How is it that birds can swim in freezing cold water and expose their feet to sub zero temperatures without suffering from frostbite?

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It’s something that’s always baffled me, birds are everywhere in the winter with their exposed feet perched on branches, in water, or on top of ice, and they rarely seem to be affected by the cold in the same way that human skin is. How do birds not get frostbite?

In: Biology
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Basically birds thermoregulate differently than mammals like humans do. Mammals use hair or fur to keep warm because they can’t change their base metabolic rate easily. Birds usually just change their base metabolic rate to create more heat. Also their feathers are a better insulator than most hair, and they have a different blood circulation system to prevent extremely cold blood from the extremities from going straight back to the heart.

I have not seen this said yet. But birds and other ducks have a counter-current heat exchange system between their arteries and veins in their feet. Basically, the arteries and veins in the legs are closely toward where heat exchange from the artery to the vein can take place. Warm artery blood goes to cold feet and makes it way back to heart. On the way back to the heart heat exchange from the artery warms up the vein blood. That is how they can swim in cold water.