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.
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