Diversity and foraging activity of flower visitors in sunflower (Helianthus annuus l.) ecosystems from the lower gangetic plains of West Bengal

The present study investigated the diversity, abundance, and foraging behaviour of insect pollinators in sunflower (Helianthus annuus L.) at Jaguli Instructional Farm, Bidhan Chandra Krishi Viswavidyalaya (BCKV), Mohanpur, Nadia, West Bengal, India, during the rabi season of 2023. A total of 16 insect species belonging to 4 orders and 7 families were recorded, with Hymenoptera being the most dominant group (56.25%). Among pollinators, Apis dorsata (17.21%), A. mellifera (16.87%), A. cerana (14.21%), and A. florea (11.83%) were the most abundant, collectively comprising over 60% of the pollinator population. The Shannon–Wiener diversity index (H′ = 2.352) and evenness index (E = 0.849) indicated moderate diversity and uniform distribution. Diurnal activity peaked between 11:00 and 13:00 h, with the highest mean visitation rate (98.36 insects/m²/3 min), aligning with the optimal temperature and solar radiation. Foraging time varied among the species, with A. dorsata and Xylocopa fenestrata spending the longest time per flower, while Halictus sp. and Tetragonula pagdeni exhibited quicker visits. Correlation analysis revealed a strong positive association between the pollinator activity, temperature, and solar radiation, and a negative correlation with the relative humidity. A key limitation of this work was the relatively short observation window, which may not adequately reflect year-to-year changes in pollinator diversity and behaviour. Nevertheless, the study provides novel evidence on species-specific diurnal activity and underscores the complementary roles of Apis and non-Apis pollinators, offering practical guidance for developing pollinator-friendly strategies in sunflower ecosystems. These findings emphasize the ecological significance of diurnal and species-specific foraging patterns in pollination success. The dominance of Apis spp. alongside native non-Apis bees underlines the importance of pollinator diversity for sustainable sunflower production in the Lower Gangetic Plains.