Malabar Grey Hornbill Ocyceros griseus


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
- - A2bc+3bc+4bc

Red List history
Year Category Criteria
2020 Vulnerable A2bc+3bc+4bc
2019 Least Concern
2016 Least Concern
2012 Least Concern
2009 Least Concern
2008 Least Concern
2004 Least Concern
2000 Lower Risk/Least Concern
1994 Lower Risk/Near Threatened
1988 Lower Risk/Least Concern
Species attributes

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

Estimate Data quality
Extent of Occurrence breeding/resident (km2) 271,000 medium
Number of locations -
Severely Fragmented -
Population and trend
Value Data quality Derivation Year of estimate
No. of mature individuals unknown not applicable not applicable 0
Population trend decreasing inferred -
Decline (3 years/1 generation past) - - -
Decline (5 years/1 generation past) - - -
Decline (10 years/1 generation past) - - -
Decline (10 years/3 generation future) 30-49 - - -
Decline (10 years/3 generation past and future) 30-49 - - -
Number of subpopulations - - -
Percentage in largest subpopulation - - -
Generation length (yrs) 5.5 - - -

Population justification: The overall global population size has not been quantified, but the species is a generally common and widely distributed species along the Western Ghats, most frequent at mid-elevations (Mudappa and Raman 2009). Highest densities were found in Reserved Forests, but the species was frequent throughout, especially in moist forest. However, recent population estimates and indices in comparison with available historical data suggest a significant and rapid decline, both locally and range-wide (D. Mudappa and T. R. S. Raman in litt. 2020).

During 2004-5, biologists estimated relative abundance (Balasubramanian et al. 2004) and population density (Mudappa and Raman 2009) from number of wildlife along the Western Ghats (Balasubramanian et al. 2004, Mudappa and Raman 2009). Significant populations were reported in moist forest habitats and mid-elevations (600-1100 m) in Agasthyamalai and Anamalai Hills, and the Periyar landscape in the southern Western Ghats (Mudappa and Raman 2009). Density estimates from a more northern location in Anshi – Dandeli – Goa landscape (9.4 individuals/km², 95% Confidence Interval = 6.1 – 14.4) were lower than in the southern Western Ghats (Mudappa and Raman 2009). 

In the Anamalai – Parambikulam landscape of the southern Western Ghats, line transect surveys during 2004-5 estimated a mean density of Malabar Grey Hornbills of 67.4 individuals/km² (95% CI =40.4 – 94.4 individuals/km²) in Reserved Forests, 28.5 individuals/km² (CI = 23.9 – 33.1) in Wildlife Sanctuaries (now Tiger Reserves), and 26.0 individuals/km² (CI = 18.6 – 33.4) in rainforest fragments on the Valparai Plateau (Mudappa and Raman 2009). Within the Anamalai Tiger Reserve, the mean density of Malabar Grey Hornbill was higher in three sites at middle elevations (700–1,000 m): Anaigundi Shola (42.7 individuals/km²), Karian Shola (48.7 individuals/km²), and Varagaliar–Manamboli–Sheikalmudi complex (40.8 individuals/km²), and broadly similar across rainforest fragments within plantations on the Valparai Plateau (21.5–33.5 individuals/km²) according to Mudappa and Raman (2009).  

Comparable estimates for the Anamalai landscape from 2017-8 (P. Pawar, D. Mudappa, and T. R. S. Raman in litt. 2020), indicate a 39% decline in population density inside the protected area (to 17.5 individuals/km², CI = 12.8-23.9) and a 55% decline in the Valparai Plateau (to 11.7 individuals/km², CI = 7.1-19.3). 

Range-wide population trend using abundance indices generated from eBird data also indicates considerable declines (SoIB 2020). The report estimates -66.8% (95% CI = -43.6 to -89.9%) long-term decline and -3.3% annual decline between 2014-2018 for the species, although the wide confidence intervals meant that the species was placed in the Moderate Concern category rather than High Concern (SoIB 2020). Supplementary temporal data for Malabar Grey Hornbill provided by the authors of SoIB (2020), indicates a higher confidence in the recent data, for which an extrapolation to three generations would be a 42% decline.

Trend justification:

Recent density estimates and indices in comparison with available historical data suggest a significant and rapid decline, both locally and range-wide. Information provided to the IUCN SSC Hornbill Specialist Group (P. Pawar, D. Mudappa & T. R. S. Raman unpublished data) shows a reduction in mean population densities of 39% within the protected area and a decline of 55% in resurveyed forest fragments outside of protected areas. 

