Biotic interactions, like competition and resource availability, play a bigger role than abiotic factors in shaping bird communities on tropical mountains. Researchers studied bird communities on two mountains in Malaysian Borneo to see how different factors affect community structure. They found that at higher elevations, birds were more similar in their evolutionary history and traits related to finding food. This suggests that limited resources and habitats drive community composition at high elevations. In contrast, lower elevation communities had more diverse traits, indicating less influence from abiotic factors and more competition among species. Overall, competition among closely related species may not be as important in shaping bird communities on tropical mountains as previously thought.