Ask A Scientist Zoology Archive

name         Mary H.
status       other
age          50s

Question -   Why don't sea gulls feet freeze?
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This is from The Birder's Handbook, CDROM version on Thayer Birding's Birds
of North America CD:

When it is cold, the lack of insulation on the legs makes them a site of
potential heat loss.  To minimize such loss, the arteries and veins in the
legs of many birds lie in contact with each other and function as a
countercurrent heat exchange system to retain heat.  Arterial blood leaves
the bird's core (trunk) at body temperature, while venous blood in the
bird's foot is quite cool.  As the cool blood returns toward the core, heat
moves by conductance from the warm arteries into the cool veins.  Thus,
arterial blood reaching the feet is already cool and venous blood reaching
the core has already been warmed.  In addition, by constricting the blood
vessels in its feet a bird may further decrease heat loss by reducing the
amount of blood flow to its feet at low temperatures.  Thus while the core
temperature of a duck or gull standing on ice may be 104 degrees F, its feet
may be only slightly above freezing.

Copyright © 1988 by Paul R. Ehrlich, David S. Dobkin, and Darryl Wheye.

J. Elliott
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