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.
Red List criteria met
Red List history
IUCN Red list criteria met and history
||not a migrant
|Land mass type
Extent of occurrence (EOO)
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.
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. 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.
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).
Important Bird and Biodiversity Areas (IBA)
BirdLife International (2021) Species factsheet: Ocyceros griseus. Downloaded from
http://www.birdlife.org on 07/03/2021.
Recommended citation for factsheets for more than one species: BirdLife International (2021) IUCN Red List for birds. Downloaded from
http://www.birdlife.org on 07/03/2021.