after a hazard, it's important to have a planning process that asks: How can we help community members and ensure all of them continue to thrive despite these challenges?

Keep in mind that urgency is sometimes intentionally or unintentionally used to exclude people from conversations. We sometimes need to slow down these preparedness processes a little bit, so we can talk to more people and consider their diverse perspectives.

Define ‘equity’ in the context of climate change adaptation?

Broadly speaking, equity deals with fairness in the distribution of harms and benefits. While people may have different goals, can we still design systems that account for those differences?

Equity also deals with fairness in the decision-making process. Are we including the perspectives of the most impacted or marginalized communities? Are we making the processes open and transparent?

How do you respond to people who take issue with the term ‘equity?’

Last year, my team and I published a paper where we looked at prior research in this field and found scholars rarely define “equity” explicitly. This vagueness has made the concept more susceptible to politicization. People often attack “equity” based on their own interpretations, while we may mean something entirely different.

If people have concerns about “equity,” I would encourage them to look at what those advocating for equity and inclusion are actually doing. Are they making resources available? Are they communicating in different languages? Are they having programs that are open to and target marginalized communities?

I encourage them to reflect on whether these are truly the things they disagree with before arriving at a conclusion.

��ý�Ļ��Ʒ Today regularly publishes Q&As with our faculty members weighing in on news topics through the lens of their scholarly expertise and research/creative work. The responses here reflect the knowledge and interpretations of the expert and should not be considered the university position on the issue. All publication content is subject to edits for clarity, brevity and university style guidelines.

As natural disasters become more frequent and intense, Environmental Studies Professor Karen Bailey wants policymakers to include a broader range of voices when making adaptation plans.

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Devastation in Asheville, North Carolina, after Hurricane Helene. (Credit: Bill McMannis)

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Devastation in Asheville, North Carolina, after Hurricane Helene. (Credit: Bill McMannis)

What if your food had a carbon footprint and human rights label?

Yvaine Ye — Wed, 09 Apr 2025 14:48:09 +0000

What if your food had a carbon footprint and human rights label? Yvaine Ye Wed, 04/09/2025 - 08:48

Yvaine Ye

Imagine walking into a grocery store where every product has a clear carbon label: “The making of a pound of beef produces 130 pounds, or 59 kilograms, of greenhouse gases and could ultimately take 2.3 hours off a human life by exacerbating climate change.”

Would these labels drive consumers to purchase food with a smaller carbon footprint and less negative impact on humans?

Zia Mehrabi wants to find out.

In a recent paper, published in the journal Nature Human Behavior, he and collaborator Ginni Braich, a senior data scientist at ��ý�Ļ��Ʒ, use existing data on deaths per pound of greenhouse gases added to the atmosphere to calculate how much high-emission products like beef, gasoline, and flights shorten life expectancy worldwide. They call for regulators to mandate labels on these products and services, indicating their contributions to climate change and their impact on human well-being.

Zia Mehrabi

This policy could encourage consumers and food manufacturers to buy and produce food with smaller impacts, Mehrabi said.

He notes that the food industry, including production and transportation, emits a quarter of greenhouse gas emissions worldwide. The developing world, however, takes the brunt of the impact of climate change, including extreme heat, drought and flooding, and resulting damage to human health.

For example, prior research suggested that the U.S., one of the world’s top emitters, caused nearly $2 trillion in climate damage to other countries between 1990 and 2014, including $310 billion in losses to Brazil and $257 billion to India.

“If you compute the number of people who die or will die due to an additional ton of carbon in the atmosphere today, the majority of them are in Sub-Saharan Africa and South Asia,” said Mehrabi, assistant professor in the Department of Environmental Studies and director of the Better Planet Laboratory. “We are hoping to communicate those consequences with people through these labels and bring the human dimension into the climate dialogues.”

Ahead of Earth Day 2025, Mehrabi shared his take on adding carbon labels to certain products.

Are there any carbon labels in use now?

Some companies are offering carbon labels on products. For example, if you use Google Flights to search, it will tell you the emissions associated with that flight. If you are a consumer who cares about the environment, the label might influence what products you buy. Unilever also puts labels on products showing their carbon footprints.

What are some problems with the current carbon labels?

For everyday citizens, even me as a scientist, it's very hard to contextualize what that emission number actually means in a real-world sense. How are 273 pounds of carbon emitted flying from Denver to Los Angeles going to impact ecosystems? How is that going to impact people in different parts of the world?

