Knobbed Hornbill Rhyticeros cassidix


Justification of Red List Category
This species has been uplisted to Vulnerable because it has a rapidly declining population owing to destruction of its forest habitat, hunting, gold mining and fires.

Population justification
The global population size has not been quantified, but the species is reported to be locally very common (del Hoyo et al. 2001, Kinnarid and O'Brien 2007).

Trend justification
The population is suspected to be declining rapidly owing to ongoing habitat destruction (16.9% forest loss per ten years during 1985-1997; 36.1% loss per ten years during 1997-2001 on Sulawesi [based on D. Holmes in litt. 1999 and Kinnaird and O’Brien 2007]) and hunting for food, gold mining and fires (del Hoyo et al. 2001).

Distribution and population

This species is endemic to Sulawesi and offshore islands of Lembeh, Togian Islands, Muna and Butung, Indonesia. It is described as 'common' in at least parts of its range (del Hoyo et al. 2001). However, a recent analysis has suggested that this species may be declining at a rate approaching 40% over three generations based on recent and ongoing rates of habitat loss on Sulawesi (D. Holmes in litt. 1999, Kinnaird and O'Brien 2007).


The species inhabits evergreen forest up to 1,800 m asl, especially in lowalnds below 1,100 m asl, where it extends into patches of secondary forest, woodland and plantations to forage. Feeds mainly on fruit, but also on animals, including insects, bird eggs and nestlings. It forages mainly in the canopy, even plucking off fruits in flight. Also digs in soft wood. Chases off other birds and primates at feeding sites. In Gorontalo, Sulawesi, the species has been observed foraging in primary and abandoned selectively logged forest, including those in fairly close proximity to human settlements (D. Mulyawati in litt. 2010). It requires large trees for breeding, nesting in natural holes 13-53 m up in tall forests trees (Kinnaird and O'Brien 1999, del Hoyo et al. 2001, F. Lambert in litt. 2011).


The species is threatened with habitat destruction, with forest on Sulawesi being lost at a rate of 16.9% per ten years during 1985-1997; and 36.1% per ten years during 1997-2001 (based on D. Holmes in litt. 1999 and Kinnaird and O’Brien 2007). The species's specialised breeding requirements (including dependence on large trees) makes them particularly vulnerable to forest loss and degradation (e.g. Winarni and Jones 2012). Hunting is a serious threat, as well as gold mining and fires (following exceptional fires in 1997, fieldwork showed a significant drop in breeding success and population recruitment in subsequent years) (del Hoyo et al. 2001)

Conservation actions

Conservation measures underway
None is known

Conservation measures proposed
Conduct further surveys to clarify its current distribution and status. Monitor trends in the population. Protect remaining extensive tracts of forest, extend existing protected areas where appropriate, and strictly control hunting in protected areas. Lobby for improved logging practices that leave patches of old growth or large trees. Design and implement hornbill conservation programmes aimed at reducing hunting levels.



Text account compilers
Gilroy, J., Westrip, J., Derhé, M., Butchart, S., Ekstrom, J.

Holmes, D., Lambert, F., Kinnaird, M., Mulyawati, D., O'Brien, T.

Recommended citation
BirdLife International (2022) Species factsheet: Rhyticeros cassidix. Downloaded from on 07/10/2022. Recommended citation for factsheets for more than one species: BirdLife International (2022) IUCN Red List for birds. Downloaded from on 07/10/2022.