Horned Screamer (Anhima cornuta) Science Article 1
An isolated population of the Homed Screamer (Anhima cornuta) in the Cauca Valley, Colombia, was studied intensively during 1983-1984. Variation of head plumage allowed me to identify individuals. This group of approximately 25 adults is the only breeding population of the species in southwestern Colombia. Home ranges were fairly large areas on the shoreline of the lagoon (K = 10.7 ha). Defense of home ranges involved both vocal displays and physical fights. Most activity occurred from 10:00 to 18:00. Long sessions of preening occurred during the early morning. Screamers fed on nine species of aquatic plants and were observed digging into mud. Besides preening and standing, seven comfort movements were identified: wing-shake, head-shake, tail-wag, wing-and-leg-stretch, two-wing stretch, one-wing stretch, and jaw-stretch. Of these movements, only the headshake was performed as a part of the courtship behavior. Reproduction took place from late November to early May. Courtship involved social preening and an elaborate display performed by the male. Nests were floating platforms located within emergent vegetation. The average clutch size was 4.5 eggs, which were incubated by both sexes throughout the 47-day incubation period.
LUIS G. NARANJO, Wilson Bull., 98(2), 1986, pp. 243-256