The Swans of Nebraska

Crane Trust Nature & Visitor Center

Trumpeter swans. (Paul A. Johnsgard)

By Paul A. Johnsgard

Because of their immaculate white plumage and their strong pair and family bonds, swans have also long served as icons of beauty, devotion and longevity in the myths and folklore of many cultures. Our personal interests in and perceptions of wild swans are often formed in childhood, by reading such classics as Hans Christian Anderson’s stories of “The Ugly Duckling” and “The Wild Swans,” E. B. White’s “The Trumpet of the Swan” or perhaps upon seeing a performance of Tchaikovsky’s “Swan Lake” ballet.

Many of the most admired human traits, such as permanent pair-bonding, extended biparental care and family cohesion, are biological facts in swans, but the sadly romantic idea of a dying swan uttering a final “swan song” is only folklore. Yet, a famous American biologist, D. G. Elliott, reported in 1898 that once, after he had shot and wounded a whistling swan in flight, it began a long glide while uttering a series of “plaintive and musical” notes that “sounded at times like the soft running of the notes of an octave” as it gradually drifted downward. Nowadays such unusual behavior would probably be interpreted as only an instinctive distress call, but might have provided an early factual basis for this commonly used expression.

Most Americans are probably personally familiar with the regal-looking mute swan of Europe, which has long been imported to American parks and zoos. Mute swans have also long been used by wealthy landowners to decorate private ponds and help control the growth of unwanted aquatic plants. When mute swans escaped from Long Island estates during hurricanes in the late 1930s, many became feral, and their offspring have since expanded over much of the Atlantic Coast, from New Hampshire south to the Carolinas. Following introductions dating back to 1919, mute swans have also spread out from the eastern shoreline of Lake Michigan, occupying much of the Great Lakes region from Wisconsin to New York, and are now considered an invasive species in several states. A few seemingly wild mute swans have been seen recently in Nebraska, but the evidence as to their origins is still too murky to add them to the official list of Nebraska birds.

Two other swans of comparable beauty but unquestionably wild origins can be seen in Nebraska. Unlike the virtually silent mute swan, both of our native American swans have loud, clarion voices that were the historic basis for their English names, whistling swan and trumpeter swan. The smaller (up to 20 pounds) whistling swan, now called the tundra swan, has a musical, more soprano-like, voice, while the trumpeter’s is louder and more baritone-like. During the 1980s, the English name tundra swan officially replaced whistling swan, to describe its high-arctic breeding habitat and to include within the same species its close Eurasian relative, the Bewick’s swan.

The trumpeter swan is a substantially larger species, with adults sometimes reaching 30 pounds, making it the heaviest of American birds. It too has a very close and slightly smaller Eurasian relative, the whooper swan, but so far these have been considered biologically distinct species. All four of these swans have loud, clarion voices and often use them in long-distance communication and territorial interactions.

These vociferous swans are also notable among waterfowl in having windpipes (tracheae) that penetrate the bony sternum and form a long internal loop within it. Just before the windpipe enters the lungs, it enters a unique bony sound box (the syrinx) with paired vibratory (tympanic) membranes that are set into motion when the lungs expel air through their paired bronchi. Varied tensions on the syringeal membranes influence the rate of their vibrations. The vibration rate sets the basic frequency of the resulting sounds, which because of subvibrations also produce overtones (harmonics) that enrich them. The windpipe then modulates and amplifies particular sound frequencies, depending in part on its volume and length. These remarkable adaptations in trumpeter and tundra swans allow for a great range of individual vocal variations and a high degree of harmonic development, making every individual swan’s voice unique and probably easily recognizable by others. Very similar structural adaptations are present in whooping and sandhill cranes and produce similarly loud and individually unique vocalizations.

As high-arctic nesters, tundra swans appear in Nebraska only during spring and fall migrations. During fall migration, those swans breeding in central Canada fly south to North Dakota, veering toward the east as they approach South Dakota. The swans then follow a southeastern route roughly paralleling the Minnesota River valley and from there continue eastward to wintering areas that extend from Chesapeake Bay south to the Carolinas.

This diagonal migration route means that only in northeastern Nebraska is one likely to encounter tundra swans, while they pass southward during November–December and return in March–April. However, in North Dakota and eastern South Dakota tundra swans are sufficiently common that so-called “sport” hunting is permitted. At least 4,000 tundra swans of the eastern North American population are legally killed annually in the Dakotas, North Carolina and Virginia. Several thousand more are killed by poachers, or are wounded but never retrieved, the total probably approaching 10,000 birds annually.

An incubating tundra swan. (Paul A. Johnsgard)

Swans from the population breeding in western Canada and Alaska take a different fall migration route, which passes from Saskatchewan and eastern Alberta southwest through Montana, Utah and Nevada, and then on to California wintering grounds. Like the eastern flock, the western North American tundra swan population probably numbers at least 100,000 birds, and it can be legally hunted in states such as Montana, Utah and Nevada. Hunting in those states, plus subsistence hunting by Natives in Alaska, probably results in the deaths of at least 10,000 swans annually, or about 10 percent of the total western population.

