Trogonidae – Trogons & Quetzals

The Trogonidae or trogons and quetzals are birds in the order Trogoniformes, which contains just one family. The family contains forty-seven species in seven genera. The fossil record of the trogons dates back 49 million years to the Early Eocene. They might constitute a member of the basal radiation of the order Coraciiformes or be closely related to mousebirds and owls. The word ‘trogon’ is Greek for ‘nibbling’ and refers to the fact that they gnaw holes in trees to make their nests.

They are residents of tropical forests worldwide. They have a cosmopolitan distribution in the world’s wet tropics, being found in the Americas, Africa and Asia. A few species are distributed into the temperate zone, with one species, the elegant trogon, reaching the south of the United States, specifically southern Arizona and the surrounding area.

The Narina trogon of Africa is slightly exceptional in that it utilises a wider range of habitats than any other trogon, ranging from dense forest to fairly open savannah, and from the Equator to southern South Africa. It is the most widespread and successful of all the trogons. The eared quetzal of Mexico is also able to use more xeric habitats, but preferentially inhabits forests. Most other species are more restricted in their habitat, with several species being restricted to undisturbed primary forest. Within forests they tend to be found in the mid-story, occasionally in the canopy.

Some species, particularly the quetzals, are adapted to cooler montane forest. There are a number of insular species; these include a number of species found in the Greater Sundas, one species in the Philippines as well as two species endemic to Cuba and Hispaniola respectively. Outside of South East Asia and the Caribbean, however, trogons are generally absent from islands, especially oceanic ones.

The greatest diversity is in the Neotropics, where four genera – Euptiloti, Pharomachrus, Priotelus & Trogon – containing thirty-two species occur. The genus Apaloderma contains the three African species. The genera Harpactes and Apalharpactes, containing twelve species, are found in southeast Asia.

Trogons are generally sedentary, with no species known to undertake long migrations. A small number of species are known to make smaller migratory movements, particularly montane species which move to lower altitudes during different seasons. This has been demonstrated using radio tracking in the resplendent quetzal in Costa Rica and evidence has been accumulated for a number of other species. The Narina trogon of Africa is thought to undertake some localised short-distance migrations over parts of its range, for example birds of Zimbabwe’s plateau savannah depart after the breeding season. A complete picture of these movements is however lacking. Trogons are difficult to study as their thick tarsi (feet bones) make ringing studies difficult.

The calls of trogons are generally loud and uncomplex, consisting of monosyllabic hoots and whistles delivered in varying patterns and sequences. The calls of the quetzals and the two Caribbean genera are the most complex. Among the Asian genera the Sumatran trogon Apalharpactes has the most atypical call of any trogon, research has not yet established whether the closely related Javan trogon has a similar call. The calls of the other Asian genus, Harpactes, are remarkably uniform. In addition to the territorial and breeding calls given by males and females during the breeding seasons, trogons have been recorded as having aggression calls given by competing males and alarm calls.

They feed on insects (particularly caterpillars), other arthropods and fruit, and their broad bills and weak legs reflect their diet and arboreal habits. The three African trogons are exclusively insectivorous, whereas the Asian and American genera consume varying amounts of fruit. Diet is somewhat correlated with size, with larger species feeding more on fruit and smaller species focusing on insects.

Although their flight is fast, they are reluctant to fly any distance. Trogons are generally not migratory, although some species undertake partial local movements. They have soft, often colourful, feathers with distinctive male and female plumage. They are the only type of animal with a heterodactyl toe arrangement (two toes forward and two backwards).

Trogons are territorial and monogamous. Males will respond quickly to playbacks of their calls and will repel other members of the same species and even other hole-nesting species from around their nesting sites. Males attract females by singing, and, in the case of the resplendent quetzal, undertaking display flights. Some species have been observed in small flocks of 3–12 individuals prior to and sometimes during the breeding season, calling and chasing each other, but the function of these flocks is unclear.

Trogons are cavity nesters, and nest are dug into rotting wood or termite nests, with one species, the Violaceous Trogon, nesting in wasp nests. Nest cavities can either be deep upward slanting tubes that lead to fully enclosed chambers, or much shallower open niches (from which the bird is visible). Nests are dug with the beak, incidentally giving the family its name. Nest digging may be undertaken by the male alone or by both sexes. In the case of nests dug into tree trunks, the wood must be strong enough not to collapse but soft enough to dig out. Trogons have been observed landing on dead tree trunks and slapping the wood with their tails, presumably to test the firmness.

The nests of trogons are thought to usually be unlined. Between two and four eggs are laid in a nesting attempt. These are round and generally glossy white or lightly coloured (buff, grey, blue or green), although they get increasingly dirty during incubation. Both parents incubate the eggs (except in the case of the Bare-cheeked Trogon, where apparently the male takes no part), with the male taking one long incubation stint a day and the female incubating the rest of the time. Incubation seems to begin after the last egg is laid. The incubation period varies by species, usually lasting between 16–19 days.

On hatching the chicks are altricial, blind and naked. The chicks acquire feathers rapidly in some of the montane species, in the case of the mountain trogon in a week, but more slowly in lowland species like the Black-headed Trogon, which may take twice as long. The nestling period varies by species and size, with smaller species generally taking 16 to 17 days to fledge, whereas larger species may take as long as 30 days, although 23–25 days is more typical.