Climate Change Affecting Body Size of Birds- Mickey Sutton

A study done by San Francisco State scientists has found that birds' wings have grown longer and birds are increasing in mass over the last 27 to 40 years. What exactly is making these birds larger? The researchers think it might have something to do with climate changes on Earth's surfaces. However, this finding seems to contradict modern thought on climate change's effect on body sizes in animals. A well-known ecological rule, called Bergmann's Rule, "states that animals tend to be larger at higher latitudes. One reason for this rule might be that larger animals conserve body heat better, allowing them to thrive in the generally colder climate of higher latitudes." Using this rule, scientists have come to believe that a rise in earth's temperature over the past 100 years would result in the reduction of size over time of animal species. However, Rae Goodman and her colleagues at SF State are thinking that the connection between temperature and body size might not be so direct. Their study showed that within the data collected from over 35,000 birds in two "banding stations" in California, that their size has actually increased in the past 40 years in both wing span and body mass. While they note that an increase in body size may be due to a change in diet and food storage in the birds, after testing and discarding numerous counter explanations, Goodman and her band of researchers are confident that climate change is behind this never before seen growth in the birds. They say that "the birds may be responding to climate-related changes in plant growth or increased climate variability in central California." These findings provide the scientific community a small glimpse at the effects of climate change over a variety of species due to the changes documented over such a short period of time. However, trying to understand her findings in an optimistic manner, Goddman said, "But in some ways, it gave me a little more hope that these birds are able to respond -- hopefully in time -- to changes in climate."
After reading about this study, I was immediately reminded of Jeff Amorello's previous post about global climate affecting species size in a negative way, that is, that they are becoming smaller. Whether or not one believes in the accuracy or validity is irrelevant to the actual study at hand. This article stood out at me for various reasons. Namely, it shows that scientific research can ultimately develop two totally contrasting ideas about why specific occurrences are happening. Throughout the year, we have conversed about the validity an reliability on certain scientific findings. We have asked the questions, "Is the source credible?" or "Are there any motives or biases that might not be seen that a driving these scientists to certain conclusions?"
In the case of this study, done by Goodman and her colleagues, I find it very intriguing that the first study done on climate change's effects on North American birds, yields a conclusion found to be opposite of other studies done in other areas on the globe. Were there perhaps any motives behind the agency to conclude at these results? Or are the effects on species in North America different than those found in studies in Asia and Europe? No matter the varying results, it is clear that scientific findings still provide us with a wide spectrum of debate. Fortunately, scientific thought does not stop after one attempt, and only if the researchers remain diligent in their studies and also their global correspondence, can the truth be found.




Sources: 1. http://www.sciencedaily.com/releases/2011/10/111031154127.htm

2. Rae E. Goodman, Gretchen Lebuhn, Nathaniel E. Seavy, Thomas Gardali, Jill D. Bluso-Demers. Avian body size changes and climate change: warming or increasing variability? Global Change Biology, 2011