Wreathed Hornbill ( Rhyticeros undulatus )

Previously considered in genus Aceros. Previously considered separate and then conspecific with Plain-pouched Hornbill. Northern mainland population (somewhat larger) and Borneo population (smaller) has been proposed as subspecies but variations appear gradual and racial separation unwarranted.

Male 100-117 cm; female 84-98 cm. Male 2043-3650 g; female 1360-2685 g. Large distinct hornbill (see Plain-pouched Hornbill for differences), male from Wrinkled Hornbill male by brown (not black) cap and nape ivory white with brown at the base (not stained bright yellow), bill with low casque and ridges on bill sides and casque, and black band across yellow pouch.

Female has distinct brown ridges on white bill and black band across blue pouch. Juveniles of both sexes resemble adult male in plumage, but bill smaller without casque. The call is a loud series of 2-3 short grunts oek-uk-uk used by both sexes, both as a soft contact call or a loud roar.

The wing-beats are audible to at least 1 km, softer during rain when feathers are wet.

Wreathed Hornbill

Ecology and habits

Occurs in extensive tracts of primary rainforest, mainly in the foothills, but has been recorded to 2,560 m elevation. Locally it will extend into coastal forest and adjacent selectively logged forest.

There it feeds mainly on fruits high in large forest trees. This hornbill is well studied; fruits of more than 30 different genera of trees have been identified and are similar to those eaten by Great Hornbill; the proportion of figs and lipid-rich drupes vary according to location and season, and ranges further when not breeding and fewer lipid-rich fruits available.

Animal food is  generally less than 5% of the diet, but more during the breeding season when extra protein is needed. Prey includes bird eggs and nestlings, reptiles, insects, snails, centipedes and crabs. Although mainly a canopy bird, it has been known to descend to the ground to collect fallen fruit or catch terrestrial prey.

Mainly sedentary but will fly far and high across the forest to visit fruiting trees, also crossing open water between islands. The home range of a breeding pair is about 10 km2 in Thailand.

Outside of the breeding season, during the so-called flocking season, the home range extends to about 28 km2, and large flocks will gather at communal evening roosts, as many as 1,000 birds having been counted in one area.

Wreathed Hornbill
Wreathed Hornbill

Breeding ecology

Well studied, especially in Thailand. Eggs laid during Apr-Jun in India, Jan-Mar in South-east Asia, extending to Jun-Aug in Borneo and Java. In Thailand nesting begins in Jan and lasts till May-Jun.

The nest is a natural cavity in a large , live forest tree often Dipterocarpaceae  (Dipterocarpus gracillis, Hopea, Shorea, Neobalanocarpus) and Myrtaceae (Cleistocalyx nervosum, Syzygium) at 6-45 m above the ground; the same tree can be used year after year.

The female seals herself in using her droppings and lays 1-3, usually 2 eggs; only a single chick fledges. The incubation period is about 90 days in the nest, and the female and the chick will break out and leave the nest together; the total nesting cycle lasts 99-161 days (average 126 days) .

The family may stick together, sometimes until the next breeding season, but fledgling may separate from its parents as soon as three months after leaving the nest.