By Matt Nusstein, NYS Parks Naturalist
With colder weather on its way you may be wondering how our wintering birds fight off the frigid air.
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. And of course, bird body feathers are like little down jackets that hold the heat of the body in. But those tiny, thin legs are completely exposed!
To deal with this birds 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.
Birds also 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 is known as countercurrent exchange. 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 has also been speculation that the scales on the feet of the bird are less likely to frostbite than skin is. For instance, we cannot get frostbite on our hair, because our hair is not actually living, much like the scales that cover birds feet.
Sometimes, however, 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 birds like chickadees, and sometimes they will lose a toe or two to frostbite!
(Reprinted with permission from the New York State Naturalist Facebook page.)