Table of Contents
Introduction
North American waterfowl present great economic, esthetic and recreational value. They are made of forty two species that include geese, swans and ducks. Graceful tundra swans are very attractive birds that deserve special mentioning. Besides their natural beauty they possess several unique characteristics that make them quite outstanding.
Tundra swans
Adult tundra swans have completely white plumage. The bills are black and often have yellow spots at the base. The feet and legs are black. Both sexes have similar appearance. An average male swan weighs around 16 pounds and a female swan – around 14 pounds. Their average length is 52 and 51.5 inches, respectively (Tundra Swan). Tundra swans look somewhat similar to trumpeter swans and that is why are often confused with them.
Habitat
Tundra swans spend their summers in tundra. They breed along the west coasts of Alaska and the Yukon as well as in the Canadian tundra areas. Tundra is a very specific place where growth is hindered by low temperatures. The vegetation in tundra is represented by dwarf shrubs, grasses, mosses, lichens and sedges. Some tundra has small scattered trees. Tundra’s landscape is frozen for the much of the year. During the warm months the surface of tundra is covered by bogs, lakes and marshes. The above conditions determine the life style of tundra’s inhabitants. For wintering, tundra swans migrate to the area stretching from British Columbia to central California. Those who live in Canada, travel to, as far as, North Carolina.
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Tundra swans are sleep afloat and winter on water. They are very good swimmers and eat immersing their heads underwater to catch shellfish and fetch plants and roots. They also got accustomed to obtaining food at farms where they find grains.
Tundra swans remain in flocks when they are outside of their breeding territory. Although majority of swans spread out for breeding, a large part of the population on the breeding grounds still can stays in flocks. These swans are not breeding. They may be young birds that have not yet bred or adult couples whose breeding attempts were not successful, or adults that bred in the past seasons but for some reason do not do it in that year (Tundra Swan – Cool Facts).
Reproduction
Tundra swans are believed to mate for life. They start courting and pairing in full swing in the late part of the winter and continue during the spring migration. Adult swans, which are already paired, strengthen their bond by vocal and visual displays. One of the most spectacular of them is the so-called ‘victory display’ when male and female face each other, extend their wings and wave them slowly, then bow the head and neck back and forth. Then, in duet, they produce loud, melodious sounds. That is the reason why tundra swans earned their nickname as the “whistling swan”.
Both male and female swans work together to build a nest. Their nest represents a mound made of uprooted plants, built near a lake or a pond. Each nest is lined with moss and grasses (Tundra Swan Cygnus Columbianus). Its size may reach from 6 to 12 feet in diameter and may be 1-2 feet over the water level. Each couple tends to have a surrounding territory with the area up to three fourths square miles. Swans can be very aggressive in case of threat to their young chicks. They may be able to fend off predators like foxes.
The female swan lays from 5 to 7 eggs. A clutch of four eggs is normal. In especially warm and favorable springs female may lay up to 7 eggs. Eggs are elliptical and cream-colored. Their average length is around 100 mm. Then the pair takes turns to incubate the nest. That is a trait that distinguishes tundra swans from many other waterfowl. During the incubation time the male swan molts and becomes flightless for a period of about a month. Young swans hatch in 31 to 35 days, usually in July and weigh up to 180 grams. Chicks fledge when they are 11-15 weeks old. Young swans stay with adult swans for a year and they are often joined by swans from previous years. Swans reach their breeding age when they are 2-3 years old (The Tundra Swan).
Predators and other threats to swan populations
Tundra habitat is often disturbed by economic undertakings of men. Such activities as oil exploration inhibit to maintain desired population of waterfowl. Construction of bridges and causeways for connecting mainland with barrier islands may present a threat since predators like foxes obtain access to their nesting areas (Sovada).
Two populations of tundra swans are recognized in North America: the western and the eastern populations. The former was estimated at around 90,000 birds and the latter - at about 100,000 birds.
Apart from humans tundra swans have few natural enemies. They are wolves, foxes, jaegers, golden eagles and bears. However, their influence on the swan population is not significant. The main factor that limits their population is adverse weather conditions. Late spring may inhibit nesting and premature freeze-ups may cause the death of young chicks. The western population experiences milder climate conditions (Hinterland Who’s Who – Tundra Swan).
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One of the threatening factors that present danger to swan populations is human activity. Water pollution in such water areas as the Chesapeake Bay and the lower Great Lakes reduces food supplies for wintering birds. Switching from aquatic plants to farm grains presents an important question. What causes tundra swans to divert from their habitual diet and switch to the new types of food: destruction and pollution of their customary food sources or preferences for new foods? That may pose a threat in case farmers change their crops in the areas of swan wintering.