Effects of feeding by frugivorous birds and Pycnonotus xanthorrhous on seed germination of the pioneer shrub Coriaria nepalensis Wall.

Coriaria nepalensis Wall. exhibits remarkable ecological restoration capacity and functions as a pioneer woody species in barren hills and post-mining landscapes. This study investigated the composition of frugivorous birds associated with C. nepalensis across three habitat types—semi-natural environments, botanical gardens, and phosphorus mine reclamation sites—and examined the feeding behavior of the dominant disperser, Pycnonotus xanthorrhous. Field observations, controlled feeding trials, and germination assays were conducted to assess the influence of different treatments on seed germination, including seeds excreted after bird digestion, seeds with manually removed pulp, acid treatment (to simulate stomach acid softening), mechanical abrasion (to simulate gizzard grinding), and untreated natural fruits of varying maturity (intact ripe black, red, and green fruits). Results identified P. xanthorrhous as the principal disperser of C. nepalensis, and passage through its digestive tract markedly enhanced germination, achieving rates up to 97.5%, thereby promoting population expansion and ecological restoration. Furthermore, frugivorous birds tolerated the toxic metabolites of C. nepalensis achenes and played a critical role in effective fruit dispersal. Seeds that passed through avian digestion exhibited substantially higher germination rates compared to other treatments. Overall, the findings demonstrated a strong mutualistic relationship between frugivorous birds and C. nepalensis, highlighting an ecologically significant mechanism through which avian-mediated seed dispersal supports natural regeneration and accelerates ecosystem recovery in degraded habitats.