contour feather
Technical ornithological term for the typical body feathers that give a bird its shape and color, as opposed to down feathers or flight feathers.
Contour feathers cover the bird's body surface and create a streamlined outline.
Compound of 正 (sei, 'proper' or 'main') and 羽 (u, 'feather'), referring to the primary body feathers that define a bird's shape.