Owls Getting Redder as Climate Warms

April 22, 2009 -- Like a living thermometer, a species of owl in Europe is turning a deep shade of red as climate change pushes temperatures ever higher, according to a new study.

Paolo Galeotti of the University of Pavia, in Italy, and a group of researchers gathered observations of the Scops Owl (Otus scops) from 1870 through 2007. A small bird that ranges through much of southern Europe and winters in the Sahel region of Africa, the Scops commonly appears in two colors: gray and rusty red.

The colors represent genetic differences in the birds that appear to correlate to climate. Gray birds survive better in years when the climate is cool and dry, while red birds thrive in warm, wet conditions.

Temperatures in Italy have been climbing steadily, at a rate of 1.1 degree Centigrade every 100 years. During that same period, Scops Owls have reddened significantly, and gray birds have become rarer, the team found.

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There are several reasons why that might be, Galeotti said. For one, red, or 'rufus'-colored birds blend in well in dense forests. Camouflage in Europe's steadily recovering woodlands may explain why they are out-competing their gray counterparts. The emergence of some new, warm-weather parasite that preys on gray owls could also account for the trend.

In the United States, Frederick Gehlbach of Baylor University has seen a similar pattern in Eastern Screech Owls. The feathers of rufus owls are more porous, dissipating body heat, while gray feathers seem to be more stout, and protective against cold.

"What I'm seeing is the rufus phase of Eastern Screech Owl is on the increase," he said. "And with continued global warming, rufus birds will become more and more prevalent."

Gehlbach said it's still too soon to be sure that the color changes in the American and European owls are happening for the same reason. Climate change appears to be the culprit, but he echoed Galeotti's caution, and said that any number of changes in the birds' environments could also be to blame.

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