The Resplendant Quetzal forages primarily by sallying for fruit, plucking it from trees on the wing. Quetzals also occasionally sally for fruits from understory shrubs or pursue lizards on the ground (Wheelwright 1983). Its large flight muscles - 21% of the total body mass- reflect its primarily aerial foraging mode (Wheelwright 1983). Additionally, the quetzal's digestive track has unique adaptations presumably associated with eating fruit with large seeds. Wheelwright (1983) found the esophagus to have a thin wall, elasticity, and rings of circular muscles, likely to aid in the regurgitation of large seeds. Quetzals lack a crop, and the intestine and caecal sacs often are full of fruit skins, probably indicating bacterial digestion (Wheelwright 1983). The flexible mandible and clavicle of the bird enable it to swallow wider fruit than predicted based on the gape.
The Resplendent Quetzal has been described as wary and cautious by Bowes and Allen (1969), who found it to sit motionless for long periods of time and orient itself so the bright red on the underside would not be visible to an intruder. It will turn its head from side to side, looking in each direction for 1-3 minutes.
Skutch (1944) observed male quetzals to commonly take flight by dropping backward off a branch. LaBastille et al. (1972) reported this behavior in both males and females.
Preening was noted on occasion by LaBastille et al. (1972), and it was described as pecking under and around the wings and breast. They once noted a female leave the nest hole, preen for five minutes, and then return to the hole.
The average territory defended by a quetzal includes a 305 m radius around the nest tree (Bowes and Allen 1969). Bowes and Allen (1969) estimated the average home range to be 15 to 25 acres per pair.
Bowes and Allen (1969) observed a female quetzal attack a stuffed quetzal placed outside her nest hole. Wheelwright (1983) observed both sexes chase off Emerald Toucanets (Aulacorhynchus prasinus).
During spring the male performs flight displays, flying above the canopy and then ascending while vocalizing (Skutch 1944). Wheelwright (1983) observed that some pairs had formed before returning to the breeding area in higher elevations of Costa Rica while some birds still were unpaired. Among the unpaired birds, Wheelwright (1983) observed up to four males simultaneously chasing females. LaBastille et al. (1972) also witnessed courtship chasing while vocalizing. Copulation is believed to occur in association with the pair's shared nest building activities (Wheelwright 1983).
Social and interspecific behavior
The species generally is solitary; Bowes and Allen (1969) never saw more than three together. Occasionally may aggregate at food sources. Wheelwright counted up to 20 individuals in a heavily fruited tree during the breeding season.
While Wheelwright (1983) indicated nest failure to be high (67-78%) and likely primarily from the long-tailed weasel (Mustela frenata), he also noted defense against squirrels and Emerald Toucanets (Aulacorhynchus prasinus). He suggested that snakes, botflies, and larger animals also may predate the nests. In contrast, he believed the predation on adults to be limited and reported only two cases of predation on an adult: one by an unidentified hawk and one brooding adult taken by a margay (Leopardus wiedii). Bowes and Allen (1969) suggested the quetzal predators may include red-bellied squirrel (Sciurus aureogaster), kinkajou (Potus flavus), and the Ornate Hawk-Eagle (Spizaetus ornatus), as well as other hawks and owls.