An online resource based on the award-winning nature guide

Birds’ Feet

When I saw these mallards swimming in a frigid brook yesterday the first thought that came to mind was how cold their feet must be.  Exactly how do birds avoid getting their legs and feet frostbitten?  We’ve all seen birds standing on one foot while the other leg is pulled up under their feathers, where it warms up. This is one way, but not the only way, birds protect their feet from freezing. Birds’ feet are mostly bone and tendons, so, unlike mammals, they have a limited supply of nerves, blood vessels or muscles to freeze.  Their feet are also covered with scales which, like our hair, aren’t living tissue and thus are less susceptible to freezing. Some birds, including waterfowl, gulls and penguins, have what is called countercurrent heat exchange — in their legs, arteries and veins run parallel and in contact with each other. As the warm blood of the arteries enters the legs, the heat is actually transferred to the returning cold blood of the veins. This allows the cooler blood to get heated up before re-entering the body, which prevents a lot of heat from being lost to the cold air.  Under very warm conditions, the countercurrent heat exchange mechanism can be bypassed.

3 responses

  1. Okay, but how do you explain the flock of female mallards I saw last week, all of them wearing Uggs?

    January 12, 2012 at 6:35 pm

    • I’d say they must have just flown in from Australia…

      January 12, 2012 at 7:15 pm

  2. I think of this marvelous technique whenever it snows. Our ducks waddle bravely out into the cold, while our chickens wait in the barn for us to ferry them. Poor tropical birds . . .

    January 13, 2012 at 1:55 am

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