capistrum

from The Century Dictionary.

• noun A bandage worn by ancient flute-players to prevent the undue distention of the cheeks in blowing their instruments.
• noun In surgery, a bandage for the head.
• noun In ornithology: Properly, the face of a bird; the part of the head about the bill, especially when distinguished in any way, as by a mask of color.
• noun A mask of color enveloping more or less of the head like a hood, as in the hooded gull, Larus capistratus.