VU
Narcondam Hornbill Rhyticeros narcondami



Taxonomy

Taxonomic note
Rhyticeros narcondami (del Hoyo and Collar 2014) was previously placed in the genus Aceros.

Taxonomic source(s)
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.

IUCN Red list criteria met and history
Red List criteria met
Critically Endangered Endangered Vulnerable
- - D1+2

Red List history
Year Category Criteria
2020 Vulnerable D1+2
2016 Endangered D
2012 Endangered D
2009 Endangered D1
2008 Vulnerable
2004 Vulnerable
2000 Vulnerable
1996 Vulnerable
1994 Vulnerable
1988 Threatened
Species attributes

Migratory status not a migrant Forest dependency High
Land mass type Average mass -
Distribution

Estimate Data quality
Extent of Occurrence breeding/resident (km2) 7 medium
Extent of Occurrence breeding/resident (km2) 7 good
Number of locations 1 -
Severely Fragmented -
Population and trend
Value Data quality Derivation Year of estimate
No. of mature individuals 300-650 good estimated 2020
Population trend Stable medium suspected -
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Population justification: The population is estimated to number between 750-1,400 individuals (R. Naniwadekar unpublished data in litt.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.


Country/territory distribution
Country/Territory Occurrence status Presence Resident Breeding Non-breeding Passage
India N Extant Yes

Important Bird and Biodiversity Areas (IBA)
Country/Territory IBA Name
India Narcondam Island Wildlife Sanctuary

Habitats & altitude
Habitat (level 1) Habitat (level 2) Importance Occurrence
Forest Subtropical/Tropical Moist Lowland major resident
Shrubland Subtropical/Tropical Moist major resident
Altitude 0 - 700 m Occasional altitudinal limits  

Threats & impact
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
Stresses
Ecosystem degradation, Ecosystem conversion
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
Stresses
Species mortality
Biological resource use Logging & wood harvesting - Unintentional effects: (subsistence/small scale) [harvest] Timing Scope Severity Impact
Ongoing Minority (<50%) No decline Low Impact: 4
Stresses
Ecosystem degradation
Climate change & severe weather Storms & flooding Timing Scope Severity Impact
Past, Likely to Return Whole (>90%) Negligible declines Past Impact
Stresses
Ecosystem degradation, Species mortality
Invasive and other problematic species, genes & diseases Diseases of unknown cause Timing Scope Severity Impact
Future Majority (50-90%) Rapid Declines Low Impact: 5
Stresses
Reduced reproductive success, Species mortality
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
Stresses
Ecosystem degradation
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
Stresses
Species mortality
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
Stresses
Ecosystem degradation
Residential & commercial development Commercial & industrial areas Timing Scope Severity Impact
Future Minority (<50%) Slow, Significant Declines Low Impact: 3
Stresses
Species disturbance, Ecosystem degradation, Ecosystem conversion

Utilisation
Purpose Primary form used Life stage used Source Scale Level Timing
Food - human - - Non-trivial Recent
Pets/display animals, horticulture - - International Non-trivial Recent

Recommended citation
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.