March 19, 2019

If you keep your eyes on the skies these days you are likely to see all sorts of birds, despite the up-and-down weather.  Geese, sandhill cranes, robins, and, most interesting to me right now, swans are on the move.  Three swan species can be found in Wisconsin - trumpeter, tundra and the non-native mute swan.  All have white plumage as adults and appear similar from a distance although the trumpeter and tundra swans are migratory species whereas mute swans tend to remain all year.

The trumpeter is a large swan (about 4 feet long with a wingspan of about 7 feet) that once nested in all but the northeastern forested regions of Wisconsin.  Hunting and trapping completely killed off the state's population in the early 1900s, and it was believed that the species had become extinct elsewhere as well.

Fortunately, a small, nonmigratory population survived in remote mountain valleys of the western United States, and in 1935, the  government established a refuge in Montana to protect the remaining birds. With a safe habitat at the refuge and in Yellowstone National Park, the trumpeter swans in Montana, Idaho and Wyoming increased to 640 birds by the late 1950s.  Some of these birds were moved to other areas with good swan habitat, and formed the core of the Midwest's restoration effort in the late 1960s with so much success that the trumpeter was removed from the Wisconsin endangered species list in 2009.  In 2012, Wisconsin biologists counted 214 nesting pairs and an aerial survey last year revealed 4,695 of the birds across the state.

Wisconsin’s trumpeter swans mate for life and may live for 20 years or more.  They form pair bonds on their wintering grounds (somewhere to the south) and migrate north in the spring to nest, sometimes arriving on the breeding grounds before the ice melts.  Large, shallow wetlands, 1-3 feet deep, with a mix of vegetation and open water offer ideal nesting habitat as these provide the swans with underwater food like sago pondweed and milfoil, as well as arrowheads, reeds, bulrushes, sedges, and wild rice.

Nest building begins in mid-April, often on top of a muskrat or beaver lodge, or just on a pile of sedges and cattail tubers pulled into a mound. The female (a pen) lays up to nine large eggs, one every other day, and then incubates them for about four weeks.  The hatchlings (cygnets) weigh only about 7 ounces but after a day or two, they take to the water and start feeding on plants and invertebrates. They grow quickly and are fully feathered by 9-10 weeks, although they can't fly until they are about 15 weeks old. By this time they weigh about 20 pounds.  In late September, the cygnets try out their wings with short flights but stay with their parents through their first winter, migrating back north to the breeding area in the spring.  Shortly afterwards, they are driven off by their parents but stick together until they're about two years old.   At that time, they seek mates and begin their adult life.

The tundra swan is the other native white swan in North America and is often confused with the less common trumpeter although slightly smaller.  A more notable difference between the two is the distinct yellow spot in front of the eye found on about 80 percent of tundra swans.  Still, the best way to distinguish between the two species is by their calls, as the trumpeter call sounds deep and (what else?) trumpet-like while the tundra swan has a high-pitched, quavering call.

Tundra swans were called whistling swans until recently because of the sound made by the powerful beating of their wings in flight.  These swans breed and nest in the tundra and in sheltered marshes on the Alaskan and Canadian coast near the Arctic Circle. They pass through Wisconsin on their way north in early March through late May, often stopping in small flocks to rest and feed before continuing on their journey to their nesting grounds.  In Wisconsin, tundra swans eat mostly wild celery and arrowhead tubers. They use their long necks to reach roots which they knock loose from the bottom of shallow water with their large feet.  On their wintering sites along the east coast, they will also eat small shellfish. In the fall, migration begins again and they head south, traveling through Wisconsin in large flocks to overwinter in flocks on shallow ponds, lakes and estuaries near the Chesapeake Bay and in the marshes of Virginia and North Carolina.

Mute swans are native to much of Eurasia and were introduced to America by European immigrants.  Close to a trumpeter in size, the mute swan is easily distinguished from other swans by its orange bill and prominent black fleshy knob extending from the base of the bill to the forehead.  The mute swan is less vocal than the noisy trumpeter but makes a variety of grunting, hoarse whistling, and snorting noises, especially in communicating with its cygnets, and usually hisses at competitors or intruders trying to enter its territory. The most familiar sound associated with the mute swan is the vibrant throbbing of the wings in flight which is unique to the species, and can be heard from quite a distance. 

 It is often kept in captivity outside its natural range, as a decoration for parks and ponds, and escapes have happened. The descendants of such birds have become naturalized in the eastern United States and the Great Lakes and have increased greatly in number, to the extent that it is considered an invasive species because of the damage its numbers cause.  In 2005, the United States Department of the Interior officially declared them a non-native, unprotected species.  In Wisconsin they are not hunted, but instead are managed to control numbers from increasing further. 

Works of classical literature referenced the myth that otherwise mute swans sing beautifully at the moment of their death.  This idea gave birth to the phrase “swan song”, and because of their lifelong, monogamous pairing, swans are also often a symbol of never ending love.  One of the most famous stories in children’s literature is “The Ugly Duckling” by Hans Christian Andersen, a  story about a cygnet who grows into a beautiful and graceful swan.   They have long been intriguing birds...