The fruit-tracking hypothesis predicts a positive association between frugivores and fruit abundance overspace and time.We documented hornbill diets and examined the relationship between fruit abundance and abundanceof three hornbill species (Buceros bicornis, Rhyticeros undulatus and Aceros nipalensis) in the Eastern Himalaya from 2009–2012. The study was carried out at three scales: at the largest scale of the study area (15km2), at the intermediate scale– eight 3-ha patches within the study area and at the smallest scale of individual fruiting trees.Ninety-one per cent of the64 foraging sightings of the great hornbill were on figs while more than 50% of the foraging sightings of the wreathed(83) and rufous-necked hornbills (87) were on non-fig fruits. At the largest scale, wreathed hornbill abundance andripe fruit abundance peaked in the non-breeding season. At the intermediate scale, wreathed hornbill abundance waspositively associated with non-fig fruit availability while rufous-necked hornbill abundance was negatively associatedwith non-fig fruit availability. At the smallest scale, great and rufous-necked hornbill abundances were correlatedwithfig and non-fig fruit crop sizes, respectively. The three hornbill species track fruit availability at different scales basedon diet, which has implications for their role in seed dispersal.
Journal of Tropical Ecology, 31:477-490