Air Date: Week of December 16, 2011

These ducks feel no pain as they stand on a frozen pond. Photo: © Mike Hamilton

Birds have adapted to cold weather to keep their legs and feet toasty, even during the coldest of winters. Michael Stein reports how it works.

Transcript

[BIRD NOTE THEME]

GELLERMAN: Baby, it’s cold outside. But birds don’t get nervous when the temperatures drop - they don't get cold feet. Bird Note's Michael Stein tells the tale.

[SOUND OF MALLARDS QUACKING]

STEIN: 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.

[HIGH PITCHED WINTER SONG OF PACIFIC WREN]

STEIN: 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, net-like 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.

[WINTER SONG OF PACIFIC WREN]

STEIN: 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.

[WINTER SONG OF PACIFIC WREN]

STEIN: What was that called again? Rete mirabile.

[WINTER SONG OF PACIFIC WREN]

GELLERMAN: Mirabile dictu! That’s Michael Stein of Bird Note relating something wonderful about birds and cold feet. To see some photos of birds standing up to the cold, make tracks to our website loe.org.

 

Links

Call of Mallard and the song of the Pacific Wren provided by The Macaulay Library of Natural Sounds at the Cornell Lab of Ornithology, Ithaca, New York. Mallard recorded by A.A. Allen, Pacific Wren by G.A. Keller.

BirdNote® Why Birds’ Feet Don’t Freeze was written by Frances Wood