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Name: Mary H
Status: other
Age: 50s
Location: N/A
Country: N/A
Date: 2002042


Question:
Why don't sea gulls feet freeze?


Replies:
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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