Independently, range-wide abundance indices calculated from eBird data also indicate a rapid population reduction in recent years (SoIB 2020). Wide confidence intervals and separate concerns over the type of data included in the long-term trend assessment for the species meant the species was not considered of High Concern, however the current trend between 2014-2018 also suggest a rapid decline, the mean of which is 3.3% annually, which equates to an exponential decline rate of 42% over three generations (16.5 years: Bird et al. 2020). 

Taken together, there is sufficient evidence to infer that there is a rapid ongoing population reduction across the range at a rate of 30-49% over three generations. This is believed likely to continue unless the critical factors driving the decline are identified and reversed.

Country/territory distribution
Country/Territory Presence Origin Resident Breeding Non-breeding Passage
India extant native yes

Important Bird and Biodiversity Areas (IBA)
Country/Territory IBA Name
India Achankovil Forest Division
India Amarambalam Reserved Forest - Nilambur
India Amboli-Tilari Reserve Forest
India Anshi National Park
India Aralam Wildlife Sanctuary
India Bandipur National Park
India Bhadra Wildlife Sanctuary
India Bhagwan Mahavir Wildlife Sanctuary (including Molem)
India Bhimashankar Wildlife Sanctuary
India Bhimgad Forests
India Bondla Wildlife Sanctuary
India Brahmagiri Wildlife Sanctuary
India Camel’s Hump Mountains
India Chandoli National Park
India Chinnar Wildlife Sanctuary
India Cotigao Wildlife Sanctuary
India Dandeli Wildlife Sanctuary
India Eravikulam National Park
India Gudavi Bird Sanctuary
India Indira Gandhi Wildlife Sanctuary and National Park
India INS - Shivaji and adjoining areas, Lonavla
India Kalakad-Mundanthurai Tiger Reserve
India Karnala Bird Sanctuary
India Kemmangundi and Bababudan Hills
India Kemphole Reserve Forest
India Koyna Wildlife Sanctuary
India Kudremukh National Park
India Kulahupuzha Reserved Forest
India Longwood Shola - Kothagiri
India Malayattur Reserve Forest
India Mankulam Forest Division
India Megamalai Mountains
India Mhadei Wildlife Sanctuary and area
India Muthikulam-Siruvani Reserve Forest
India Nagarhole National Park
India Navelim wetland
India Nelliyampathy (Nemmara Division)
India Netravali Wildlife Sanctuary
India Neyyar Wildlife Sanctuary
India Peechi - Vazhani Wildlife Sanctuary
India Peppara Wildlife Sanctuary
India Periyar Wildlife Sanctuary
India Phansad Wildlife Sanctuary
India Pushpagiri Wildlife Sanctuary
India Radhanagari Wildlife Sanctuary
India Sharavathi Valley Wildlife Sanctuary
India Shendurney Wildlife Sanctuary
India Silent Valley National Park
India Someshwara Wildlife Sanctuary
India Srivilliputhur Wildlife Sanctuary
India Talakaveri Wildlife Sanctuary
India Thattekkad Wildlife Sanctuary
India Vazhachal Forest Division
India Wynaad Wildlife Sanctuary

Habitats & altitude
Habitat (level 1) Habitat (level 2) Importance Occurrence
Artificial/Terrestrial Plantations major resident
Artificial/Terrestrial Rural Gardens major resident
Forest Subtropical/Tropical Dry suitable resident
Forest Subtropical/Tropical Moist Lowland major resident
Forest Subtropical/Tropical Moist Montane major resident
Altitude 50 - 1500 m Occasional altitudinal limits (min) 0 m

Threats & impact
Threat (level 1) Threat (level 2) Impact and Stresses
Agriculture & aquaculture Annual & perennial non-timber crops - Scale Unknown/Unrecorded Timing Scope Severity Impact
Ongoing Minority (<50%) Slow, Significant Declines Low Impact: 5
Species disturbance, Ecosystem degradation, Ecosystem conversion, Reduced reproductive success
Agriculture & aquaculture Annual & perennial non-timber crops - Small-holder farming Timing Scope Severity Impact
Ongoing Minority (<50%) Slow, Significant Declines Low Impact: 5
Species disturbance, Ecosystem degradation, Ecosystem conversion, Reduced reproductive success

Recommended citation
BirdLife International (2023) Species factsheet: Ocyceros griseus. Downloaded from on 03/06/2023. Recommended citation for factsheets for more than one species: BirdLife International (2023) IUCN Red List for birds. Downloaded from on 03/06/2023.