Photo above by Shavez Cheema shows an adult male Helmeted hornbill about to feed a Ficus forstenii fig to the female hornbill inside the nesting cavity at Tawau.
Helmeted Hornbills are known to be fig specialists which feed largely on the fruit of strangling figs of many species supplemented with small mammals and birds and large insects. See Fig Ecology: Helmeted Hornbill
This article by Ravinder Kaur describes the food fed to their single offspring by a pair of nesting Helmeted hornbills on the Kinabatangan River between 2013-2017.
Food brought to the nest consisted mainly of figs, including Ficus stupenda, Ficus benjamina, Ficus stricta and Ficus crassiramea. The adult Helmeted hornbills delivered stick insects, beetles and praying mantis, whilst the chick itself caught and consumed a giant millipede.
Ravinder also notes that the patents fed unripe figs to the young bird. Due to the way figs are pollinated by fig wasps, unripe figs often contain large numbers of fig wasps. These wasps all leave the fig before they ripen. Thus unripe figs may contain higher levels of protein than ripe figs
As the fledging of the chick approached the male and female brought unripe figs as noted elsewhere (Chong 2011).