Larus ridibundus  

The black spots on it's head disappears in Summer. It's the most popular kind of seagull in Poland. Unfortunatelly, the seagull in a part of dumps and so on. 

My own observations of laughing seagull I have done on the Bulwar Nadmorski w Gdyni (Seaside Bulwark in Gdynia). Birds are domesticate here. Very interesting is seagull's way to get a food - it don't land on water, often it puts into the water only its head, while fly. If people throw food for seagulls, they catch it in the air. The other interesting thing is, that if seagull , while fly, meet wind lift it can glide then very long time, whitout sway of wings.