The giant sunbird has a more varied diet than most other sunbirds, feeding not only on nectar, but also on invertebrates. It feeds by hovering in front of flowers (4), like a hummingbird but with slower wingbeats (5), and also pierces the base of flowers to obtain the rich, sugary nectar. While creeping along branches, the giant sunbird probes bark, moss and lichen with its long bill, searching for invertebrate prey (2) (4).
Sunbirds, known for being aggressive and territorial, usually construct nests of fine moss and cobwebs, suspended from twigs and branches (5). Nests of the giant sunbird have been found in late December and early January (2).