Source: 1 = Anamalai Hills (P. Y. Pawar, D. Mudappa, and T. R. S. Raman, unpublished data; 2 = Anamalai Hills (31
Mudappa, D.C. and Kannan, R. (1997). Nest-site characteristics and nesting success of the Malabar Gray Hornbill in the southern Western Ghats, India. Wilson Bull.. 109(1): 102-111.
); 3 = Anamalai Hills (20
Abraham, M. M. (2016). Distribution population density and conservation of hornbills in southern Western Ghats. Ph.D. dissertation, Gandhigram Rural Institute, Dindigul, Tamil Nadu, India.
), 4 = Mudumalai (32
Maheswaran, B., and P. Balasubramanian (2003). Nest tree utilization by the Malabar Grey Hornbill Ocyceros griseus in the semi-evergreen forest of Mudumalai Wildlife Sanctuary (S India). Acta Ornithologica 38: 33-37.
)