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August 17, 2009

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Smaller birds tied to global warming

SOME species of Australian birds are shrinking and the trend will likely continue because of global warming, a scientist said yesterday.

Janet Gardner, an Australian National University biologist, led a team of scientists who measured museum specimens to plot the decline in size of eight species of Australian birds over the past century.

The research, published last week in the British journal Proceedings of the Royal Society B: Biological Sciences, found the birds in Australia's southeast had become 2 to 4 percent smaller.

Over the same century, Australia's average daily temperature rose 0.7 degrees Celsius, with the sharpest increase since the 1950s.

The research concluded the birds were likely downsizing because smaller bodies shed heat faster than larger ones.

"It's the broad scale, consistent pattern that we're seeing that makes us conclude that global warming is likely to be causing the changes," Gardner said.

She said she suspected other Australian birds beyond the species studied were also shrinking and the trend will accelerate in the future as a result of global climate change.

"Simply because the predictions are that the warming is going to increase over the coming decades, so you might expect this (shrinking) response to increase as well," Gardner said.

Michael Kearney, a Melbourne University zoologist who is independent of the research, described its findings as both alarming and providing some hope.

"This study strongly suggests that rising air temperatures in recent history have been stressful enough to prevent the larger individuals of a species from surviving and breeding," Kearney said.

"That we are seeing a potential evolutionary shift to smaller, and thus more heat-tolerant individuals is an alarming reminder of the consequences of global warming," he added. "But it also gives us some hope that evolutionary change will provide a temporary buffer in some cases."

Other studies have found similar trends of shrinking birds and mammals in Britain, Denmark, Israel and New Zealand.


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