Justification of Red List Category
This species has an extremely large range, and hence does not approach the thresholds for Vulnerable under the range size criterion (extent of occurrence <20,000 km2 combined with a declining or fluctuating range size, habitat extent/quality, or population size and a small number of locations or severe fragmentation). The population trend appears to be stable, and hence the species does not approach the thresholds for Vulnerable under the population trend criterion (>30% decline over ten years or three generations). The population size has not been quantified, but it is not believed to approach the thresholds for Vulnerable under the population size criterion (<10,000 mature individuals with a continuing decline estimated to be >10% in ten years or three generations, or with a specified population structure). For these reasons the species is evaluated as Least Concern.
The global population size has not been quantified, but the species is reported to be the commonest Asian hornbill (del Hoyo et al. 2001). During a national population survey in 2004-2008 in Thailand, the population density was estimated at 21 individuals/km2 in Khao Yai National Park, while abundance indices in other areas ranged from 0.01-0.9 individuals/km2 in eight forest complexes (Poonswad et al. 2013). In eastern Malaysia, population density estimates range from 2.22 individuals/km2 in Tawan Hills to 19.65 individuals/km2 in Pulau Tiga Park (Lakim and Biun 2005). In Kuala Lompat in Peninsular Malaysia, the population density is 1 individual/km2 (Medway and Wells 1971).
Long-term surveys conducted at five protected areas in Bangladesh since 2005 indicate a gradual decline in population density. Twenty years ago, the species used to occur in 14 protected areas surveyed, but was recently found only in eight of these, of which all but one show population decreases (S. U. Chowdhury in litt. 2019).
In India, a study in 2007-2008 in Arunachal Pradesh found densities of around 19 individuals/km2 in Pakke Tiger Reserve, which dropped to five individuals/km2 in the less protected adjoining Reserved Forests (Dasgupta and Hilaluddin 2012). In a 2013 study, the density estimate was 14 individuals/km2 in the Pakke Tiger Reserve (Naniwadekar and Datta unpubl. data). Despite it being more common in secondary forest, the species was detected in only three of 14 sites surveyed, although reported as present in nine sites by locals and not seen in the previous five years at two sites (Naniwadekar et al. 2015) in a survey in Arunachal Pradesh. In a survey across five states in north-east India, the the average habitat-use probability of the species in the 370 sampled grids was 0.69 (SE 0.01). Of a total of 3,153 grids (covering 154,497 km2), the number of grids with relatively high probability of habitat use (≥ 0.75) was 1,167 (57,183 km2) (Naniwadekar et al. 2016).
In Singapore, the species is breeding in Pulau Ubin, Changi, Pasir Ris Park and a few other locations. The population is increasing in Singapore, benefiting from green corridors. A study carried out in 2018 showed that the distribution area increased from four subzone areas in 2004-2006 to 61 subzone areas in 2016-2018 based on compiled sightings (per B. C. Strange in litt. 2020).
The population is suspected to be stable in the absence of evidence for any declines or substantial threats.
Anthracoceros albirostris is a widespread resident in northern South Asia. It occurs in southern Nepal, southern China, southern Bhutan, northern Bangladesh, northern and north-eastern India, Myanmar, Viet Nam, Laos, Cambodia, in parts of Thailand, Singapore, north-eastern Peninsular Malaysia and western Indonesia and Brunei.
In Thailand, it is the most common and most abundant hornbill in many forest complexes, except in the north and north-east (Poonswad et al. 2013). Also in Bangladesh, it is the most widespread hornbill, but shows declining trends over the past ten years (S. Chowdhury in litt. 2020).
In India, the species is among the most common hornbills and is abundant in the northern, eastern and north-eastern part of the country. Its range overlaps with that of the Malabar Pied Hornbill Anthracoceros coronatus in Jharkand, Bihar, Odisha and north-eastern Andhra Pradesh. Both species are recorded in north-eastern Andhra Pradesh and Odisha, albeit in different areas (A. Datta in litt. 2020, eBird 2020). The species is observed in small cities and towns in India, including highly urbanised cities with large areas of green cover, like Chandigarh and Delhi (A. Datta in litt. 2020). The record from Chandigarh is among the westernmost record of this species (Datta et al. 2018).
In Peninsular Malaysia, Sabah and Sarawak, the species is found in protected and non-protected areas (Kemp and Kemp 1974, Davies and Payne 1982, Siti Hawa Yatim et al. 1985, Davison 1987, Muda and Suib 1989, Wells 1990, Chong 1993, Siti Hawa Yatim 1993, Davison 1995, Chong 1998, Smythies 1999, Wells 1999, Lim and Tan 2000, Ong et al. 2000, Choo and Teresa 2001, Norsham and Teresa 2001, Sheldon et al. 2001, Sim and Liam 2001, Abdul Kadir Abu Hashim 2002, Tuen 2005, Styring et al. 2011, Yong et al. 2011, David et al. 2017, McKenzie and Tuyah 2017, Unggang et al. 2017). Most of these areas have been identified as Important Hornbill Landscapes (IHL), which are designated as Important Bird Areas and linked to the Central Forest Spine Masterplan for Peninsular Malaysia (Yeap and Perumal in press).
The species can be found in forest edge, open, moist deciduous and evergreen forests, riverine forest, secondary, logged forests and even gardens and agricultural fields. The species shows a preference for secondary growth, river-margin forests (Datta 1998). It is usually recorded in elevations up to 700 m. Flocks of up to 170 individuals have been recorded in Khao Yai National Park during the non-breeding season (Poonswad et al. 2013).
