Bird species with similar effect traits maintain the temporal stability of community functions under disturbances of tropical cyclones

Climate change is altering the frequency and intensity of extreme climatic events such as tropical cyclones, raising concerns about ecological stability under these disturbances. This study examined how functional richness and functional redundancy influenced the stability of two key ecological functions-insect predation and seed dispersal-in forest bird communities with contrasting histories of cyclone exposure. Using total biomass of insectivores and frugivores as functional indicators, we found that the stability of insect predation increased with redundancy in function-delivering traits under cyclone disturbances, whereas the stability of seed dispersal was enhanced by redundancy in both function-delivering and response-related traits. In forests frequently exposed to cyclones, both functional groups occupied a smaller overall trait space, while frugivores showed greater trait similarity among individuals. These results suggest that the stability in insect predation and seed dispersal largely stems from the abundance of species performing similar functional roles. High cyclone frequency appears to exclude species with extreme traits and concentrate functional space around a few dominant species with convergent traits. Because such convergence buffers cyclone impacts, the loss of even a few redundant species could increase functional uniqueness and, consequently, reduce the functional stability of forest bird communities.