My apologies to the 50+/- NC readers who responded with great creativity to the latest Mystery Photo! The photographer and I had a miscommunication, and I misdirected readers about the actual mystery you were to solve! I thought the photographer had observed a goose making the two parallel lines in the ice with their feet (nails) as they landed. However, these two lines are actually just cracks in the ice, as many readers guessed (Susan Cloutier was the first to correctly identify them). While Canada Geese do use their feet as well as their wings as brakes to slow themselves down before they land and they do have a hind toe which conceivably could scratch the ice, the landing imprints of the geese (and what I should have asked readers to identify) are actually in the upper half of the photo (see red circle) where the snow has been plowed aside, revealing the darker ice underneath. The presence of a considerable amount of goose droppings confirms the identity of the birds landing on the ice.
Observers often ask how Canada Geese or other waterfowl can stand for long periods of time on frozen lakes and ponds.The legs and feet of waterfowl play an important part in maintaining their body temperature. In the summer, their large, flat feet cool their body by releasing a good deal of heat. In winter, the heat exchange system (counter-current circulation) in a bird’s legs prevents a great deal of body heat loss due to the fact that the warm arterial blood going into the bird’s feet is cooled by the colder blood traveling back to the body in adjacent veins. Constricted blood vessels in their legs further conserves heat. (Photo by Mike Hebb)
Naturally Curious is supported by donations. If you choose to contribute, you may go to http://www.naturallycuriouswithmaryholland.wordpress.com and click on the yellow “donate” button.