The odd thing about Black headed gulls is that they don't always have a black head!
All about Black-headed gulls - Cornell
Black-headed gull - BTO
When we lived in Caerphilly in S. Wales we had a man-made lake or pond right next to the house and it gave me plenty of opportunities for photographing the many Black headed gulls that visited regularly.
They do have a beautiful wing shape.
You can see these gulls almost anywhere these days, their high pitched screech is quite easy to identify.