It's not just in Pembrokeshire that Manx Shearwaters are being displaced; individuals have been found as far inland as Wigan (Gtr Manchester) and Draycote Water (Worcs).
With any Atlantic low like this, there's always the chance of an American songbird or two making landfall in the British Isles. How about a Brown-headed Cowbird?
But, as these photos taken by Tim Campbell in Antrim show, not every dark bird with a brown hood is a cowbird! This striking young male Blackbird has largely moulted its body feathers but has yet to moult its brown juvenile head feather; not terribly unusual in itself but we've never seen one as clearcut as this before. Certainly a striking bird!
Blackbird - Tim Campbell, Antrim