Ducks, Geese, Swans, and Screamers: Anseriformes

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DUCKS, GEESE, SWANS, AND SCREAMERS: Anseriformes

PHYSICAL CHARACTERISTICS

Waterfowl, including ducks, geese, and swans, vary greatly in size and weight. The smallest is the tropical pygmy-goose, which weighs just 10 ounces (269 grams) and stands 12 inches (30 centimeters) tall. The largest is the trumpeter swan, which stands at 72 inches (183 centimeters) and weighs more than 38 pounds (17 kilograms). Screamers are large birds, standing 30 to 37 inches (76 to 95 centimeters) and weighing anywhere from 6 to 88 pounds (3 to 40 kilograms). Their wingspan is 5.6 feet (170 centimeters).

These birds have compact bodies with long necks and full webbing between the three forward-pointing toes. The lower bill is flat while the upper is cone-shaped with a sort of nail at the tip. Waterfowl are unable to glide but can fly quickly with their necks outstretched. Five species are flightless, including three of the four species of steamer-ducks, the Auckland Island teal, and the Campbell Island teal. Screamers look like geese but they have a small, chicken-like head. Their feathers are gray or greenish-black, with some white on the head and neck, fading into the forewing. The screamer has a feathered "horn" on the front top of its head, and its eyes range from yellow to orange. Screamers, like waterfowl, have webbing between their toes.

Ducks, swans, and geese have broad wings that come to a point. Feather coloration varies from the white of most swans to the brown of many geese to the bright patterns of many northern ducks. Male coloration is more vibrant than that of females. Geese and swans molt, shed their feathers, once a year while ducks molt twice each year. During the molting season, waterfowl are flightless except for the magpie goose. Screamers molt gradually and so are never rendered flightless.

GEOGRAPHIC RANGE

Screamers are found only in South America, whereas ducks, geese, and swans are found throughout the world except in the Arctic region.

HABITAT

Waterfowl and screamers can be found in virtually any wetland as long as there is sufficient food available. Screamers inhabit tropical and subtropical wetlands such as marshes, swamps, and lagoons. They also are found on savannas, a tropical plant environment made up of shrubs, trees, and grasses, and the flood plains of tropical forests. Some waterfowl are found in saltwater environments outside of breeding season.

DIET

The herbivorous, plant-eating, screamer and waterfowl eat mostly leaves, flowers, and seeds of aquatic vegetation. They also small fish, insects, and plankton.

BEHAVIOR AND REPRODUCTION

Most waterfowl are active during the day and seek the safety of shelter at night. When not nesting, they are social birds and gather in groups during the winter months. These groups can reach up to three thousand birds. When nesting, though, they prefer to be alone for the most part. Screamers are solitary, alone, nesters as well.

Screamers build their nests out of weeds and sticks and choose sites close to the water. A seasonally monogamous, one mate per season, bird, screamers often return to the same nest for many seasons, and some use the same nest for life. Both sexes build and defend the nest. They lay two to seven eggs, which parents will take turns incubating, warming, for forty-two to forty-five days. They cover the eggs with weeds if they must both leave the nest. New chicks are tended to for just a couple days, and they are ready for flight by eight to ten weeks. They are completely independent by fourteen weeks of age.

Screamers get their name for the loud vocalizations used to defend territory and to call out to one another. Their screams can be heard from a distance of 1.9 miles (3 kilometers).

Some species of waterfowl build their nests near the water, while others nest more than a mile from the waters' edge. Those that nest far away are surface-feeding ducks that can walk without difficulty. Most nest on the ground while others build their homes in trees. The nest is made of whatever can be found around the site, and shortly before the eggs are laid, females pluck the soft down from their undersides and line the nest with it. Clutch, number of eggs laid, sizes vary greatly, from two to twenty-two. Incubation lasts from twenty-two to forty days, and with the exception of a few species, males do not assist in this duty. Chicks are born with a covering of down that becomes water repellent as it rubs against the mother's feathers. Ducklings feed independently the first day. Ducks care for their young until they are able to fly, between forty to seventy days. Geese and swans care for their young until the following spring.

Predators of waterfowl and screamers include red fox, coyote, weasel and mink, crow, owl, raccoon, badger, skunk, magpie, and skuas.

MASS KILLING OF MUTE SWANS HALTED

In September 2003 the U.S. Fish and Wildlife Service withdrew all permits to hunt mute swans nationwide.

Mute swans have been blamed for damaging the environment because they consume large amounts of submerged aquatic vegetation (SAV). This consumption, some experts argue, threatens the vegetation as well as wildlife that depend on it. Most experts agree, however, that the greatest threat to SAV in the Chesapeake Bay is lack of light, which prohibits photosynthesis, the process in which plants use sunlight as energy for growth.

Mute swans have been blamed for the difficulties reintroducing trumpeter swans in Wisconsin because they are aggressive.

Mute swans are not native to the United States, but were introduced in the 1800s; their population now exceeds fourteen thousand along the East Coast.

DUCKS, GEESE, SWANS, SCREAMERS AND PEOPLE

Humans hunt waterfowl as a food source, and waterfowl are domesticated for their eggs, liver, and meat. Eiders are raised for their feathers, which are used in comforters, sleeping bags, and pillows.

CONSERVATION STATUS

Six species of Anseriformes are listed as Extinct, no longer existing, and another fourteen are listed as Endangered, facing a very high risk of extinction in the wild in the near future. Twelve are listed as Vulnerable, facing a high risk of extinction in the wild in the medium-term future, and eight are listed as Near Threatened, in danger of becoming threatened with extinction. The reasons for the threats to these populations are habitat destruction, human hunting and collecting, and toxic poisoning due to modern agricultural methods.

FOR MORE INFORMATION

Books:

Burnie, David, and Don E. Wilson, eds. Smithsonian Institution Animal: The Definitive Visual Guide to the World's Wildlife. New York: DK Publishing, 2001.

LeMaster, Richard. Waterfowl Identification: The LeMaster Method. Mechanisburg, PA: Stackpole Books, 1996.

Miller, Sara Swan. From Swans to Screamers. New York: Scholastic Library Publishing, 2000.

Smith, Christopher. Field Guide to Waterfowl and Upland Birds. Belgrade, MT: Wilderness Adventures Press, Ltd., 2000.

Wexo, John. Ducks, Geese, and Swans (Zoobook Series). Poway, CA: Wildlife Education, Ltd., 2001.

Periodicals:

"No Swansong in the Chesapeake Bay—Spectrum—Mute Swan Killing Stopped." Environment (December 2003): 7.

Quick, Suzanne. "Plan to End Protection of Mute Swans Raise Flaps." Milwaukee Journal Sentinel Online (May 16, 2004). Online at http://www.jsonline.com/news/state/may04/229949.asp (accessed on May 27, 2004).