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Why Birds' Feet Don't Freeze

"Rete mirabile" - a wonderful net

Have you ever watched ducks walking around in freezing temperatures and wondered why their feet don't freeze? And how do birds, including this Northern Flicker, sit on metal perches with no problem? Birds' feet have a miraculous adaptation that keeps them from freezing. Rete mirabile - Latin for "wonderful net" - is a fine, netlike pattern of arteries that interweaves warm blood from a bird's heart with the veins carrying cold blood from its feet and legs.

Full Transcript

Transcript: 
BirdNote®
Why Birds' Feet Don’t Freeze

Written by Frances Wood

This is BirdNote!
[Mallards quacking]
Have you ever watched ducks walking around in freezing temperatures and wondered how they keep their feet from freezing? The ducks seem oblivious to the cold, even as they stand on ice-covered lakes and streams. Or perhaps you’ve been concerned that the tiny feet of songbirds will freeze to metal perches.
[Winter song of Pacific Wren]
Unlike our feet, birds’ feet are little more than bone, sinew, and scale, with very few nerves. But it takes more than a lack of nerves to keep their feet from freezing. A miraculous adaptation called rete mirabile is responsible. This fine netlike pattern of arteries that carry warm blood from the bird’s heart is interwoven with the veins carrying cold blood from the feet and legs. This interweaving warms the cold blood in these veins before it reaches the bird’s heart. This system keeps the bird’s legs and feet warm, even without leggings and slippers.
[More song of songbird]
And those little songbirds’ feet?—don’t worry. Birds’ feet lack sweat glands and stay dry. So, there is no danger of them freezing to metal perches.
What was that called again? Rete mirabile.
(Winter to summer, throughout the year, the BirdNote calendar features photos of the birds you hear about on BirdNote. Find it on our website, BirdNote.org.)
###
Call of Mallard and the song of the Winter Wren provided by The Macaulay Library of Natural Sounds at the Cornell Lab of Ornithology, Ithaca, New York. Mallard recorded by A.A. Allen, Winter Wren by G.A. Keller.
Producer: John Kessler
Executive Producer: Chris Peterson
© 2013 Tune In to Nature.org   December 2013   Narrator: Michael Stein

ID#121905reteKPLU  rete-01b
 

 

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