They are just rats with wings as far as I am concerned. I had my car roof badly scratched a few years ago in Penzance. Ask the people there what should be done !
About 4 years ago, I was sitting on the Pier at St Ives, having a cup of tea, and a gull swooped down and took the pasty out of the hands of a little girl sitting nearby. She was only about 5-6 and there were plenty of other people around when it happened. She was really upset and became hysterical.
There are signs all over Cornwall that tell you not to feed the gulls, and yet people still do. There is a daft old woman that feeds them loads of loaves of bread most days on the Promenade at Penzance, so its not just waste food and overflowing bins that are to be blame for the situation.
I fail to see why these nuisances can't be culled once or twice a year. They poo everywhere and they are just a ruddy plague on our seaside resorts. If it were rats doing all this damage, it would soon be sorted out. After all, rats are "part of nature" in the same way gulls and for the same reason.