Swan (bird) - biology.

Swan (bird) - biology. I INTRODUCTION Swan (bird), a large water bird that belongs to the same family of waterfowl as ducks and geese. Swans are larger than geese and ducks, and they are easily recognized by their very long necks. Some swans arch their necks in a graceful curve, while others carry their necks upright. Most swans have pure white feathers, but two species that live in the southern hemisphere are completely or partially black. Male and female adult swans look alike. The male swan is called a cob, the female is a pen, and baby swans are cygnets. Noted for their graceful movements in the water, swans have been the subject of many poems, fairy tales, legends, and musical compositions. Among the best known are Swan Lake, a ballet with music by Peter Ilyich Tchaikovsky, and "The Ugly Duckling," a fairy tale by Hans Christian Andersen about the misadventures of an unhappy young bird who is ridiculed for his looks but grows up to become a beautiful swan. The hero of the opera Lohengrin by Richard Wagner arrives and departs in a boat drawn by a swan; the opera is based on a German legend. According to another legend, the swan sings a beautiful song just before it dies. This legend is the origin of the expression, "swan song," which refers to a final, farewell appearance. II DESCRIPTION AND BEHAVIOR OF SWANS Swans are the largest waterfowl. The largest swan in the world is the trumpeter swan of North America. It measures as long as 1.8 m (72 in), has a wingspan as great as 2.5 m (8.2 ft), and weighs up to 16 kg (35 lbs). The smallest swan is the coscoroba swan of South America, though it is hardly a small bird, measuring about 1 m (40 in) in length. Some experts believe this bird is more closely related to geese. Many swans have loud, boisterous calls. The trumpeter swan, for example, is named for its bugle-like call, which carries a long distance. The whistling swan (known in North America as the tundra swan) has a whistle-like call. The coscoroba swan produces a loud call that sounds like "cos-cor-ooo." The mute swan is an exception, although it is not entirely silent as the name implies. However, it is far quieter than other swans. Swans spend much of their time swimming in ponds, lakes, coastal bays, and rivers, and they are noted for their graceful movement. Although they fly well, they need a large stretch of water for takeoff. To become airborne, swans patter along the top of the water, flapping their wings, until they gain sufficient speed for takeoff. Most swans are migratory; in North America, flying from breeding grounds in the north to wintering grounds farther south. Swans that live year-round in the southern United States do not migrate. Swans feed both in water and on land, and their diet consists mainly of plants. Their long necks enable them to feed underwater without diving. They reach underwater and pull up stems, leaves, and roots with their large bills. The young sometimes eat insects and small water invertebrates. The necks and faces of white swans may become stained as the result of iron or other minerals in the water they feed in. III MATING AND REPRODUCTION Swans usually form pairs for life, although in some species swans are known to change mates occasionally, especially if the pairs fail to breed. Swans choose mates when they are two or three years old, although they usually do not breed until they are at least four. Breeding pairs build nests of grasses, rushes, and reeds, usually near water and sometimes on the top of muskrat lodges. The female usually lays four to six eggs, sometimes more. She incubates them until they hatch about 35 days later. The male guards the nest from predators and may take over incubation so that the female can feed. Both parents tend the cygnets, which are sometimes seen riding on the back of a swimming parent. The cygnets learn to fly after a few months, but they usually stay with their parents through the winter. Young swans are pale gray or grayish-brown in color and do not grow their white feathers until the next summer. Swans may live as long as 35 years. IV KINDS OF SWANS Three species of swans inhabit North America: the trumpeter swan, the mute swan, and the tundra swan. The largest swan in the world is the trumpeter swan. This pure white swan has a black bill. Its neck is nearly twice as long as its body, helping the swan produce its loud, resonant trumpeting call. The trumpeter swan is found mainly in the Pacific Northwest, where it swims in lakes, ponds, and coastal bays from Alaska to the Puget Sound region of Washington state. Trumpeter pairs require a large territory for themselves and may attack intruders, including dogs and children. Trumpeter swans were once hunted for their feathers, which were used to make quill pens. As a result the swans were close to extinction by the early 1900s, but they have since made a comeback. The mute swan also has pure white feathers. Its orange bill has a black knob at the base. The swan is native to Asia but today is commonly found in lakes in urban parks. It is the tamest of the swans and the least fearful near human habitation. According to long tradition the mute swans on England's River Thames and its tributaries belong to the monarch. Each summer a census of the royal swans is taken during a ceremony called Swan Upping. The tundra swan is the North American variant of the whistling swan, named for the whistling sound it makes. In Europe and Asia, the whistling swan is known as the Bewick's swan. This all-white swan with a black bill resembles the trumpeter swan, although it is smaller than the trumpeter and is the smallest of the North American swans. As its name suggests it nests in the Arctic tundra, generally near the coast. Tundra swans migrate long distances from the Arctic Circle of Canada and Alaska to California and to bays and estuaries along the mid-Atlantic coast. They stay in large flocks except when they are breeding. The whooper swan is the European and Asian counterpart of the trumpeter swan. This large white bird has a yellow bill with a black tip. It breeds across northern Europe and Siberia and winters as far south as North Africa. Its trumpeting call is loud; in flight it makes a "hoop-hoop" call that gives the whooper its name. The small coscoroba swan of South American has a short neck, white body, red bill, and red legs. The black swan of Australia and New Zealand has brownish-black feathers and a red bill with a white tip. The black-necked swan of southern South America has a black head and neck, a white body, and a bright red knob on its black bill. Scientific classification: Swans belong to the family Anatidae. The mute swan is classified as Cygnus olor, the trumpeter swan as C. buccinator, the whooper swan as C. cygnus, the tundra swan as C. columbianus, the black swan as C. atratus, the black-necked swan as C. melanocorypha, and the coscoroba swan as Coscoroba coscoroba. Microsoft ® Encarta ® 2009. © 1993-2008 Microsoft Corporation. All rights reserved.