What if, instead, you knew that taking a transatlantic flight would end up removing 16 hours of someone else's life due to the impact of climate change? Or that eating a kilogram of steak costs more than five hours of someone else’s life?

These are tangible impacts, that the products we consume and the services we use are directly stripping life from other people.

An example cigarette package label (left). A food label that illustrates human effects of climate change (right). (Credit: Zia Mehrabi/��ý�Ļ��Ʒ)

Why is incorporating human impacts in these labels important?

It's an undeniable fact that the key perpetrators of climate change are the ones who feel the impacts the least, and the ones who are most affected are the people who have contributed least to the problem.

Embed human rights in that labeling so that you don't just know the number of greenhouse gas emissions that are associated with it, you also know the number of people that were impacted and how.

As consumers, as members of the public, and as citizens of our country and our world, we should have access to such information.

Should we put the burden of addressing climate change on individuals?

With these labels, consumers are not the main target. We want to drive the companies, the food manufacturers for example, to make changes.

If we can mandate such labels on high-emission food products, companies would be incentivized to reduce emissions elsewhere in their supply chain to compensate for the carbon-intensive products they sell to avoid those labels.

There are many solutions for reconfiguring the supply chain, so that the product is better for the environment. For example, there are more climate-friendly ways to farm food, using cleaner forms of energy. We have many of these solutions in the world right now. But producers, manufacturers and retailers are not really pressured in any way to take action.

What would the rollout look like?

There is needed discussion on how such labels should be rolled out. About 90% of the projected emissions over the next 50 years will come from the top 10% income earners of society. This indicates high-income brackets of society might be targeted.

According to the United Nations resolution on the human right to a healthy environment, everyone has a right to access a clean, healthy and sustainable environment.

To do this companies need to change their practices, and they need to be forced to do this through regulation.

Could steps like this really slow down climate change?

I think carbon labeling, when incorporating human rights impacts, opens an opportunity for individuals to affect change through the choices they make. More critically, it can pressure companies toward more sustainable practices.

There is a lot of evidence that such labels work in practice in other domains, like high sugar labeling and tobacco labels.

There is a massive gap between what we need to do to tackle climate change, and what is actually being done in the world. We need all of our tools at our disposal. And we need ones that elicit rapid and radical change.

Assistant professor Zia Mehrabi wants you to know how what you eat impacts the planet—and other humans. He lays out his plan in a new paper.

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A grocery store aisle. (Credit: Franki Chamaki/Unsplash)

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Thawing the mysteries of ancient climate changes

Megan Maneval — Thu, 03 Apr 2025 20:11:59 +0000

Thawing the mysteries of ancient climate changes Megan Maneval Thu, 04/03/2025 - 14:11

INSTAAR

A new study from Chloe Brashear, Tyler Jones and others suggests abrupt warming events were preceded by periods of unusually stable temperatures during the last ice age. The researchers point toward shifting sea ice as a potential driver of the phenomenon.

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Drone experiment reveals how Greenland ice sheet is changing

Yvaine Ye — Thu, 27 Mar 2025 14:54:06 +0000

Drone experiment reveals how Greenland ice sheet is changing Yvaine Ye Thu, 03/27/2025 - 08:54

Yvaine Ye

For the first time, researchers have collected detailed measurements of water vapor high above the surface of the Greenland ice sheet. Their research, aided by a custom-designed drone, could help scientists improve ice loss calculations in rapidly warming polar regions.

Kevin Rozmiarek (Credit: Hayley Bennett)

“We will be able to understand how water moves in and out of Greenland in the next few years,” said first author Kevin Rozmiarek, a doctoral student at the Institute of Arctic and Alpine Research (INSTAAR) at ��ý�Ļ��Ʒ. “As a major freshwater reservoir, we need to understand how Greenland’s environment is going to change in the future.”

The findings were published March 14 in JGR Atmospheres.

According to the National Oceanic and Atmospheric Administration (NOAA), Greenland lost about 55 gigatons of ice and snow between fall 2023 and fall 2024. The island is shedding ice for the 28th year in a row, and scientists estimate that it has lost more than 5 trillion tons of ice since 1992.

The Greenland ice sheet contains about 8% of the planet’s freshwater, and its meltwater could contribute significantly to rising sea levels, changing ocean circulation and ecosystems worldwide.

