Hello,
first: thanks to all for this interesting thread, especially Alison for posting it!
And yes, I thought from the pictures I can see a wedge shaped tail, full, substantial and long in relation to the body, which gave this bird a good impression of a Raven for me.
But surely biased by the other comments (thanks again!), I see a BH gull now too.
And yes, it's good to be cautious with less than perfect pictures and videos, as artifacts, single picture effects ... could well change features (sorry Alison no offense intended you will soon learn when you stay with BF which I hope), and therefore MacNara is right. But normally he uses other words (please see his numerous posts here on BF, filled with expert comments, helpful enhancement of pictures, his own pictures and friendly offers to other members here, including accommodation and optic gifts. Thanks again for this!) and please read his comment with this in mind.
(And please note, that I could roule out an alien spacecraft of the vast majority of races in our solar system with confidence. Normally I really hope for confirmation or correction and I am grateful for this you know. But not in this case, I could give reasons, but then I would reveal my cloak...
Sorry, no offense Alison and as you hopefully have already learned we are a friendly bunch. Welcome to BF once more, Alison!)