Frontal shield

Located just above the upper mandible, and protruding along the forehead, it is composed of two main parts: a hard, proteinaceous callus and a soft, fleshy corium.

It is thought to play roles in protection, mate identification, sexual selection, and territorial defense.

The corium is a thick, dense mass of connective tissue fibers that makes up the largest portion of the frontal plate.

A posterior muscle attachment and cell layers within the corium allow it to change shape between enlarged, semi-enlarged, and flattened.

It consists of a hard or fleshy plate of specialised skin extending from the base of the upper bill over the forehead.

[1] Functionality appears to relate to protection of the face while feeding in, or moving through, dense vegetation, as well as to courtship display and territorial defence.