This photo of a petrel was taken by Mick Sway at Ria de Alvor earlier in October after very stormy weather with southerly winds:
*(This has been posted on BF as part of his trip report and I am posting it here without Mick's permission - I hope he doesn't mind).
We both saw the bird, but not at the same time, and to be honest there is a possibility that we saw different birds since during fierce storms many petrels get blown to shore (and often die, as was the case last winter).
I had good, close views (10 metres) but no photos. Mick said that the bird was further away from the shore when he got this image. It was clearly in difficulty, and appeared to me to be totally "wrecked".
My impressions of the bird were that it was larger than a Storm Petrel, the tail was slightly forked, the white rump/underside was almost separated by the dark flank "indent", and the underwing bar (conspiculously white on Storm Petrel) was pale grey (and not as obvious as it appears on this photo).
Any "Petrel experts" care to comment?