Classification and Range
Crested screamers are part of order Anseriformes, in the family Anhimidae (screamers). There are three species of screamers in the two genera of this family: Anhima and Chauna. In Anhima, the single species is the horned screamer (A. cornuta). In Chauna, the other two species are northern screamer (C. chavaria) and the crested or southern screamer (C. torquata). Crested screamers live in the southern part of South America, in the countries of Peru, Bolivia, Paraguay, north and eastern Argentina, southern Brazil and Uruguay.
Freshwater locales, such as tropical and sub-tropical wetlands, including lakes, marshes, flooded grasslands and lagoons.
The crested screamer is a large gray bird with occasional black and brown feathers. Certain individuals may have a green-black coloration. The body shape and size of crested screamers resemble that of a goose or turkey. Their head is small, covered with downy feathers and features a short, conical, hooked beak. A pair of rings encircles their neck, one is bare white skin, and the other is black feathers. They may also have white feathers on their head, neck or forewings. Ornamental feathers grow in tufts on the back of the head and also form a slim tuft on the forehead.
Juvenile plumage is usually duller in comparison to adults. Red skin surrounds their yellow or orange eyes. Large feet with slender toes support their long, thick and strong legs. Their feet have only vestigial and barely noticeable webbing at the base of the toes. However, the toes are long and help support these birds as they walk across dense mats of floating vegetation or wade on soft, muddy bottoms of swamp areas.
Male and female coloration is identical, as these birds are not sexually dimorphic. Both adult sexes have two large, bony spurs on the inner side of each wing. Each spur is up to 2 inches (5 cm) in length. Male crested screamers that are not paired off use these spurs to fight for females, while both sexes use them to protect their territory from predators or disputes with other screamer pairs. An easy way to distinguish juveniles from adults is the fact that the spurs on juveniles are shorter.
Body length varies, between 28 – 37 inches (71 – 94 cm). For adults, the wingspan is approximately 69 inches (170 cm) in length.
Females may be slightly smaller in weight and height compared to males.Body weight varies greatly, between 4 – 11 pounds (1.8 – 5 kg).
In the wild, estimated to be 15 years. In zoos, they can live up to 35 years.
In the wild: unlike some species of waterfowl, they do not filter their food. Instead, they eat a variety of vegetation, such as the grasses, stems, seeds, berries and leaves of several different kinds of plants. They also occasionally eat insects and small animals.
At the zoo: waterfowl pellets, romaine lettuce and an occasional apple.
Crested screamers establish monogamous relationships that last several years in a row or possibly for the pair's entire lifetime. Some populations breed any time throughout the year, but others breed only in springtime (October – December). Before breeding, courtship involves the pair engaging in loud, continual duets and mutual preening of each other. Courtship also involves un-paired males competing with rivals, as they kick and strike with their sharp beak and robust wings.
When the pair is ready to make a nest, they create a huge platform of reeds, sticks, straws and other aquatic plants on the ground near a source of shallow water. Together, the pair tries to build the nest in an area that is inaccessible to most predators and they vigorously defend this territory. The pair may use the same nest or nest area year after year. The pair mates on land, with the male holding the back of the female's neck with his bill.
At two day intervals, the female lays two to seven white or beige eggs in the nest. The incubation period lasts 40 – 46 days, with the male and female taking turns. At birth, the chicks are precocial and are covered in gray-yellow down feathers. After hatching, the chicks leave the nest and begin to eat on their own. For the next few weeks, the chicks remain close to the nest as their parents watch over, feed or point out food items to them. The chicks fledge after 8 – 10 weeks of parental care and are fully independent at just 12 – 14 weeks of age. Juveniles join non-breeding birds or form their own groups before forming pair bonds in the next breeding season.
Although these birds easily swim through the water, they prefer to move on the ground. Unlike many other species in Anseriformes, they do not dive for their food. They are non-migratory birds but are also excellent flyers. When not breeding, they gather in large flocks numbering hundreds of birds to search for food. During the winter, the flock lives a semi-nomadic lifestyle, grazing together in open grasslands and moving as water conditions change. Other times, the flock circles the skies in a large group. This behavior usually involves calling loudly to each other, as they spiral until they are almost out of view.
