Archives of Ask A Scientist!

About "Ask A Scientist!"

On September 17th, 1998 the Ithaca Journal ran its first "Ask A Scientist!" article in which Professor Neil Ashcroft , who was then the director of CCMR, answered the question "What is Jupiter made of?" Since then, we have received over 1,000 questions from students and adults from all over the world. Select questions are answered weekly and published in the Ithaca Journal and on our web site. "Ask A Scientist!" reaches more than 21,000 Central New York residents through the Ithaca Journal and countless others around the world throught the "Ask a Scientist!" web site.

Across disciplines and across the state, from Nobel Prize winning scientist David Lee to notable science education advocate Bill Nye, researchers and scientists have been called on to respond to these questions. For more than seven years, kids - and a few adults - have been submitting their queries to find out the answer to life's everyday questions.

Previous Week's Question Published: 7 April, 2005 Next Week's Question
Birds have several tricks to keep their legs from freezing
Question
Why don't birds' legs get frostbite? Because they are not covered with feathers, they could get frozen, couldn't they?

Question
This is a great question, and every time I watch Chickadees at my feeder, I marvel that they can stay warm at all. How DO they keep their feet from frostbite?

Did you know that a chickadee held in your hand would be smaller than 2 Hershey's Kisses and weigh less too? And like us, and all other animals you can think of with fur, birds must keep their body temperature high and stable in order to survive. Our body temperature is 98.7°F. Most birds keep their body temperature at closer to 104°F, a little warmer than we do.

Also, like us, birds are able to stay this warm by burning the calories contained in their food, seeds, fruit and insects. But unlike us, they are so small they lose their heat quickly. Birds have a number of ways to generate more heat, such as shivering their flight muscles.

But you did not ask how birds keep warm. Of course, bird body feathers are like little down jackets that hold the heat of the body in. But those tiny, thin, toothpick legs of theirs are completely exposed!

Birds actually use several tricks to keep their legs from freezing. For instance, they can stand on one leg and pull the other up under their feathers when one leg starts getting too cold. And if it gets really cold, they can squat on their perches and cover both legs. If you see a bird doing this, he or she very well may be getting uncomfortably cold legs.

Some birds, like gulls and penguins, have a very special trick. Like all other animals, birds send the warm blood of the body into the legs, and so this helps. But unlike most other animals some birds do this in a special way; the blood vessels going into the legs lie right next to the blood vessels leaving the legs. So, as the nice warm blood from the body flows next to the cooler blood leaving the feet, that cooler blood gets heated up before re-entering the body. This prevents more heat from being lost to the cold air then is necessary, which is a key part of not losing cold parts to frostbite.

There are two more things I want to say. The first is that even we scientists don't have all the answers to questions like this. Blood flow and hiding feet cannot be the whole story. Maybe the scales on the feet of the bird are less likely to frostbite than skin is. For instance, we can not get frostbite on our hair, because our hair is not actually living, much like the scales that cover birds feet. Maybe bird feet are so skinny so that there is less flesh in there to freeze!

The last thing is this: sometimes birds toes do get frostbit. Mourning Doves in particular have a hard time dealing with our cold winters. Mourning Doves have not lived in our cold climate as long as tough little birds like chickadees, and sometimes they will lose a toe or two to frostbite! Even nature is not perfect, but it is always being perfected.