It isn’t always easy to remember how much we humans rely on technology for every facet of our modern American lives. We can easily take hot running water for granted and it is often that we forget how lucky we are to have fresh food at our disposal. Even more wondrous is the fact that we have built homes that are kept warm even when outdoor temperatures plummet.
Last weekend, while visiting my brother-in-law, we took advantage of a temporary break in the cold weather by sitting outside on his deck and enjoying cigars with some fine Scotch. The non-stop conversation flitted from one topic to another, like a hummingbird visiting different flowers in a garden, but one inescapable theme was the cold of winter. It makes sense when you think of it because this winter has been a cold one, but even a moment of 50-degree temperatures didn’t allow us to forget the recent below-zero nights that we’ve had.
At some point in our time on the deck one of us brought up the notion of being a soldier stuck in the cold. Valley Forge came up, as did the Battle of the Bulge, and then we somehow shifted our attention to the birds that live around us. How do blue jays manage to survive the cold? Even more astounding is the idea that there are birds that live their lives in water even when the bitter winter winds blow. How does that work?
As it happened, I knew the answer to that question. It is something that I learned when I was a student at UMass Amherst in the late 1980s and I have never forgotten it. It all has to do with feathers and blood flow, but I think I need to slow down here and break out a few details to make this more clear.
First off, ducks and geese and other water birds have feathers that are rendered waterproof by secretions of the uropygial gland, which is a structure located at the top of the base of the tail. During their preening sessions, ducks can often be seen nibbling at the feathers in this region, but what they are really doing is activating an oil dispenser that produces chemicals that condition feathers. Constant and fastidious attention to their feathers ensures that the birds are surrounded by a waterproof layer of warmth that prevents cold water from ever touching their bodies.
But then there is the question of the birds’ legs and feet. Without any feathers at all, how does this one area of bare skin manage to come in contact with frigid water without killing the birds? The answer here is a marvel of evolution; a heat exchange system that allows the ducks to regulate the temperature of their blood to protect them from hypothermia.
The heart is located in the core of the body where temperatures are warmest. Warm blood goes to the lungs to pick up oxygen and then back to the heart for distribution throughout the body. A network of arteries carries this oxygen-rich blood to the head, internal organs and the legs. As the arteries move down through the legs, they create a close-contact network with veins that are bringing cold blood back from the feet and here is where the magic of heat exchange does its job.
As the warm blood from the heart heads toward the feet, the cold blood heading back toward the body chills it. Simultaneously, the cold blood heading back to the body is warmed so that there is no shock to the bird’s core body temperature. This heat exchange is so efficient that ducks and geese can keep their feet healthy with oxygen and nutrients while minimizing heat loss at the same time. These birds can spend hour after hour in water that would kill a human being in a matter of minutes. Even more amazing are the ducks that dive underwater to find their food every day during the winter. Science may explain it, but it is still incredible that it works.
So the next time you find yourself all snoodled up on a cold winter’s day, looking out the window and wondering how the little birds survive the cold, allow your mind to wander to the east where many species of ducks and geese have spent every winter day floating around in the coastal waters of the Atlantic Ocean. Just thinking about it makes me want to take a trip to the coast where I can find a restaurant that serves clam chowder and has a view of the water. Perhaps I’ll see you there, too.
Bill Danielson has been a professional writer and nature photographer for 24 years. He has worked for the National Park Service, the U.S. Forest Service, the Nature Conservancy and the Massachusetts State Parks and he currently teaches high school biology and physics. For more in formation visit his website at www.speakingofnature.com, or head over to Speaking of Nature on Facebook.