These birds are more than capable of defending themselves from most predators. Their noisy call discourages all but the most determined hunters. However, some predators such as foxes, wild cats or hunting dogs will hunt screamers. When encountering large predators, screamers escape by flying to the treetops and wait until it is safe to return to ground.
Life in a Marsh
In addition to their deafening and non-melodic call, all species of screamer birds have unique adaptations to survive in a variety of environments. First, they have a layer of insulating air cells separating the outer skin from the body. Unlike most birds they do not possess feather tracks. Their feathers grow evenly all over their entire body without any bare spaces in between. Even though they are large birds, their relatively low body weight helps them navigate their aquatic surroundings. Screamers have a low body weight relative to size due to the fact that they possess more extensive hollow spaces in their bones compared to other birds. Additionally, screamers lack an uncinate process, which is an extension of bone on each rib that projects towards the tail of the animal. Via these extensions, ligaments join the ribs together and this uncinate process strengthens the rib cage. The uncinate process is present in almost all species of birds. Interestingly, screamers are the only living species of bird lacking an uncinate process; the only other species that lack this are the extinct and ancient species of Archaeopteryx. Lastly, their tongue has many rough bumps on it to help the screamer grab and swallow tough plants.
Location at the Zoo
Crested screamers are on exhibit in the Temperate Forest. They are in their own exhibit with the Chiloe wigeons, next to the Chilean flamingos and Coscoroba swans. The Temperate Forest also includes the Family Farm, Bug World, Wetlands and Asian cranes. Other birds on exhibit in the Temperate Forest include: various pheasant species, curassows and trumpeters from South America, and several softbills (jays, laughing thrushes, turacos, whistling thrushes, birds of paradise and mynahs).
Crested screamers are the most common of the three screamer species and are not endangered. However, at least 27 other species of waterfowl in Anseriformes are either vulnerable, endangered or critically endangered. Crested screamers have a large range within South America, as their stable populations cover at least 1.35 million square miles (3.5 million km2). Crested screamers also have a minimum population of at least 100,000 with up to as many as 1,000,000.
Although native peoples sometimes hunt crested screamers in the wild, this practice does not currently threaten these birds. Hunters or predators may take their eggs, but as sentinels, these birds often startle or warn other members of the flock. The biggest threats to crested screamers (and many other species of waterfowl) are loss of habitat and other human–caused activities. These activities include drainage of wetlands for agriculture, logging, pollution and construction of roads. Fortunately, some screamers can adapt to these impacts by foraging in and eventually colonizing cultivated fields. In turn, local peoples consider them pests as they raid crops and compete for food or other resources with domesticated species of birds.
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Sources and Suggested Reading
Campbell, Bruce and Elizabeth Lack, editors. 1985. A Dictionary of Birds. Published for the British Ornithologists' Union by Buteo Books, Vermillion, SD. 670 p.
The Columbia Encyclopedia, 6th ed. 2001 – 07. screamer. New York: Columbia University Press. Accessed March 1, 2008 at www.bartleby.com/65/.
del Hoyo, Josep et al. 1992. Handbook of the Birds of the World, Volume 1: Ostrich to Ducks. Lynx Edicions, Barcelona, Spain. 696 p.
InfoNatura: Animals and Ecosystems of Latin America. 2007. NatureServe. Accessed March 1, 2008 at http://www.natureserve.org/infonatura.
Integrated Taxonomic Information System: Chauna torquata. 2008. Accessed March 1, 2008 at http://www.itis.gov.
The Sacramento Zoo Species Fact Sheet: Southern Crested Screamer. Accessed March 1, 2008 at http://www.saczoo.com.
Sibley, Charles G., and Burt L. Monroe. 1991. Distribution and Taxonomy of Birds of the World. Yale University Press, New Haven, CT. 11,360 p.