Heaviest horn for hornbill

The hornbills are a family (Bucerotidae) of large birds from tropical Africa and Asia named after the very conspicuous horn-like structure known scientifically as a casque situated on top of their bill's upper mandible. Usually, despite its size, the casque is very light, being hollow, but uniquely in the helmeted hornbill Rhinoplax vigil of Malaysia and Indonesia it is solid, being filled with ivory and used as a battering ram. Consequently, it is very heavy. Indeed, the skull of this species (including its casque) can account for up to ten per cent of the bird's total weight of approximately 3 kg.