19 January 2013

Notes on Nebraska Fauna ... Trumpeter Swan

The discovery of swan colonies at Red Rocks Lake, Montana, Yellowstone National Park and several other isolated locations, brought the known population in 1932 to 69 birds. Only the enactment of protective legislation and establishment of a national wildlife refuge at Red Rocks Lake, served to reverse the trumpeter's slide toward extinction.

Adult trumpeters are almost completely white with a rusty stain on the white head and neck from feeding in southern marshes with ferrous-rich soils. The legs and bills are black with the lower bill having a flesh colored strip along the upper portion. Juvenile swans resemble adults but have brownish-gray plumage.

Original art by Neal Anderson.

Adult males have a wingspan of eight feet, females average six feet. A mature cob weighs from 21 to 38 pounds, and the more demur pen from 20 to 25 pounds.

The call of the trumpeter swan is perhaps the most important identifying feature. The loud, clear call has been compared to the notes of a French horn, and is maintained over a wide vocal range. Uttered singly or in widely spaced staccato fashion, a trumpeter's call can be heard up to a mile away.

As with all swans, the trumpeter is monogamous. A pair usually mates for life, though remating will occur if one is lost. The pair bond is usually when the birds are four to six years old, but optimum breeding conditions may permit individuals to pair and breed at an earlier age.

Nests are built in extensive beds of marsh vegetation. Found in water one to three feet deep, the nests are surrounded by open water that results from the uprooting of vegetation by the pair. Sedges, cattails and bulrushes are removed, primarily by the cob, and used by the pen to construct the nest. Nests are impressive, from six to 12 feet in diameter and averaging 18 inches in height. In areas where muskrats are found, the nest is typically placed on a muskrat den. The same nest will commonly be used for several years by the same pair.

Once the nest is prepared, a clutch of four to six off-white eggs is laid, one every other day. Incubation begins with the last egg. Although both parents are present at the nest, only the pen incubates, and in 33 to 37 days, the clutch hatches. The hatchlings are brooded at the nest for 24 hours before the family group moves off to feed and swim in the marsh.

During their early days, cygnets feed on aquatic insects, crustacea, and aquatic plants in shallow water.

Young trumpeter swans hatch out at seven to eight ounces but develop rapidly and may weigh 19 pounds at 10 weeks of age. The steadily growing cygnets are fully feathered in about 10 weeks but are unable to fly until 13 to 15 weeks old. Once the young swans have learned to fly, they spend the winter with the parents in a closely knit family group until driven off by the pen and cob when the mating period begins the following spring.

Since 1968, the largest of Nebraska's waterfowl has slowly made a comeback and is presently found in limited numbers in Cherry and Sheridan counties. With continued expansion, the trumpeter swan's distinctive voice and graceful presence will once again become commonplace across Nebraska's lake and marsh country.

November 1979. Nebraskaland Magazine 57(11): 50.