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How Birds Stay Warm
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110 years ago on December 25th, ornithologists started a tradition of counting birds.  The Christmas Bird Count, organized by the National Audubon Society, has become the longest-running census of wildlife in the U.S. About 900 people in Connecticut are expected to count birds out in the cold this year. WNPR’s Nancy Cohen is wondering about the birds themselves and how they survive the winter.

I recently watched a Blue Jay perching near the top of a hydrangea bush. It was bitter cold. The wind was blowing, whipping the branches up and down. But the Blue Jay held tight. And I wondered how it managed to stay warm. Ecologist Robert Askins of Connecticut College says feathers provide a kind of adjustable blanket:

“Every feather is a movable part and they can arrange the position of the feathers so the entire body covering is very mobile. They can raise their feathers to trap more  air  and provide more insulation. They can open the feathers like louvers and release heat if it gets too warm so they can  adjust the insulation in a very refined way.”

But what happens to them at night? Askins says birds sleep tucked behind the dense foliage of an evergreen or inside a tree cavity or an abandoned woodpecker hole. Some species like the winter wren and the nuthatch bunker down in groups:

“So you can have large numbers of these birds huddled together inside a cavity and of course that means they have the added heat from the bodies of the other birds. They can survive the winters, even very cold winters very effectively that way.”

Askins says the data collected by volunteers who head out into the cold during the Christmas Bird Count is enormously useful, allowing scientists to follow population changes over decades. This year’s bird count wraps up January 5th.

For WNPR, I'm Nancy Cohen.