This sounds like just the sort of sign a business with a collection of trained and domesticated seagulls would post.

If they just gave the seagulls a job, they wouldn't have to steal!

I only got robbed once in my life.

First day of vacation, the sun is shining and I’m walking down a street in Porto. Bakeries are advertising their freshly baked goods. Happily I enter one, see above sign, chuckle and proceed to buy one of these delicious looking pastries. I leave the bakery, in my hands is a pastel de nata. Tasty. With a big smile I continue my walk down the street. I turn my head and admire some flowers. Then it hits me. Quite literally. Something hit me in my face, and the bag of pastries is pulled out of my hands. I stand there, baffled. The people around me stare at me. I look at my hands, still trying to process what happened. The dude next to me stares at me, I look at him, looking for my pastry. He points at a seagull. There I see it: a freaking seagull flying away with my pastry. It dived down, mid flight and stole the bag I held in my hands. The hit in my face was its wing. I got robbed by a seagull.