The chickadee in the snowbank: A 'canary in the coal mine' for climate change in the Sierra Nevada mountains

• As we reach the remote research site, I duck under a tarp and open a laptop.
• A chorus of identification numbers are shouted back and forth as fellow behavioral ecologist Vladimir Pravosudov and I program “smart” bird feeders for an upcoming experiment.

• In recent history, intense winters are often followed by drought years here in the Sierra Nevada and in much of the U.S. West.
• Our research shows that a mountain chickadee facing deep snow is, to borrow a cliche, like a canary in a coal mine – its survivability tells us about the challenges ahead.

The extraordinary memory of a chickadee

• Cognition is the processes by which animals acquire, process, store and act on information from their environment.
• Then, they use their specialized spatial memory to retrieve those food caches in the months to come.
• We measure the spatial memory of chickadees using a classic associative learning task but in a very atypical location.
• The setup allows us to measure the spatial memory performance of individual chickadees, because they have to remember which feeder their key enables them to open.

What’s the problem?

• Harpold works to understand variations in climate patterns within forest environments, and one of his field sites lies alongside our chickadee research site.
• The Sierra Nevada and other mountain ranges in western North America have been experiencing more extreme snow years and drought years, amplified by climate change.
• In 2023’s record winter, over 17 feet (5 meters) of snow covered the landscape that our chickadees were using every day.

The cascading harms from too much snow

• And if they do survive the winter, their nesting sites – tree cavities – may be buried under feet of snow in the spring.
• Extreme snow oscillations also affect insects that are critical for feeding chickadee chicks.

• Snow cover is good for overwintering insects in most cases, as it provides an insulating blanket that saves them from dying during those freezing months.
• However, if the snow persists too long into the summer, insects can run out of energy and die before they can emerge, or emerge after chickadees really need them.
• This leads to a decline in chickadee populations in years with worse whiplash – drought followed by high snow on repeat – especially at high elevations.

Lessons for the future

• Our long-term research following these chickadees provides a unique window into the relationships between winter snow, chickadee populations and the biological community around them, such as coniferous forests and insect populations.
• These relationships illustrate that climate change is a more complicated story than just the temperature climb – and that its whiplash and cascading effects can destabilize ecosystems.

Benjamin Sonnenberg receives funding from the National Science Foundation.