The Sandwich Tern (Sterna sandvicensis), is a seabird.
The Sandwich Tern is a medium-large tern with grey upperparts, white underparts, a yellow-tipped black bill and a shaggy black crest which becomes less extensive in winter with a white crown. Young birds bear grey and brown scalloped plumage on their backs and wings. It is a vocal bird. It nests in a ground scrape and lays one to three eggs.The Sandwich tern is a very white tern, with a black cap on its head, a long black bill with a yellow tip and short black legs. In flight it shows grey wedges on its wings tips and it has a short forked tail. In the UK, many of the important colonies survive because they are on nature reserves.
The Sandwich Tern feeds by plunge diving for fish, usually in marine environments, and the offering of fish by the male to the female is part of the courtship display.
where you can see them
There are colonies of Sandwich terns scattered around the UK coasts including the North Norfolk coast; Minsmere, Suffolk; and Dungeness, Kent.
refences RSPB
http://www.rspb.org.uk/wildlife/birdguide/name/s/sandwichtern/index.aspx