Plumbeous Kites are typically of a mild disposition until it is perceived that their nests or young are threatened, at which point they can become combative. Plumbeous Kites have often been observed to perch for an hour at a time in the top of a tree or, if it is hot, to seek shelter in a shaded spot on a lower branch. Their flight has been described as "buoyant, easy, and graceful" with their tails spread out and veering from one side to another (Sutton 1944).
The Plumbeous Kite typically forages in flight, either in continuous flight (aerial hunts), or after taking flight from a perch (perch hunts) (Seavy et al 1997). They have been described to hunt and eat ants and other insects while flying, catching their prey with their small, and often dangling, feet (Sick 1993). Aerial hunts can take place anywhere from canopy level to several hundred meters above and typically occur by one of three methods: quick grabs; short, flapping climbs; and/or diving pursuits. In addition to aerial hunts, Plumbeous Kites use the foraging technqiue of perch hunts. In perch hunts, the bird either drops down from its perch on a branch or carries out a short, flapping flight to reach its prey (Seavy et al. 1997). In southeastern Brazil, Plumbeous Kites have formed a foraging association with Buffy-headed Marmosets, feeding on the prey - primarily cicadas - flushed by the marmosets in the course of their own foraging (Ferrari 1990). Individuals forage alone, in pairs, or in groups. At a nest site in Tikal National Park in Guatemala, two adults captured a Northern Rough-winged Swallow (Stelgidopteryx serripennis) and fed it to their nestling. Such tandem hunting, however, is limited to more elusive prey - those that are not insects - and is not commonly observed (Seavy et al. 1997).