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.
The first of hopefully many nature mysteries was interpreted and documented with photographs taken by the observers. A brief explanation of this story in the snow accompanies the photographs. Mystery photos are welcome–please check the submission guidelines (see link in menu at the top of my blog) prior to sending your photograph/questions.
This story took place in Sharon, Vermont, where Francie and Ron Schmidt commonly observe a pair of mallards on or near their pond. One morning this winter they spotted a red-tailed hawk perched in a tree, feeding on something. Being naturally curious, they decided to buckle on their snowshoes and see if they could find any signs of the kill in order to determine exactly what the hawk was dining on. The pictures they took tell the tale of the misfortune of one mallard drake.
After killing the mallard, the hawk proceeded to pluck many of its feathers while standing on the surface of the snow. It ate some of the duck’s organs and then took off for the tree with the front end of the duck in its talons, leaving the hind portion behind on the snow along with all the plucked feathers. The repeated indentations in the snow made by the hawk’s feet and wings indicate that the hawk had a bit of a struggle trying to take off with such a heavy load. However, it succeeded in reaching the tree, where they had initially seen it. Having documented this entire story with their camera, the Schmidts decided to return home. On their way back, they happened to notice a female mallard, most likely the other member of the mallard pair, hiding in a nearby shrub. Later, they photographed the hawk off the corner of their deck when he returned to the kill site