Justification of Red List Category
This species is considered intolerant of habitat loss, requiring large areas of undisturbed forest, in a region which is experiencing high rates of deforestation. High hunting pressure is likely exacerbating the population decline caused by habitat loss. The species is suspected to undergo a large population reduction over the next three generations. Therefore, it is listed as Vulnerable.
The global population size has not been quantified, but the species is reported to be locally common in several areas across its wide range (del Hoyo et al. 2001).
The population is suspected to be in decline owing to ongoing habitat destruction and fragmentation (del Hoyo et al. 2001). An analysis of deforestation between 2000 and 2012 estimated forest loss within the species's range at 32.8% over three generations (57 years) (Tracewski et al. 2016). The rate of population decline is suspected to be greater than this because the species is intolerant of degraded and secondary habitat, but requires large tracts of undisturbed forest. In addition, it is also threatened by hunting. Thus, the rate of decline is precautionarily placed in the band 30-49% over three generations. Since this species has a long generation length, with three generations stretching over 57 years, there is insufficient evidence to calculate the magnitude of reduction over the past three generations. Assuming the recent rate of decline remains constant, the species is projected to decline by 30-49% over the next three generations.
The species occurs in south-east Asia from southern Bhutan, Bangladesh and north-east India east to Cambodia, Laos and Vietnam, and south through Malaysia and Thailand to Indonesia (Sumatra, Borneo, Java, Bali and several nearby islands) and Brunei.
The species occurs in extensive primary rainforest, mainly in the lowlands (Poonswad et al. 2013, Kemp and Boesman 2018). During the non-breeding season, it ranges higher uphill (A. Datta and R. Naniwadekar in litt. 2018), up to 2,560 m. It tolerates selective logging (Kemp and Boesman 2018), but generally avoids disturbed habitats and proximity to human population (A. Datta and R. Naniwadekar in litt. 2018).The species forages in the canopy of large trees, where it mainly consumes different fruits (Poonswad et al. 2013, Kemp and Boesman 2018). Nests are placed in natural cavities high up in Dipterocarpus or Syzygium trees (Kemp and Boesman 2018). The same cavity is often used several times throughout suscessive breeding seasons (Kemp and Boesman 2018).
Forest destruction in the Sunda region has been extensive as a result of commercial and illegal logging, conversion to agriculture (particularly plantations) and increasing human population pressure. The species generally prefers areas with extensive forest cover, while it avoids areas with even low human population (A. Datta and R. Naniwadekar in litt. 2018). The species has a very large home range (Keartumsom et al. 2011) and therefore requires large tracts of undisturbed forest. Its preferred lowland forest habitat is particularly impacted by deforestation, even within protected areas (Kemp et al. 2018). An analysis of forest loss from 2000 to 2012 estimated deforestation within the species's range at 32.8% over three generations (Tracewski et al. 2016). In north-eastern India, only 5% of the landscape offers suitable habitat (Naniwadekar et al. 2016). There, the species has disappeared from places where it used to be common (A. Choudhury in litt. 2018), while it declined in abundance at sites where it still persists (A. Datta and R. Naniwadekar in litt. 2018).
Even though the species is less hunted than the Great Horbill Buceros bicornis (A. Datta and R. Naniwadekar in litt. 2018), hunting poses a substantial threat. A survey in north-eastern India found that the species is mainly targeted for its meat or as a trophy (A. Datta and R. Naniwadekar in litt. 2018). Apart from that, its feathers are used as for cultural reasons by local communities and and its fat is highly prized for medical purposes (A. Datta and R. Naniwadekar in litt. 2018). The species may also be taken as 'bycatch' by hunters targeting Helmeted Hornbill Rhinoplax vigil (R. Wirth in litt. 2017).
Conservation Actions Underway
CITES Appendix II. Occurs in several protected areas across its range, including Khao Yai National Park in Thailand, Ulu Belum and Gunung Mulu National Parks in Malaysia and Bali Barat National Park in Bali (Kemp and Boesman 2018).
Conservation Actions Proposed
Monitor populations across its range to determine the magnitude of declines and rates of range contraction. Campaign for the protection of remaining extensive tracts of forest throughout its range, including lowland and adjacent foothill forest. Develop a programme to reduce hunting of the species through raising awareness of the status of the species within communities that target the species.
Text account compilers
Hermes, C., Ekstrom, J., Westrip, J., Butchart, S.
Wirth, R., Datta, A., Naniwadekar, R.N., Choudhury, A.
BirdLife International (2020) Species factsheet: Rhyticeros undulatus. Downloaded from http://www.birdlife.org on 31/05/2020. Recommended citation for factsheets for more than one species: BirdLife International (2020) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 31/05/2020.