Vegetation structure and morphology shape the functional diversity of understory bird communities during tropical forest succession, northwest Ecuador

Assessing the recovery of tropical forest communities requires metrics that capture both species composition and functional roles. While functional diversity indices are often proposed as more informative than taxonomic measures, it remains unclear which indices reliably track patterns consistent with community change during forest succession. To this end, we evaluated understory bird communities in the Chocó rainforest of northwest Ecuador, combining LiDAR‐derived forest structure measurements with species‐level functional traits, to better understand relationships between traits and diversity indices across successional habitats. We observed contrasting patterns in taxonomic and functional diversity across successional habitats. Species richness and Shannon diversity were highest in early successional habitats dominated by open canopies, and in contrast, functional dispersion and Rao's quadratic entropy were greater in secondary and old‐growth forests and associated with increases in canopy height and canopy. Functional divergence, evenness, and redundancy were also strongly associated with changes in morphological traits, such as increases in hand‐wing ratios, beak dimensions, and tarsus length, whereas functional richness was not. These patterns indicate that successional changes in bird communities were characterized less by expansion of the overall functional trait space and more by shifts in the abundance and distribution of functional traits within communities. Functional dispersion and Rao's quadratic entropy provided stronger evidence of successional changes in functional structure than richness‐based metrics, highlighting the importance of incorporating species abundances and trait distributions when assessing community reassembly. Overall, our results demonstrate that taxonomic and functional diversity can follow divergent trajectories during tropical forest succession and that selecting functional diversity metrics that capture abundance‐weighted trait structure can provide more ecologically informative assessments of community recovery in regenerating tropical forests.