I doubt if you saw any Laughing Gulls (Larus atricila) because they're all on the other side of the Atlantic:) I presume you mean Black-headed Gulls (L ridibundus).

Mind you, the Germans call the Black-headed a Lachenmoewe which translates as ... laughing gull.

Which is arguably far more sensible, since Black-headed Gulls never have black heads.