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There are three living species in the screamer family: horned screamers (Anhima cornuta), northern horned screamers (Chauna chavaria), and southern or crested screamers (Chauna torquata). Horned screamers were first described by Linnaeus in eastern Brazil in 1766 as Palamedea cornut. Although screamers (family Anhimidae) are more like game-birds in appearance, they closely related to geese, swans, and ducks (in the order Anseriformes). Fossil remains of screamers are known from deposits of the Quaternary Period in Argentina.
Horned screamers are less vocal than their relatives, southern screamers, but their vocalizations are are very loud. There are three main vocalizations: “mo-coo-ca”, a honking “yoik-yok”, and the trumpet. When calling, the birds’ necks are fully inflated and often shaking. Calling can be done from the ground and from the air. Vocal communication is used for territorial defense, mating, and other purposes. More specifically, the “mo-coo-ca” is used to alarm others of a disturbance of potential predators or the relocation of other screamers. Honking is used for greeting and distance calling. Trumpeting is typically used for distance calling, the morning wake-up call, and as a high-intensity greeting. It was also noted that once or twice each day the screamers will perform loud calls. Often these are initiated by an adult bird, or group of birds, and the response is given by neighbors. Typically, male birds have lower frequency calls than females. Screamers are named for their loud vocalizations. Also, a local Indian name given to the birds is “mahooka” based on the sound of their calls.
Communication Channels: visual ; acoustic
Other Communication Modes: duets ; choruses
Perception Channels: visual ; tactile ; acoustic ; chemical
Anhima cornuta is currently not considered threatened. Populations are sometimes controlled by hunters.
US Migratory Bird Act: no special status
US Federal List: no special status
CITES: no special status
State of Michigan List: no special status
IUCN Red List of Threatened Species: least concern
Other than the deafening screech of the horned screams, no negative effects have been noted.
Horned screamers are hunted for food in South America. Additionally, young screamers are sometimes caught and tamed by local people. They readily take to captivity and can be kept with chickens in farmyards, where they defend the chickens against birds of prey and other enemies. Also, it is not uncommon to see them walk about freely in South American zoos and parks.
Positive Impacts: pet trade ; food
Screamers are primary consumers, eating plants. Their grazing may influence the composition of plant communities where they live. Their nests of twigs and plant life creates habitat for small invertebrates.
Ecosystem Impact: creates habitat
Horned screamers are mainly herbivorous, eating foliage, grains, and other plant parts. Insects are thought to be a main component of juvenile diet. Screamers graze during mid-morning to late afternoon along grasses and sedges near the water. They peck at leaves, stems, flowers, and vines and graze with lateral head movements. Food is swallowed almost immediately unless the food is longer than the bird’s beak. A less common technique for finding food is digging and filtering through wet mud. Horned screamers rarely drink from their local water source but when they do, they dip their heads in and take large gulps. Their horned tongues allow these birds to manipulate and eat tough plants.
Animal Foods: insects
Plant Foods: leaves; roots and tubers; wood, bark, or stems; seeds, grains, and nuts; flowers
Primary Diet: herbivore (Folivore )
Horned screamers are a native species of the Neotropical region. These non-migratory birds live in a range throughout northern South America that stretches from the Amazonian regions of Venezuela, to the eastern llanos of Columbia, to eastern Bolivia and south-central Brazil. They are now extinct in Trinidad.
Biogeographic Regions: neotropical (Native )
Horned screamers are found in the vicinity of tropical lowland fresh water, such as lakes, ponds, rivers, marshes, and swamps. They often roost in trees and shrubs of wooded river banks and wet savannas.
Average elevation: 1,000 m.
Habitat Regions: tropical ; terrestrial ; freshwater
Terrestrial Biomes: savanna or grassland
Aquatic Biomes: lakes and ponds; rivers and streams; coastal
Wetlands: marsh ; swamp
Other Habitat Features: riparian
There is no known information on the lifespan of Anhima cornuta.
