A Fregatta storm-petrel seen off Severn Beach 0820-0830hrs, before drifting towards Wales, has just re-appeared briefly.
Of the two Fregatta species proposed, White-bellied F. grallaria or Black-bellied F. tropica, observers on scene are favouring the latter. Both occur in the southern oceans, and either would be an amazing record!
http://www.patteson.com/Antarctica%2...el3554vent.jpg - Black-bellied Storm-petrel
http://peter.fullagar.com/uploaded_i...043-740604.jpg - White-belllied Storm-petrel
Aside from the (variable) belly difference, Harrison (Seabirds, 1983) suggests that Black-bellied has a darker upperwing, with a less obvious carpal bar.