To me (not a bird watcher) this looks like a seagull. They seem to get everywhere. Here we were wondering around the Roman Forum listening to our very good tour guide and I was taking photos. Sometimes you have to stand back from the camera and just look around. It was in doing this that I noticed this seagull sitting quite close to our large group. The Colosseum background seemed somehow fitting. As if he was guarding this ancient site from other birds?