The Common Tern (Sterna hirundo) is a seabird of the tern family Sternidae. This bird has a circumpolar distribution breeding in temperate and sub-Arctic regions of Europe, Asia and east and central North America. It is strongly migratory, wintering in coastal tropical and subtropical regions. The Common Teern is sometimes known as the sea swallow. Like all Sterna terns, the Common Tern feeds by plunge-diving for fish, from either the sea or freshwater lakes and large rivers. It usually dives directly, and not from the "stepped-hover" favoured by Arctic Tern. Generally, they are found in flocks. The tibetana subspecies can be found singly on in pairs in inland lakes and rivers.
The Common Tern breeds in colonies on coasts and islands and often inland on suitable freshwater lakes. This latter practice is assisted by the provision of floating "tern rafts" to give a safe breeding area. The nest varies from a scantily lined scratching in the sand or mud to a good nest made of grass, reeds, rubbish etc. The eggs number two or three and vary. It lays two to four eggs. Like many white terns, it is very defensive of its nest and young and will attack humans and other large predators.
Source: en.wikipedia.org/wiki/Common_Tern - 09.10.2010
The vastness and blankness of the surrounding makes the slender Common Tern looking smaller as it is, with its wing-span of about 75 cm.