Northern Parula. Photo: Tara Tanaka/Audubon Photography Awards

This audio story is brought to you by BirdNote, a partner of The National Audubon Society. BirdNote episodes air daily on public radio stations nationwide.

Transcript:

This is BirdNote.



During a rainstorm, you’re more likely to see birds perched and hunkered down than flying around. Most birds are mostly waterproof. Their feathers, combined with oil from preen glands, keep them pretty watertight. So why do birds avoid flying during rainstorms? It’s not just about getting wet. It may have more to do with the air than with the water.

Storms alter the medium in which flight takes place: the air itself. Rainstorms tend to occur when atmospheric pressure is low. Air in a low-pressure system is less dense. But it’s dense air that gives birds the aerodynamic lift they need to take wing. Falling rain and high humidity also add lots of water molecules to the air. That water takes up space in the air, making it even less dense.

So rather than fly, many birds perch and conserve energy during a storm. They sit it out under the cover of a tree. Or perch on a fence wire facing into the wind, reducing their air resistance — and limiting the loss of precious body heat. But when the storm passes, birds once again take to the skies.

For BirdNote, I’m Mary McCann.

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Credits:

Written by Bob Sundstrom

Producer: John Kessler

Managing Producer: Jason Saul

Associate Producer: Ellen Blackstone

Bird sounds provided by The Macaulay Library of Natural Sounds at the Cornell Lab of Ornithology, Ithaca, New York. #16 Thunderstorm Nature Sound Essentials and #47 Deciduous Forest Morning recorded by Gordon Hempton.

BirdNote’s theme music was composed and played by Nancy Rumbel and John Kessler.

© 2017 Tune In to Nature.org

July/August 2017 ID# flight-13-2017-07-14 flight-13