Data Zone
Justification of Red List category
This hornbill has been downlisted to Vulnerable because the total population size is estimated to be larger than previously believed, although remains very small. It may have increased since 2000, or previous estimates may have been too low. The population is currently believed to be stable, though there are plausible future threats from introduced mammals, the potential introduction of disease or natural disasters, as Narcondam Hornbill remains restricted to one tiny island. As such it is assessed as Vulnerable under Criterion D1 + 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The population is estimated to number between 750-1,400 individuals (R. Naniwadekar unpublished data in litt.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.
This species is endemic to the tiny (6.82 km2) island of Narcondam, east of the Andaman Islands, India. The population has been estimated a number of times in the last few decades and appears to be roughly stable, however estimates since the removal of goats, almost all cats and since hunting ceased have been consistently higher, with the most recent population estimate from 2019-2020 now 750-1,400 individuals, and densities of 150 individuals/km2 (R. Naniwadekar unpublished data in litt. to the IUCN SSC Hornbill Specialist Group 2020).
Previous population estimates (before 2005) had been lower. In 1998 the population was estimated at 295-320 birds and considered stable with an estimated 68-85 breeding pairs, while during fieldwork in 2000 the population was estimated to be 432 individuals (Yahya and Zarri 2002). In 2003, Vivek and Vijayan (2003) reported 320-340 individuals. The overall density of the species was estimated at between 54 and 71 individuals per km2 (Vivek and Vijayan 2003).
It is resident in fairly open mixed forest, which covers most of the island, from sea-level to the peak at c. 700 m asl, although the majority of nests are below 200 m asl (Vijayan 2009).
This hornbill species is found in the island’s deciduous-dominated forest in the northern and north-eastern portion with the rest of the island having evergreen forest with cloud forest on the top. Nests up to 450 m asl have been found (Manchi 2017). It uses mature, undisturbed forests with large trees for nesting and roosting. The species nests in holes on the trunk or broken branches of large trees and the female is sealed into a nest-cavity for the duration of egg-laying and chick-rearing (the breeding period spanning at least from February until April). At this time, the female sheds her flight feathers and is incapable of flight. Each pair generally raise two young. Breeding birds are over four years old and constitute c. 46-53% of the population (Vijayan 2009). Twenty-one nests of the species that were observed showed 93% success (Manchi 2017).
Hussain (1984) noted seeds of the following food tree species below nests: Anamirta cocculus, Capparis sepiaria, C. tenera var. latifolia, Garuga pinnata, Amoora rohituka, Terminalia catappa and Ixora brunniscens. The birds are also known to consume invertebrates and occasionally small reptiles (Vijayan 2009). Manchi (2017) recorded 22 species of fruits during the breeding season including species like Canarium euphyllum and Aglaia andamanica. In a recent 3-month study, 23 species of food plants were documented. Some of the species in their diet from December to February included Ficus rumphii, Ficus glabberima, Endocomia sp., Chionanthus sp. and Aidea densiflorum (Rohit Naniwadekar in litt. 2020).
Nests were documented in at least 12 different species including Tetrameles nudiflora, Zanthoxylum sp., Aglaia sp., Neonauclea sp., and Ficus nervosa among others (Rohit Naniwadekar in litt. 2020)
A small police outpost was established on the island in 1969. Approximately 20 hectares of forest had been lost since then to the creation of the post and plantations of coconut, areca, banana and vegetable plots (Raman et al. 2013), however current estimates suggest that only 5-7 ha is actively cultivated with the rest lying fallow/unused (Rohit Naniwadekar in litt. 2020). At least 10 living trees used to be cut each year for fuel wood for the camp and further wood was also cut periodically for maintenance purposes, and live chickens were also brought to the island by police stationed on the island (Raman et al. 2013). Currently, only dry, dead wood is occasionally collected (Rohit Naniwadekar in litt. 2020). A proposal to install a radar station on the island was rejected after clear demonstration of the likely detrimental impact on the population of the species (Ministry of Environment and Forests 2012, Raman et al. 2013); it was approved again (Mudappa and Raman in litt. 2020), but subsequently the plan was modified and no radar installation has been built on the island (Rohit Naniwadekar in litt. 2020).
There is the potential for avian disease to affect the population via further introductions of domestic animals, and there is also the potential impact of the accidental introduction of non-native predators.
Previously up to 400 feral goats Capra hircus were living on the island and limiting natural forest regeneration, but all have now been removed (Rohit Naniwadekar in litt. 2020). A sizeable population of feral cats Felis catus used to occur on the island, however now there are only 2 males (Rohit Naniwadekar in litt. 2020). Rats (Rattus sp.) are abundant on the island. They can be seen even in the higher elevations, in the daytime in the forest floor. They have been documented to feed on seeds of several hornbill food plant species such as Caryota mitis, Endocomia, Canarium, Sideroxylon, among others. A study has been initiated in 2019 to assess the impacts of rodent seed predation on key hornbill food plants (Rohit Naniwadekar in litt. 2020).
Hunting for food was estimated to be causing an annual loss of 25-40 birds at the start of the 2000s (Islam and Rahmani 2010), but an awareness campaign has reduced this level (Raman et al. 2013) and it is not believed to be a significant threat at present.
Most threats like the presence of the introduced goats, forest clearing, hunting of the species mentioned in past studies, do not exist anymore (Manchi 2017). However, Narcondam Hornbill has a small population and a tiny range, making it susceptible to stochastic events that could rapidly drive the population to a highly threatened state, in particular disease and natural disasters: while the 2004 tsunami did not impact the species, the impact of a typhoon may be devastating.
Conservation Actions Underway
CITES Appendix II. It is protected under the Wildlife Protection Act and Narcondam Island is a wildlife sanctuary. Goats have been removed successfully (Manchi 2017, Rohit Naniwadekar in litt. 2020). Strict instructions not to hunt the species have been issued to the personnel on the island. In 1992, the Salim Ali Centre for Ornithology and Natural History (SACON) began preliminary surveys of the avifauna on the Andaman Islands, with an emphasis on several target species, including Narcondam Hornbill. Gas cylinders and stoves are used by the police personnel to reduce dependence on fuel wood (Rohit Naniwadekar in litt. 2020)
45-50 cm. Small, distinctive, dark hornbill with pale blue gular pouch and all-white tail. Males have rufous head, neck and upper breast, blackish remainder of underparts and reddish base to bill. Females have black head to upper breast. Juveniles resemble males, but are duller-billed. Voice Cackling ka-ka-ka-ka-ka.
Text account compilers
Datta, A., Patil, I., Martin, R.
Contributors
Derhé, M., Khwaja, N., Mudappa, D., Naniwadekar, R.N., Raman, T.R.S., Sivakumar, K. & Symes, A.
Recommended citation
BirdLife International (2024) Species factsheet: Narcondam Hornbill Rhyticeros narcondami. Downloaded from
https://datazone.birdlife.org/species/factsheet/narcondam-hornbill-rhyticeros-narcondami on 23/11/2024.
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 23/11/2024.