 The terns , family Sternidae , are small to medium @-@ sized seabirds closely related to the gulls , skimmers and skuas . They are gull @-@ like in appearance , but typically have a lighter build , long pointed wings ( which give them a fast , buoyant flight ) , a deeply forked tail and short legs . Most species are grey above and white below , and have a black cap that is reduced or flecked with white in the winter . 
