Rhyticeros narcondami (del Hoyo and Collar 2014) was previously placed in the genus Aceros.
del Hoyo, J., Collar, N.J., Christie, D.A., Elliott, A. and Fishpool, L.D.C. 2014. HBW and BirdLife International Illustrated Checklist of the Birds of the World. Volume 1: Non-passerines. Lynx Edicions BirdLife International, Barcelona, Spain and Cambridge, UK.
|Migratory status||not a migrant||Forest dependency||High|
|Land mass type||Average mass||-|
|Extent of Occurrence breeding/resident (km2)||7||medium|
|Extent of Occurrence breeding/resident (km2)||7||good|
|Number of locations||1||-|
|Value||Data quality||Derivation||Year of estimate|
|No. of mature individuals||300-650||good||estimated||2020|
|Decline (3 years/1 generation past)||-||-||-|
|Decline (5 years/1 generation past)||-||-||-|
|Decline (10 years/1 generation past)||-||-||-|
|Decline (10 years/3 generation future)||0||-||-||-|
|Decline (10 years/3 generation past and future)||-||-||-|
|Number of subpopulations||1||-||-||-|
|Percentage in largest subpopulation||100||-||-||-|
|Generation length (yrs)||7.2||-||-||-|
Population justification: The population is estimated to number between 750-1,400 individuals (R. Naniwadekar unpublished data in litt. to the IUCN SSC Hornbill Specialist Group 2020). This is based on the 95% confidence interval from an extrapolation of the density estimates derived during fieldwork between December 2019 and February 2020. To estimate the number of mature individuals, two pieces of additional information are used. A previous study investigating the species estimated that the breeding population was 46-53% of the total number of individuals (Vijayan and Sankaran 2000). Second, a male-biased sex-ratio (56/44) was recorded by Manchi (2017), which would slightly reduce the number of mature individuals to consider in the assessment. Using the most recent estimate, the population size is between 345 – 742 mature individuals when applying the proportion of the breeding population from Vijayan and Sankaran 2000, but further reduced if we account for the skewed sex ratio to 304-653 mature individuals, rounded to 300-650 mature individuals.
The earliest known estimate of Narcondam Hornbill population was by Osmaston (1905) who collected ten hornbill specimens and gave a ‘liberal estimate’ of not more than 200 on the island. Based on an approximately month-long survey in March-April 1972, Hussain (1984, 1993) suggested a higher ‘liberal estimate’ of around 400 birds on the island. The first transect-based estimate, based on a 3-month survey in 1998, reported around 330 – 360 birds on Narcondam (Vijayan and Sankaran 2000). Yahya and Zarri (2002) made a brief survey in March 2000 using two line transect methods and estimated the hornbill density at 72/km² and 83/km², suggesting a total population of 432 or 498 birds over 6 km² of habitat estimated to be available. In 2003, Vivek and Vijayan (2003) found the overall density of the species was estimated at around 54 individuals per km² (Vivek and Vijayan 2003). The population was estimated to number 320-340 individuals, based on an effective area of habitat of 6 km2.
The results of these studies were interpreted by Kinnaird and O'Brien (2007) to equate to fewer than 250 mature individuals, hence the population was placed in the band 50-249 mature individuals. However, since 2010 all studies indicate that the numbers are higher. In a 4-day survey in April 2010, the density of Narcondam Hornbills estimated using variable-width line transect surveys on trails in lowland forest was found to be around 167 birds/km² (95% confidence interval of 63.3–271 individuals/km²) (Raman et al. 2013). Raman et al. 2013 emphasised that the density should not be extrapolated to the island as the trails surveyed were non-randomly placed. Manchi (2017) reported a density of 190 ± 81 birds/km2 based on transect surveys with an estimated population of 1295 birds (extrapolated for the whole island). However, most of the population is distributed below 500 m above msl, hence the total population was likely an overestimate.
Trend justification: Its population appears to be stable or increasing following efforts to reduce hunting and habitat degradation, as well as the removal of feral goats and almost all introduced cats (Manchi 2017, R. Naniwadekar in litt. 2020). Although recent (2010 onwards) density estimates are higher than in previous years, as different methods were used, it is difficult to conclude strongly whether there has been an increase in population and number of mature individuals.
|India||Narcondam Island Wildlife Sanctuary|
|Habitat (level 1)||Habitat (level 2)||Importance||Occurrence|
|Forest||Subtropical/Tropical Moist Lowland||major||resident|
|Altitude||0 - 700 m||Occasional altitudinal limits|
|Threat (level 1)||Threat (level 2)||Impact and Stresses|
|Agriculture & aquaculture||Annual & perennial non-timber crops - Small-holder farming||Timing||Scope||Severity||Impact|
|Past, Likely to Return||Minority (<50%)||Negligible declines||Past Impact|
|Biological resource use||Hunting & trapping terrestrial animals - Intentional use (species is the target)||Timing||Scope||Severity||Impact|
|Ongoing||Minority (<50%)||Negligible declines||Low Impact: 4|
|Biological resource use||Logging & wood harvesting - Unintentional effects: (subsistence/small scale) [harvest]||Timing||Scope||Severity||Impact|
|Ongoing||Minority (<50%)||No decline||Low Impact: 4|
|Climate change & severe weather||Storms & flooding||Timing||Scope||Severity||Impact|
|Past, Likely to Return||Whole (>90%)||Negligible declines||Past Impact|
|Invasive and other problematic species, genes & diseases||Diseases of unknown cause||Timing||Scope||Severity||Impact|
|Future||Majority (50-90%)||Rapid Declines||Low Impact: 5|
|Invasive and other problematic species, genes & diseases||Invasive non-native/alien species/diseases - Capra hircus||Timing||Scope||Severity||Impact|
|Past, Unlikely to Return||Whole (>90%)||Negligible declines||Past Impact|
|Invasive and other problematic species, genes & diseases||Invasive non-native/alien species/diseases - Felis catus||Timing||Scope||Severity||Impact|
|Ongoing||Minority (<50%)||No decline||Low Impact: 4|
|Invasive and other problematic species, genes & diseases||Invasive non-native/alien species/diseases - Unspecified species||Timing||Scope||Severity||Impact|
|Past, Unlikely to Return||Minority (<50%)||Negligible declines||Past Impact|
|Residential & commercial development||Commercial & industrial areas||Timing||Scope||Severity||Impact|
|Future||Minority (<50%)||Slow, Significant Declines||Low Impact: 3|
|Purpose||Primary form used||Life stage used||Source||Scale||Level||Timing|
|Food - human||-||-||Non-trivial||Recent|
|Pets/display animals, horticulture||-||-||International||Non-trivial||Recent|
BirdLife International (2021) Species factsheet: Rhyticeros narcondami. Downloaded from http://www.birdlife.org on 14/04/2021. Recommended citation for factsheets for more than one species: BirdLife International (2021) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 14/04/2021.