The Southern Screamer is one of three species of screamers. It is endemic to South America. It occurs subtropical to tropical wetlands and marshes, and can be found in crop fields. The Southern Screamer is herbivorous with a diet of aquatic plants, seeds, and other vegetation. This species is well known for its loud and harsh vocalization during flight.
The Southern Screamer is most similar to the Northern Screamer (Chauna chavaria), but the neck of the Northern Screamer is almost entirely black, and it has a contrasting white throat and sides of the face. The two species do not overlap geographically.
The following description is based on Blake (1977):
Sexes similar. Large bodied, with stout tarsi and toes, and a relatively short, "chicken-like" bill. Rear crown has a crest, usually recumbent, of elongated, pointed feathers. Head and upperparts gray. Remiges and rectrices fuscous. Collar, composed of feathers with a velvety texture, around base of neck black; usually there is a faint white neck ring above the black. Foreneck, breast and sides pale gray, with indistinct white mottling and streaking; belly less marked, almost uniform pale gray or white. Underwing coverts white. Manus has two sharp, spike-like spurs, the more proximal of which is the longer of the two.
Unlike other Anseriformes, screamers molts gradually; hey do not have a flightless period during their molt (Carboneras 1992). Otherwise, little information. In the two other species of screamer, the Horned Screamer (Anhima cornuta) and the Northern Screamer (Chauna chavaria), primary molt commences with the innermost primary (P1) and follows a descending sequence in early stages: 1-2-3 or 1-2-3-4; the middle and outer primaries, however, apparently are replaced in no regular sequence. The sequence of molt of the rectrices also seems to be irregular in screamers (Haffer 1968). In Argentina, molt is in the southern "summer and autumn" (Weller 1967), implying that molting follows breeding.
Iris brown (Blake 1977) or orange-brown (Belton 1984). Orbital skin rosy (Blake 1977) or reddish pink (Belton 1984), cere pinkish gray (Belton 1984).
Bill grayish brown.
Linear measurements from Blake (1977):
Total length: 830-900 mm
Wing length (flat), male: mean 549.7 mm (range 525-568, n=7)
Wing length (flat), female: mean 530.8 mm (range 498-562 mm, n=8)
Tail length, male: mean 238.4 mm (range 226-265 mm, n=7)
Tail length, female: mean 226 mm (range 216-232 mm, n=8)
Culmen (from base), male: mean 44.6 mm (range 41-48 mm, n=7)
Culmen (from base), female: mean 46.1 mm (range 40-54 mm, n=8)
Mass: ca 4400 g (n=1, female; Belton 1984)