Common Terns, but not so 'common'!
Adults, I believe the one with the blue and silver rings, one on each leg is the male, based on his behaviour. The female does not appear to have any leg rings. I'm not too sure about the marks on his head, but think they might be some form of contamination from fishing (oil on the water?) and while he appears to be shouting, looking at the last two photos, I think he's having 40 winks!