February 7, 2017 by Kelly April Tyrrell
The polar vortex of 2013 and 2014 brought the coldest winter many parts of the Midwest had experienced in decades. In Dane County, Wisconsin, it was the coldest it had been in 35 years.
By coincidence, that same winter, University of Wisconsin–Madison graduate student Christopher Latimer was gathering data in fragments of forests and woodlots throughout the county. He wanted to know whether these forest "islands" created their own unique climates—microclimates—and what that could mean for overwintering birds like the black-capped chickadee.
In a recent study in the journal Ecography, Latimer and his co-author and advisor, UW–Madison forest and wildlife ecology Professor Ben Zuckerberg, show that these forest refuges may mean the difference between life and death for chickadees and their overwintering songbird kin.
"All our predictions about climate change, from shifting temperatures to altered precipitation, play out over small-scale differences in microclimate, and they can be just as big as global climate," Zuckerberg says.
For example, Latimer and Zuckerberg found the microclimate variability was so high within the 30-mile study area—which they call the "fragmentation gradient" in recognition of the mosaic nature of wooded areas in Dane County—that a bird living in one part of the study area might experience a climate similar to Chicago while another might experience conditions more like those found in Minneapolis–Saint Paul, 400 miles to the northwest.
Overall, they found that forests at slightly higher elevations, with more trees, and those closer to urban centers, provide warmer conditions for birds trying to survive frigid winters in southern Wisconsin. This is important, Latimer and Zuckerberg say, because chickadees must double the amount of energy they expend to keep warm when temperatures dip below minus 18 degrees Celsius or about zero degrees Fahrenheit.