Horned screamers are large, heavy bodied, fowl-like birds that are most recognizable by their two bone spurs at the bend of each wing and the 15 cm, yellowish-white horn-like projection at the top of their heads. The 2 to 5 cm long bone spurs are a result of fused carpel bones and are covered with keratin. The horn-like projection, which gives these birds their name, is composed of cartilage. When young are born they lack the horn but it slowly grows as they age. Horns seem to be ornamental as they do not have a defensive purpose. They are not firmly attached to the skull, swing back and forth as the birds’ heads move, and are easily broken off. After breaking off they will grow back over time.
Typically, Anhima cornuta has a gray or black body that fades into a white abdomen. In addition to the abdomen, the wings and crown are also white. The head is small in proportion to the body and has a variety of patterns and colors of plumage. The bill is short with a downward curve and the irises of the eyes are bright orange or yellow. The feathers of the body grow evenly and cover the skin without any bare spaces. Horned screamers have long reddish legs with strong, stout, ash grey feet that lack webbing. The feet lack arches, thus the hind toe is at the same level as the front three on each foot. On the alular digit, screamers have a small, nonfunctional claw. Males and females are similar in appearance.
Horned screamers possess some additional unusual anatomical features. Most of their bones are permeated with abundant air sacs that also exist in the subcutaneous tissue in the dermis of the skin. This construction results in a rumbling or crackling noise when these birds take off as the air sacs rapidly collapse. The presence of subcutaneous air sac diverticula allows horned screamers to regularly use soaring flight instead of using muscle energy to remain airborne. These air filled spaces may also act to facilitate pneumatic movement. Horned screamers also lack uncinate processes on their ribs (which act as strengthening elements in all other birds except the extinct Archeopteryx). They have an extraordinarily light-weight bone structure in comparison to birds of similar size.
Of the three species of screamers, A. cornuta is the largest in size. The other screamer species, crested or southern screamers (Chauna torquata) and northern screamers (Chauna chavaria), lack the horn-like projection and differ in color and patterning.
Average mass: 3150 g.
Range length: 71 to 92 cm.
Average wingspan: 1.7 m.
Other Physical Features: endothermic ; homoiothermic; bilateral symmetry
Sexual Dimorphism: sexes alike; ornamentation
Humans, who hunt Anhima cornuta for food, are the only known predators of these birds.
Known Predators:
Horned screamers pair for life, or for at least several years. Pairs stay together throughout the year, seeking isolation in marshy areas in late winter and early spring to trumpet in duets. There are different mating behaviors in Anhima cornuta. “Head bobbing” occurs when one screamer approaches its partner and both birds stretch their necks out and bob their heads up and down one to three times. The main courtship behavior, done all year long, is known as “social preening.” This occurs when two birds preen the feathers on each other’s necks and heads. Often times there are fights connected with pair formation. Males will use the sharp spurs on their wings as weapons against one another.
Before copulation males walks around females with their bills pressed downward against their inflated crops, neck retracted, and dorsal feathers partially erected. After circling, males will bow their head 1 to 3 times in front of females. During copulation, which takes place on land, males will mount females for ten seconds while grabbing the female's neck with his bill and flapping both wings slowly.
Mating System: monogamous
Horned screamers are year-round breeders with no particular breeding season. When large flocks of non-breeding birds are sighted it suggests that maturation has been delayed for several years. Anhima cornuta individuals build large nests of plant materials, such as reeds and sticks, that are 8 to 10 centimeters deep. Nests are near or in marshy vegetation in shallow water, typically around eight centimeters deep. Two to eight smooth yellowish-white oval eggs are laid at intervals of 35 to 40 hours by the female. Both parents spend time incubating the eggs. The eggs average 84 mm in length and weigh an average of 150 grams.
Breeding interval: Horned screamers breed continuously throughout the year, the interval of egg laying is not known and may depend on available nutrition for females.
Breeding season: Screamers breed during any season.
Range eggs per season: 2 to 8.
Average eggs per season: 3.
