Bamboozling Interactions: Interspecific associations within mixed-species bird flocks in bamboo in the Eastern Himalaya

Bamboo is one of the most rarely studied habitats in the world, even though it is widespread and supports significant biodiversity wherever it occurs. Several species across taxonomic groups - including birds - are partial to bamboo habitat, with some species being obligate bamboo specialists. Mixed-species bird flocks (hereafter, flocks) are an important and regular feature of tropical and temperate forest bird communities, and have been very well-studied. However, how and why flocks might differ between bamboo and non-bamboo habitats has never been examined. We studied flocks in rainforest and bamboo stands in winter and summer in the Eastern Himalaya, and used network analysis and null models to quantify and compare the composition of flocks and interspecific associations. We found that bamboo and rainforest flocks differed greatly in their composition and interspecific associations, with bamboo flocks being more cohesive, less modular and their species more connected with each other. Further, bamboo flocks were more consistent in their composition across seasons whereas rainforest flocks were highly diverse and variable. Rainforest flocks partially disintegrated in summer, probably due to an increase in the abundance of arthropods. The loss of arthropods in an entire substrate in bamboo in summer and the increase in arthropod abundance in other substrates was probably not sufficient for flocking to cease in bamboo. We discuss species’ roles and the potential costs and benefits for species in flocks in bamboo and rainforest. Our study is one of the few to describe bamboo flocks, and the results highlight the need to conserve bamboo stands to ensure the persistence of these obligate bamboo specialists in the Eastern Himalaya. ### Competing Interest Statement The authors have declared no competing interest.