Thanks Derek - I am pretty sure that the first terns I saw were sandwich, diving in from about 20 - 25 feet. There were some others yesterday in the estuary and these seemed to dip in from a lower height so possibly these were common terns. And thanks for the steer re the auks - that's what I thought. Also a disappointing lack of petrels and shearwaters but I think it was too calm so they did not come inshore.
You are probably right about the terns, how the bird is feeding does help to identify the species, especially if used with other characters and plumage details.
Shearwaters and petrels are best looked for in a north west or west north west wind when they are pushed into the shore and sometimes in the mouth of the estuary. A recent article on Manx Shearwaters breeding on Lundy shows that they feed just off the mouth of the estuary. In July, whilst carrying out survey work, over 800 were watched feeding here together with a single Sooty Shearwater.
For the latest(ish) sightings from around the estuary please visit the website below,