supercilium

Supercilium is a term with uses in anatomy and biology, derived from Latin for “above the eyelid.” In ornithology it refers to a line or patch of feathers located above the eye on many birds. In human anatomy the term describes the eyebrow region and the overlying soft tissues; the underlying bony brow ridge is called the superciliary arch.

In birds, the supercilium can be white, pale, buff, or dark and its extent ranges from a thin line to a broad, conspicuous band. It may be continuous or broken by feather gaps and is especially prominent in many passerines, where it often serves as a recognizable field mark for species identification. The appearance of the supercilium can vary with age, season, and plumage molt, and in some species it shows sexual dimorphism.

Functions attributed to the avian supercilium include aiding social signaling and species or individual recognition. Its contrasting appearance can help birds identify conspecifics or deter rivals, while in some cases it may play a role in camouflage or glare management, though the exact function is species-specific and not universal.

In humans and other mammals, the term often refers to the eyebrow area. The brow ridge of the skull, formed by the superciliary arches of the frontal bone, provides structural protection for the eye and contributes to facial expression.

See also: eyebrow, brow ridge, plumage pattern, facial markings.