Plant-disperser mutualistic networks

Understanding the role of hornbills in plant-disperser networks

This project aims to understand the relative importance of hornbills and other frugivores as seed dispersers for tree species across a gradient of seed sizes and fruit types using the network approach.

  • Great Hornbill. Picture by Malyasri Bhattacharya/Eastern Himalaya Program

  • Rufous-necked Hornbill with a Lauraceae fruit! Painting by Sartaj Ghuman

  • A sample of seeds that are dispersed by hornbills in Pakke

  • Arillate dehiscent capsular fruit of Chisocheton cumingianus whose seeds are dispersed widely by hornbills

  • Small-seeded fruits of Ilex which are eaten by hornbills

  • Great Hornbill feeding on arillate fruit of Dysoxylum binectariferum. Picture by Aakanksha Rathore/Eastern Himalaya Program

  • Hornbills are often driven locally extinct by high hunting pressures for their meat and other body parts!

  • Our understanding of the impacts of hornbill loss on plants is limited! A freshly shot Rufous-necked Hornbill.

  • Great Hornbill regurgitating seed of Horsfieldia kingii

Coming soon.



  • Hari Sridhar


  • International Foundation for Science (Sweden)


  • Report
    Understanding impacts of hornbill loss on plants.
    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”.

    PDF, 21.2 MB

    While large avian frugivores are known to be key dispersers for large-seeded plants, their role in the wider plant-disperser networks is still poorly known. In this study, we evaluate the role of large avian frugivores in plant-disperser communities using network and seed dispersal effectiveness approaches in a tropical forest site in north-east India. We systematically-collected tree watch data from 46 plant species, representing 85 percent of typically bird-dispersed plant species, spanning over 2055 h. We found that the plant-disperser community was modular with a distinct community of large-sized seed plants and frugivores. While intermediate-sized birds such as barbets and bulbuls were the most connected, large-sized dispersers such as hornbills and Imperial-pigeons were moderately well-connected. Imperial-pigeons consistently fed on large-sized fruits, highlighting their importance for dispersal of large-seeded plants. In addition to frugivore-fruit size matching, frugivore dietary choices might play an important role in governing the organization of modules. There was a gradient in qualitative and quantitative roles played by different dispersers, with hornbills removing significantly larger number of fruits and consistently swallowing larger proportions of fruits as compared to other avian groups. Under simulated extinction scenarios, observed networks were far less resilient to disperser loss along a gradient of body 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 and reported local extinctions of large frugivores like hornbills, this study is important in highlighting that loss of large avian frugivores might have irreplaceable quantitative and qualitative damages to plant communities.

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