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Chauna torquatasouthern screamer

By Jessica Nolle

Geographic Range

Southern Screamers (Chauna torquata) are neotropical and permanent residents throughout south eastern South America, including south eastern Peru, Paraguay, Bolivia (Parker, 1982), Northern Argentina, and Uruguay. They are commonly found wading in open marshes and weedy lakes (Belton 1984). Small populations have also been seen in Rio Grande do Sul near Uruguay (Belton, 1984). (Belton, 1984; Parker, 1982)

Habitat

Chauna torquata is primarily found in marshy, wetland environments where vegetation is abundant. They are especially common within the Pantanal floodplains of Brazil. (Heckman, Charles W. 1998). Southern Screamers will often flock together in large groups around shallow pools during the non-breeding season and are dispersed more sporadically during the breeding season. They are easily found grazing along shallow waters as well as perched in low trees and bushes (Belton, 1948). (Belton, 1984; Heckman, 1998)

  • Aquatic Biomes
  • lakes and ponds
  • rivers and streams

Physical Description

Southern Screamers are large, heavy bodied birds primarily covered in light gray feathers. Their pink, fleshy legs are long and end in long anisodactyl toes. Curiously, these birds have a layer of small air sacs known as “subcutaneous diverticula,” under their skin that likely makes the bird lighter for swimming and flying (Picasso, 2014). Other unique anatomical features include a lack of uncinate processes and a skeleton that is considered the most pneumatic of all bird species (Fox et al. 2019). Chauna torquatas have small, chicken-like heads with downward curving bill and pink skin around the eyes and bill. A thin, gray crest extends horizontally from the top of the head. These screamers have a thick neck with a white collar composed of very small and thin feathers, giving this portion of the neck a “bald” appearance. Directly below the white collar is a black collar that can sometimes cover up the smaller white feathers above it. The wings are primarily gray and black. Both male and female screamers have two spurs on the metacarpals of each wing that they use during territorial disputes. (Rand, A. 1954). There is little sexual dimorphism among southern screamers, males tend to have a slightly larger wingspan (549.7mm) than females (530.8mm) (Blake, 1977). Juvenile screamers are covered in yellow down and have the same thick pink legs as the adults and stand at about 15-20 cm tall (Belton, 1984). (Belton, 1984; Lana and et al, 2019; Picasso, 2014; Rand, 1954)

  • Sexual Dimorphism
  • sexes alike

Reproduction

Southern Screamer pair bonds begin in the spring (October/November) and are long-lived, some lasting many years while others are life-long. When a pair is bonded they will regularly call and duet with each other from miles away. Both males and females help build nests on the ground with large sticks, typically near a shallow water source. Eggs are laid from July to December (Belton, 1984). Females can lay between 2-7 white eggs, with incubation lasting 43-46 days (Stonor 1939). Chicks become independent at about 13 weeks. Paired couples will regularly preen and call to each other during both the breeding and non-breeding season. Both males and females incubate the eggs and care for the chicks. (Belton, 1984)

Paired couples will regularly preen and call to each other during both the breeding and non-breeding season.

  • Breeding interval
    Southern Screamers breed once yearly.
  • Breeding season
    July to December
  • Range eggs per season
    2 to 7
  • Average eggs per season
    4
  • Average time to hatching
    43-46 days
  • Average time to independence
    13 weeks

Both males and females incubate the eggs and care for the chicks until independence.

  • Parental Investment
  • pre-hatching/birth
    • provisioning
    • protecting
      • male
      • female
  • pre-weaning/fledging
    • provisioning

Behavior

Southern screamers are capable swimmers but they are most often found wading in shallow water or perched in trees along the water. They graze in large groups of up to 100 individuals (Carboneras 1992) during the non-breeding season and become solitary and fiercely territorial during the breeding season. Screamers will call loudly when they are startled or when they spot predators. (Carboneras, 1992)

Home Range

There is insufficient data on individual territory or home range size. However, males and females do become highly territorial of their nests during the breeding season.

Communication and Perception

Both males and females produce an extremely loud, two-toned, trumpeting call that can be heard up to three km away. This “ca-WOOW” call is used primarily as an alarm call or between pairs (Blake, 1977). Chauna torquata have a very small vocabulary, other calls include an “a-ta-HAAA” and a kind of a throaty honk, both are commonly used as alarm calls. Males calls have been described as slightly lower pitched than the females (Belton, 1984). (Belton, 1984)

  • Other Communication Modes
  • duets

Food Habits

Southern Screamers are herbivores, primarily eating grass and aquatic plants. This species hosts a small row of lamellae inside the bill that is likly used for stripping aquatic plants (Olson and Feduccia, 1980). C. torquata has been described as a generalist, eating the most common and easily available plant material (Luz, 2015). They will rarely consume insects and small vertebrates. (Luz, 2015; Olson, 1980)

