While large avian frugivores are known to be key dispersers for large-seeded plants, their role inthe wider plant-disperser networks is still poorly known. In this study, we evaluate the role of largeavian frugivores in plant-disperser communities using network and seed dispersal effectivenessapproaches in a tropical forest site in north-east India. We systematically-collected tree watch datafrom 46 plant species, representing 85 percent of typically bird-dispersed plant species, spanningover 2055 h. We found that the plant-disperser community was modular with a distinct communityof large-sized seed plants and frugivores. While intermediate-sized birds such as barbets andbulbuls were the most connected, large-sized dispersers such as hornbills and Imperial-pigeonswere moderately well-connected. Imperial-pigeons consistently fed on large-sized fruits,highlighting their importance for dispersal of large-seeded plants. In addition to frugivore-fruitsize matching, frugivore dietary choices might play an important role in governing the organizationof modules. There was a gradient in qualitative and quantitative roles played by differentdispersers, with hornbills removing significantly larger number of fruits and consistentlyswallowing larger proportions of fruits as compared to other avian groups. Under simulatedextinction scenarios, observed networks were far less resilient to disperser loss along a gradient ofbody size from large to small as compared to extinctions that were random or based on rarity.Given the paucity of information on plant-disperser networks from the South Asian region andreported local extinctions of large frugivores like hornbills, this study is important in highlightingthat loss of large avian frugivores might have irreplaceable quantitative and qualitative damagesto plant communities.
Final report submitted to Arunachal Pradesh Forest Department, Itanagar, Arunachal Pradesh towards completion of the research project titled “Understanding Impacts of Hornbill Loss on Plants”.