Use the diagram above to answer the question that follows. The structure labelled I is adapted for

The diagram shows a bird's head with two labelled structures. Structure I is the upper mandible (upper beak), which is long, slender, and curved. Structure II is the lower mandible.

This beak shape is characteristic of nectar-feeding birds such as sunbirds and hummingbirds. The long, thin, curved beak is adapted for reaching deep into tubular flowers to extract nectar by sucking.

Other feeding adaptations in birds produce distinctly different beak shapes:

• Tearing beaks are short, strongly hooked, and powerful, as seen in raptors like eagles and hawks.
• Sieving beaks are broad and flat with comb-like lamellae along the edges, as seen in ducks and flamingos.
• Boring beaks are strong, straight, and chisel-shaped, as seen in woodpeckers.

The slender, curved beak labelled I is therefore adapted for sucking nectar from flowers.