Bulbuls and crows provide complementary seed dispersal for China's endangered trees

Background Different functional frugivores generally exhibit unequal contributions, both in terms of quantity (seed removal) and quality (seedling recruitment), to effective seed dispersal of plant species. However, variations in this dispersal pattern generated by frugivores across different regions are still unknown.

Methods In our study, we evaluated the contributions of two functional frugivore bird groups, the bulbuls (Pycnon-otidae) and crows (Corvidae), in both the seed removal and seedling recruitment of the endangered Chinese yew tree (Taxus chinensis) across three different geographical regions in eastern China.

Results The dominant crow species, Urocissa erythrorhyncha, was the most common disperser crow species at all sites, while the dominant bulbul species varied across the three sites. Furthermore, the two functional groups of dispersers diverged in the aspects of seed removal (quantity) and seedling recruitment pattern (quality). While bulbuls outperformed crows in seed removal (quantity), crows took more seeds to a safer site for seedlings (quality).

Conclusions Our results highlight the importance of variations in the effective seed dispersal patterns of different functional disperser groups across different regions in the conservation and management of endangered tree species.