HomeGlossary Bird topography Casque A helmet-like growth on top of the bill or head. Found in hornbills and cassowaries; its size and colour are key identification features. Bird topographyRelated termsFull glossary Culmen The upper ridge of the bill from its tip to where the feathers begin. Tertials The innermost flight feathers, next to the body, which often cover the folded primaries on a perched bird. Speculum A bright, often iridescent patch on the secondaries of many ducks. Primaries The outermost flight feathers of the wing, attached to the "hand"; they provide most of the forward thrust. Mantle The upper back, between the nape and the scapulars. Tarsus The lower, usually bare, part of the leg above the toes.
Tertials The innermost flight feathers, next to the body, which often cover the folded primaries on a perched bird.
Primaries The outermost flight feathers of the wing, attached to the "hand"; they provide most of the forward thrust.