Structurally Coloured Pattern Marks on the Inner Webs of Flight Feathers.

Summary. Some Psittacidae and Coraciidae show the unusual feature of blue and green pattern marks restricted to reverse surfaces of flight feathers. The optical causes of the colours of these marks are identical with, and the morphological configurations similar to, those which typically cause these colours on obverse surfaces of feathers in the same families. The atypical marks may, however, have been evolved independently from the typically located colour. Colour patterns on flight feathers are discussed in relation to the mechanics of flight and to optical effect.