The species is generally active, and it frequently twitches its tail, flicks its wings, and will raise its crest if alarmed. Alarm behavior, such as mobbing, commonly is observed (Willis 1985). This species prefers to hide in undergrowth in the presence of humans (Skutch 1954, 1989, Restall et al. 2007,). However, it will come to investigate squeaking or pishing (Ridgley and Tudor 1989). The tanager’s conspicuous yellow underparts may be related to its nervous antipredator behavior (Willis 1985). Mobbing behavior has been reported directed at several species of bird, an ocelot (Felis pardalis), a squirrel (Sciurus sp.) and an opossum (Didelphis marsupialis).
Foraging: Gray-headed Tanagers forage both in association with army ants as well as away from them. When foraging away from ants, the Gray-headed Tanager typically feeds from perches 5-15 m above ground (Willis 1985). They forage mostly by sallying from their perches, snapping arthropods off the underside of leaves (Willis 1985). Hovering and foliage gleaning sometimes also are used (Willis 1985).
In Central America and north and west of the Andes in South America, they frequent army ant swarms. They are described as professional ant-followers known to attend army ant swarms (Eciton burchelli, Labidus praedator) as a means of finding insects (Oniki 1971, Isler and Isler 1999, Roberts et al. 2000, Restall et al. 2006). When foraging in association with ants, the Gray-headed Tanager spends its foraging time close to the ground, rarely going higher than 10 m. Once an active ant bivouac has been spotted, the Gray-headed Tanager perches quietly and then darts into a swarm to go after any insects that flee from the ants (Swartz 2001). Boinski and Scott (1988) note a similar strategy is used in the wet season with squirrel (Saimiri oerstedi) and capuchin monkeys (Cebus capucinis) in Costa Rica. The tanagers perch on a low branch below active monkeys and sally out for insects as the monkeys disturb the foliage above. There are only two other species of birds known to follow monkeys in Costa Rica (Boinski and Scott 1988). In a similar manner, Gray-headed Tanagers have also been observed eating insects that have been scratched up by chickens in Costa Rica (Isler and Isler 1999).
Agonistic Behavior: Both interspecific and intraspecific agonsitic behavior was commonly observed by Willis (1985). Gray-headed Tanagers compete with a variety of other species for access to ant swarm centers. Interspecific agressive behaviors used in these encounters include beak snapping, gaping, hissing, and pecking (Willis 1985). When challenged by members of its own species, the Gray-headed Tanager employs a variety of behaviors (Willis 1985). These include loud vocalizations, rapid flying back and forth, and exaggerating various aspects of their plumage including the throat, crest, tail, and wings. Willis (1985) noted that in aggressive displays in Panama, the crest is held flat; however, east of the Andes, he observed that the crest is raised in aggressive displays.
Self-maintenance: Preening usually takes place on horizontal branches, after which the bird often sits quietly, with its body feathers fluffed to help conserve energy (Willis 1985). The species scratches its head over the wings; yawning, flexing the wings above the back, and stretching the wing, tail and leg have all been observed (Willis 1985). Willis (1985) noted frequent sunbathing, but observed bathing in water only once.