Seagulls on my property?

I have young seagulls squatting in my garden, closely watched by adults who swoop at me if I go out there. Does anyone have any idea what I can do or how long I can expect them to stay? This is their 5th day now. I've heard that if I try to get rid of them they will remember me and swoop if they see me in the street. Has anyone heard of this?