I've just answered my own question from the species display board on another photo. I would be very surprised if the Greater Black-backed Gulls do not eventually kill and eat other birds in here. I know what they can do to waterfowl -- the Oystercatchers would be especially vulnerable, and I would expect the odd disembowelled penguin. But I could be wrong, the gulls could be entirely peaceful & non-predatory. What do real experts like Vogelcommando think?