The majority of ice loss comes from large ice chunks breaking off from glaciers and the melting of surface ice and snow. Sublimation, the process of solids turning into gases without turning into liquids first, may also play a role. Prior studies have suggested that in some parts of Greenland, about 30% of summer surface snow could sublimate to water vapor.

A drone landed on the Greenland snow surface at EastGRIP. (Credit: Ole Zeising/Alfred-Wegener-Institute)

Tracking water in the sky

It is unclear where the water vapor goes, said Rozmiarek, who's also a student in the Department of Geological Sciences. Some might fall back down as snow or recondense on the surface later, but some could leave Greenland’s water system entirely.

Collecting air samples in the Arctic is an expensive and technically challenging task, because it traditionally involves flying a plane to the middle of an ice sheet in harsh weather and carrying air samples back to the laboratory.

Rozmiarek and his team overcame the challenges by loading air sampling equipment on a large drone with a 10-foot wingspan.

Throughout the summer of 2022, the team flew the drone 104 times from the East Greenland Ice-Core Project camp—managed by the University of Copenhagen— in the island’s interior. The drone collected air samples at different heights of up to nearly 5,000 feet above the ground.

The team aimed to look into the type of hydrogen and oxygen atoms in the air’s water vapor. Water molecules from different sources contain distinct combinations of hydrogen and oxygen. Scientists call these variations in isotopes.

A launched drone bound for collecting air samples for isotopic analysis at EastGRIP, Greenland. (Credit: Ole Zeising/Alfred-Wegener-Institute)

“Isotopes are water’s fingerprints. By following these fingerprints, we can trace back to the source where the water vapor came from,” Rozmiarek said. Scientists have collected high-quality data on the source of water in Greenland, including water that flows from the tropics, and the sink, which is the surface snow on the Greenland ice sheet. “But we don’t know much about the isotopic composition of water in motion, which is the vapor between the source and sink,” he added.

When the team compared their drone-based measurements with an existing computer simulation that models the Arctic water cycle, they found the simulation underestimated the amount of precipitation that fell on Greenland. By incorporating the isotopic data observed in the simulation, the model rendered an accurate prediction of how water moves over Greenland.

“It’s really important to be able to predict what’s going to happen to Greenland in the warming world as accurately as possible,” Rozmiarek said. “We demonstrated how useful water vapor isotope data is by successfully improving an existing model.”

Melting ice sheet

About 125,000 years ago, when Earth was warmer than preindustrial levels, Greenland was covered by a significantly smaller ice sheet, and the sea level was as much as 19 feet higher than today. As the planet continues to warm, the Greenland ice sheet could see dramatic changes and even shrink to its size back then, Rozmiarek said.

The Greenland ice sheet contains a massive amount of freshwater, and that water, if leaving the system, could lead to significant increases in global sea level. The United Nations estimated that rising sea levels caused by climate change currently impact 1 billion people worldwide.

Rozmiarek hopes to return to Greenland and other parts of the Arctic to conduct more flights and gather additional data.

“It’s like we just figured out how to discover fingerprints at a crime scene. This is a concrete step forward in understanding where water is going and where it is coming from in this important system at a time when we need it most,” he said.

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A ��ý�Ļ��Ʒ-led study measured water vapor in Greenland’s air, collecting data crucial for improving climate models and forecasting Arctic changes.

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A drone landed on the Greenland snow surface at EastGRIP.(Credit: Kevin Rozmiarek/��ý�Ļ��Ʒ)

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A drone landed on the Greenland snow surface at EastGRIP.(Credit: Kevin Rozmiarek/��ý�Ļ��Ʒ)

Wildfires, windstorms and heatwaves: How extreme weather threatens nature's essential services

Yvaine Ye — Mon, 24 Mar 2025 16:19:06 +0000

Wildfires, windstorms and heatwaves: How extreme weather threatens nature's essential services Yvaine Ye Mon, 03/24/2025 - 10:19

Yvaine Ye

How much will strawberry harvests shrink when extreme heat harms pollinators? How much will timber production decline when windstorms flatten forests? How much will recreational value disappear when large wildfires sweep through Colorado’s mountain towns?

These are some critical questions that a new computer simulation, co-developed by a ��ý�Ļ��Ʒ ecologist, can answer. In a paper published March 5 in Nature Ecology & Evolution, researchers presented a model that aims to understand how extreme weather events, worsened by climate change, will affect ecosystems and the benefits they provide to humans.

Laura Dee

Based on the model, a Minnesota forest could lose up to 50% of its timber revenue if a severe windstorm hits.

