by Dan Gibson
The birds are getting bigger, and I suspect they're probably going to be pissed about the spicy chicken sandwich I like to eat for lunch sometimes.
Birds are getting bigger in central California, and that was a big surprise for Rae Goodman and her colleagues. Goodman uncovered the trend while working as a graduate student for Associate Professor of Biology Gretchen LeBuhn, analyzing data from thousands of birds caught and released each year at two sites near San Francisco Bay and Point Reyes National Seashore.
The SF State scientists found that birds' wings have grown longer and birds are increasing in mass over the last 27 to 40 years.
What's making the birds bigger? The researchers think that the trend is due to climate change, but their findings put a twist in the usual thinking about climate change and body size. 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.
Under this reasoning, some scientists have predicted that animals would get smaller as Earth has warmed up over the past 100 years. But the study, published in the journal Global Change Biology, suggests that the connection may not be so simple.