Data Zone
Justification of Red List category
This species is impacted by ongoing forest loss and fragmentation in the lowlands of Sulawesi thought to be causing an ongoing decline of 30-39% over three generations. It is therefore listed as Vulnerable.
Population justification
The global population size of this species has not been quantified although it is described as uncommon (Eaton et al. 2021).
Trend justification
This species is suspected to be declining rapidly because of ongoing lowland forest loss in its range. Because it is a highly forest-dependent species, the rate of forest cover loss is suspected to be matched, if not exceeded, by population size declines. Remote sensing data (Global Forest Watch [2021], using data from Hansen et al. [2013] and methods disclosed therein) indicate that over the past three generations (21 years; Bird et al. 2020) forest loss in this species' range has been equivalent to 26-28% and this rate is suspected to continue, perhaps even accelerate (see Voigt et al. 2021), into the future. Moreover, its requirement of mature trees with large hollows for nesting means that it will also likely be impacted by selecting logging (see Winarni and Jones 2012), which remote sensing data do not elucidate. There may also be local impacts of hunting. Consequently, the species is suspected to be declining at a fairly continuous rate of 30-39% over three generations.
This species is endemic to Sulawesi, Indonesia. The nominate subspecies, R. e. exarhatus, occurs in northern Sulawesi and Lembeh island; subspecies R. e. sanfordi occurs in southern Sulawesi and the islands of Muna and Butung.
The species occurs in lowland primary forest, occasionally tall secondary forest, usually below 650 m asl but sometimes up to 1,100 m. Family groups are sometimes in more open habitats (del Hoyo et al. 2001). Its diet consists mainly of fruit (85%), but also some small animals, mainly invertebrates. It forages mostly through foliage below the canopy. 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). Large trees are predictors of their occupancy (Winarni and Jones 2012). It requires large forest trees for breeding (del Hoyo et al. 2001, F. Lambert in litt. 2011), nesting in natural cavities or old woodpecker holes. It nests in some sites used by Knobbed Hornbill Aceros cassidix. The species breeds co-operatively. Two to ten birds (on average four) tend to one nest; helpers can be both male or female. Eggs are laid between April and October. Incubation occurs for 28-30 days, followed by 55-70 day of fledging period. Usually two eggs are reported in the wild (Pooswad et al. 2013).
The species is threatened with habitat destruction with forest on Sulawesi below 650 m being lost at a rate of nearly 30% over three generations (c.21 years; Bird et al. 2020) (Global Forest Watch [2021], using data from Hansen et al. [2013] and methods disclosed therein). The species' specialised breeding requirements (including a dependence on large trees) makes it particularly vulnerable to forest loss and degradation (e.g. Winarni and Jones 2012). Hunting, both for food and for keeping as pets, is a very localised serious threat (del Hoyo et al. 2001), however is not suspected to be driving significant population declines (T. O’Brien and M. Kinnaird in litt. 2020). MacKinnon and MacKinnon (1980) documented a dramatic crash in the population at Tangkoko in 1978-1979 which may have been driven by disease introduced by domestic poultry into wild populations (T. O’Brien and M. Kinnaird in litt. 2006).
Conservation Actions Underway
It occurs in a handful of protected areas (eBird 2021). The known North American ex-situ population of this species stands at approximately ten birds. There have been low levels of consistent breeding since 2000, but mainly centered at one or two institutions. The majority of this ex-situ population is captive bred (P. Schutz in litt. 2020).
Conservation Actions Proposed
Conduct further surveys to clarify its 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
Berryman, A.
Contributors
Derhé, M., Holmes, D., Kinnaird, M., Lambert, F., Mulyawati, D., O'Brien, T., Schutz, P., Symes, A. & Westrip, J.R.S.
Recommended citation
BirdLife International (2024) Species factsheet: Sulawesi Hornbill Rhabdotorrhinus exarhatus. Downloaded from
https://datazone.birdlife.org/species/factsheet/sulawesi-hornbill-rhabdotorrhinus-exarhatus on 23/12/2024.
Recommended citation for factsheets for more than one species: BirdLife International (2024) IUCN Red List for birds. Downloaded from
https://datazone.birdlife.org/species/search on 23/12/2024.