The most detailed profile of the behavior of the Horned Screamer is by Naranjo (1986), the primary source for the following summary.
A Horned Screamer's time is mainly spent standing, sleeping, preening and foraging. Flying is rare, especially in comparison with the two other screamer species. To move from one foraging site to another, Horned Screamers wade or walk for an average of 22.0 seconds; flights commonly are short, lasting 5 seconds on average. Standing is by far the most common behavior, especially as the day progresses. Horned Screamers stand with their neck partially retracted, wings folded, and sometimes, with one leg raised. Preening is more common in the early morning and the most time preening is spent on the breast.
There are other behaviors associated with standing and preening such as wing-shake, head-shake, and tail-wag. In between bouts of standing and preening, Horned Screamers also perform the jaw-stretch, wing-and-leg-stretch, and both-wings-stretch. When sleeping, the birds close their eyes and rest the bill on the retracted neck or buried in the back feathers.
There is some indication that Horned Screamers' home ranges are defended territory. Barrow et al. (1986) reported territorial calls after sunrise by birds perched in trees within their territory. In one study, there were one or more choruses of loud calls every day that may suggest territory defense. In the same study, which lasted a year, there were two displays of territoriality consisting of an attack on the foreigner and increased vocalizations. The low number of displays of territoriality in this study, however, could be accounted for by the reduced size of population, as a higher frequency of displays was recorded in other studies (Naranjo 1986).
The home range is large; in one site in Colombia, the mean home range size was 10.7 ha (± 8 ha) (Naranjo 1986).
Unlike other screamer species, the Horned Screamer is known to have a courtship display. Before copulation, the male screamer walks around a standing female with his bill pointing downward, neck retracted, dorsal feathers partially erected, and wings partially opened with the carpal joint facing towards the floor. After circling 1-3 times, the male bows in front of the female (Naranjo 1986) Occasionally, there will also be head-flicking (Barrow et al. 1986, Naranjo 1986).
The Horned Screamer is a monogamous species and pair-bonding behavior includes allopreening, calling, head-arching, and mock-preening (Naranjo 1986, Kear 2005). In Naranjo's study, these bonds were stable, but there was one instance of a juvenile courting an adult female that ended in aggression. The male adult mate and the male juvenile became engaged in a fight that involved the carpal spurs, crop inflation, and neck grappling. After 40 seconds, the male adult left the site and the male juvenile and adult female vocalized in duet form (Naranjo 1986).
Social and interspecific behavior
Horned Screamers tend to aggregate in pairs. Sometimes these pairs socialize in larger groups, but these groups rarely are larger than six. Solitary individuals also are common (Gill et al. 1974, Naranjo 1986). Social behaviors among these birds are social-preening and head-bobbing (Naranjo 1986). They also call between groups (Gill et al. 1974).
Interspecifically, Horned Screamers have been reported interacting with Southern Lapwings (Vanellus chilensis), which sometimes mob screamers. Naranjo reported that if a Southern Lapwing in flight came near a standing screamer, the screamer stretched the neck in the alarm posture, then bowed and called (Naranjo 1986).
There is no information regarding natural predation on Horned Screamers. However, the eggs of screamers are consumed in human households in the Amazon (Gonzales 1999).