Why are toucan bills large but lightweight?

Although the toucan's bill appears large and potentially heavy, it is remarkably lightweight due to its unique internal structure. It is composed of extremely thin, light bone reinforced by a network of fine, crisscrossing bony fibers that provide significant strength while maintaining a low overall weight. The exterior of the bill is covered in keratin, the same material found in human fingernails.12

While the bill's size may seem disproportionate, its lightweight construction allows the bird to manage it effectively despite its appearance. The bill serves several functions, including species recognition through its bright coloration, acting as a tool for foraging—such as tearing open fruit or securing insects—and potentially serving as a deterrent against other birds.12