Range time to hatching: 40 to 47 days.
Range fledging age: 60 to 75 days.
Average time to independence: 1 years.
Key Reproductive Features: iteroparous ; year-round breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization ; oviparous
Horned screamer females usually incubate the eggs during the day, taking short breaks when the male takes over. Males incubate the eggs at night. When the young screamers hatch their eyes are open and they are covered with down. They are nidifugous (young leave the nest immediately after birth) and can run as soon as they are hatched. The young are precocial and follow both parents who offer some food to the young for 60 to 75 days. The parents will also pick up and drop food items in front of the chicks, presumably to encourage feeding.
Parental Investment: precocial ; pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth (Provisioning: Male, Female, Protecting: Male, Female); pre-weaning/fledging (Protecting: Male, Female); pre-independence (Protecting: Male, Female)
The horned screamer (Anhima cornuta) is a member of a small family of birds, the Anhimidae, which occurs in wetlands of tropical South America. There are three screamer species, the other two being the southern screamer and the northern screamer in the genus Chauna. They are related to the ducks, geese and swans, which are in the family Anatidae, but have bills looking more like those of game birds.
Already known in the 17th century,[2] the horned screamer was described in 1766 by the Swedish naturalist Carl Linnaeus in the twelfth edition of his Systema Naturae. He introduced the binomial name Palamedea cornuta.[3] The horned screamer is now the only species placed in the genus Anhima that was introduced by the French zoologist Mathurin Jacques Brisson in 1760.[4][5] The specific epithet cornuta is the Latin word for "horned".[6] The German naturalist Georg Marcgrave had used the Latin name Anhima in 1648 for the horned screamer in his Historia naturalis Brasiliae.[7] The name was from the word for the bird in the Tupi language of South America.[8]
The horned screamer is a massive 84–95 cm (33–37.5 in) long, 3.5 kg (7.7 lb) bird, with a small chicken-like bill. The upperparts, head, and breast are black, with white speckles on the crown, throat and wing coverts. There is a long spiny structure projecting forward from the crown. This structure is unique among birds and is not derived from a feather but is a cornified structure that is loosely attached to the skull and grows continuously while often breaking at its tip.[9] This gives this species its name. It has very long and lanky legs and three large toes in each. The belly and under wing coverts are white. It has two sharp spurs on its wings and feet which are only partially webbed.
The horned screamer's call, as the name suggests, is a very loud and repetitive echoing sound.[10] It is called "el clon-clon" in Ecuador because of this peculiar feature.
The horned screamer is found in lowlands from Colombia, Venezuela, Brazil, Bolivia, Peru, Ecuador, French Guiana, Suriname, and Guyana.[11] It has been possibly extirpated from Trinidad.[1] Despite having declined locally, it remains widespread and is fairly common overall. Its range in Brazil appears to have expanded in recent years.
Screamers, like most birds, tend to group together, but are for the most part semi-social. The existence of the screamer is rather sedentary.[12] It lives in well-vegetated marshes and feeds on water plants.
Its nest is a large pile of floating vegetation anchored in shallow water. Three olive-brown eggs are laid, and the young, like those of most Anseriformes, can run as soon as they are hatched.
The horned screamer is the official bird of both the Department of Arauca and the Municipality of Arauca in Colombia,[13] as well as a symbol of the National Reserve of Churute in Ecuador.[14] The department and its capital are named after the bird, which is called arauco or aruco in Spanish.
In Brazil, the bird is known as Anhuma in the Portuguese language, it is the symbolic bird of the State of Goiás. The horned screamer also appears in the flags and coats of arms of the municipalities of Guarulhos and Tietê, both located in the State of São Paulo.[15]
The horned screamer (Anhima cornuta) is a member of a small family of birds, the Anhimidae, which occurs in wetlands of tropical South America. There are three screamer species, the other two being the southern screamer and the northern screamer in the genus Chauna. They are related to the ducks, geese and swans, which are in the family Anatidae, but have bills looking more like those of game birds.
