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Climate change causes bigger birds, say scientists

In the past 40 years birds have grown progressively bigger, says new research carried out in California, USA. Rae Goodman, a Phd student at San Francisco State University, published her thesis which showed birds' wing spans have grown longer and birds' overall mass has increased over the past 27 to 40 years.

Gretchen LeBuhn, the supervising professor on the thesis, said: "I'm completely surprised. It's one of those moments where you ask, 'what's happening here?' The results are so unexpected."

Data was collected from more than 32,000 specimens dating from 1971 up to 2010 at the Palomarin Field Station, near the southern end of the Point Reyes National Seashore in Marin County, which is 30 miles from San Francisco. Ms Goodman said: "We had the good fortune to find an unexpected result – a gem in research science. But we were then left with the puzzle of figuring out what was going on."

Ms Goodman and her colleagues at Point Reyes Bird Observatory (PRBO) who collected the data, believe the size increases must be due to climate change. She said the birds may be responding to increased plant growth or increased climate variability: "The fingerprint of climate change is showing up in many of our ecosystems. The challenge is to use the long-term data we've been collecting to understand how, where and why these changes are occurring."

Nat Seavy, research director at PRBO, said: "What will happen to our ecosystems as some species get larger and others get smaller? We need long-term monitoring to help us understand the impact of these changes."