This was a pleasant mistake. I had knocked the camera into Tv mode which blurred the motion and gave the background a longer exposure, resulting in this almost 3-D focus on the gull. Not sure I could repeat it if I tried (but I may try it again).
Gulls are pushy. If you're anywhere near a food establishment they will expect to share your eats and will take it from you if you aren't watching. Lots of people willingly feed them too, so they show no fear when they settle right down next to you and say "howdy".