“With climate change, there’s an urgent need to incorporate the impacts of extreme events like mega-fires and hurricanes have on the benefits nature provides,” said Laura Dee, the paper’s first author and associate professor in the Department of Ecology and Evolutionary Biology. “This research is an important step toward anticipating impacts to ecosystem services so that we can adapt management strategies accordingly.”

Scientists use the term “ecosystem services” or “nature’s contributions to people” to refer to the essential functions that nature provides to support human life and well-being. Tree roots purify water, insects pollinate crops and forests lock away carbon, helping to stabilize the climate. In addition to these tangible benefits, mountains, lakes and oceans offer recreational enjoyment for people and hold cultural significance for communities.

Previous models for predicting how ecosystems respond to climate change tend to assume that changes are steady. For example, a gradual increase in global temperatures of up to 1.5°C. But as climate change makes extreme weather events like wildfires and floods more frequent and severe, the impacts from rapid disturbances have become significant.

Dee and her team developed a new mathematical model that tracks how the probability of an extreme weather event affects certain species and the ecosystem services they provide. The model also incorporates how people value these services.

To show the model’s potential, the team applied it to calculate the possible consequences of extreme windstorms in a mid-latitude forest in northern Minnesota. The model considered how winds have different effects on different tree species, each of which has distinct economic value. For example, thick white cedar trees are more resilient to windstorms than balsam fir trees, but the balsam fir can sell at a higher price.

The model suggested that a windstorm, depending on its intensity, can slash the total timber value of the forest by 23% to 50%. Recreational opportunities like hiking and camping would also take a hit.

"We know that all aspects of ecological health are important, but monetizing the services we get from nature is illuminating," said Peter Reich, the paper's co-author from the University of Michigan.

Dee said that researchers and land management officials could use the model to evaluate the impacts of any disturbances, from drought to invasive species.

Dee’s research group at ��ý�Ļ��Ʒ studies how prescribed fire strategies, or deliberately burning specific areas under controlled conditions, can reduce wildfire risks in Colorado.

The new model also helps to identify the areas where scientists should prioritize burning to achieve the greatest reduction in fire risk, while also considering other benefits trees provide, such as removing carbon dioxide from the atmosphere and filtering water.

“Nature’s contributions to people have not typically been valued and are usually left out of key decision-making processes when developing land management policies and strategies,” Dee said.

The United Nation’s World Meteorological Organization announced on Tuesday that more than 150 unprecedented extreme weather events struck Earth last year. With disturbances becoming more common, future Gross Domestic Product analyses, for example, should start incorporating the impacts of climate change, Dee added.

“If we fail to consider the growing risks from extreme weather events, we could lose more than we realize,” she said.

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Our sustainability impact by the numbers:

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A new model suggests that timber production in Minnesota could decrease by half as windstorms intensify with climate change.

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A forest in Minnesota. (Credit: James St. John/Flickr)

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A forest in Minnesota. (Credit: James St. John/Flickr)

CUriosity: What makes Colorado so windy—and will it stay that way?

Daniel William Strain — Fri, 21 Mar 2025 22:12:10 +0000

CUriosity: What makes Colorado so windy—and will it stay that way? Daniel William… Fri, 03/21/2025 - 16:12

Daniel Strain

In CUriosity, experts across the ��ý�Ļ��Ʒ campus answer pressing questions about humans, our planet and the universe beyond.

This week, meteorologists Andrew Winters and McKenzie Larson weigh in on the question: “What makes Colorado so windy—and will it stay that way?”

Winds swoop over Colorado's Rocky Mountains. (Credit: CC photo by Zach Dischner via Flickr)

Whoosh. This month, a series of windy days went roaring through Colorado’s Front Range. Gusts topped out at more than 80 miles per hour on March 17 in Boulder and caused a few power outages.

It’s not an unusual occurrence for the region in its colder months, said the aptly named meteorologist Andrew Winters. In Boulder, locals are no strangers to getting knocked off their bikes by winds that can hit 90 or even 100 miles per hour.

McKenzie Larson installs a precipitation wind shield at the ��ý�Ļ��Ʒ Mountain Research Station at Niwot Ridge in 2023. (Credit: McKenzie Larson)

“You’ll hear people from a lot of places saying, ‘You don’t like the weather, just wait five minutes.’ I think the Front Range has a pretty good claim to being where that’s most true,” said Winters, assistant professor in the Department of Atmospheric and Oceanic Sciences (ATOC) at ��ý�Ļ��Ʒ. “We get severe thunderstorms, tornadoes, hail, strong winds. The only phenomenon we don’t get here in Colorado is hurricanes.”

