What is the currently understood purpose of the great hornbill's casque?

What is the currently understood purpose of the great hornbill's casque?

• A. It stores water
• B. The purpose is not fully understood, but it may be used for display or in fighting
• C. It helps regulate body temperature
• D. It is used to crack nuts

Answer: (B)

The main idea is that the casque’s function isn’t yet proven and is mainly inferred from how it looks and how birds behave around it. In the great hornbill, the casque is a large, conspicuous hollow structure on top of the bill. Observations show that it stands out during social interactions, especially in courting and confrontations with other birds, which makes it a likely visual signal. This signaling could help attract a mate or deter rivals, so the casque may be used in display or in fights. There are other ideas, like storing water or helping crack nuts or regulating temperature, but there isn’t solid evidence for those roles. So the best-supported view right now is that the casque’s purpose isn’t fully understood, but it may be used for display or in fighting.