I'll put it out there - I just don't trust seagulls. Have you noticed how they sit, "innocently" viewing the landscape. I tell you, they're up to no good. Just take a look at this photo!
On the more serious side, did you know that seagulls can live for 20 or more years? The same seagull has most probably been attacking your seaside picnics for 20 years! No wonder there are so many of them around!