Hornbill abundance in unlogged forest, selectively logged forest and a forest plantation in Arunachal Pradesh, India

Abstract

The responses of hornbills to selective logging were determined by comparing their diversity and abundance in five habitats classified according to logging history. Relative abundance of three hornbill species was compared along trails in recently logged forest, 20–25-year-old logged forest, unlogged primary forest, a relatively disturbed primary forest and a plantation in Pakhui Wildlife Sanctuary and adjoining reserve forests in western Arunachal Pradesh. The species recorded were the Oriental pied hornbill Anthracoceros albirostris, wreathed hornbill Aceros undulatus and great hornbill Buceros bicornis. The great hornbill was the most common species overall and its abundance varied across habitats, being highest in unlogged forest. The Oriental pied hornbill, which was recorded in only two habitats, seemed to show a distinct habitat preference for secondary growth, rivermargin forests. Wreathed hornbill abundance did not differ between habitats. Differences in species abundance probably reflect aspects of their ecology, such as degree of territoriality, diet and movement patterns, and differential vulnerability to hunting and disturbance. Great hornbill abundance was correlated with large tree density (GBH ≥ 150 cm) and basal area characteristic of unlogged primary forests, while Oriental pied hornbill abundance was negatively correlated with tall forest, indicating its greater numbers in low-stature river-margin forest. Wreathed hornbill abundance was not correlated with any vegetation variable, which is probably related to its reported nomadic movements in search of fruit patches. Hornbill abundance was not correlated with densities of potential food and nest tree species. Although hornbill abundance was not correlated with fig tree density, this was probably because areas where relative fig tree densities were lower often contained a few large fruiting figs. Because hornbills are large mobile birds, they can find resources such as fruiting figs even in otherwise unsuitable habitat.