No heat is escaped from the cool fins.
Human the toes are prickly in the cold, but the birds survive all winter with their bare feet.
Their legs are dry sticks: almost nothing but bone, leather and tendons. The cold-sensitive soft tissue, muscles that move the legs, and most nerves are housed in feathers.
In addition, the fatty acids in the cell membranes of birds ’feet are more fluid than ours. So the duck can stand on the ice and the fins work, but the avant-garde needs slippers to prevent his feet from getting wet even before going into the water.
The bird is able to direct warm blood to its feet as needed.
If a bird threatens to freeze from its fins, it will be able to direct warm arterial blood to its legs. The nervous system opens blood vessels.
On the way to the lower extremities, the blood cools down, and the temperature on the toes is just a little on the plus side. Because the fins are cool, they do not escape heat.
The cooled blood, on the other hand, has time to warm up on its way back to the heart as it flows along deep veins. Blood travels to the veins under the skin, for example during a flight, when the bird has to remove too much heat from its body.
Duck barely tramples or stands on the ice for fun, though can even rest on icy ground.
Then it lies down and pulls its foot into the feather of the feather. And it’s not about any lightweight jacket, but a thermal suit that is plush with the bird’s mass.
Source: Esa Hohtola, Professor Emeritus of Animal Physiology, University of Oulu
Published in Science Nature 1/2021
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