Rhinoplax vigil
Red List Status: CR – Critically Endangered, criteria A3cd (IUCN 2020)
Distribution: Sunda subregion; south Myanmar, south Thailand, Peninsular Malaysia and Borneo plus Sumatra. Absent from Java and smaller offshore islands; a historical record from Singapore is doubtful.
Description: 110-127 cm. Male 3060 g; female 2610-2840 g. Very large hornbill with characteristic elongated central tail feathers of extra 30-45 cm; wings with creamy-white trailing edge. The relatively short bill and front of a high red casque are cosmetically stained with yellow from preen oil. Male has a bare redneck. The heavy anterior casque is solid ‘ivory’. The female is smaller with pale bluish skin on neck and smaller casque. Juvenile has a shorter tail, small yellow bill with low casque and light greenish-blue head and neck.
Voice: The male makes a unique call that can be heard over 2 km away; it is one of the distinguishing sounds of undisturbed Sundaic rainforest. The male positions himself high in the forest; the call starts as a series of slow deep honking notes, in the beginning far apart; then the notes build up gradually in speed, before climaxing in loud maniacal laughter. Bouts of penetrating calls like this, with a few minutes interval, can last for one hour; the female will sometimes join in in a duet, her pitch a bit higher.
Audio for this species is restricted for the safety of the species. If you would like to find out more or ask recordists for their audio files, the xeno-canto page is linked here.
Habits: Found in large expanses of primary Sundaic rainforest; extends into adjacent closed secondary forest. Seemingly prefers hilly terrain away from the coast, often at 300-1,100 m elevation, occasionally to 1,500 m. It is shy and wary and rarely comes to the forest edges, preferring remote and rugged terrain. The food is mainly fruits, especially many fig species. In southern Thailand, besides figs, other dominant fruits recorded are in families Annonaceae (Polyalthia), Meliaceae (Aglaia, Dysoxylum), Arecaceae (Oncosperma horridum), Lauraceae (Litsea) and Myristicaceae (Horsfieldia and Myristica). Throughout its range, this is the hornbill with the most specialised diet. Surveys of Helmeted Hornbill have shown that it spends about half the day actively hunting animal prey, including rodents, reptiles and nestlings, even smaller sympatric hornbill species. It moves about high in large forest trees and is surprisingly quick and agile when chasing down prey; probes into bark and cavities with its short, strong bill. It is a bit of a loner, and even a pair will split up and feed separately within their home range. Largely territorial and sedentary; males and females have been observed banging the solid casques together, often in flight presumably in status or territorial disputes. Aerial jousting is not uncommon but jousting to death is rare. It will fly far across the forest to visit good fruiting trees and will mix with other hornbills while feeding; outside of the breeding season up to 27 birds have been reported together.
