Chauna torquata

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).

• Biogeographic Regions
• neotropical neotropical
  • native native

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).

• Habitat Regions
• tropical tropical
• terrestrial terrestrial
• freshwater freshwater

• Aquatic Biomes
• lakes and ponds
• rivers and streams

• Wetlands
• marsh marsh
• swamp swamp

• Other Habitat Features
• agricultural agricultural
• riparian riparian

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).

• Other Physical Features
• endothermic endothermic
• homoiothermic
• bilateral symmetry bilateral symmetry

• 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.

• Mating System
• monogamous monogamous

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

• Key Reproductive Features
• iteroparous iteroparous
• seasonal breeding seasonal breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual sexual
• oviparous oviparous

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.

• Key Behaviors
• flies
• glides
• diurnal diurnal
• motile motile

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).

• Communication Channels
• acoustic acoustic

• Other Communication Modes
• duets duets

• Perception Channels
• visual visual
• tactile tactile
• acoustic acoustic
• chemical chemical

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.

• Primary Diet
• herbivore herbivore
  • folivore folivore

• 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.

• 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).

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).

Additional Links

Encyclopedia of Life

Contributors

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

References

Belton, W. 1984.

Birds of Rio Grande do Sul, Brazil. Part 1. Rheidae through Furnariidae

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

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.

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