Forest structure predicts species richness and functional diversity in Amazonian mixed‐species bird flocks

Secondary forest has the potential to act as an important habitat for biodiversity and restoring ecological benefits. Functional diversity, which includes morphological and behavioral traits that mediate species interactions with the surrounding environment, relates to the resilience of ecosystems. To assess the relationship between habitat structural differences in primary and secondary forest and the resultant differences in functional diversity of avian species, we followed 11 mixed‐species flocks at the Biological Dynamics of Forest Fragments Project, near Manaus, Brazil. We used remote sensing LiDAR to assess which three‐dimensional forest structural features are most closely associated with variation in species richness and functional diversity in secondary and primary tropical forest flocks. The species richness of flocks in primary forest increased in areas with higher elevation and higher leaf area density in the understory and subcanopy but was not correlated with habitat structure in secondary forest. Functional diversity increased at lower elevations and with a denser subcanopy in both primary forest and secondary forest but only increased with greater understory leaf area density in primary forest. Together, these results indicate that a dense subcanopy and understory can be important for mixed‐species flocks and that flock richness and functional diversity can be predicted by vegetation structure. in Portuguese is available with online material. A floresta secundária podeatuar como um habitat importante para a biodiversidade e restaurar os benefícios ecológicos. A diversidade funcional, que inclui características morfológicas e comportamentais que medeiam as interações das espécies com o ambiente circundante, relaciona‐se com a resiliência dos ecossistemas. Para avaliar a relação entre as diferenças estruturais de habitat em florestas primárias e secundárias e as diferenças resultantes na diversidade funcional de espécies de aves, acompanhamos 11 bandos mistos no Projeto de Dinâmica Biológica de Fragmentos Florestais, perto de Manaus, Brasil. Usamos LiDAR de sensoriamento remoto para avaliar quais características estruturais tridimensionais da floresta estão mais intimamente associadas à variação na riqueza de espécies e diversidade funcional em bandos de florestas tropicais secundárias e primárias. A riqueza de espécies dos bandos na floresta primária aumentou em áreas com maior elevação e maior densidade de área foliar no sub‐bosque e no su