Survival Of The Fattest: Climate Change Makes Upland Birds Evolve?

Could climate change be turning the upland bird hunter's traditional "handful of feathers" into an armful? Maybe, according to one recent California-based study.

From this story in The Bay Citizen:

Scientists have discovered an unexpected consequence of climate change in the Bay Area: bigger songbirds. The researchers found that the weight and wingspan of thousands of small birds--including finches, robins, swallows and hummingbirds--increased a small amount almost every year during the past three decades, according to a study published this month in the journal Global Change Biology.

_The discovery contrasts with findings from another region in the country, highlighting the haphazard and sometimes unpredictable consequences of global warming."We were very much surprised," said Point Reyes Bird Observatory research director Nat Seavy, one of the scientists who analyzed 40 years of bird measurements from Point Reyes National Seashore and 27 years of data from Milpitas. The research concluded that the 73 bird species studied increased in size by 0.02 percent to 0.1 percent annually, according to Seavy. The scientists detected the growth in both migratory birds and birds that live in California their whole lives.
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The California study contradicts findings from a similar study in Pennslyvania that found songbirds there were actually decreasing in size.

"One of the things that makes climate change difficult is that the way it changes ecosystems is going to be very different throughout the world," Seavy said. "It's going to manifest itself in different ways." Ecologists generally expect animals to become thinner and smaller as temperatures rise. According to Bergmann's rule, a theory developed in the 19th century, warm-blooded animals in cold climates will be larger than their cousins in warmer zones, because bigger animals are better at retaining body heat.

Seavy and his team expected the birds would decrease in size in order to stay cool as temperatures around the globe increased. But the counterintuitive findings suggest that global warming is affecting animals' body size in a different way. While climate change brings warmer overall temperatures, it also increases the frequency of storms, droughts, wildfires and other conditions that sometimes force animals to endure extended food shortages.

The researchers behind the California study believe the results show birds could be evolving larger in order to increase fat and muscle reserves that help them survive extended periods of bad weather, and while the study doesn't explicitly mention gamebirds, it would stand to reason quail, grouse and pheasants might respond in a similar fashion.

What do you think? Think climate change would grow or shrink your favorite gamebird? Will the bobwhite of 2112 be the size of a grouse, or the size of a mouse?