  • Animal Foods
  • mammals
  • reptiles
  • insects
  • Plant Foods
  • leaves
  • flowers

Predation

Predation of the southern screamer is uncommon due to their large size, loud alarm calls, and their sharp spurs. To defend themselves Chauna torquata will use its powerful wings and spurs to gouge potential predators (Barrows et al., 2005)

Ecosystem Roles

Southern Screamers are generalist herbivores that inhabit the riparian zones of South America (Lozano, Malo 2013). Chauna torquata graze on grasses, aquatic plants, and terrestrial plants, they may also act as seed dispersers for some species. (Lozano and Malo, 2016)

  • Ecosystem Impact
  • disperses seeds

Economic Importance for Humans: Positive

Southern Screamers are sensitive to human presence and activity, making them a potential indicator species for how their ecosystem is affected by heavy human presence (Lozano, Malo 2013). Due to the screamers incredibly loud calls, local people use this species as guard birds to protect livestock. Chauna torquata has been recorded consuming a considerable amount of invasive plant matter, especially Trifolium repens (white clover) (Luz, 2015). (Lozano and Malo, 2016; Luz, 2015)

Economic Importance for Humans: Negative

The call of the Southern Screamer is extremely loud and can be heard up to 3 km away, this could easily be considered an annoyance. Some local farmers may consider southern screamers pests because they like to gather in crop fields, however there is little recorded evidence of this.

  • Negative Impacts
  • crop pest

Conservation Status

Southern Screamers are classified as “least concern” by the IUCN red list. However, southern screamers are affected by deforestation and the draining of wetlands for agricultural development (Klass and Lynch, 2017). (Klass and Lynch, 2017; "The IUCN Red List of Threatened Species", 2019)

Contributors

Jessica Nolle (author), Northern Michigan University, Alec Lindsay (editor), Northern Michigan University.

Glossary

Neotropical

living in the southern part of the New World. In other words, Central and South America.

World Map

acoustic

uses sound to communicate

agricultural

living in landscapes dominated by human agriculture.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

chemical

uses smells or other chemicals to communicate

diurnal
  1. active during the day, 2. lasting for one day.
duets

to jointly display, usually with sounds in a highly coordinated fashion, at the same time as one other individual of the same species, often a mate

endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

folivore

an animal that mainly eats leaves.

freshwater

mainly lives in water that is not salty.

herbivore

An animal that eats mainly plants or parts of plants.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

marsh

marshes are wetland areas often dominated by grasses and reeds.

monogamous

Having one mate at a time.

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

riparian

Referring to something living or located adjacent to a waterbody (usually, but not always, a river or stream).

seasonal breeding

breeding is confined to a particular season

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

swamp

a wetland area that may be permanently or intermittently covered in water, often dominated by woody vegetation.

tactile

uses touch to communicate

terrestrial

Living on the ground.

tropical

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

visual

uses sight to communicate

References

2019. "The IUCN Red List of Threatened Species" (On-line). Accessed January 30, 2020 at https://www.iucnredlist.org/en.

Belton, W. 1984.

Birds of Rio Grande do Sul, Brazil. Part 1. Rheidae through Furnariidae
. Bulletin of the American Museum of Natural History, 178(4): 369–636..

Carboneras, C. 1992. Family Anhimidae (Screamers). Handbook of the birds of the world, volume 1: 528-535.

Heckman, C. 1998. The Pantanal of Poconé: Biota and Ecology in the Northern Section of the World’s Largest Pristine Wetland. Springer Science & Business Media.

Klass, J., C. Lynch. 2017. Population analysis and breeding and transfer plan: crested screamer (Chauna torquata). AZA SSP Yellow Program: 1-36.

Lana, F., et al. 2019. Mortality of Four Captive-Born Crested Screamer Chicks (Chauna torquata).

Open Veterinary Journal
, vol. 9, no. 2: 25-120.

Lozano, J., A. Malo. 2016. Relationships Between Human Activity and Richness and Abundance of Some Bird Species in the Paraguay River (Pantanal, Brazil). Ardeola, 60: 99-112.

Luz, X. 2015. Ecologia alimentar da ave herbívora Chauna torquata no Taim, sul do Brasil. repositorio.furg.br.

Olson, S. 1980. Presbyornis and the Origin of the Anseriformes (Aves: Charadriomorphae). Smithsonian Contributions to Zoology, 323: 1-24.

Parker, T. 1982. Observations of Some Unusual Rainforest and Marsh Birds in Southeastern Peru. The Wilson Bulletin, 94: 477-493.

Picasso, M. 2014. Senckenberg Vertebrate Zoology. A peculiar association: the skin and the subcutaneus diverticula of the Southern Screamer (Chauna torquata, Anseriformes), 25: 245-249.

Rand, A. 1954. On the Spurs on Birds' Wings. The Wilson Bulletin, 66: 127-134.

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