Avian Diversity and Abundance in the Muga Silkworm (Antheraea assamensis) Ecosystem of Assam Across Larval Instars and Agro-climatic Zones

Open rearing of the muga silkworm (Antheraea assamensis) exposes developing larvae to a diverse assemblage of visiting birds. This study characterised avian abundance, species richness, Shannon diversity and predatory/depredatory composition at six muga-rearing locations in Assam's Upper Brahmaputra Valley Zone (UBVZ; Sivasagar) and North Bank Plain Zone (NBPZ; Lakhimpur), covering all five larval instars. Line-transect observations conducted during the Chotua and Jethua rearing seasons in 2020–2022 yielded 9,724 bird records. The NBPZ accounted for 5,961 records (61.3%), compared with 3,763 (38.7%) in the UBVZ. Across locations, the mean classified composition was 66.45% predatory and 33.55% depredatory birds. Gobindapur had the greatest overall abundance (2,238 records) and species richness (43 species), whereas MSDP Borahibari had the lowest (1,167 records; 29 species). Abundance was highest during the third instar (2,949 records) and lowest during the first instar (1,035 records); mean Shannon diversity also peaked in the third instar (3.011). Maximum single-location richness, however, was greatest during the fourth instar (34 species). During the fourth and fifth instars combined, common myna was the most abundant species in both districts. These descriptive patterns indicate that bird visitation varies spatially and across larval development. Because bird counts do not directly measure predation or silkworm mortality, the findings support stage-specific monitoring and consideration of non-harmful management rather than estimates of bird-induced crop loss.