After moulting, the young terns resemble the adult, but still have a variegated wing pattern with a dark bar on the inner flight feathers.

Juveniles have a pronounced dark bar on the rear body at the level of the soft dorsal fin.

The tornus has a dark bar, narrowing and continuing obscurely to the midpoint of the costal margin.

Sections perpendicular to an optic axis of a biaxial mineral under the same conditions show a dark bar which on rotation becomes curved to a hyperbolic shape.

Sport has many of its origins in dark bars around the country.