The species’s diet consists of figs, non-figs and animal prey (Smythies 1999, Wells 1999). 94% of the diet was figs and non-figs (in equal proportions) and 6% animal matter in the non-breeding season in Arunachal Pradesh (Datta and Rawat 2003). The species has also been seen feeding on papaya, rambutan, mango, banana and other cultivated fruit crops close to villages and beach resorts. Amongst wild fruits other than figs, it prefers Polyalthia, Horsfieldia, Strombosia and Dysoxylum. Animal prey include insects, centipedes, millipedes, scorpions, spiders, snails, earthworms, lizards, small birds and eggs, rats and sometimes fish and crabs from near streams (Poonswad et al. 2013). The species is adapting to urban conditions by taking advantage of feeding stations and taking leftovers from rubbish bins on Pulau Pangkor (C. A. Yeap pers. obs.) and attempting to snatch song birds in cages in Singapore (Stolarchuk 2018).
The species does not depend on primary forest habitat even for breeding, preferring forest edges, open woodland, coastal and riverine scrub and cultivation instead (Poonswad et al. 2013). Data collected in Piasau Nature Reserve in northern Sarawak suggests that the species may breed twice per year. Eggs are laid at different times of the year across various parts of the range; in February-April on the Asian mainland and in September-May on many Malaysian and Indonesian islands. In north-east India, nest entry is in the 1st to 2nd week of April and chicks fledge between June and July (Datta 2001). The nest is usually found up to a height of 30 m often in Dipterocarpus or Cliestocalyx in Thailand (Poonswad et al. 2013) and on Tetrameles nudiflora in north-east India (Datta 2001). The species often competes for nest cavities with several other hole-nesting birds such as Hill Mynas, Great Slaty Woodpeckers, Broad-billed Rollers and Red-breasted Parakeets, or bees and monitor lizards (Datta and Rawat 2004). The female lays 1-4 eggs which are incubated for 25-33 days, but usually only one or sometimes two chicks successfully fledge. The last chick to hatch is weak and is usually starved to death or eaten by the mother or the sibling. On average, the nesting cycle takes 85-90 days in Thailand (Poonswad et al. 2013) and 94 days in north-east India (Datta 2001).
The species was extremely rare in southern China, but appears to be recovering with better anti-hunting and forest protection campaigns in recent years, with sightings from areas where it was formerly extirpated. In the Thai-Malay Peninsula, the species may be threatened by off-take for the trade in fledglings and forest clearance (Wells 1999). There is some evidence that the species has traditionally been captured for the local pet trade, as historically one to two were reportedly kept in every village in at least some areas of Myanmar (Tickell 1864 in Kemp 1995). Some trade is reported from China (KFBG unpubl. data). The casques of Oriental Pied Hornbills are common souvenirs in the markets of Thailand, Laos and Vietnam; however, the extent of this trade has not been measured (Kinnaird and O’Brien 2007). In India, chicks have been captured for trade in some areas, while in north-east India it has mainly been hunted for meat, feathers and fat, though the level of hunting is much lower than in larger hornbill species (Naniwadekar et al. 2016).
Overall, this species is considered the most adaptable of the hornbills to landscape modification and thus the least threatened owing to its very wide range, small size and broad habitat preferences (S. Mahood in litt. 2012, D. Bakewell in litt. 2012).
Conservation Measures Underway
The species occurs in many protected areas throughout its range, including Rajaji National Park Corbett Tiger Reserve, Buxa Tiger Reserve, Nameri and Pakke Tiger Reserves, Dihing-Patkai Wildlife Sanctuary/Jeypore Reserved Forest (India), Khao Yai National Park (Thailand) and Taman Negara National Park (Malaysia).
Community-based conservation programmes, such as the Hornbill Nest Adoption Programs in north-east India, protects the nest trees of the species, monitors breeding and protects the species from being hunted. In a nine-year period, annually, an average of around 10 chicks fledged successfully from 10 to 22 protected and monitored nests (Datta and Pradhan 2019). In Singapore, the provision of artificial nest boxes in 2005 installed by the Singapore Hornbill Project in Pulau Ubin, Istana and Sungei Buloh Wetland Reserve (SBWR) has secured the return of the species as a nesting breeder, with 50-60 individuals in 2010 (Cremades et al. 2011, Ng et al. 2011, Cremades and Ng 2012, G. Davison in litt. 2012). Between 2008 and 2013, individuals were reintroduced to three locations in Singapore.
19 individuals (including 9 males, 9 females and one juvenile in 2020) are kept in zoos across Europe. A very small captive population of less than 5 individuals in North America shows little breeding success.
Conservation Measures Proposed
Conduct research to determine the population size and trend.
Text account compilers
Bakewell, D., Brouwer, K., Butchart, S., Chan, B., Chowdhury, S.U., Datta, A., Davison, G., Derhé, M., Duckworth, W., Ekstrom, J., Goes, F., Kemp, A.C., Kinnaird, M., Lo, P., Mahood, S., O'Brien, T., Patil, I., Schutz, P., Sherub, Sir, L., Strange, B., Thompson, P., Yeap, C.A. & Zheng, N.
BirdLife International (2021) Species factsheet: Anthracoceros albirostris. Downloaded from http://www.birdlife.org on 07/05/2021. Recommended citation for factsheets for more than one species: BirdLife International (2021) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 07/05/2021.