Aranya Jha, Sangeeta Jha and Ajeya Jha
Abstract
Mixed-species grouping behaviour in birds is a widely recognized ecological phenomenon observed across different habitats of the world. Researchers have extensively examined aspects such as timing of flock formation, flock size, species composition, and the ecological advantages associated with such behaviour. These associations are believed to provide several benefits, including enhanced protection from predators, improved foraging efficiency, and better communication among species. However, the Eastern Himalayan region, despite being one of the worldâs richest biodiversity hotspots, remains comparatively underexplored with regard to mixed-species bird groups. Moreover, the internal structure and species hierarchy within these groups have received limited scientific attention. The present study was conducted in the forests of Sikkim, located in the Eastern Himalayas, where more than twenty mixed-species bird groups were observed in their natural habitat. Detailed records were maintained regarding the constituent species and the number of individuals participating in each group. The findings revealed that certain species consistently acted as nucleus species and were present in almost every flock, while several other species joined less frequently and appeared only occasionally. The study highlights important structural patterns in mixed-species bird associations and provides a foundation for similar ecological investigations in other Himalayan and non- Himalayan regions.