A female Brown-throated Sunbird (Anthreptes malacensis) spotted at Pasir Ris Park on 9 July 2022. Soh Kam Yung saw it stealing nectar (primary nectar robbing) from Hibiscus flowers by piercing the flower base. Nectar robbing does not aid in flower pollination. Secondary nectar robbing occurs when nectar is stolen from the base of flower that had been pierced by another nectar seeker earlier.
Read these posts which also document other birds nectar robbing: