The Emerald Toucanet (Aulacorhynchus prasinus) is a near-passerine bird occurring in mountainous regions from Mexico, through Central America, to northern Venezuela and along the Andes as far south as central Bolivia. Some taxa currently included in this species are sometimes split into separate species (see Taxonomy).
Like other toucans, the Emerald Toucanet is brightly marked and has a large bill. The adult is 30–35 cm (12–14 in) long and weight can range from 118–230 g (4.2–8.1 oz) The sexes are alike in appearance, although the female generally is smaller and slightly shorter-billed. It is, as other members of the genus Aulacorhynchus, mainly green. The vent and tail-tip are rufous. The bill is black with yellow to the upper mandible (amount depends on the exact subspecies) and, in all except the nominate (prasinus) and wagleri groups (see Taxonomy), a white band at the base of the bill. The members of the caeruleogularis group have a rufous patch near the base of the upper mandible, while some members of the albivitta group have a rufous patch near the base of the lower mandible. The throat is white in the nominate and the wagleri group, blue in the caeruleogularis and cognatus group, pale grey-blue in the lautus group, blue or black in the atrogularis group, and white or grey-blue in the albivitta group. The eye-ring ranges from blue to red, in some subspecies very dark, almost appearing blackish from a distance. The legs are dull greyish and the iris is dark.
Juveniles are duller, including the throat, and, depending on subspecies, the black areas of the bill are replaced with dusky or the bill is entirely yellowish.
The Emerald Toucanet is a generally common in humid forest and woodland, mainly at higher elevations. The 3–4 white eggs are laid in an unlined hole in a tree, usually an old woodpeckernest, but sometimes a natural cavity. Both sexes incubate the eggs for 14–15 days, and the chicks remain in the nest after hatching. They are blind and naked at birth, and have short bills and specialised pads on their heels to protect them from the rough floor of the nest. They are fed by both parents, and fledge after about 6 weeks. They are fed for several weeks after leaving the nest.
Small flocks, usually consisting of 5–10 birds, move through the forest in “follow-my-leader” style with a direct and rapid flight. This species is primarily an arboreal fruit-eater, but will also take insects, lizards, bird eggs, and other small prey.
The calls of the Emerald Toucanet are a loud dry rrip rrip rrip rrip rrip and a graval graval graval. It has been suggested that the two different calls are given by the two sexes. There are also croaking alarm and aggression calls.