Back to the seagull problem. I don't think this is the way to encourage visitors not to feed the gulls. The council, I presume, has decided to make gulls a fluffy and cuddly bird which amuses children.
I can understand this as other creatures have been made fluffy and cuddly, like the polar bear or the tiger. This is so that their plight can be brought into mind, but the creatures themselves are anything but fluffy and cuddly. They are in actual fact carnivorous predators who would tear you to bits in a moment if you were available.
But the gull is not a bird that is under threat of extinction by the actions of man. It is a threat to man. Making it cuffy and fluddly, er fluffy and cuddly, will not make people treat it as the bothersome bird that some folk think it is.
They're a nuisance, though, I agree. But not quite as much a nuisance as those who casually throw litter away, or bits of unwanted food, or even those who are amused by feeding them.
If gulls are nesting on your building, you can do something about it. I looked at the rear of the library building in Queen Street and four window sills had nests on them. All that needs to be done is hang wire from one side of the frontage to the other - problem solved! But I bet the council would say there is no money for that, but their building is gradually deteriorating with all the muck and stuff the birds are throwing at it.
If your shop or office has seagull muck on the pavement, do what I did yesterday. I spent half an hour with a stiff brush and a bucket of water and cleaned up the dirt from in front of the harbour museum. Some come on, folks, do your bit.