the deep fork points towards Monteiro's BUT Madeiran Storm-petrels can have a forked tail when moulting their central rectrices and this bird is moulting its rump feathers (otherwise there would never be dark spottings in the middle of the white rump band); the bill also seems a bit too stout for Monteiro's although an overlap in bill size exists with Madeiran, therefore I will not conclude.
