Hornbill abundance and habitat relationships in a human-impacted protected area in the Indian Eastern Himalaya

Abstract

Asian forest hornbills play an important functional role as seed dispersers. Three of the large-bodied hornbill species in the Eastern Himalaya are declining globally. To understand their global population status, it is important to obtain reliable abundance estimates across their range. Protected areas are the strongholds for hornbill species in the Eastern Himalaya but differ in degree of disturbances and human pressures. We estimated the abundances of four hornbill species (Great Hornbill, Wreathed Hornbill, Rufous-necked Hornbill, and Oriental Pied-Hornbill) in the human-impacted Buxa Tiger Reserve in northern West Bengal. This is the first study in Asia to obtain abundance estimates of the hornbill species through comprehensive spatial coverage of the reserve. The densities of the three large-bodied species were low (< 1 bird per km2), while that of the small-bodied Oriental Pied hornbill was around 11 birds per km2. Abundance estimates ranged from a mean of 27 birds for the Rufous-necked Hornbill that is confined to the hilly areas to 161 for the Great Hornbill, 375 for the Wreathed Hornbill and 8050 for the Oriental Pied-Hornbill. Habitat quality was poor in most of the reserve with low tree density and basal area with only a few patches with higher tree density. Oriental Pied-Hornbills were associated with lower elevations and higher fruiting tree density. Despite the relatively low abundance of the large-bodied hornbill species, Buxa is an important site for hornbill conservation due to the presence of breeding populations and nests. While past and ongoing human pressures have resulted in habitat degradation, poaching pressures are low and hornbills are able to persist and breed in this landscape. Ecologically meaningful forest restoration with diverse native tree species is urgently needed to improve the habitat quality for hornbills and other wildlife.