Sinharaja is Sri Lanka’s ecological apex – a UNESCO World Heritage primary rainforest with an endemic tree species proportion exceeding 60 percent and bird species found nowhere else on earth. Walking its interior with a trained naturalist guide is a process of continuous revelation at every scale, from the mixed-species bird flocks moving through the canopy overhead to the endemic frogs and geckos in the leaf litter underfoot. The mixed-species foraging flocks unique to this forest – where multiple endemic bird species travel and feed together in coordinated groups – are one of the most extraordinary wildlife phenomena in South Asian natural history.