22-5-2016 RACO DE OLLA, VALENCIA - COMMON TERN (Sterna hirundo)

The Common tern (Sterna hirundo) is a seabird that has a circumpolar distribution. it has four subspecies breeding in temperate and subarctic regions of Europe, Asia, and North America. Its large population and huge breeding range mean that this species is classed as being of least concern, although numbers in North America have declined sharply in recent decades.

Known for its attractive plumage and graceful flight, Common terns have a slender body and a smoothly rounded head, and long pointed wings. Their breeding plumage is light silvery-gray upperparts and clear black outer primaries on its wingtips. Outside the breeding season, the birds keep some of their distinguishable black cap, but their forehead and face turn white. Their legs and bill turn black, losing their orange-red coloration. Male and female are similar in appearance throughout the year. Juvenile Common terns have pale grey upper wings with a dark carpal bar. The crown and nape are brown, and the forehead is ginger, wearing to white by autumn. The upper parts are ginger with brown and white scaling, and the tail lacks the adult's long outer feathers. Birds in their first post-juvenile plumage, which normally remain in their wintering areas, resemble the non-breeding adult but have a duskier crown, dark carpal bar, and often very worn plumage. By their second year, most young terns are either indistinguishable from adults, or show only minor differences such as a darker bill or white forehead.