Bird diversity peaks at intermediate bamboo cover in the Argentinian Atlantic Forest

Bamboos play an important role in shaping ecosystem diversity and productivity, yet their role remains underrepresented in studies of bird forest diversity. In the Neotropics, research has focused mainly on bamboo specialists, while the broader effects of bamboo on bird communities remain less explored. Combining autonomous recording units and in-person surveys, we sampled 42 739 min and identified all birds that vocalized or were seen across 256 count points in the Argentinian Atlantic Forest, a biodiversity hotspot. At each point, we measured the proportional cover of the most common bamboo genera in our study area—Chusquea and Merostachys—within plots. Using spatial multispecies occupancy models with 136 bird species, we evaluated how bamboo cover influences bird occupancy and richness. Our results show that Chusquea and Merostachys were associated with avian diversity, but shaped communities in distinct ways. Chusquea spp. showed a strong community-level association, whereas no community-level association was observed for Merostachys claussenii. For Chusquea spp., a more aggressive colonizer, bird occupancy and species-richness increased sharply, peaking at ~75% cover before declining. In contrast, for M. claussenii, bird diversity increased linearly and more gradually. Invertebrate-eating species were more strongly associated with bamboo than other dietary groups. Overall, these findings highlight that bamboo—a common yet often overlooked component of the Atlantic Forest—influences not only bird community composition but also occupancy and richness: moderate bamboo cover enhances avian diversity probably by adding structural heterogeneity, whereas excessive cover, linked to disturbance and reduced forest regeneration, can have neutral or negative effects.