So how does the Front Range’s weather get so blustery—and will it stay that way as the planet’s climate changes?

It’s a topic that McKenzie Larson, a doctoral student in Winters’ lab, is exploring. She’s originally from Florida but earned her bachelor’s and master’s degrees at ��ý�Ļ��Ʒ. In the process, she became taken by the state’s more mercurial weather.

“In Boulder, our proximity to the Flatirons and complex terrain pose quite a challenge for weather forecasts,” Larson said. “We can get a lot of temperature whiplashes.”

She explained that, in the Front Range, severe winds tend to come in two flavors: chinook and bora winds.

Boras usually arrive just after a cold front snaps through Colorado, while chinooks bring warmer winds. (The gusts on March 17 fell into that warmer category). They both tend to peak in the winter months and both occur when winds arriving from the west slam into the Rocky Mountains.

“Those warmer winds come more often from the southwest or the west,” she said. “The boras, along with the associated the cold fronts, often come from the northwest.”

When that happens, those westerly winds feel the squeeze. The moving air is forced between the tops of the mountains and what meteorologists call a “stable layer” of the atmosphere—a layer where the temperature of the atmosphere increases with altitude rather than decreases, which is more common. Winds pick up speed as they pass between the mountain tops and this stable layer and, by the time they near Boulder, are ready to scream downhill.

Previously in CUriosity

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But will living in Colorado always feel like being in the Wizard of Oz?

That’s not clear, Larson said. She noted that as the state warms, that stable layer above the mountains could climb higher in the atmosphere. Without that lid, winds may not feel as much of a squeeze as they pass over the mountains and could slow down.

Larson and Winters took part in a recent study that unearthed the first hints that such a slowdown may already be happening. The research was led by scientists at the U.S. National Science Foundation National Center for Atmospheric Research (NSF NCAR). The group reported that scientists at NCAR recorded one blast of air in Boulder in 1971 moving at a staggering 147 miles per hour. Today, measurements at roughly the same location rarely exceed 100 miles per hour.

Scientists need to do a lot more research before they can say for sure how climate change could shift Colorado’s erratic winds. But those kinds of questions matter for more than just weather buffs, Winters said. Chinook winds moving east were one of the main factors that made the Marshall Fire in 2021 so devastating for Boulder County.

“Even if winds slow down, these events are still going to happen, and they’re going to happen in an environment that will likely have less wintertime snow cover than in the past,” Winters said. “That could lead to more events like the Marshall Fire, especially when we have more people living closer to the mountains.”

March 2025 has been a gusty month for Colorado's Front Range. Meteorologists Andrew Winters and McKenzie Larson break down what makes the region's weather so mercurial.

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Researchers coin ‘thirstwaves’ as new term for prolonged periods of atmospheric thirst

Megan Maneval — Fri, 21 Mar 2025 13:24:27 +0000

Researchers coin ‘thirstwaves’ as new term for prolonged periods of atmospheric thirst Megan Maneval Fri, 03/21/2025 - 07:24

CIRES

Most people have heard of heatwaves: extended periods of abnormally hot weather. But researchers from CIRES and the University of Idaho have coined a new term to describe extended periods of atmospheric thirst. Studying these ”thirstwaves“ can help farmers better manage their water resources and improve crop yields.

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CIRES hosting international meeting of Arctic researchers

Megan Maneval — Thu, 20 Mar 2025 19:20:00 +0000

CIRES hosting international meeting of Arctic researchers Megan Maneval Thu, 03/20/2025 - 13:20

CIRES

A summit underway at ��ý�Ļ��Ʒ through March 28 is bringing an estimated 800 people from more than 40 countries to plan for the future of the Arctic.

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Small bird, big trick: How a hummingbird chick acts like a caterpillar to survive

Yvaine Ye — Mon, 17 Mar 2025 14:53:18 +0000

Small bird, big trick: How a hummingbird chick acts like a caterpillar to survive Yvaine Ye Mon, 03/17/2025 - 08:53

Yvaine Ye

When Jay Falk and Scott Taylor first saw the white-necked Jacobin hummingbird chick in Panama’s dense rainforest, the bird biologists didn’t know what they were looking at.