Luckily, America’s largest swan, the trumpeter, is fully protected. It was on the list of federally endangered species for many years and was not removed from that list until it became apparent that a large and previously unstudied population of swans in southern Alaska were actually trumpeter swans rather than tundra swans. Additionally, since the 1960s great efforts have been made to relocate trumpeter swans from surviving populations in the Rocky Mountains region to historical breeding areas of the northern Great Plains, substantially increasing the species’ total population, which by 2012 numbered over 46,000 birds.

Nebraska’s historic breeding trumpeter swans were extirpated by 1900 but were later reestablished during the 1960s as a result of releases of cygnets at Lacreek National Wildlife Refuge, S.D. Restoration efforts there, at the northern edge of the Sandhills, were so successful that by 1987 the population had reached nearly 300 individuals. Expansion southward into the Nebraska Sandhills followed, so that by 1999 there were nearly 600 records for the Nebraska Sandhills, with Cherry and Garden counties accounting for about 70 percent of the total, as well as 160 nesting records. Nesting now occurs in many Sandhills lakes and large, shallow marshes. Additionally, some spring-fed streams of the Sandhills, such as the North Loup River and Blue Creek, usually remain unfrozen all winter, eliminating the need for long seasonal migrations. The current Nebraska breeding population probably numbers in the several hundreds.

Trumpeter swans mate permanently, and each pair returns to its nesting area in spring as soon as the weather allows. Nesting marshes in Nebraska are typically large, shallow and well vegetated, with abundant shoreline plants and submerged aquatic vegetation. Marshes having muskrat present are favored, as their “houses” provide a convenient nest substrate, protected from most wave action. Nesting territories average more than 30 acres and sometimes exceed 100 acres. They are vigorously defended, the adults even excluding their own offspring of previous years. The male performs most territorial defense, but after territorial disputes the female participates in “triumph ceremonies” that are marked by loud mutual calling and wing waving. She also helps defend the nest site when needed.

Both sexes help construct the often bulky nest, which may simply be the flattened top of a muskrat house or consist of piled-up reeds and bent-down emergent vegetation that provide an elevated platform. Nesting behavior in the Sandhills has been seen as early as April 28. The eggs (typically four to six) are then laid at two-day intervals, with incubation starting only after the clutch is complete. The female performs most incubation over the 32–37-day period to hatching, while the male patrols the territory.

Trumpeter swans with young. (Paul A. Johnsgard)

Hatching in Nebraska is likely to occur during late May or early June. The cygnets hatch within a few hours of each other and are led from the nest within 24 hours of hatching. The cygnets’ fledging period to initial flight is approximately 100 days, which means that the brood’s first flights might not occur until September. The cygnets remain with their parents for at least their first year of life but are evicted from the nesting territory by the following spring. From four to seven years might pass before they begin to breed, although sexual maturity is reached much sooner.

As a protected species, trumpeter swans often live for 10 years or more and are known to have survived for at least 24 years. Wild tundra swans appear to have somewhat shorter life expectancies that rarely exceed 10 years, perhaps in part because of hunting-related mortality, their much longer and more stressful migration routes and the rigors of arctic nesting.

Some of the places near Nebraska highways where trumpeter swans can usually be seen during summer are on larger marshes off U.S. Highway 2 in Grant and Sheridan counties, at a wetland off the South Loup River in Buffalo County, near the southern edge of Ravenna and along U.S. Highway 83 in Cherry County, between Valentine and Valentine National Wildlife Refuge. In 2011 four pairs produced 11 cygnets at Valentine National Wildlife Refuge, making it one of the state’s premier swan sites.

Continued releases of trumpeter swans in the Midwest, especially in Minnesota, have greatly increased the chances of seeing trumpeter swans in the region. By 2012 there were perhaps 10,000 trumpeter swans in the eastern North American population, breeding from South Dakota east to Ontario. Because of highly successful restoration efforts in Minnesota (with a 2012 population of 5,500 birds), thousands of trumpeter swans migrate though Iowa each spring and fall, supplementing that state’s own reestablished population of breeding birds.

One of the increasingly important regional wintering areas for trumpeter swans near Nebraska is Squaw Creek National Wildlife Refuge, near Mound City, Mo. From November through winter as many as 255 swans have been seen, as well as up to a half million or more migrating snow geese and countless other waterfowl. It provides a visual spectacle that one is likely to remember and cherish for a lifetime.

References

Johnsgard, Paul A. “Ducks, Geese and Swans of the World.” Revised ed. 2010. http://digitalcommons.unl.edu/biosciducksgeeseswans/.

Johnsgard, Paul A. “Waterfowl of North America.” Revised ed. 2010. http://digitalcommons.unl.edu/biosciwaterfowlna/1

Image Credits: Paul A. Johnsgard

Immigration in Nebraska

Subscribe to Prairie Fire today.