All actions have intended and unintended consequences. My intended consequences of writing this blog are to share knowledge and a love for the natural world through images and writing. The unintended consequences of writing this blog are less benign. As I type into my computer, I am using electricity to power the light in my room, the heater on my wall, and the computer on my desk. In Wyoming, our electricity is provided primarily by burning coal, with a limited amount of renewable energy mixed in. By creating this blog entry, I am contributing to carbon emissions produced by burning fossil fuels, which are contributing to global weirding.
In the 1600’s through the 1800’s, writing came at a different cost. Writers used paper, quill, and ink to record their thoughts. Quills were made from many different types of feathers, and the quill of choice was made from trumpeter swan flight feathers. As demand increased, trumpeter swans were hunted and pushed to the brink of extinction. In 1918, the Migratory Bird Treaty Act was passed by Congress, which protected swans from hunting. Even with this protection, there were only 69 trumpeter swans left in the lower 48 states by 1936. Since then, reintroduction programs have been widely successful in reestablishing the trumpeter swan throughout its historic range.
Today, the trumpeter swan is in the conservation category of “least concern,” which is a status worth celebrating. Trumpeter swans have inherent value to the ecosystem as a whole, and they are also beautiful and fascinating creatures.
The trumpeter swan is the largest waterfowl native to North America, standing up to four feet tall and weighing 20-30 pounds. In flight, trumpeter swans can reach speeds of 40 to 80 miles per hour.
The life span of trumpeter swans is between 20 and 30 years. At age four, mating bonds form. Once bonds form, the mating pair is rarely seen apart. Males that have been separated from their mates have been known to live a solitary life.
When trumpeter swans hatch, the plumage is grey. These young swans, called cygnets, slowly molt into white feathers. Between 110 and 120 days after hatching, cygnets begin to fly, and by the end of the year, the young swans have entirely white plumage.
Occasionally, swans can be seen with rust-colored heads. This coloration is not a natural color, and is actually caused by their feeding habits. Swans are often seen feeding in rivers and lakes with tails and feet in the air. With their long necks and large bodies, the swans feed on aquatic vegetation and invertebrates. If the water that swans feed in has a high iron content, the feathers on the swan’s head may be stained a rust color.
Of all of the cool facts about swans (and there are a lot!), there is one fact that trumps them all. Every year, swans lose their ability to fly.
In the warmest months of the year, swans molt all of their feathers. During this period of up to two months, trumpeter swans are flightless. As you can imagine, swans are incredibly vulnerable to predation in this period of their lives.
Swans are commonly seen in the Greater Yellowstone Ecosystem throughout the fall and winter months. Trumpeter swans are migratory, and the GYE is the primary winter habitat for migrants from Canada.
Swans have incredible winter adaptations that allow them to survive the winter. One of their adaptations, countercurrent heat exchange, is related to their circulatory system. Ordinarily, veins and arteries (the vessels that transport blood in the circulatory system) are isolated. In trumpeter swans (and other waterfowl), the arteries and veins are wrapped around each other. This allows for heat exchange between blood that is leaving the core of the body and blood that is returning from the extremities. Warm blood leaving the core of the body is pre-cooled as it loses heat to the blood returning from the extremities. Likewise, the blood leaving the extremities is pre-warmed as it re-enters the core. In this way, the foot of the swan is maintained at a lower temperature than the body, which allows for a smaller temperature gradient between the foot and the cold snow. Remember the lesson on thermodynamics? As temperature gradients are reduced, the rate of heat exchange slows down.
If you weren’t bogged down by the physiology and thermodynamics crash course that I just put you through, you might be wondering why the swan’s feet don’t freeze. Swans have two adaptations that prevent frostbite- one adaptation is behavioral and the other is physiological. In the winter, swans will frequently be seen standing on one leg, with the other leg tucked under their feathers. The feathers act as insulation, allowing the foot to warm up. In addition to this behavioral adaptation, warm blood is periodically pulsed through the foot in order to prevent tissue damage due to the cold.
Throughout the winter, I have seen swans on Flat Creek in the National Elk Refuge just north of Jackson. On Sunday, I counted five pairs of swans on a quarter mile stretch of open water. As I watched, swans fed on aquatic plants in the river, preened their feathers, and rested in the snow on the edge of the water.
Life in the Cold by Peter J. Marchand