A white-necked jacobin hummingbird chick. (Credit: Michael Castaño-Díaz)

The day-old bird, smaller than a pinky finger, had brown fuzz all over its body. When Falk and Taylor walked closer to the nest, the chick began twitching and shaking its head—a behavior they had never seen in birds before.

It turns out the hummingbird might fend off predators by mimicking a poisonous caterpillar that lives in the same region. In a new paper published March 17 in Ecology, Taylor, associate professor in the Department of Ecology and Evolutionary Biology at ��ý�Ļ��Ʒ, and his team described this unusual mimicry behavior for the first time in hummingbirds.

“We know so little about what nesting birds do in the tropics,” said Falk, the paper’s first author and postdoctoral fellow in Taylor’s lab. “But if we put more effort into observing the natural world, we might discover these kinds of behavior are very common."

A chance discovery

White-necked jacobin hummingbirds are common in Central and South America. Male birds have shimmering blue and green feathers, while females tend to sport low-key green plumage.

The tropical rainforest is a dangerous place for small birds, said Falk, who’s also a researcher at the Smithsonian Tropical Research Institute. Snakes, monkeys, birds and even insects all prey on them. Prior studies have suggested that bird chicks in the tropics are more likely to be eaten by predators than those in temperate forests.

So how can tiny hummingbird chicks survive? Falk may have stumbled on the answer during a trip to Soberanía National Park in Panama in 2024.

A white-necked jacobin hummingbird was incubating its eggs. (Credit: Michael Castaño-Díaz)

Despite the birds’ frequent visits to Falk’s feeders outside his research station in Panama, Falk had never seen a white-necked jacobin chick or its nest before.

But last March, co-authors Michael Castaño at the Smithsonian Tropical Research Institute and Sebastian Gallan-Giraldo at the University of Antioquia in Colombia discovered a female jacobin hummingbird incubating an egg in its nest, not far from a forest trail. The nest, smaller than Falk’s palm, was made of plant parts to blend in perfectly with the surrounding environment.

Over the following month, the team closely monitored the nest and witnessed a chick hatch from the egg. Unlike most hummingbirds that are born naked, the jacobin chick was covered in long brown feathers, looking nearly identical to the nest material. That’s when the team witnessed the chick’s unusual jerking behavior. Scientists had never reported a similar behavior in any other hummingbird species.

“I started texting a video to people and asking them, ‘What does this look like?’” said Taylor. “And invariably, they said, ‘That looks like a caterpillar.’ It was very exciting.”

On the second day after the egg hatched, the team saw a predatory wasp approach the chick when the mother was away. As the wasp hovered above the nest, the chick started to twitch its body vigorously like it had for the researchers, swinging its head from side to side. A few seconds later, the wasp flew away.

Surviving the tropical rainforest

The jacobin hummingbird chick reminded Falk and Taylor of a paper they came across previously. Another team of researchers reported that a young cinereous mourner, a songbird native to the Amazonian rainforest, might resemble toxic orange caterpillars from the region by having a bright orange coat and waving its head from side to side when disturbed.

Falk and his colleagues looked into other caterpillars in this region of Panama and found that many have similar-looking brown hairs that can give painful stings to predators and even kill them. Some of these caterpillars also shake their heads when they feel threatened, much like the chick.

Scientists refer to this survival strategy of mimicking the defensive signaling of a harmful species as Batesian mimicry. For example, some non-venomous milk snakes have developed a pattern of red, yellow and black coloring similar to that of venomous coral snakes to ward off predators.

“A lot of these really classic examples of Batesian mimicry involve butterflies mimicking other butterflies, or snakes mimicking other snakes. But here, we have a bird potentially mimicking an insect, a vertebrate mimicking an invertebrate,” Taylor said.

While the study described a single observation, the researchers hope to test their theory in the future through experiments like placing artificial chicks with different looks and behaviors in nests to see which are more likely to be attacked by predators. They also hope to encourage birdwatchers and citizen scientists to document more hummingbird nests.

“Our perception of the natural world is very biased by our own thoughts about what could be possible,” Taylor said. “It’s incredible what we can discover, but we really have to think broadly.”

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For the first time, scientists described a hummingbird chick potentially mimicking a poisonous caterpillar to avoid getting eaten.

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The hummingbird chick was covered in long brown feathers. (Credit: Scott Taylor/��ý�Ļ��Ʒ)

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A white-necked jacobin hummingbird chick. (Credit: Scott Taylor/��ý�Ļ��Ʒ)

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